kv-music/js/bulk-download-writer.ts

import { triggerDownload } from './download-utils';

/**
 * A single entry to be included in a ZIP archive or written directly to a folder.
 */
export interface WriterEntry {
    name: string;
    lastModified: Date;
    input: Blob | string | ArrayBuffer | Uint8Array;
}

/** Minimal interface for the Neutralino bridge used by ZipNeutralinoWriter */
interface NeutralinoBridge {
    os: {
        showSaveDialog(
            title: string,
            options: { defaultPath: string; filters: Array<{ name: string; extensions: string[] }> }
        ): Promise<string | null>;
    };
    filesystem: {
        writeBinaryFile(path: string, buffer: ArrayBuffer): Promise<void>;
        appendBinaryFile(path: string, buffer: ArrayBuffer): Promise<void>;
    };
}

async function loadClientZip() {
    try {
        return await import('client-zip');
    } catch (error) {
        console.error('Failed to load client-zip:', error);
        throw new Error('Failed to load ZIP library');
    }
}

/**
 * Interface for writing a collection of file entries to an output destination.
 * Each implementation handles its own output selection (save dialog, directory picker, etc.)
 * and throws a DOMException with name 'AbortError' if the user cancels.
 */
export interface IBulkDownloadWriter {
    write(files: AsyncIterable<WriterEntry>): Promise<void>;
}

/**
 * Streams a ZIP archive to a file via the File System Access API.
 * Prompts the user to choose a save location with showSaveFilePicker.
 */
export class ZipStreamWriter implements IBulkDownloadWriter {
    constructor(private readonly suggestedFilename: string) {}

    async write(files: AsyncIterable<WriterEntry>): Promise<void> {
        // showSaveFilePicker is part of the File System Access API (not yet in all TS DOM libs)
        // eslint-disable-next-line @typescript-eslint/no-explicit-any
        const fileHandle = await (window as any).showSaveFilePicker({
            suggestedName: this.suggestedFilename,
            types: [{ description: 'ZIP Archive', accept: { 'application/zip': ['.zip'] } }],
        });
        const { downloadZip } = await loadClientZip();
        const writable = await fileHandle.createWritable();
        const response = downloadZip(files);
        if (!response.body) throw new Error('ZIP response body is null');
        await response.body.pipeTo(writable);
    }
}

/**
 * Collects a ZIP archive into a Blob and triggers a browser download.
 * Works on all browsers without requiring the File System Access API.
 */
export class ZipBlobWriter implements IBulkDownloadWriter {
    constructor(private readonly filename: string) {}

    async write(files: AsyncIterable<WriterEntry>): Promise<void> {
        const { downloadZip } = await loadClientZip();
        const response = downloadZip(files);
        const blob = await response.blob();
        triggerDownload(blob, this.filename);
    }
}

/**
 * Writes a ZIP archive to the filesystem via the Neutralino desktop bridge,
 * showing a native save dialog first.
 */
export class ZipNeutralinoWriter implements IBulkDownloadWriter {
    constructor(private readonly folderName: string) {}

    async write(files: AsyncIterable<WriterEntry>): Promise<void> {
        const bridge = (await import('./desktop/neutralino-bridge.js')) as unknown as NeutralinoBridge;

        const savePath = await bridge.os.showSaveDialog(`Select save location for ${this.folderName}.zip`, {
            defaultPath: `${this.folderName}.zip`,
            filters: [{ name: 'ZIP Archive', extensions: ['zip'] }],
        });

        if (!savePath) {
            throw new DOMException('User cancelled save dialog', 'AbortError');
        }

        const { downloadZip } = await loadClientZip();
        await bridge.filesystem.writeBinaryFile(savePath, new ArrayBuffer(0));

        const response = downloadZip(files);
        if (!response.body) throw new Error('ZIP response body is null');

        const reader = response.body.getReader();
        let receivedLength = 0;

        while (true) {
            const { done, value } = await reader.read();
            if (done) break;
            const chunk = value.buffer.slice(value.byteOffset, value.byteOffset + value.byteLength);
            await bridge.filesystem.appendBinaryFile(savePath, chunk);
            receivedLength += value.length;
        }

        console.log(`[ZIP] Download complete. Total size: ${receivedLength} bytes.`);
    }
}

/**
 * Writes files directly into a user-chosen folder using the standard browser
 * File System Access API (showDirectoryPicker). Subdirectories embedded in
 * file entry names are created automatically.
 *
 * Use the static {@link FolderPickerWriter.create} method to obtain an instance;
 * the constructor is private so the directory handle is always set before use.
 */
export class FolderPickerWriter implements IBulkDownloadWriter {
    private constructor(private readonly dirHandle: FileSystemDirectoryHandle) {}

    /**
     * Prompts the user to pick a writable directory.
     * Returns a new {@link FolderPickerWriter} bound to the chosen directory.
     * If the user dismisses the picker, the promise rejects with a DOMException
     * whose name is "AbortError".
     */
    static async create(): Promise<FolderPickerWriter> {
        // showDirectoryPicker is part of the File System Access API (not yet in all TS DOM libs)
        // eslint-disable-next-line @typescript-eslint/no-explicit-any
        const dirHandle: FileSystemDirectoryHandle = await (window as any).showDirectoryPicker({
            mode: 'readwrite',
        });
        return new FolderPickerWriter(dirHandle);
    }

    async write(files: AsyncIterable<WriterEntry>): Promise<void> {
        for await (const file of files) {
            const parts = file.name.split('/').filter(Boolean);
            if (parts.length === 0) continue;

            let currentDir: FileSystemDirectoryHandle = this.dirHandle;
            for (let i = 0; i < parts.length - 1; i++) {
                currentDir = await currentDir.getDirectoryHandle(parts[i], { create: true });
            }

            const filename = parts[parts.length - 1];
            const fileHandle = await currentDir.getFileHandle(filename, { create: true });
            const writable = await fileHandle.createWritable();

            const { input } = file;
            if (input instanceof Blob) {
                await writable.write(input);
            } else if (typeof input === 'string') {
                await writable.write(new Blob([input], { type: 'text/plain' }));
            } else {
                // ArrayBuffer or Uint8Array – wrap in a Blob to guarantee strict typing.
                // Use byteOffset/byteLength so only the view's range is included, not the
                // whole backing ArrayBuffer (which may be larger due to pooling).
                const buf =
                    input instanceof Uint8Array
                        ? input.buffer.slice(input.byteOffset, input.byteOffset + input.byteLength)
                        : input;
                await writable.write(new Blob([buf as ArrayBuffer]));
            }

            await writable.close();
        }
    }
}