export class MusicDatabase {
    constructor() {
        this.dbName = 'MonochromeDB';
        this.version = 2;
        this.db = null;
    }

    async open() {
        if (this.db) return this.db;

        return new Promise((resolve, reject) => {
            const request = indexedDB.open(this.dbName, this.version);

            request.onerror = (event) => {
                console.error("Database error:", event.target.error);
                reject(event.target.error);
            };

            request.onsuccess = (event) => {
                this.db = event.target.result;
                resolve(this.db);
            };

            request.onupgradeneeded = (event) => {
                const db = event.target.result;

                // Favorites stores
                if (!db.objectStoreNames.contains('favorites_tracks')) {
                    const store = db.createObjectStore('favorites_tracks', { keyPath: 'id' });
                    store.createIndex('addedAt', 'addedAt', { unique: false });
                }
                if (!db.objectStoreNames.contains('favorites_albums')) {
                    const store = db.createObjectStore('favorites_albums', { keyPath: 'id' });
                    store.createIndex('addedAt', 'addedAt', { unique: false });
                }
                if (!db.objectStoreNames.contains('favorites_artists')) {
                    const store = db.createObjectStore('favorites_artists', { keyPath: 'id' });
                    store.createIndex('addedAt', 'addedAt', { unique: false });
                }
                if (!db.objectStoreNames.contains('favorites_playlists')) {
                    const store = db.createObjectStore('favorites_playlists', { keyPath: 'uuid' });
                    store.createIndex('addedAt', 'addedAt', { unique: false });
                }
            };
        });
    }

    // Generic Helper
    async performTransaction(storeName, mode, callback) {
        const db = await this.open();
        return new Promise((resolve, reject) => {
            const transaction = db.transaction(storeName, mode);
            const store = transaction.objectStore(storeName);
            const request = callback(store);

            transaction.oncomplete = () => {
                resolve(request?.result);
            };
            transaction.onerror = (event) => {
                reject(event.target.error);
            };
        });
    }

    // Favorites API
    async toggleFavorite(type, item) {
        const storeName = `favorites_${type}s`; // tracks, albums, artists
        const key = type === 'playlist' ? item.uuid : item.id;
        const exists = await this.isFavorite(type, key);

        if (exists) {
            await this.performTransaction(storeName, 'readwrite', (store) => store.delete(key));
            return false; // Removed
        } else {
            const entry = { ...item, addedAt: Date.now() };
            await this.performTransaction(storeName, 'readwrite', (store) => store.put(entry));
            return true; // Added
        }
    }

    async isFavorite(type, id) {
        const storeName = `favorites_${type}s`;
        try {
            const result = await this.performTransaction(storeName, 'readonly', (store) => store.get(id));
            return !!result;
        } catch (e) {
            return false;
        }
    }

    async getFavorites(type) {
        const storeName = `favorites_${type}s`;
        const db = await this.open();
        return new Promise((resolve, reject) => {
            const transaction = db.transaction(storeName, 'readonly');
            const store = transaction.objectStore(storeName);
            const index = store.index('addedAt');
            const request = index.getAll(); // Returns sorted by addedAt ascending

            request.onsuccess = () => {
                // Reverse to show newest first
                resolve(request.result.reverse());
            };
            request.onerror = () => reject(request.error);
        });
    }

    _minifyItem(type, item) {
        if (!item) return item;
        
        // Base properties to keep
        const base = {
            id: item.id,
            addedAt: item.addedAt
        };

        if (type === 'track') {
            return {
                ...base,
                title: item.title,
                duration: item.duration,
                explicit: item.explicit,
                // Keep minimal artist info
                artists: item.artists?.map(a => ({ id: a.id, name: a.name })) || [],
                // Keep minimal album info
                album: item.album ? {
                    id: item.album.id,
                    cover: item.album.cover,
                    releaseDate: item.album.releaseDate
                } : null,
                // Fallback date
                streamStartDate: item.streamStartDate,
                // Keep version if exists
                version: item.version
            };
        }

        if (type === 'album') {
            return {
                ...base,
                title: item.title,
                cover: item.cover,
                releaseDate: item.releaseDate,
                explicit: item.explicit,
                // UI uses singular 'artist'
                artist: item.artist ? { name: item.artist.name, id: item.artist.id } : (item.artists?.[0] ? { name: item.artists[0].name, id: item.artists[0].id } : null),
                // Keep type and track count for UI labels
                type: item.type,
                numberOfTracks: item.numberOfTracks
            };
        }

        if (type === 'artist') {
            return {
                ...base,
                name: item.name,
                picture: item.picture || item.image // Handle both just in case
            };
        }

        if (type === 'playlist') {
            return {
                uuid: item.uuid,
                addedAt: item.addedAt,
                title: item.title,
                // UI checks squareImage || image || uuid
                image: item.image || item.squareImage,
                numberOfTracks: item.numberOfTracks,
                user: item.user ? { name: item.user.name } : null
            };
        }

        return item;
    }

    async exportData() {
        const tracks = await this.getFavorites('track');
        const albums = await this.getFavorites('album');
        const artists = await this.getFavorites('artist');
        const playlists = await this.getFavorites('playlist');

        const data = {
            favorites_tracks: tracks.map(t => this._minifyItem('track', t)),
            favorites_albums: albums.map(a => this._minifyItem('album', a)),
            favorites_artists: artists.map(a => this._minifyItem('artist', a)),
            favorites_playlists: playlists.map(p => this._minifyItem('playlist', p))
        };
        return data;
    }

    async importData(data) {
        // Clear existing? Or merge? Prompt says "Sync" or "Export/Import".
        // Let's merge by put (replaces if ID exists).
        const db = await this.open();
        
        const importStore = async (storeName, items) => {
            if (!items || !Array.isArray(items)) return;
            const transaction = db.transaction(storeName, 'readwrite');
            const store = transaction.objectStore(storeName);
            for (const item of items) {
                store.put(item);
            }
        };

        await importStore('favorites_tracks', data.favorites_tracks);
        await importStore('favorites_albums', data.favorites_albums);
        await importStore('favorites_artists', data.favorites_artists);
        await importStore('favorites_playlists', data.favorites_playlists);
    }
}

export const db = new MusicDatabase();