pub use crate::{
    diagnostic_set::DiagnosticSet,
    highlight_map::{HighlightId, HighlightMap},
    proto, BracketPair, Grammar, Language, LanguageConfig, LanguageRegistry, LanguageServerConfig,
    PLAIN_TEXT,
};
use crate::{
    diagnostic_set::{DiagnosticEntry, DiagnosticGroup},
    outline::OutlineItem,
    range_from_lsp, Outline,
};
use anyhow::{anyhow, Result};
use clock::ReplicaId;
use futures::FutureExt as _;
use gpui::{fonts::HighlightStyle, AppContext, Entity, ModelContext, MutableAppContext, Task};
use lazy_static::lazy_static;
use lsp::LanguageServer;
use parking_lot::Mutex;
use postage::{prelude::Stream, sink::Sink, watch};
use similar::{ChangeTag, TextDiff};
use smol::future::yield_now;
use std::{
    any::Any,
    cell::RefCell,
    cmp::{self, Ordering},
    collections::{BTreeMap, HashMap},
    ffi::OsString,
    future::Future,
    iter::{Iterator, Peekable},
    ops::{Deref, DerefMut, Range, Sub},
    path::{Path, PathBuf},
    str,
    sync::Arc,
    time::{Duration, Instant, SystemTime, UNIX_EPOCH},
    vec,
};
use sum_tree::TreeMap;
use text::{operation_queue::OperationQueue, rope::TextDimension};
pub use text::{Buffer as TextBuffer, Operation as _, *};
use theme::SyntaxTheme;
use tree_sitter::{InputEdit, Parser, QueryCursor, Tree};
use util::{post_inc, TryFutureExt as _};

#[cfg(any(test, feature = "test-support"))]
pub use tree_sitter_rust;

pub use lsp::DiagnosticSeverity;

thread_local! {
    static PARSER: RefCell<Parser> = RefCell::new(Parser::new());
}

lazy_static! {
    static ref QUERY_CURSORS: Mutex<Vec<QueryCursor>> = Default::default();
}

// TODO - Make this configurable
const INDENT_SIZE: u32 = 4;

pub struct Buffer {
    text: TextBuffer,
    file: Option<Box<dyn File>>,
    saved_version: clock::Global,
    saved_mtime: SystemTime,
    language: Option<Arc<Language>>,
    autoindent_requests: Vec<Arc<AutoindentRequest>>,
    pending_autoindent: Option<Task<()>>,
    sync_parse_timeout: Duration,
    syntax_tree: Mutex<Option<SyntaxTree>>,
    parsing_in_background: bool,
    parse_count: usize,
    diagnostics: DiagnosticSet,
    remote_selections: TreeMap<ReplicaId, SelectionSet>,
    selections_update_count: usize,
    diagnostics_update_count: usize,
    language_server: Option<LanguageServerState>,
    deferred_ops: OperationQueue<Operation>,
    #[cfg(test)]
    pub(crate) operations: Vec<Operation>,
}

pub struct BufferSnapshot {
    text: text::BufferSnapshot,
    tree: Option<Tree>,
    diagnostics: DiagnosticSet,
    diagnostics_update_count: usize,
    remote_selections: TreeMap<ReplicaId, SelectionSet>,
    selections_update_count: usize,
    is_parsing: bool,
    language: Option<Arc<Language>>,
    parse_count: usize,
}

#[derive(Clone, Debug)]
struct SelectionSet {
    selections: Arc<[Selection<Anchor>]>,
    lamport_timestamp: clock::Lamport,
}

#[derive(Clone, Debug, PartialEq, Eq)]
pub struct GroupId {
    source: Arc<str>,
    id: usize,
}

#[derive(Clone, Debug, PartialEq, Eq)]
pub struct Diagnostic {
    pub code: Option<String>,
    pub severity: DiagnosticSeverity,
    pub message: String,
    pub group_id: usize,
    pub is_valid: bool,
    pub is_primary: bool,
    pub is_disk_based: bool,
}

struct LanguageServerState {
    server: Arc<LanguageServer>,
    latest_snapshot: watch::Sender<Option<LanguageServerSnapshot>>,
    pending_snapshots: BTreeMap<usize, LanguageServerSnapshot>,
    next_version: usize,
    _maintain_server: Task<Option<()>>,
}

#[derive(Clone)]
struct LanguageServerSnapshot {
    buffer_snapshot: text::BufferSnapshot,
    version: usize,
    path: Arc<Path>,
}

#[derive(Clone, Debug)]
pub enum Operation {
    Buffer(text::Operation),
    UpdateDiagnostics {
        diagnostics: Arc<[DiagnosticEntry<Anchor>]>,
        lamport_timestamp: clock::Lamport,
    },
    UpdateSelections {
        replica_id: ReplicaId,
        selections: Arc<[Selection<Anchor>]>,
        lamport_timestamp: clock::Lamport,
    },
}

#[derive(Clone, Debug, Eq, PartialEq)]
pub enum Event {
    Edited,
    Dirtied,
    Saved,
    FileHandleChanged,
    Reloaded,
    Reparsed,
    DiagnosticsUpdated,
    Closed,
}

pub trait File {
    fn mtime(&self) -> SystemTime;

    /// Returns the path of this file relative to the worktree's root directory.
    fn path(&self) -> &Arc<Path>;

    /// Returns the absolute path of this file.
    fn abs_path(&self) -> Option<PathBuf>;

    /// Returns the path of this file relative to the worktree's parent directory (this means it
    /// includes the name of the worktree's root folder).
    fn full_path(&self) -> PathBuf;

    /// Returns the last component of this handle's absolute path. If this handle refers to the root
    /// of its worktree, then this method will return the name of the worktree itself.
    fn file_name(&self) -> Option<OsString>;

    fn is_deleted(&self) -> bool;

    fn save(
        &self,
        buffer_id: u64,
        text: Rope,
        version: clock::Global,
        cx: &mut MutableAppContext,
    ) -> Task<Result<(clock::Global, SystemTime)>>;

    fn load_local(&self, cx: &AppContext) -> Option<Task<Result<String>>>;

    fn format_remote(&self, buffer_id: u64, cx: &mut MutableAppContext)
        -> Option<Task<Result<()>>>;

    fn buffer_updated(&self, buffer_id: u64, operation: Operation, cx: &mut MutableAppContext);

    fn buffer_removed(&self, buffer_id: u64, cx: &mut MutableAppContext);

    fn as_any(&self) -> &dyn Any;
}

pub(crate) struct QueryCursorHandle(Option<QueryCursor>);

#[derive(Clone)]
struct SyntaxTree {
    tree: Tree,
    version: clock::Global,
}

#[derive(Clone)]
struct AutoindentRequest {
    before_edit: BufferSnapshot,
    edited: Vec<Anchor>,
    inserted: Option<Vec<Range<Anchor>>>,
}

#[derive(Debug)]
struct IndentSuggestion {
    basis_row: u32,
    indent: bool,
}

struct TextProvider<'a>(&'a Rope);

struct BufferChunkHighlights<'a> {
    captures: tree_sitter::QueryCaptures<'a, 'a, TextProvider<'a>>,
    next_capture: Option<(tree_sitter::QueryMatch<'a, 'a>, usize)>,
    stack: Vec<(usize, HighlightId)>,
    highlight_map: HighlightMap,
    theme: &'a SyntaxTheme,
    _query_cursor: QueryCursorHandle,
}

pub struct BufferChunks<'a> {
    range: Range<usize>,
    chunks: rope::Chunks<'a>,
    diagnostic_endpoints: Peekable<vec::IntoIter<DiagnosticEndpoint>>,
    error_depth: usize,
    warning_depth: usize,
    information_depth: usize,
    hint_depth: usize,
    highlights: Option<BufferChunkHighlights<'a>>,
}

#[derive(Clone, Copy, Debug, Default)]
pub struct Chunk<'a> {
    pub text: &'a str,
    pub highlight_style: Option<HighlightStyle>,
    pub diagnostic: Option<DiagnosticSeverity>,
}

pub(crate) struct Diff {
    base_version: clock::Global,
    new_text: Arc<str>,
    changes: Vec<(ChangeTag, usize)>,
}

