/**
 * Asset Registry Service
 * 资产注册表服务
 *
 * 负责扫描项目资产目录，为每个资产生成唯一GUID，
 * 并维护 GUID ↔ 路径 的映射关系。
 *
 * Responsible for scanning project asset directories,
 * generating unique GUIDs for each asset, and maintaining
 * GUID ↔ path mappings.
 */

import { Core } from '@esengine/ecs-framework';
import { MessageHub } from './MessageHub';

// Simple logger for AssetRegistry
const logger = {
    info: (msg: string, ...args: unknown[]) => console.log(`[AssetRegistry] ${msg}`, ...args),
    warn: (msg: string, ...args: unknown[]) => console.warn(`[AssetRegistry] ${msg}`, ...args),
    error: (msg: string, ...args: unknown[]) => console.error(`[AssetRegistry] ${msg}`, ...args),
    debug: (msg: string, ...args: unknown[]) => console.debug(`[AssetRegistry] ${msg}`, ...args),
};

/**
 * Asset GUID type (simplified, no dependency on asset-system)
 */
export type AssetGUID = string;

/**
 * Asset type for registry (using different name to avoid conflict)
 */
export type AssetRegistryType = string;

/**
 * Asset metadata (simplified)
 */
export interface IAssetRegistryMetadata {
    guid: AssetGUID;
    path: string;
    type: AssetRegistryType;
    name: string;
    size: number;
    hash: string;
    lastModified: number;
}

/**
 * Asset catalog entry for export
 */
export interface IAssetRegistryCatalogEntry {
    guid: AssetGUID;
    path: string;
    type: AssetRegistryType;
    size: number;
    hash: string;
}

/**
 * Asset file info from filesystem scan
 */
export interface AssetFileInfo {
    /** Absolute path to the file */
    absolutePath: string;
    /** Path relative to project root */
    relativePath: string;
    /** File name without extension */
    name: string;
    /** File extension (e.g., '.png', '.btree') */
    extension: string;
    /** File size in bytes */
    size: number;
    /** Last modified timestamp */
    lastModified: number;
}

/**
 * Asset registry manifest stored in project
 * 存储在项目中的资产注册表清单
 */
export interface AssetManifest {
    version: string;
    createdAt: number;
    updatedAt: number;
    assets: Record<string, AssetManifestEntry>;
}

/**
 * Single asset entry in manifest
 */
export interface AssetManifestEntry {
    guid: AssetGUID;
    relativePath: string;
    type: AssetRegistryType;
    hash?: string;
}

/**
 * Extension to asset type mapping
 */
const EXTENSION_TYPE_MAP: Record<string, AssetRegistryType> = {
    // Textures
    '.png': 'texture',
    '.jpg': 'texture',
    '.jpeg': 'texture',
    '.webp': 'texture',
    '.gif': 'texture',
    // Audio
    '.mp3': 'audio',
    '.ogg': 'audio',
    '.wav': 'audio',
    // Data
    '.json': 'json',
    '.txt': 'text',
    // Custom types
    '.btree': 'btree',
    '.ecs': 'scene',
    '.prefab': 'prefab',
    '.tmx': 'tilemap',
    '.tsx': 'tileset',
};

/**
 * File system interface for asset scanning
 */
interface IFileSystem {
    readDir(path: string): Promise<string[]>;
    readFile(path: string): Promise<string>;
    writeFile(path: string, content: string): Promise<void>;
    exists(path: string): Promise<boolean>;
    stat(path: string): Promise<{ size: number; mtime: number; isDirectory: boolean }>;
    isDirectory(path: string): Promise<boolean>;
}

/**
 * Simple in-memory asset database
 */
class SimpleAssetDatabase {
    private readonly _metadata = new Map<AssetGUID, IAssetRegistryMetadata>();
    private readonly _pathToGuid = new Map<string, AssetGUID>();
    private readonly _typeToGuids = new Map<AssetRegistryType, Set<AssetGUID>>();

    addAsset(metadata: IAssetRegistryMetadata): void {
        const { guid, path, type } = metadata;
        this._metadata.set(guid, metadata);
        this._pathToGuid.set(path, guid);

        if (!this._typeToGuids.has(type)) {
            this._typeToGuids.set(type, new Set());
        }
        this._typeToGuids.get(type)!.add(guid);
    }

    removeAsset(guid: AssetGUID): void {
        const metadata = this._metadata.get(guid);
        if (!metadata) return;

        this._metadata.delete(guid);
        this._pathToGuid.delete(metadata.path);

