/**
 * Local File Storage
 * 
 * Stores uploaded files locally in the uploads/ directory.
 * Files are served via Express static middleware.
 */

import fs from "fs/promises";
import path from "path";
import { fileURLToPath } from "url";
import { nanoid } from "nanoid";

// Get directory name in ESM
const __filename = fileURLToPath(import.meta.url);
const __dirname = path.dirname(__filename);

// Base directory for uploads (relative to project root)
const UPLOADS_DIR = path.resolve(__dirname, "../uploads");

// Subdirectories
const TRACKS_DIR = path.join(UPLOADS_DIR, "tracks");
const STEMS_DIR = path.join(UPLOADS_DIR, "stems");

/**
 * Ensure upload directories exist
 */
export async function ensureUploadDirs(): Promise<void> {
  await fs.mkdir(TRACKS_DIR, { recursive: true });
  await fs.mkdir(STEMS_DIR, { recursive: true });
}

/**
 * Get the uploads base directory path
 */
export function getUploadsDir(): string {
  return UPLOADS_DIR;
}

/**
 * Save an uploaded track file
 * 
 * @param userId User ID
 * @param fileName Original filename
 * @param data File data as Buffer
 * @returns Object with fileKey (relative path) and filePath (absolute path)
 */
export async function saveTrackFile(
  userId: number,
  fileName: string,
  data: Buffer
): Promise<{ fileKey: string; filePath: string; fileUrl: string }> {
  await ensureUploadDirs();
  
  // Create user-specific directory
  const userDir = path.join(TRACKS_DIR, String(userId));
  await fs.mkdir(userDir, { recursive: true });
  
  // Generate unique filename
  const ext = path.extname(fileName) || ".mp3";
  const uniqueName = `${nanoid(16)}${ext}`;
  const filePath = path.join(userDir, uniqueName);
  
  // Write file
  await fs.writeFile(filePath, data);
  
  // Generate relative key for database storage
  const fileKey = `tracks/${userId}/${uniqueName}`;
  
  // URL path for serving (will be served via /uploads/ route)
  const fileUrl = `/uploads/${fileKey}`;
  
  return { fileKey, filePath, fileUrl };
}

/**
 * Save a stem file from ML processing
 * 
 * @param trackId Track ID
 * @param stemType Stem type (vocals, drums, bass, other)
 * @param sourcePath Source file path from ML output
 * @returns Object with fileKey, filePath, and fileUrl
 */
export async function saveStemFile(
  trackId: number,
  stemType: string,
  sourcePath: string
): Promise<{ fileKey: string; filePath: string; fileUrl: string }> {
  await ensureUploadDirs();
  
  // Create track-specific stems directory
  const trackStemsDir = path.join(STEMS_DIR, String(trackId));
  await fs.mkdir(trackStemsDir, { recursive: true });
  
  // Get extension from source
  const ext = path.extname(sourcePath) || ".mp3";
  const uniqueName = `${stemType}-${nanoid(8)}${ext}`;
  const filePath = path.join(trackStemsDir, uniqueName);
  
  // Copy file from ML output to uploads directory
  await fs.copyFile(sourcePath, filePath);
  
  // Generate relative key for database storage
  const fileKey = `stems/${trackId}/${uniqueName}`;
  
  // URL path for serving
  const fileUrl = `/uploads/${fileKey}`;
  
  return { fileKey, filePath, fileUrl };
}

/**
 * Get the absolute path for a file key
 */
export function getFilePath(fileKey: string): string {
  return path.join(UPLOADS_DIR, fileKey);
}

/**
 * Check if a file exists
 */
export async function fileExists(fileKey: string): Promise<boolean> {
  try {
    await fs.access(getFilePath(fileKey));
    return true;
  } catch {
    return false;
  }
}

/**
 * Delete a file
 */
export async function deleteFile(fileKey: string): Promise<void> {
  try {
    await fs.unlink(getFilePath(fileKey));
  } catch {
    // Ignore if file doesn't exist
  }
}

/**
 * Get file stats
 */
export async function getFileStats(fileKey: string): Promise<{ size: number } | null> {
  try {
    const stats = await fs.stat(getFilePath(fileKey));
    return { size: stats.size };
  } catch {
    return null;
  }
}

/**
 * Create a temp directory for ML processing output
 */
export async function createTempDir(prefix: string): Promise<string> {
  const tempDir = path.join(UPLOADS_DIR, "temp", `${prefix}-${nanoid(8)}`);
  await fs.mkdir(tempDir, { recursive: true });
  return tempDir;
}

/**
 * Clean up a temp directory
 */
export async function cleanupTempDir(tempDir: string): Promise<void> {
  try {
    await fs.rm(tempDir, { recursive: true, force: true });
  } catch {
    // Ignore errors
  }
}