#[derive(Clone, Copy)]
struct DiagnosticEndpoint {
    offset: usize,
    is_start: bool,
    severity: DiagnosticSeverity,
}

impl Buffer {
    pub fn new<T: Into<Arc<str>>>(
        replica_id: ReplicaId,
        base_text: T,
        cx: &mut ModelContext<Self>,
    ) -> Self {
        Self::build(
            TextBuffer::new(
                replica_id,
                cx.model_id() as u64,
                History::new(base_text.into()),
            ),
            None,
        )
    }

    pub fn from_file<T: Into<Arc<str>>>(
        replica_id: ReplicaId,
        base_text: T,
        file: Box<dyn File>,
        cx: &mut ModelContext<Self>,
    ) -> Self {
        Self::build(
            TextBuffer::new(
                replica_id,
                cx.model_id() as u64,
                History::new(base_text.into()),
            ),
            Some(file),
        )
    }

    pub fn from_proto(
        replica_id: ReplicaId,
        message: proto::Buffer,
        file: Option<Box<dyn File>>,
        cx: &mut ModelContext<Self>,
    ) -> Result<Self> {
        let fragments_len = message.fragments.len();
        let buffer = TextBuffer::from_parts(
            replica_id,
            message.id,
            &message.visible_text,
            &message.deleted_text,
            message
                .undo_map
                .into_iter()
                .map(proto::deserialize_undo_map_entry),
            message
                .fragments
                .into_iter()
                .enumerate()
                .map(|(i, fragment)| {
                    proto::deserialize_buffer_fragment(fragment, i, fragments_len)
                }),
            message.lamport_timestamp,
            From::from(message.version),
        );
        let mut this = Self::build(buffer, file);
        for selection_set in message.selections {
            this.remote_selections.insert(
                selection_set.replica_id as ReplicaId,
                SelectionSet {
                    selections: proto::deserialize_selections(selection_set.selections),
                    lamport_timestamp: clock::Lamport {
                        replica_id: selection_set.replica_id as ReplicaId,
                        value: selection_set.lamport_timestamp,
                    },
                },
            );
        }
        let snapshot = this.snapshot();
        let entries = proto::deserialize_diagnostics(message.diagnostics);
        this.apply_diagnostic_update(
            DiagnosticSet::from_sorted_entries(entries.into_iter().cloned(), &snapshot),
            cx,
        );

        let deferred_ops = message
            .deferred_operations
            .into_iter()
            .map(proto::deserialize_operation)
            .collect::<Result<Vec<_>>>()?;
        this.apply_ops(deferred_ops, cx)?;

        Ok(this)
    }

    pub fn to_proto(&self) -> proto::Buffer {
        proto::Buffer {
            id: self.remote_id(),
            visible_text: self.text.text(),
            deleted_text: self.text.deleted_text(),
            undo_map: self
                .text
                .undo_history()
                .map(proto::serialize_undo_map_entry)
                .collect(),
            version: From::from(&self.version),
            lamport_timestamp: self.lamport_clock.value,
            fragments: self
                .text
                .fragments()
                .map(proto::serialize_buffer_fragment)
                .collect(),
            selections: self
                .remote_selections
                .iter()
                .map(|(replica_id, set)| proto::SelectionSet {
                    replica_id: *replica_id as u32,
                    selections: proto::serialize_selections(&set.selections),
                    lamport_timestamp: set.lamport_timestamp.value,
                })
                .collect(),
            diagnostics: proto::serialize_diagnostics(self.diagnostics.iter()),
            deferred_operations: self
                .deferred_ops
                .iter()
                .map(proto::serialize_operation)
                .chain(
                    self.text
                        .deferred_ops()
                        .map(|op| proto::serialize_operation(&Operation::Buffer(op.clone()))),
                )
                .collect(),
        }
    }

    pub fn with_language(
        mut self,
        language: Option<Arc<Language>>,
        language_server: Option<Arc<LanguageServer>>,
        cx: &mut ModelContext<Self>,
    ) -> Self {
        self.set_language(language, language_server, cx);
        self
    }

    fn build(buffer: TextBuffer, file: Option<Box<dyn File>>) -> Self {
        let saved_mtime;
        if let Some(file) = file.as_ref() {
            saved_mtime = file.mtime();
        } else {
            saved_mtime = UNIX_EPOCH;
        }

        Self {
            saved_mtime,
            saved_version: buffer.version(),
            text: buffer,
            file,
            syntax_tree: Mutex::new(None),
            parsing_in_background: false,
            parse_count: 0,
            sync_parse_timeout: Duration::from_millis(1),
            autoindent_requests: Default::default(),
            pending_autoindent: Default::default(),
            language: None,
            remote_selections: Default::default(),
            selections_update_count: 0,
            diagnostics: Default::default(),
            diagnostics_update_count: 0,
            language_server: None,
            deferred_ops: OperationQueue::new(),
            #[cfg(test)]
            operations: Default::default(),
        }
    }

    pub fn snapshot(&self) -> BufferSnapshot {
        BufferSnapshot {
            text: self.text.snapshot(),
            tree: self.syntax_tree(),
            remote_selections: self.remote_selections.clone(),
            diagnostics: self.diagnostics.clone(),
            diagnostics_update_count: self.diagnostics_update_count,
            is_parsing: self.parsing_in_background,
            language: self.language.clone(),
            parse_count: self.parse_count,
            selections_update_count: self.selections_update_count,
        }
    }

    pub fn file(&self) -> Option<&dyn File> {
        self.file.as_deref()
    }

    pub fn format(&mut self, cx: &mut ModelContext<Self>) -> Task<Result<()>> {
        let file = if let Some(file) = self.file.as_ref() {
            file
        } else {
            return Task::ready(Err(anyhow!("buffer has no file")));
        };

        if let Some(LanguageServerState { server, .. }) = self.language_server.as_ref() {
            let server = server.clone();
            let abs_path = file.abs_path().unwrap();
            let version = self.version();
            cx.spawn(|this, mut cx| async move {
                let edits = server
                    .request::<lsp::request::Formatting>(lsp::DocumentFormattingParams {
                        text_document: lsp::TextDocumentIdentifier::new(
                            lsp::Url::from_file_path(&abs_path).unwrap(),
                        ),
                        options: Default::default(),
                        work_done_progress_params: Default::default(),
                    })
                    .await?;

                if let Some(edits) = edits {
                    this.update(&mut cx, |this, cx| {
                        if this.version == version {
                            for edit in &edits {
                                let range = range_from_lsp(edit.range);
                                if this.clip_point_utf16(range.start, Bias::Left) != range.start
                                    || this.clip_point_utf16(range.end, Bias::Left) != range.end
                                {
                                    return Err(anyhow!(
                                        "invalid formatting edits received from language server"
                                    ));
                                }
                            }

                            for edit in edits.into_iter().rev() {
                                this.edit([range_from_lsp(edit.range)], edit.new_text, cx);
                            }
                            Ok(())
                        } else {
                            Err(anyhow!("buffer edited since starting to format"))
                        }
                    })
                } else {
                    Ok(())
                }
            })
        } else {
            let format = file.format_remote(self.remote_id(), cx.as_mut());
            cx.spawn(|_, _| async move {
                if let Some(format) = format {
                    format.await?;
                }
                Ok(())
            })
        }
    }

    pub fn save(
        &mut self,
        cx: &mut ModelContext<Self>,
    ) -> Result<Task<Result<(clock::Global, SystemTime)>>> {
        let file = self
            .file
            .as_ref()
            .ok_or_else(|| anyhow!("buffer has no file"))?;
        let text = self.as_rope().clone();
        let version = self.version();
        let save = file.save(self.remote_id(), text, version, cx.as_mut());
        Ok(cx.spawn(|this, mut cx| async move {
            let (version, mtime) = save.await?;
            this.update(&mut cx, |this, cx| {
                this.did_save(version.clone(), mtime, None, cx);
            });
            Ok((version, mtime))
        }))
    }

    pub fn set_language(
        &mut self,
        language: Option<Arc<Language>>,
        language_server: Option<Arc<lsp::LanguageServer>>,
        cx: &mut ModelContext<Self>,
    ) {
        self.language = language;
        self.language_server = if let Some(server) = language_server {
            let (latest_snapshot_tx, mut latest_snapshot_rx) = watch::channel();
            Some(LanguageServerState {
                latest_snapshot: latest_snapshot_tx,
                pending_snapshots: Default::default(),
                next_version: 0,
                server: server.clone(),
                _maintain_server: cx.background().spawn(
                    async move {
                        let mut prev_snapshot: Option<LanguageServerSnapshot> = None;
                        while let Some(snapshot) = latest_snapshot_rx.recv().await {
                            if let Some(snapshot) = snapshot {
                                let uri = lsp::Url::from_file_path(&snapshot.path).unwrap();
                                if let Some(prev_snapshot) = prev_snapshot {
                                    let changes = lsp::DidChangeTextDocumentParams {
                                        text_document: lsp::VersionedTextDocumentIdentifier::new(
                                            uri,
                                            snapshot.version as i32,
                                        ),
                                        content_changes: snapshot
                                            .buffer_snapshot
                                            .edits_since::<(PointUtf16, usize)>(
                                                prev_snapshot.buffer_snapshot.version(),
                                            )
                                            .map(|edit| {
                                                let edit_start = edit.new.start.0;
                                                let edit_end = edit_start
                                                    + (edit.old.end.0 - edit.old.start.0);
                                                let new_text = snapshot
                                                    .buffer_snapshot
                                                    .text_for_range(
                                                        edit.new.start.1..edit.new.end.1,
                                                    )
                                                    .collect();
                                                lsp::TextDocumentContentChangeEvent {
                                                    range: Some(lsp::Range::new(
                                                        lsp::Position::new(
                                                            edit_start.row,
                                                            edit_start.column,
                                                        ),
                                                        lsp::Position::new(
                                                            edit_end.row,
                                                            edit_end.column,
                                                        ),
                                                    )),
                                                    range_length: None,
                                                    text: new_text,
                                                }
                                            })
                                            .collect(),
                                    };
                                    server
                                        .notify::<lsp::notification::DidChangeTextDocument>(changes)
                                        .await?;
                                } else {
                                    server
                                        .notify::<lsp::notification::DidOpenTextDocument>(
                                            lsp::DidOpenTextDocumentParams {
                                                text_document: lsp::TextDocumentItem::new(
                                                    uri,
                                                    Default::default(),
                                                    snapshot.version as i32,
                                                    snapshot.buffer_snapshot.text().to_string(),
                                                ),
                                            },
                                        )
                                        .await?;
                                }