        const typeSet = this._typeToGuids.get(metadata.type);
        if (typeSet) {
            typeSet.delete(guid);
        }
    }

    getMetadata(guid: AssetGUID): IAssetRegistryMetadata | undefined {
        return this._metadata.get(guid);
    }

    getMetadataByPath(path: string): IAssetRegistryMetadata | undefined {
        const guid = this._pathToGuid.get(path);
        return guid ? this._metadata.get(guid) : undefined;
    }

    findAssetsByType(type: AssetRegistryType): AssetGUID[] {
        const guids = this._typeToGuids.get(type);
        return guids ? Array.from(guids) : [];
    }

    exportToCatalog(): IAssetRegistryCatalogEntry[] {
        const entries: IAssetRegistryCatalogEntry[] = [];
        this._metadata.forEach((metadata) => {
            entries.push({
                guid: metadata.guid,
                path: metadata.path,
                type: metadata.type,
                size: metadata.size,
                hash: metadata.hash
            });
        });
        return entries;
    }

    getStatistics(): { totalAssets: number } {
        return { totalAssets: this._metadata.size };
    }

    clear(): void {
        this._metadata.clear();
        this._pathToGuid.clear();
        this._typeToGuids.clear();
    }
}

/**
 * Asset Registry Service
 */
export class AssetRegistryService {
    private _database: SimpleAssetDatabase;
    private _projectPath: string | null = null;
    private _manifest: AssetManifest | null = null;
    private _fileSystem: IFileSystem | null = null;
    private _messageHub: MessageHub | null = null;
    private _initialized = false;

    /** Manifest file name */
    static readonly MANIFEST_FILE = 'asset-manifest.json';
    /** Current manifest version */
    static readonly MANIFEST_VERSION = '1.0.0';

    constructor() {
        this._database = new SimpleAssetDatabase();
    }

    /**
     * Initialize the service
     */
    async initialize(): Promise<void> {
        if (this._initialized) return;

        // Get file system service
        const IFileSystemServiceKey = Symbol.for('IFileSystemService');
        this._fileSystem = Core.services.tryResolve(IFileSystemServiceKey) as IFileSystem | null;

        // Get message hub
        this._messageHub = Core.services.tryResolve(MessageHub) as MessageHub | null;

        // Subscribe to project events
        if (this._messageHub) {
            this._messageHub.subscribe('project:opened', this._onProjectOpened.bind(this));
            this._messageHub.subscribe('project:closed', this._onProjectClosed.bind(this));
        }

        this._initialized = true;
        logger.info('AssetRegistryService initialized');
    }

    /**
     * Handle project opened event
     */
    private async _onProjectOpened(data: { path: string }): Promise<void> {
        await this.loadProject(data.path);
    }

    /**
     * Handle project closed event
     */
    private _onProjectClosed(): void {
        this.unloadProject();
    }

    /**
     * Load project and scan assets
     */
    async loadProject(projectPath: string): Promise<void> {
        if (!this._fileSystem) {
            logger.warn('FileSystem service not available, skipping asset registry');
            return;
        }

        this._projectPath = projectPath;
        this._database.clear();

        // Try to load existing manifest
        await this._loadManifest();

        // Scan assets directory
        await this._scanAssetsDirectory();

        // Save updated manifest
        await this._saveManifest();

        logger.info(`Project assets loaded: ${this._database.getStatistics().totalAssets} assets`);

        // Publish event
        this._messageHub?.publish('assets:registry:loaded', {
            projectPath,
            assetCount: this._database.getStatistics().totalAssets
        });
    }

    /**
     * Unload current project
     */
    unloadProject(): void {
        this._projectPath = null;
        this._manifest = null;
        this._database.clear();
        logger.info('Project assets unloaded');
    }

    /**
     * Load manifest from project
     */
    private async _loadManifest(): Promise<void> {
        if (!this._fileSystem || !this._projectPath) return;

        const manifestPath = this._getManifestPath();

        try {
            const exists = await this._fileSystem.exists(manifestPath);
            if (exists) {
                const content = await this._fileSystem.readFile(manifestPath);
                this._manifest = JSON.parse(content);
                logger.debug('Loaded existing asset manifest');
            } else {
                this._manifest = this._createEmptyManifest();
                logger.debug('Created new asset manifest');
            }
        } catch (error) {
            logger.warn('Failed to load manifest, creating new one:', error);
            this._manifest = this._createEmptyManifest();
        }
    }

