import { randomUUID } from "crypto";
import fs from "fs";
import path from "path";
import { Readable } from "stream";

const TEMP_STORAGE_PATH = process.env.TEMP_STORAGE_PATH || "/app/temp-storage";
const MAX_FILE_AGE_MS = 24 * 60 * 60 * 1000; // 24 小時

export class ObjectNotFoundError extends Error {
  constructor() {
    super("Object not found");
    this.name = "ObjectNotFoundError";
    Object.setPrototypeOf(this, ObjectNotFoundError.prototype);
  }
}

export interface LocalFile {
  path: string;
  url: string;
  exists(): Promise<boolean>;
  delete(): Promise<void>;
  getMetadata(): Promise<{ contentType: string; size: number }>;
  createReadStream(): fs.ReadStream;
}

export class LocalTempStorageService {
  private storagePath: string;

  constructor() {
    this.storagePath = TEMP_STORAGE_PATH;
    this.ensureStorageDir();
    this.startCleanupInterval();
  }

  private ensureStorageDir(): void {
    if (!fs.existsSync(this.storagePath)) {
      fs.mkdirSync(this.storagePath, { recursive: true });
    }
  }

  // 定期清理舊檔案
  private startCleanupInterval(): void {
    setInterval(() => {
      this.cleanupOldFiles().catch((err) => {
        console.error("[LocalTempStorage] Cleanup error:", err);
      });
    }, 60 * 60 * 1000); // 每小時執行一次
  }

  private async cleanupOldFiles(): Promise<void> {
    try {
      const now = Date.now();
      const files = fs.readdirSync(this.storagePath);
      
      let deletedCount = 0;
      for (const file of files) {
        const filePath = path.join(this.storagePath, file);
        const stats = fs.statSync(filePath);
        
        if (now - stats.mtimeMs > MAX_FILE_AGE_MS) {
          fs.unlinkSync(filePath);
          deletedCount++;
        }
      }
      
      if (deletedCount > 0) {
        console.log(`[LocalTempStorage] Cleaned up ${deletedCount} old files`);
      }
    } catch (error) {
      console.error("[LocalTempStorage] Error during cleanup:", error);
    }
  }

  async saveFile(buffer: Buffer, filename: string, contentType: string = "application/octet-stream"): Promise<LocalFile> {
    const fileId = randomUUID();
    const ext = path.extname(filename) || "";
    const savedFilename = `${fileId}${ext}`;
    const filePath = path.join(this.storagePath, savedFilename);
    
    fs.writeFileSync(filePath, buffer);
    
    // 儲存 metadata
    const metadataPath = `${filePath}.meta`;
    fs.writeFileSync(metadataPath, JSON.stringify({ contentType, originalName: filename }));
    
    return this.getFile(savedFilename);
  }

  getFile(filename: string): LocalFile {
    const filePath = path.join(this.storagePath, filename);
    const url = `/api/temp-storage/${filename}`;
    
    return {
      path: filePath,
      url,
      async exists() {
        return fs.existsSync(filePath);
      },
      async delete() {
        if (fs.existsSync(filePath)) {
          fs.unlinkSync(filePath);
        }
        const metadataPath = `${filePath}.meta`;
        if (fs.existsSync(metadataPath)) {
          fs.unlinkSync(metadataPath);
        }
      },
      async getMetadata() {
        const metadataPath = `${filePath}.meta`;
        if (fs.existsSync(metadataPath)) {
          const meta = JSON.parse(fs.readFileSync(metadataPath, "utf-8"));
          const stats = fs.statSync(filePath);
          return {
            contentType: meta.contentType || "application/octet-stream",
            size: stats.size,
          };
        }
        const stats = fs.statSync(filePath);
        return {
          contentType: "application/octet-stream",
          size: stats.size,
        };
      },
      createReadStream() {
        return fs.createReadStream(filePath);
      },
    };
  }

  async downloadFile(file: LocalFile): Promise<Response> {
    const exists = await file.exists();
    if (!exists) {
      throw new ObjectNotFoundError();
    }

    const metadata = await file.getMetadata();
    const nodeStream = file.createReadStream();
    const webStream = Readable.toWeb(nodeStream) as ReadableStream;

    const headers: Record<string, string> = {
      "Content-Type": metadata.contentType,
      "Content-Length": String(metadata.size),
      "Cache-Control": "public, max-age=3600",
    };

    return new Response(webStream, { headers });
  }

  // 從 URL 提取檔案名稱
  extractFilenameFromUrl(url: string): string | null {
    const match = url.match(/\/api\/temp-storage\/([^?]+)/);
    return match ? match[1] : null;
  }

  // 清理所有檔案 (用於測試或維護)
  async cleanupAll(): Promise<void> {
    const files = fs.readdirSync(this.storagePath);
    for (const file of files) {
      const filePath = path.join(this.storagePath, file);
      fs.unlinkSync(filePath);
    }
    console.log(`[LocalTempStorage] Cleaned up all ${files.length} files`);
  }
}

// 單例實例
export const localTempStorage = new LocalTempStorageService();