                                prev_snapshot = Some(snapshot);
                            }
                        }
                        Ok(())
                    }
                    .log_err(),
                ),
            })
        } else {
            None
        };

        self.reparse(cx);
        self.update_language_server();
    }

    pub fn did_save(
        &mut self,
        version: clock::Global,
        mtime: SystemTime,
        new_file: Option<Box<dyn File>>,
        cx: &mut ModelContext<Self>,
    ) {
        self.saved_mtime = mtime;
        self.saved_version = version;
        if let Some(new_file) = new_file {
            self.file = Some(new_file);
        }
        if let Some(state) = &self.language_server {
            cx.background()
                .spawn(
                    state
                        .server
                        .notify::<lsp::notification::DidSaveTextDocument>(
                            lsp::DidSaveTextDocumentParams {
                                text_document: lsp::TextDocumentIdentifier {
                                    uri: lsp::Url::from_file_path(
                                        self.file.as_ref().unwrap().abs_path().unwrap(),
                                    )
                                    .unwrap(),
                                },
                                text: None,
                            },
                        ),
                )
                .detach()
        }
        cx.emit(Event::Saved);
    }

    pub fn file_updated(
        &mut self,
        new_file: Box<dyn File>,
        cx: &mut ModelContext<Self>,
    ) -> Option<Task<()>> {
        let old_file = self.file.as_ref()?;
        let mut file_changed = false;
        let mut task = None;

        if new_file.path() != old_file.path() {
            file_changed = true;
        }

        if new_file.is_deleted() {
            if !old_file.is_deleted() {
                file_changed = true;
                if !self.is_dirty() {
                    cx.emit(Event::Dirtied);
                }
            }
        } else {
            let new_mtime = new_file.mtime();
            if new_mtime != old_file.mtime() {
                file_changed = true;

                if !self.is_dirty() {
                    task = Some(cx.spawn(|this, mut cx| {
                        async move {
                            let new_text = this.read_with(&cx, |this, cx| {
                                this.file.as_ref().and_then(|file| file.load_local(cx))
                            });
                            if let Some(new_text) = new_text {
                                let new_text = new_text.await?;
                                let diff = this
                                    .read_with(&cx, |this, cx| this.diff(new_text.into(), cx))
                                    .await;
                                this.update(&mut cx, |this, cx| {
                                    if this.apply_diff(diff, cx) {
                                        this.saved_version = this.version();
                                        this.saved_mtime = new_mtime;
                                        cx.emit(Event::Reloaded);
                                    }
                                });
                            }
                            Ok(())
                        }
                        .log_err()
                        .map(drop)
                    }));
                }
            }
        }

        if file_changed {
            cx.emit(Event::FileHandleChanged);
        }
        self.file = Some(new_file);
        task
    }

    pub fn close(&mut self, cx: &mut ModelContext<Self>) {
        cx.emit(Event::Closed);
    }

    pub fn language(&self) -> Option<&Arc<Language>> {
        self.language.as_ref()
    }

    pub fn parse_count(&self) -> usize {
        self.parse_count
    }

    pub fn selections_update_count(&self) -> usize {
        self.selections_update_count
    }

    pub fn diagnostics_update_count(&self) -> usize {
        self.diagnostics_update_count
    }

    pub(crate) fn syntax_tree(&self) -> Option<Tree> {
        if let Some(syntax_tree) = self.syntax_tree.lock().as_mut() {
            self.interpolate_tree(syntax_tree);
            Some(syntax_tree.tree.clone())
        } else {
            None
        }
    }

    #[cfg(any(test, feature = "test-support"))]
    pub fn is_parsing(&self) -> bool {
        self.parsing_in_background
    }

    #[cfg(test)]
    pub fn set_sync_parse_timeout(&mut self, timeout: Duration) {
        self.sync_parse_timeout = timeout;
    }

    fn reparse(&mut self, cx: &mut ModelContext<Self>) -> bool {
        if self.parsing_in_background {
            return false;
        }

        if let Some(grammar) = self.grammar().cloned() {
            let old_tree = self.syntax_tree();
            let text = self.as_rope().clone();
            let parsed_version = self.version();
            let parse_task = cx.background().spawn({
                let grammar = grammar.clone();
                async move { Self::parse_text(&text, old_tree, &grammar) }
            });

            match cx
                .background()
                .block_with_timeout(self.sync_parse_timeout, parse_task)
            {
                Ok(new_tree) => {
                    self.did_finish_parsing(new_tree, parsed_version, cx);
                    return true;
                }
                Err(parse_task) => {
                    self.parsing_in_background = true;
                    cx.spawn(move |this, mut cx| async move {
                        let new_tree = parse_task.await;
                        this.update(&mut cx, move |this, cx| {
                            let grammar_changed = this
                                .grammar()
                                .map_or(true, |curr_grammar| !Arc::ptr_eq(&grammar, curr_grammar));
                            let parse_again =
                                this.version.changed_since(&parsed_version) || grammar_changed;
                            this.parsing_in_background = false;
                            this.did_finish_parsing(new_tree, parsed_version, cx);

                            if parse_again && this.reparse(cx) {
                                return;
                            }
                        });
                    })
                    .detach();
                }
            }
        }
        false
    }

    fn parse_text(text: &Rope, old_tree: Option<Tree>, grammar: &Grammar) -> Tree {
        PARSER.with(|parser| {
            let mut parser = parser.borrow_mut();
            parser
                .set_language(grammar.ts_language)
                .expect("incompatible grammar");
            let mut chunks = text.chunks_in_range(0..text.len());
            let tree = parser
                .parse_with(
                    &mut move |offset, _| {
                        chunks.seek(offset);
                        chunks.next().unwrap_or("").as_bytes()
                    },
                    old_tree.as_ref(),
                )
                .unwrap();
            tree
        })
    }

    fn interpolate_tree(&self, tree: &mut SyntaxTree) {
        for edit in self.edits_since::<(usize, Point)>(&tree.version) {
            let (bytes, lines) = edit.flatten();
            tree.tree.edit(&InputEdit {
                start_byte: bytes.new.start,
                old_end_byte: bytes.new.start + bytes.old.len(),
                new_end_byte: bytes.new.end,
                start_position: lines.new.start.to_ts_point(),
                old_end_position: (lines.new.start + (lines.old.end - lines.old.start))
                    .to_ts_point(),
                new_end_position: lines.new.end.to_ts_point(),
            });
        }
        tree.version = self.version();
    }

    fn did_finish_parsing(
        &mut self,
        tree: Tree,
        version: clock::Global,
        cx: &mut ModelContext<Self>,
    ) {
        self.parse_count += 1;
        *self.syntax_tree.lock() = Some(SyntaxTree { tree, version });
        self.request_autoindent(cx);
        cx.emit(Event::Reparsed);
        cx.notify();
    }

    pub fn update_diagnostics<T>(
        &mut self,
        version: Option<i32>,
        mut diagnostics: Vec<DiagnosticEntry<T>>,
        cx: &mut ModelContext<Self>,
    ) -> Result<Operation>
    where
        T: Copy + Ord + TextDimension + Sub<Output = T> + Clip + ToPoint,
    {
        fn compare_diagnostics(a: &Diagnostic, b: &Diagnostic) -> Ordering {
            Ordering::Equal
                .then_with(|| b.is_primary.cmp(&a.is_primary))
                .then_with(|| a.is_disk_based.cmp(&b.is_disk_based))
                .then_with(|| a.severity.cmp(&b.severity))
                .then_with(|| a.message.cmp(&b.message))
        }

        let version = version.map(|version| version as usize);
        let content = if let Some(version) = version {
            let language_server = self.language_server.as_mut().unwrap();
            language_server
                .pending_snapshots
                .retain(|&v, _| v >= version);
            let snapshot = language_server
                .pending_snapshots
                .get(&version)
                .ok_or_else(|| anyhow!("missing snapshot"))?;
            &snapshot.buffer_snapshot
        } else {
            self.deref()
        };

        diagnostics.sort_unstable_by(|a, b| {
            Ordering::Equal
                .then_with(|| a.range.start.cmp(&b.range.start))
                .then_with(|| b.range.end.cmp(&a.range.end))
                .then_with(|| compare_diagnostics(&a.diagnostic, &b.diagnostic))
        });

        let mut sanitized_diagnostics = Vec::new();
        let mut edits_since_save = content.edits_since::<T>(&self.saved_version).peekable();
        let mut last_edit_old_end = T::default();
        let mut last_edit_new_end = T::default();
        'outer: for entry in diagnostics {
            let mut start = entry.range.start;
            let mut end = entry.range.end;