    /**
     * Save manifest to project
     */
    private async _saveManifest(): Promise<void> {
        if (!this._fileSystem || !this._projectPath || !this._manifest) return;

        const manifestPath = this._getManifestPath();
        this._manifest.updatedAt = Date.now();

        try {
            const content = JSON.stringify(this._manifest, null, 2);
            await this._fileSystem.writeFile(manifestPath, content);
            logger.debug('Saved asset manifest');
        } catch (error) {
            logger.error('Failed to save manifest:', error);
        }
    }

    /**
     * Get manifest file path
     */
    private _getManifestPath(): string {
        const sep = this._projectPath!.includes('\\') ? '\\' : '/';
        return `${this._projectPath}${sep}${AssetRegistryService.MANIFEST_FILE}`;
    }

    /**
     * Create empty manifest
     */
    private _createEmptyManifest(): AssetManifest {
        return {
            version: AssetRegistryService.MANIFEST_VERSION,
            createdAt: Date.now(),
            updatedAt: Date.now(),
            assets: {}
        };
    }

    /**
     * Scan assets directory and register all assets
     */
    private async _scanAssetsDirectory(): Promise<void> {
        if (!this._fileSystem || !this._projectPath) return;

        const sep = this._projectPath.includes('\\') ? '\\' : '/';
        const assetsPath = `${this._projectPath}${sep}assets`;

        try {
            const exists = await this._fileSystem.exists(assetsPath);
            if (!exists) {
                logger.info('No assets directory found');
                return;
            }

            await this._scanDirectory(assetsPath, 'assets');
        } catch (error) {
            logger.error('Failed to scan assets directory:', error);
        }
    }

    /**
     * Recursively scan a directory
     */
    private async _scanDirectory(absolutePath: string, relativePath: string): Promise<void> {
        if (!this._fileSystem) return;

        try {
            const entries = await this._fileSystem.readDir(absolutePath);
            const sep = absolutePath.includes('\\') ? '\\' : '/';

            for (const entry of entries) {
                const entryAbsPath = `${absolutePath}${sep}${entry}`;
                const entryRelPath = `${relativePath}/${entry}`;

                try {
                    const isDir = await this._fileSystem.isDirectory(entryAbsPath);

                    if (isDir) {
                        // Recursively scan subdirectory
                        await this._scanDirectory(entryAbsPath, entryRelPath);
                    } else {
                        // Register file as asset
                        await this._registerAssetFile(entryAbsPath, entryRelPath);
                    }
                } catch (error) {
                    logger.warn(`Failed to process entry ${entry}:`, error);
                }
            }
        } catch (error) {
            logger.warn(`Failed to read directory ${absolutePath}:`, error);
        }
    }

    /**
     * Register a single asset file
     */
    private async _registerAssetFile(absolutePath: string, relativePath: string): Promise<void> {
        if (!this._fileSystem || !this._manifest) return;

        // Get file extension
        const lastDot = relativePath.lastIndexOf('.');
        if (lastDot === -1) return; // Skip files without extension

        const extension = relativePath.substring(lastDot).toLowerCase();
        const assetType = EXTENSION_TYPE_MAP[extension];

        // Skip unknown file types
        if (!assetType) return;

        // Get file info
        let stat: { size: number; mtime: number };
        try {
            stat = await this._fileSystem.stat(absolutePath);
        } catch {
            return;
        }

        // Check if already in manifest
        let guid: AssetGUID;
        const existingEntry = this._manifest.assets[relativePath];

        if (existingEntry) {
            guid = existingEntry.guid;
        } else {
            // Generate new GUID
            guid = this._generateGUID();
            this._manifest.assets[relativePath] = {
                guid,
                relativePath,
                type: assetType
            };
        }

        // Get file name
        const lastSlash = relativePath.lastIndexOf('/');
        const fileName = lastSlash >= 0 ? relativePath.substring(lastSlash + 1) : relativePath;
        const name = fileName.substring(0, fileName.lastIndexOf('.'));

        // Create metadata
        const metadata: IAssetRegistryMetadata = {
            guid,
            path: relativePath,
            type: assetType,
            name,
            size: stat.size,
            hash: '', // Could compute hash if needed
            lastModified: stat.mtime
        };

        // Register in database
        this._database.addAsset(metadata);
    }

    /**
     * Generate a unique GUID
     */
    private _generateGUID(): AssetGUID {
        // Simple UUID v4 generation
        return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, (c) => {
            const r = (Math.random() * 16) | 0;
            const v = c === 'x' ? r : (r & 0x3) | 0x8;
            return v.toString(16);
        });
    }