            // Some diagnostics are based on files on disk instead of buffers'
            // current contents. Adjust these diagnostics' ranges to reflect
            // any unsaved edits.
            if entry.diagnostic.is_disk_based {
                while let Some(edit) = edits_since_save.peek() {
                    if edit.old.end <= start {
                        last_edit_old_end = edit.old.end;
                        last_edit_new_end = edit.new.end;
                        edits_since_save.next();
                    } else if edit.old.start <= end && edit.old.end >= start {
                        continue 'outer;
                    } else {
                        break;
                    }
                }

                let start_overshoot = start - last_edit_old_end;
                start = last_edit_new_end;
                start.add_assign(&start_overshoot);

                let end_overshoot = end - last_edit_old_end;
                end = last_edit_new_end;
                end.add_assign(&end_overshoot);
            }

            let range = start.clip(Bias::Left, content)..end.clip(Bias::Right, content);
            let mut range = range.start.to_point(content)..range.end.to_point(content);
            // Expand empty ranges by one character
            if range.start == range.end {
                range.end.column += 1;
                range.end = content.clip_point(range.end, Bias::Right);
                if range.start == range.end && range.end.column > 0 {
                    range.start.column -= 1;
                    range.start = content.clip_point(range.start, Bias::Left);
                }
            }

            sanitized_diagnostics.push(DiagnosticEntry {
                range,
                diagnostic: entry.diagnostic,
            });
        }
        drop(edits_since_save);

        let set = DiagnosticSet::new(sanitized_diagnostics, content);
        self.apply_diagnostic_update(set.clone(), cx);
        Ok(Operation::UpdateDiagnostics {
            diagnostics: set.iter().cloned().collect(),
            lamport_timestamp: self.text.lamport_clock.tick(),
        })
    }

    fn request_autoindent(&mut self, cx: &mut ModelContext<Self>) {
        if let Some(indent_columns) = self.compute_autoindents() {
            let indent_columns = cx.background().spawn(indent_columns);
            match cx
                .background()
                .block_with_timeout(Duration::from_micros(500), indent_columns)
            {
                Ok(indent_columns) => self.apply_autoindents(indent_columns, cx),
                Err(indent_columns) => {
                    self.pending_autoindent = Some(cx.spawn(|this, mut cx| async move {
                        let indent_columns = indent_columns.await;
                        this.update(&mut cx, |this, cx| {
                            this.apply_autoindents(indent_columns, cx);
                        });
                    }));
                }
            }
        }
    }

    fn compute_autoindents(&self) -> Option<impl Future<Output = BTreeMap<u32, u32>>> {
        let max_rows_between_yields = 100;
        let snapshot = self.snapshot();
        if snapshot.language.is_none()
            || snapshot.tree.is_none()
            || self.autoindent_requests.is_empty()
        {
            return None;
        }

        let autoindent_requests = self.autoindent_requests.clone();
        Some(async move {
            let mut indent_columns = BTreeMap::new();
            for request in autoindent_requests {
                let old_to_new_rows = request
                    .edited
                    .iter()
                    .map(|anchor| anchor.summary::<Point>(&request.before_edit).row)
                    .zip(
                        request
                            .edited
                            .iter()
                            .map(|anchor| anchor.summary::<Point>(&snapshot).row),
                    )
                    .collect::<BTreeMap<u32, u32>>();

                let mut old_suggestions = HashMap::<u32, u32>::default();
                let old_edited_ranges =
                    contiguous_ranges(old_to_new_rows.keys().copied(), max_rows_between_yields);
                for old_edited_range in old_edited_ranges {
                    let suggestions = request
                        .before_edit
                        .suggest_autoindents(old_edited_range.clone())
                        .into_iter()
                        .flatten();
                    for (old_row, suggestion) in old_edited_range.zip(suggestions) {
                        let indentation_basis = old_to_new_rows
                            .get(&suggestion.basis_row)
                            .and_then(|from_row| old_suggestions.get(from_row).copied())
                            .unwrap_or_else(|| {
                                request
                                    .before_edit
                                    .indent_column_for_line(suggestion.basis_row)
                            });
                        let delta = if suggestion.indent { INDENT_SIZE } else { 0 };
                        old_suggestions.insert(
                            *old_to_new_rows.get(&old_row).unwrap(),
                            indentation_basis + delta,
                        );
                    }
                    yield_now().await;
                }

                // At this point, old_suggestions contains the suggested indentation for all edited lines with respect to the state of the
                // buffer before the edit, but keyed by the row for these lines after the edits were applied.
                let new_edited_row_ranges =
                    contiguous_ranges(old_to_new_rows.values().copied(), max_rows_between_yields);
                for new_edited_row_range in new_edited_row_ranges {
                    let suggestions = snapshot
                        .suggest_autoindents(new_edited_row_range.clone())
                        .into_iter()
                        .flatten();
                    for (new_row, suggestion) in new_edited_row_range.zip(suggestions) {
                        let delta = if suggestion.indent { INDENT_SIZE } else { 0 };
                        let new_indentation = indent_columns
                            .get(&suggestion.basis_row)
                            .copied()
                            .unwrap_or_else(|| {
                                snapshot.indent_column_for_line(suggestion.basis_row)
                            })
                            + delta;
                        if old_suggestions
                            .get(&new_row)
                            .map_or(true, |old_indentation| new_indentation != *old_indentation)
                        {
                            indent_columns.insert(new_row, new_indentation);
                        }
                    }
                    yield_now().await;
                }

                if let Some(inserted) = request.inserted.as_ref() {
                    let inserted_row_ranges = contiguous_ranges(
                        inserted
                            .iter()
                            .map(|range| range.to_point(&snapshot))
                            .flat_map(|range| range.start.row..range.end.row + 1),
                        max_rows_between_yields,
                    );
                    for inserted_row_range in inserted_row_ranges {
                        let suggestions = snapshot
                            .suggest_autoindents(inserted_row_range.clone())
                            .into_iter()
                            .flatten();
                        for (row, suggestion) in inserted_row_range.zip(suggestions) {
                            let delta = if suggestion.indent { INDENT_SIZE } else { 0 };
                            let new_indentation = indent_columns
                                .get(&suggestion.basis_row)
                                .copied()
                                .unwrap_or_else(|| {
                                    snapshot.indent_column_for_line(suggestion.basis_row)
                                })
                                + delta;
                            indent_columns.insert(row, new_indentation);
                        }
                        yield_now().await;
                    }
                }
            }
            indent_columns
        })
    }

    fn apply_autoindents(
        &mut self,
        indent_columns: BTreeMap<u32, u32>,
        cx: &mut ModelContext<Self>,
    ) {
        self.autoindent_requests.clear();
        self.start_transaction();
        for (row, indent_column) in &indent_columns {
            self.set_indent_column_for_line(*row, *indent_column, cx);
        }
        self.end_transaction(cx);
    }

    fn set_indent_column_for_line(&mut self, row: u32, column: u32, cx: &mut ModelContext<Self>) {
        let current_column = self.indent_column_for_line(row);
        if column > current_column {
            let offset = Point::new(row, 0).to_offset(&*self);
            self.edit(
                [offset..offset],
                " ".repeat((column - current_column) as usize),
                cx,
            );
        } else if column < current_column {
            self.edit(
                [Point::new(row, 0)..Point::new(row, current_column - column)],
                "",
                cx,
            );
        }
    }

    pub(crate) fn diff(&self, new_text: Arc<str>, cx: &AppContext) -> Task<Diff> {
        // TODO: it would be nice to not allocate here.
        let old_text = self.text();
        let base_version = self.version();
        cx.background().spawn(async move {
            let changes = TextDiff::from_lines(old_text.as_str(), new_text.as_ref())
                .iter_all_changes()
                .map(|c| (c.tag(), c.value().len()))
                .collect::<Vec<_>>();
            Diff {
                base_version,
                new_text,
                changes,
            }
        })
    }

    pub(crate) fn apply_diff(&mut self, diff: Diff, cx: &mut ModelContext<Self>) -> bool {
        if self.version == diff.base_version {
            self.start_transaction();
            let mut offset = 0;
            for (tag, len) in diff.changes {
                let range = offset..(offset + len);
                match tag {
                    ChangeTag::Equal => offset += len,
                    ChangeTag::Delete => self.edit(Some(range), "", cx),
                    ChangeTag::Insert => {
                        self.edit(Some(offset..offset), &diff.new_text[range], cx);
                        offset += len;
                    }
                }
            }
            self.end_transaction(cx);
            true
        } else {
            false
        }
    }

    pub fn is_dirty(&self) -> bool {
        !self.saved_version.observed_all(&self.version)
            || self.file.as_ref().map_or(false, |file| file.is_deleted())
    }

    pub fn has_conflict(&self) -> bool {
        !self.saved_version.observed_all(&self.version)
            && self
                .file
                .as_ref()
                .map_or(false, |file| file.mtime() > self.saved_mtime)
    }

    pub fn subscribe(&mut self) -> Subscription {
        self.text.subscribe()
    }

    pub fn start_transaction(&mut self) -> Option<TransactionId> {
        self.start_transaction_at(Instant::now())
    }

    pub fn start_transaction_at(&mut self, now: Instant) -> Option<TransactionId> {
        self.text.start_transaction_at(now)
    }

    pub fn end_transaction(&mut self, cx: &mut ModelContext<Self>) -> Option<TransactionId> {
        self.end_transaction_at(Instant::now(), cx)
    }

    pub fn end_transaction_at(
        &mut self,
        now: Instant,
        cx: &mut ModelContext<Self>,
    ) -> Option<TransactionId> {
        if let Some((transaction_id, start_version)) = self.text.end_transaction_at(now) {
            let was_dirty = start_version != self.saved_version;
            self.did_edit(&start_version, was_dirty, cx);
            Some(transaction_id)
        } else {
            None
        }
    }

    pub fn set_active_selections(
        &mut self,
        selections: Arc<[Selection<Anchor>]>,
        cx: &mut ModelContext<Self>,
    ) {
        let lamport_timestamp = self.text.lamport_clock.tick();
        self.remote_selections.insert(
            self.text.replica_id(),
            SelectionSet {
                selections: selections.clone(),
                lamport_timestamp,
            },
        );
        self.send_operation(
            Operation::UpdateSelections {
                replica_id: self.text.replica_id(),
                selections,
                lamport_timestamp,
            },
            cx,
        );
    }

    pub fn remove_active_selections(&mut self, cx: &mut ModelContext<Self>) {
        self.set_active_selections(Arc::from([]), cx);
    }

    fn update_language_server(&mut self) {
        let language_server = if let Some(language_server) = self.language_server.as_mut() {
            language_server
        } else {
            return;
        };
        let abs_path = self
            .file
            .as_ref()
            .map_or(Path::new("/").to_path_buf(), |file| {
                file.abs_path().unwrap()
            });

        let version = post_inc(&mut language_server.next_version);
        let snapshot = LanguageServerSnapshot {
            buffer_snapshot: self.text.snapshot(),
            version,
            path: Arc::from(abs_path),
        };
        language_server
            .pending_snapshots
            .insert(version, snapshot.clone());
        let _ = language_server
            .latest_snapshot
            .blocking_send(Some(snapshot));
    }

    pub fn edit<I, S, T>(&mut self, ranges_iter: I, new_text: T, cx: &mut ModelContext<Self>)
    where
        I: IntoIterator<Item = Range<S>>,
        S: ToOffset,
        T: Into<String>,
    {
        self.edit_internal(ranges_iter, new_text, false, cx)
    }

    pub fn edit_with_autoindent<I, S, T>(
        &mut self,
        ranges_iter: I,
        new_text: T,
        cx: &mut ModelContext<Self>,
    ) where
        I: IntoIterator<Item = Range<S>>,
        S: ToOffset,
        T: Into<String>,
    {
        self.edit_internal(ranges_iter, new_text, true, cx)
    }

    /*
    impl Buffer
        pub fn edit
        pub fn edit_internal
        pub fn edit_with_autoindent
    */

    pub fn edit_internal<I, S, T>(
        &mut self,
        ranges_iter: I,
        new_text: T,
        autoindent: bool,
        cx: &mut ModelContext<Self>,
    ) where
        I: IntoIterator<Item = Range<S>>,
        S: ToOffset,
        T: Into<String>,
    {
        let new_text = new_text.into();

        // Skip invalid ranges and coalesce contiguous ones.
        let mut ranges: Vec<Range<usize>> = Vec::new();
        for range in ranges_iter {
            let range = range.start.to_offset(self)..range.end.to_offset(self);
            if !new_text.is_empty() || !range.is_empty() {
                if let Some(prev_range) = ranges.last_mut() {
                    if prev_range.end >= range.start {
                        prev_range.end = cmp::max(prev_range.end, range.end);
                    } else {
                        ranges.push(range);
                    }
                } else {
                    ranges.push(range);
                }
            }
        }
        if ranges.is_empty() {
            return;
        }

        self.start_transaction();
        self.pending_autoindent.take();
        let autoindent_request = if autoindent && self.language.is_some() {
            let before_edit = self.snapshot();
            let edited = ranges
                .iter()
                .filter_map(|range| {
                    let start = range.start.to_point(self);
                    if new_text.starts_with('\n') && start.column == self.line_len(start.row) {
                        None
                    } else {
                        Some(self.anchor_before(range.start))
                    }
                })
                .collect();
            Some((before_edit, edited))
        } else {
            None
        };

        let first_newline_ix = new_text.find('\n');
        let new_text_len = new_text.len();

        let edit = self.text.edit(ranges.iter().cloned(), new_text);

        if let Some((before_edit, edited)) = autoindent_request {
            let mut inserted = None;
            if let Some(first_newline_ix) = first_newline_ix {
                let mut delta = 0isize;
                inserted = Some(
                    ranges
                        .iter()
                        .map(|range| {
                            let start =
                                (delta + range.start as isize) as usize + first_newline_ix + 1;
                            let end = (delta + range.start as isize) as usize + new_text_len;
                            delta +=
                                (range.end as isize - range.start as isize) + new_text_len as isize;
                            self.anchor_before(start)..self.anchor_after(end)
                        })
                        .collect(),
                );
            }

            self.autoindent_requests.push(Arc::new(AutoindentRequest {
                before_edit,
                edited,
                inserted,
            }));
        }

        self.end_transaction(cx);
        self.send_operation(Operation::Buffer(text::Operation::Edit(edit)), cx);
    }

    fn did_edit(
        &mut self,
        old_version: &clock::Global,
        was_dirty: bool,
        cx: &mut ModelContext<Self>,
    ) {
        if self.edits_since::<usize>(old_version).next().is_none() {
            return;
        }

        self.reparse(cx);
        self.update_language_server();

        cx.emit(Event::Edited);
        if !was_dirty {
            cx.emit(Event::Dirtied);
        }
        cx.notify();
    }

    fn grammar(&self) -> Option<&Arc<Grammar>> {
        self.language.as_ref().and_then(|l| l.grammar.as_ref())
    }

    pub fn apply_ops<I: IntoIterator<Item = Operation>>(
        &mut self,
        ops: I,
        cx: &mut ModelContext<Self>,
    ) -> Result<()> {
        self.pending_autoindent.take();
        let was_dirty = self.is_dirty();
        let old_version = self.version.clone();
        let mut deferred_ops = Vec::new();
        let buffer_ops = ops
            .into_iter()
            .filter_map(|op| match op {
                Operation::Buffer(op) => Some(op),
                _ => {
                    if self.can_apply_op(&op) {
                        self.apply_op(op, cx);
                    } else {
                        deferred_ops.push(op);
                    }
                    None
                }
            })
            .collect::<Vec<_>>();
        self.text.apply_ops(buffer_ops)?;
        self.deferred_ops.insert(deferred_ops);
        self.flush_deferred_ops(cx);
        self.did_edit(&old_version, was_dirty, cx);
        // Notify independently of whether the buffer was edited as the operations could include a
        // selection update.
        cx.notify();
        Ok(())
    }

    fn flush_deferred_ops(&mut self, cx: &mut ModelContext<Self>) {
        let mut deferred_ops = Vec::new();
        for op in self.deferred_ops.drain().iter().cloned() {
            if self.can_apply_op(&op) {
                self.apply_op(op, cx);
            } else {
                deferred_ops.push(op);
            }
        }
        self.deferred_ops.insert(deferred_ops);
    }

    fn can_apply_op(&self, operation: &Operation) -> bool {
        match operation {
            Operation::Buffer(_) => {
                unreachable!("buffer operations should never be applied at this layer")
            }
            Operation::UpdateDiagnostics {
                diagnostics: diagnostic_set,
                ..
            } => diagnostic_set.iter().all(|diagnostic| {
                self.text.can_resolve(&diagnostic.range.start)
                    && self.text.can_resolve(&diagnostic.range.end)
            }),
            Operation::UpdateSelections { selections, .. } => selections
                .iter()
                .all(|s| self.can_resolve(&s.start) && self.can_resolve(&s.end)),
        }
    }

    fn apply_op(&mut self, operation: Operation, cx: &mut ModelContext<Self>) {
        match operation {
            Operation::Buffer(_) => {
                unreachable!("buffer operations should never be applied at this layer")
            }
            Operation::UpdateDiagnostics {
                diagnostics: diagnostic_set,
                ..
            } => {
                let snapshot = self.snapshot();
                self.apply_diagnostic_update(
                    DiagnosticSet::from_sorted_entries(diagnostic_set.iter().cloned(), &snapshot),
                    cx,
                );
            }
            Operation::UpdateSelections {
                replica_id,
                selections,
                lamport_timestamp,
            } => {
                if let Some(set) = self.remote_selections.get(&replica_id) {
                    if set.lamport_timestamp > lamport_timestamp {
                        return;
                    }
                }

                self.remote_selections.insert(
                    replica_id,
                    SelectionSet {
                        selections,
                        lamport_timestamp,
                    },
                );
                self.text.lamport_clock.observe(lamport_timestamp);
                self.selections_update_count += 1;
            }
        }
    }

    fn apply_diagnostic_update(&mut self, diagnostics: DiagnosticSet, cx: &mut ModelContext<Self>) {
        self.diagnostics = diagnostics;
        self.diagnostics_update_count += 1;
        cx.notify();
        cx.emit(Event::DiagnosticsUpdated);
    }