    // ==================== Public API ====================

    /**
     * Get asset metadata by GUID
     */
    getAsset(guid: AssetGUID): IAssetRegistryMetadata | undefined {
        return this._database.getMetadata(guid);
    }

    /**
     * Get asset metadata by relative path
     */
    getAssetByPath(relativePath: string): IAssetRegistryMetadata | undefined {
        return this._database.getMetadataByPath(relativePath);
    }

    /**
     * Get GUID for a relative path
     */
    getGuidByPath(relativePath: string): AssetGUID | undefined {
        const metadata = this._database.getMetadataByPath(relativePath);
        return metadata?.guid;
    }

    /**
     * Get relative path for a GUID
     */
    getPathByGuid(guid: AssetGUID): string | undefined {
        const metadata = this._database.getMetadata(guid);
        return metadata?.path;
    }

    /**
     * Convert absolute path to relative path
     */
    absoluteToRelative(absolutePath: string): string | null {
        if (!this._projectPath) return null;

        const normalizedAbs = absolutePath.replace(/\\/g, '/');
        const normalizedProject = this._projectPath.replace(/\\/g, '/');

        if (normalizedAbs.startsWith(normalizedProject)) {
            return normalizedAbs.substring(normalizedProject.length + 1);
        }

        return null;
    }

    /**
     * Convert relative path to absolute path
     */
    relativeToAbsolute(relativePath: string): string | null {
        if (!this._projectPath) return null;

        const sep = this._projectPath.includes('\\') ? '\\' : '/';
        return `${this._projectPath}${sep}${relativePath.replace(/\//g, sep)}`;
    }

    /**
     * Find assets by type
     */
    findAssetsByType(type: AssetRegistryType): IAssetRegistryMetadata[] {
        const guids = this._database.findAssetsByType(type);
        return guids
            .map(guid => this._database.getMetadata(guid))
            .filter((m): m is IAssetRegistryMetadata => m !== undefined);
    }

    /**
     * Get all registered assets
     */
    getAllAssets(): IAssetRegistryMetadata[] {
        const entries = this._database.exportToCatalog();
        return entries.map(entry => this._database.getMetadata(entry.guid))
            .filter((m): m is IAssetRegistryMetadata => m !== undefined);
    }

    /**
     * Export catalog for runtime use
     * 导出运行时使用的资产目录
     */
    exportCatalog(): IAssetRegistryCatalogEntry[] {
        return this._database.exportToCatalog();
    }

    /**
     * Export catalog as JSON string
     */
    exportCatalogJSON(): string {
        const entries = this._database.exportToCatalog();
        const catalog = {
            version: '1.0.0',
            createdAt: Date.now(),
            entries: Object.fromEntries(entries.map(e => [e.guid, e]))
        };
        return JSON.stringify(catalog, null, 2);
    }

    /**
     * Register a new asset (e.g., when a file is created)
     */
    async registerAsset(absolutePath: string): Promise<AssetGUID | null> {
        const relativePath = this.absoluteToRelative(absolutePath);
        if (!relativePath) return null;

        await this._registerAssetFile(absolutePath, relativePath);
        await this._saveManifest();

        const metadata = this._database.getMetadataByPath(relativePath);
        return metadata?.guid ?? null;
    }

    /**
     * Unregister an asset (e.g., when a file is deleted)
     */
    async unregisterAsset(absolutePath: string): Promise<void> {
        const relativePath = this.absoluteToRelative(absolutePath);
        if (!relativePath || !this._manifest) return;

        const metadata = this._database.getMetadataByPath(relativePath);
        if (metadata) {
            this._database.removeAsset(metadata.guid);
            delete this._manifest.assets[relativePath];
            await this._saveManifest();
        }
    }

    /**
     * Refresh a single asset (e.g., when file is modified)
     */
    async refreshAsset(absolutePath: string): Promise<void> {
        const relativePath = this.absoluteToRelative(absolutePath);
        if (!relativePath) return;

        // Re-register the asset
        await this._registerAssetFile(absolutePath, relativePath);
        await this._saveManifest();
    }

    /**
     * Get database statistics
     */
    getStatistics() {
        return this._database.getStatistics();
    }

    /**
     * Check if service is ready
     */
    get isReady(): boolean {
        return this._initialized && this._projectPath !== null;
    }

    /**
     * Get current project path
     */
    get projectPath(): string | null {
        return this._projectPath;
    }
}