    #[cfg(not(test))]
    pub fn send_operation(&mut self, operation: Operation, cx: &mut ModelContext<Self>) {
        if let Some(file) = &self.file {
            file.buffer_updated(self.remote_id(), operation, cx.as_mut());
        }
    }

    #[cfg(test)]
    pub fn send_operation(&mut self, operation: Operation, _: &mut ModelContext<Self>) {
        self.operations.push(operation);
    }

    pub fn remove_peer(&mut self, replica_id: ReplicaId, cx: &mut ModelContext<Self>) {
        self.remote_selections.remove(&replica_id);
        cx.notify();
    }

    pub fn undo(&mut self, cx: &mut ModelContext<Self>) -> Option<TransactionId> {
        let was_dirty = self.is_dirty();
        let old_version = self.version.clone();

        if let Some((transaction_id, operation)) = self.text.undo() {
            self.send_operation(Operation::Buffer(operation), cx);
            self.did_edit(&old_version, was_dirty, cx);
            Some(transaction_id)
        } else {
            None
        }
    }

    pub fn undo_transaction(
        &mut self,
        transaction_id: TransactionId,
        cx: &mut ModelContext<Self>,
    ) -> bool {
        let was_dirty = self.is_dirty();
        let old_version = self.version.clone();

        if let Some(operation) = self.text.undo_transaction(transaction_id) {
            self.send_operation(Operation::Buffer(operation), cx);
            self.did_edit(&old_version, was_dirty, cx);
            true
        } else {
            false
        }
    }

    pub fn redo(&mut self, cx: &mut ModelContext<Self>) -> Option<TransactionId> {
        let was_dirty = self.is_dirty();
        let old_version = self.version.clone();

        if let Some((transaction_id, operation)) = self.text.redo() {
            self.send_operation(Operation::Buffer(operation), cx);
            self.did_edit(&old_version, was_dirty, cx);
            Some(transaction_id)
        } else {
            None
        }
    }

    pub fn redo_transaction(
        &mut self,
        transaction_id: TransactionId,
        cx: &mut ModelContext<Self>,
    ) -> bool {
        let was_dirty = self.is_dirty();
        let old_version = self.version.clone();

        if let Some(operation) = self.text.redo_transaction(transaction_id) {
            self.send_operation(Operation::Buffer(operation), cx);
            self.did_edit(&old_version, was_dirty, cx);
            true
        } else {
            false
        }
    }
}

#[cfg(any(test, feature = "test-support"))]
impl Buffer {
    pub fn set_group_interval(&mut self, group_interval: Duration) {
        self.text.set_group_interval(group_interval);
    }

    pub fn randomly_edit<T>(
        &mut self,
        rng: &mut T,
        old_range_count: usize,
        cx: &mut ModelContext<Self>,
    ) where
        T: rand::Rng,
    {
        let mut old_ranges: Vec<Range<usize>> = Vec::new();
        for _ in 0..old_range_count {
            let last_end = old_ranges.last().map_or(0, |last_range| last_range.end + 1);
            if last_end > self.len() {
                break;
            }
            old_ranges.push(self.text.random_byte_range(last_end, rng));
        }
        let new_text_len = rng.gen_range(0..10);
        let new_text: String = crate::random_char_iter::RandomCharIter::new(&mut *rng)
            .take(new_text_len)
            .collect();
        log::info!(
            "mutating buffer {} at {:?}: {:?}",
            self.replica_id(),
            old_ranges,
            new_text
        );
        self.edit(old_ranges.iter().cloned(), new_text.as_str(), cx);
    }

    pub fn randomly_undo_redo(&mut self, rng: &mut impl rand::Rng, cx: &mut ModelContext<Self>) {
        let was_dirty = self.is_dirty();
        let old_version = self.version.clone();

        let ops = self.text.randomly_undo_redo(rng);
        if !ops.is_empty() {
            for op in ops {
                self.send_operation(Operation::Buffer(op), cx);
                self.did_edit(&old_version, was_dirty, cx);
            }
        }
    }
}

impl Entity for Buffer {
    type Event = Event;

    fn release(&mut self, cx: &mut gpui::MutableAppContext) {
        if let Some(file) = self.file.as_ref() {
            file.buffer_removed(self.remote_id(), cx);
        }
    }
}

impl Deref for Buffer {
    type Target = TextBuffer;

    fn deref(&self) -> &Self::Target {
        &self.text
    }
}

impl BufferSnapshot {
    fn suggest_autoindents<'a>(
        &'a self,
        row_range: Range<u32>,
    ) -> Option<impl Iterator<Item = IndentSuggestion> + 'a> {
        let mut query_cursor = QueryCursorHandle::new();
        if let Some((grammar, tree)) = self.grammar().zip(self.tree.as_ref()) {
            let prev_non_blank_row = self.prev_non_blank_row(row_range.start);

            // Get the "indentation ranges" that intersect this row range.
            let indent_capture_ix = grammar.indents_query.capture_index_for_name("indent");
            let end_capture_ix = grammar.indents_query.capture_index_for_name("end");
            query_cursor.set_point_range(
                Point::new(prev_non_blank_row.unwrap_or(row_range.start), 0).to_ts_point()
                    ..Point::new(row_range.end, 0).to_ts_point(),
            );
            let mut indentation_ranges = Vec::<(Range<Point>, &'static str)>::new();
            for mat in query_cursor.matches(
                &grammar.indents_query,
                tree.root_node(),
                TextProvider(self.as_rope()),
            ) {
                let mut node_kind = "";
                let mut start: Option<Point> = None;
                let mut end: Option<Point> = None;
                for capture in mat.captures {
                    if Some(capture.index) == indent_capture_ix {
                        node_kind = capture.node.kind();
                        start.get_or_insert(Point::from_ts_point(capture.node.start_position()));
                        end.get_or_insert(Point::from_ts_point(capture.node.end_position()));
                    } else if Some(capture.index) == end_capture_ix {
                        end = Some(Point::from_ts_point(capture.node.start_position().into()));
                    }
                }

                if let Some((start, end)) = start.zip(end) {
                    if start.row == end.row {
                        continue;
                    }

                    let range = start..end;
                    match indentation_ranges.binary_search_by_key(&range.start, |r| r.0.start) {
                        Err(ix) => indentation_ranges.insert(ix, (range, node_kind)),
                        Ok(ix) => {
                            let prev_range = &mut indentation_ranges[ix];
                            prev_range.0.end = prev_range.0.end.max(range.end);
                        }
                    }
                }
            }

            let mut prev_row = prev_non_blank_row.unwrap_or(0);
            Some(row_range.map(move |row| {
                let row_start = Point::new(row, self.indent_column_for_line(row));

                let mut indent_from_prev_row = false;
                let mut outdent_to_row = u32::MAX;
                for (range, _node_kind) in &indentation_ranges {
                    if range.start.row >= row {
                        break;
                    }

                    if range.start.row == prev_row && range.end > row_start {
                        indent_from_prev_row = true;
                    }
                    if range.end.row >= prev_row && range.end <= row_start {
                        outdent_to_row = outdent_to_row.min(range.start.row);
                    }
                }

                let suggestion = if outdent_to_row == prev_row {
                    IndentSuggestion {
                        basis_row: prev_row,
                        indent: false,
                    }
                } else if indent_from_prev_row {
                    IndentSuggestion {
                        basis_row: prev_row,
                        indent: true,
                    }
                } else if outdent_to_row < prev_row {
                    IndentSuggestion {
                        basis_row: outdent_to_row,
                        indent: false,
                    }
                } else {
                    IndentSuggestion {
                        basis_row: prev_row,
                        indent: false,
                    }
                };

                prev_row = row;
                suggestion
            }))
        } else {
            None
        }
    }

    fn prev_non_blank_row(&self, mut row: u32) -> Option<u32> {
        while row > 0 {
            row -= 1;
            if !self.is_line_blank(row) {
                return Some(row);
            }
        }
        None
    }

    pub fn chunks<'a, T: ToOffset>(
        &'a self,
        range: Range<T>,
        theme: Option<&'a SyntaxTheme>,
    ) -> BufferChunks<'a> {
        let range = range.start.to_offset(self)..range.end.to_offset(self);

        let mut highlights = None;
        let mut diagnostic_endpoints = Vec::<DiagnosticEndpoint>::new();
        if let Some(theme) = theme {
            for entry in self.diagnostics_in_range::<_, usize>(range.clone()) {
                diagnostic_endpoints.push(DiagnosticEndpoint {
                    offset: entry.range.start,
                    is_start: true,
                    severity: entry.diagnostic.severity,
                });
                diagnostic_endpoints.push(DiagnosticEndpoint {
                    offset: entry.range.end,
                    is_start: false,
                    severity: entry.diagnostic.severity,
                });
            }
            diagnostic_endpoints
                .sort_unstable_by_key(|endpoint| (endpoint.offset, !endpoint.is_start));

            if let Some((grammar, tree)) = self.grammar().zip(self.tree.as_ref()) {
                let mut query_cursor = QueryCursorHandle::new();

                // TODO - add a Tree-sitter API to remove the need for this.
                let cursor = unsafe {
                    std::mem::transmute::<_, &'static mut QueryCursor>(query_cursor.deref_mut())
                };
                let captures = cursor.set_byte_range(range.clone()).captures(
                    &grammar.highlights_query,
                    tree.root_node(),
                    TextProvider(self.text.as_rope()),
                );
                highlights = Some(BufferChunkHighlights {
                    captures,
                    next_capture: None,
                    stack: Default::default(),
                    highlight_map: grammar.highlight_map(),
                    _query_cursor: query_cursor,
                    theme,
                })
            }
        }

        let diagnostic_endpoints = diagnostic_endpoints.into_iter().peekable();
        let chunks = self.text.as_rope().chunks_in_range(range.clone());

        BufferChunks {
            range,
            chunks,
            diagnostic_endpoints,
            error_depth: 0,
            warning_depth: 0,
            information_depth: 0,
            hint_depth: 0,
            highlights,
        }
    }

    pub fn language(&self) -> Option<&Arc<Language>> {
        self.language.as_ref()
    }

    fn grammar(&self) -> Option<&Arc<Grammar>> {
        self.language
            .as_ref()
            .and_then(|language| language.grammar.as_ref())
    }

    pub fn range_for_syntax_ancestor<T: ToOffset>(&self, range: Range<T>) -> Option<Range<usize>> {
        if let Some(tree) = self.tree.as_ref() {
            let root = tree.root_node();
            let range = range.start.to_offset(self)..range.end.to_offset(self);
            let mut node = root.descendant_for_byte_range(range.start, range.end);
            while node.map_or(false, |n| n.byte_range() == range) {
                node = node.unwrap().parent();
            }
            node.map(|n| n.byte_range())
        } else {
            None
        }
    }

    pub fn outline(&self, theme: Option<&SyntaxTheme>) -> Option<Outline<Anchor>> {
        let tree = self.tree.as_ref()?;
        let grammar = self
            .language
            .as_ref()
            .and_then(|language| language.grammar.as_ref())?;

        let mut cursor = QueryCursorHandle::new();
        let matches = cursor.matches(
            &grammar.outline_query,
            tree.root_node(),
            TextProvider(self.as_rope()),
        );

        let mut chunks = self.chunks(0..self.len(), theme);

        let item_capture_ix = grammar.outline_query.capture_index_for_name("item")?;
        let name_capture_ix = grammar.outline_query.capture_index_for_name("name")?;
        let context_capture_ix = grammar
            .outline_query
            .capture_index_for_name("context")
            .unwrap_or(u32::MAX);

        let mut stack = Vec::<Range<usize>>::new();
        let items = matches
            .filter_map(|mat| {
                let item_node = mat.nodes_for_capture_index(item_capture_ix).next()?;
                let range = item_node.start_byte()..item_node.end_byte();
                let mut text = String::new();
                let mut name_ranges = Vec::new();
                let mut highlight_ranges = Vec::new();

                for capture in mat.captures {
                    let node_is_name;
                    if capture.index == name_capture_ix {
                        node_is_name = true;
                    } else if capture.index == context_capture_ix {
                        node_is_name = false;
                    } else {
                        continue;
                    }

                    let range = capture.node.start_byte()..capture.node.end_byte();
                    if !text.is_empty() {
                        text.push(' ');
                    }
                    if node_is_name {
                        let mut start = text.len();
                        let end = start + range.len();

                        // When multiple names are captured, then the matcheable text
                        // includes the whitespace in between the names.
                        if !name_ranges.is_empty() {
                            start -= 1;
                        }

                        name_ranges.push(start..end);
                    }

                    let mut offset = range.start;
                    chunks.seek(offset);
                    while let Some(mut chunk) = chunks.next() {
                        if chunk.text.len() > range.end - offset {
                            chunk.text = &chunk.text[0..(range.end - offset)];
                            offset = range.end;
                        } else {
                            offset += chunk.text.len();
                        }
                        if let Some(style) = chunk.highlight_style {
                            let start = text.len();
                            let end = start + chunk.text.len();
                            highlight_ranges.push((start..end, style));
                        }
                        text.push_str(chunk.text);
                        if offset >= range.end {
                            break;
                        }
                    }
                }

                while stack.last().map_or(false, |prev_range| {
                    !prev_range.contains(&range.start) || !prev_range.contains(&range.end)
                }) {
                    stack.pop();
                }
                stack.push(range.clone());

                Some(OutlineItem {
                    depth: stack.len() - 1,
                    range: self.anchor_after(range.start)..self.anchor_before(range.end),
                    text,
                    highlight_ranges,
                    name_ranges,
                })
            })
            .collect::<Vec<_>>();

        if items.is_empty() {
            None
        } else {
            Some(Outline::new(items))
        }
    }

    pub fn enclosing_bracket_ranges<T: ToOffset>(
        &self,
        range: Range<T>,
    ) -> Option<(Range<usize>, Range<usize>)> {
        let (grammar, tree) = self.grammar().zip(self.tree.as_ref())?;
        let open_capture_ix = grammar.brackets_query.capture_index_for_name("open")?;
        let close_capture_ix = grammar.brackets_query.capture_index_for_name("close")?;

        // Find bracket pairs that *inclusively* contain the given range.
        let range = range.start.to_offset(self).saturating_sub(1)..range.end.to_offset(self) + 1;
        let mut cursor = QueryCursorHandle::new();
        let matches = cursor.set_byte_range(range).matches(
            &grammar.brackets_query,
            tree.root_node(),
            TextProvider(self.as_rope()),
        );

        // Get the ranges of the innermost pair of brackets.
        matches
            .filter_map(|mat| {
                let open = mat.nodes_for_capture_index(open_capture_ix).next()?;
                let close = mat.nodes_for_capture_index(close_capture_ix).next()?;
                Some((open.byte_range(), close.byte_range()))
            })
            .min_by_key(|(open_range, close_range)| close_range.end - open_range.start)
    }

    /*
    impl BufferSnapshot
      pub fn remote_selections_in_range(&self, Range<Anchor>) -> impl Iterator<Item = (ReplicaId, impl Iterator<Item = &Selection<Anchor>>)>
      pub fn remote_selections_in_range(&self, Range<Anchor>) -> impl Iterator<Item = (ReplicaId, i
    */

    pub fn remote_selections_in_range<'a>(
        &'a self,
        range: Range<Anchor>,
    ) -> impl 'a + Iterator<Item = (ReplicaId, impl 'a + Iterator<Item = &'a Selection<Anchor>>)>
    {
        self.remote_selections
            .iter()
            .filter(|(replica_id, set)| {
                **replica_id != self.text.replica_id() && !set.selections.is_empty()
            })
            .map(move |(replica_id, set)| {
                let start_ix = match set.selections.binary_search_by(|probe| {
                    probe
                        .end
                        .cmp(&range.start, self)
                        .unwrap()
                        .then(Ordering::Greater)
                }) {
                    Ok(ix) | Err(ix) => ix,
                };
                let end_ix = match set.selections.binary_search_by(|probe| {
                    probe
                        .start
                        .cmp(&range.end, self)
                        .unwrap()
                        .then(Ordering::Less)
                }) {
                    Ok(ix) | Err(ix) => ix,
                };

                (*replica_id, set.selections[start_ix..end_ix].iter())
            })
    }

    pub fn diagnostics_in_range<'a, T, O>(
        &'a self,
        search_range: Range<T>,
    ) -> impl 'a + Iterator<Item = DiagnosticEntry<O>>
    where
        T: 'a + Clone + ToOffset,
        O: 'a + FromAnchor,
    {
        self.diagnostics.range(search_range.clone(), self, true)
    }

    pub fn diagnostic_groups(&self) -> Vec<DiagnosticGroup<Anchor>> {
        let mut groups = Vec::new();
        self.diagnostics.groups(&mut groups, self);
        groups
    }

    pub fn diagnostic_group<'a, O>(
        &'a self,
        group_id: usize,
    ) -> impl 'a + Iterator<Item = DiagnosticEntry<O>>
    where
        O: 'a + FromAnchor,
    {
        self.diagnostics.group(group_id, self)
    }

    pub fn diagnostics_update_count(&self) -> usize {
        self.diagnostics_update_count
    }

    pub fn parse_count(&self) -> usize {
        self.parse_count
    }

    pub fn selections_update_count(&self) -> usize {
        self.selections_update_count
    }
}

impl Clone for BufferSnapshot {
    fn clone(&self) -> Self {
        Self {
            text: self.text.clone(),
            tree: self.tree.clone(),
            remote_selections: self.remote_selections.clone(),
            diagnostics: self.diagnostics.clone(),
            selections_update_count: self.selections_update_count,
            diagnostics_update_count: self.diagnostics_update_count,
            is_parsing: self.is_parsing,
            language: self.language.clone(),
            parse_count: self.parse_count,
        }
    }
}

impl Deref for BufferSnapshot {
    type Target = text::BufferSnapshot;

    fn deref(&self) -> &Self::Target {
        &self.text
    }
}

impl<'a> tree_sitter::TextProvider<'a> for TextProvider<'a> {
    type I = ByteChunks<'a>;

    fn text(&mut self, node: tree_sitter::Node) -> Self::I {
        ByteChunks(self.0.chunks_in_range(node.byte_range()))
    }
}

struct ByteChunks<'a>(rope::Chunks<'a>);

impl<'a> Iterator for ByteChunks<'a> {
    type Item = &'a [u8];

    fn next(&mut self) -> Option<Self::Item> {
        self.0.next().map(str::as_bytes)
    }
}

unsafe impl<'a> Send for BufferChunks<'a> {}

impl<'a> BufferChunks<'a> {
    pub fn seek(&mut self, offset: usize) {
        self.range.start = offset;
        self.chunks.seek(self.range.start);
        if let Some(highlights) = self.highlights.as_mut() {
            highlights
                .stack
                .retain(|(end_offset, _)| *end_offset > offset);
            if let Some((mat, capture_ix)) = &highlights.next_capture {
                let capture = mat.captures[*capture_ix as usize];
                if offset >= capture.node.start_byte() {
                    let next_capture_end = capture.node.end_byte();
                    if offset < next_capture_end {
                        highlights.stack.push((
                            next_capture_end,
                            highlights.highlight_map.get(capture.index),
                        ));
                    }
                    highlights.next_capture.take();
                }
            }
            highlights.captures.set_byte_range(self.range.clone());
        }
    }

    pub fn offset(&self) -> usize {
        self.range.start
    }

    fn update_diagnostic_depths(&mut self, endpoint: DiagnosticEndpoint) {
        let depth = match endpoint.severity {
            DiagnosticSeverity::ERROR => &mut self.error_depth,
            DiagnosticSeverity::WARNING => &mut self.warning_depth,
            DiagnosticSeverity::INFORMATION => &mut self.information_depth,
            DiagnosticSeverity::HINT => &mut self.hint_depth,
            _ => return,
        };
        if endpoint.is_start {
            *depth += 1;
        } else {
            *depth -= 1;
        }
    }

    fn current_diagnostic_severity(&mut self) -> Option<DiagnosticSeverity> {
        if self.error_depth > 0 {
            Some(DiagnosticSeverity::ERROR)
        } else if self.warning_depth > 0 {
            Some(DiagnosticSeverity::WARNING)
        } else if self.information_depth > 0 {
            Some(DiagnosticSeverity::INFORMATION)
        } else if self.hint_depth > 0 {
            Some(DiagnosticSeverity::HINT)
        } else {
            None
        }
    }
}

impl<'a> Iterator for BufferChunks<'a> {
    type Item = Chunk<'a>;

    fn next(&mut self) -> Option<Self::Item> {
        let mut next_capture_start = usize::MAX;
        let mut next_diagnostic_endpoint = usize::MAX;

        if let Some(highlights) = self.highlights.as_mut() {
            while let Some((parent_capture_end, _)) = highlights.stack.last() {
                if *parent_capture_end <= self.range.start {
                    highlights.stack.pop();
                } else {
                    break;
                }
            }

            if highlights.next_capture.is_none() {
                highlights.next_capture = highlights.captures.next();
            }

            while let Some((mat, capture_ix)) = highlights.next_capture.as_ref() {
                let capture = mat.captures[*capture_ix as usize];
                if self.range.start < capture.node.start_byte() {
                    next_capture_start = capture.node.start_byte();
                    break;
                } else {
                    let highlight_id = highlights.highlight_map.get(capture.index);
                    highlights
                        .stack
                        .push((capture.node.end_byte(), highlight_id));
                    highlights.next_capture = highlights.captures.next();
                }
            }
        }

        while let Some(endpoint) = self.diagnostic_endpoints.peek().copied() {
            if endpoint.offset <= self.range.start {
                self.update_diagnostic_depths(endpoint);
                self.diagnostic_endpoints.next();
            } else {
                next_diagnostic_endpoint = endpoint.offset;
                break;
            }
        }

        if let Some(chunk) = self.chunks.peek() {
            let chunk_start = self.range.start;
            let mut chunk_end = (self.chunks.offset() + chunk.len())
                .min(next_capture_start)
                .min(next_diagnostic_endpoint);
            let mut highlight_style = None;
            if let Some(highlights) = self.highlights.as_ref() {
                if let Some((parent_capture_end, parent_highlight_id)) = highlights.stack.last() {
                    chunk_end = chunk_end.min(*parent_capture_end);
                    highlight_style = parent_highlight_id.style(highlights.theme);
                }
            }

            let slice =
                &chunk[chunk_start - self.chunks.offset()..chunk_end - self.chunks.offset()];
            self.range.start = chunk_end;
            if self.range.start == self.chunks.offset() + chunk.len() {
                self.chunks.next().unwrap();
            }

            Some(Chunk {
                text: slice,
                highlight_style,
                diagnostic: self.current_diagnostic_severity(),
            })
        } else {
            None
        }
    }
}

impl QueryCursorHandle {
    pub(crate) fn new() -> Self {
        QueryCursorHandle(Some(
            QUERY_CURSORS
                .lock()
                .pop()
                .unwrap_or_else(|| QueryCursor::new()),
        ))
    }
}

impl Deref for QueryCursorHandle {
    type Target = QueryCursor;

    fn deref(&self) -> &Self::Target {
        self.0.as_ref().unwrap()
    }
}

impl DerefMut for QueryCursorHandle {
    fn deref_mut(&mut self) -> &mut Self::Target {
        self.0.as_mut().unwrap()
    }
}

impl Drop for QueryCursorHandle {
    fn drop(&mut self) {
        let mut cursor = self.0.take().unwrap();
        cursor.set_byte_range(0..usize::MAX);
        cursor.set_point_range(Point::zero().to_ts_point()..Point::MAX.to_ts_point());
        QUERY_CURSORS.lock().push(cursor)
    }
}

trait ToTreeSitterPoint {
    fn to_ts_point(self) -> tree_sitter::Point;
    fn from_ts_point(point: tree_sitter::Point) -> Self;
}

impl ToTreeSitterPoint for Point {
    fn to_ts_point(self) -> tree_sitter::Point {
        tree_sitter::Point::new(self.row as usize, self.column as usize)
    }

    fn from_ts_point(point: tree_sitter::Point) -> Self {
        Point::new(point.row as u32, point.column as u32)
    }
}

impl operation_queue::Operation for Operation {
    fn lamport_timestamp(&self) -> clock::Lamport {
        match self {
            Operation::Buffer(_) => {
                unreachable!("buffer operations should never be deferred at this layer")
            }
            Operation::UpdateDiagnostics {
                lamport_timestamp, ..
            }
            | Operation::UpdateSelections {
                lamport_timestamp, ..
            } => *lamport_timestamp,
        }
    }
}

impl Default for Diagnostic {
    fn default() -> Self {
        Self {
            code: Default::default(),
            severity: DiagnosticSeverity::ERROR,
            message: Default::default(),
            group_id: Default::default(),
            is_primary: Default::default(),
            is_valid: true,
            is_disk_based: false,
        }
    }
}

pub fn contiguous_ranges(
    values: impl Iterator<Item = u32>,
    max_len: usize,
) -> impl Iterator<Item = Range<u32>> {
    let mut values = values.into_iter();
    let mut current_range: Option<Range<u32>> = None;
    std::iter::from_fn(move || loop {
        if let Some(value) = values.next() {
            if let Some(range) = &mut current_range {
                if value == range.end && range.len() < max_len {
                    range.end += 1;
                    continue;
                }
            }

            let prev_range = current_range.clone();
            current_range = Some(value..(value + 1));
            if prev_range.is_some() {
                return prev_range;
            }
        } else {
            return current_range.take();
        }
    })
}
