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

// Storage base path (local filesystem)
const STORAGE_BASE_PATH = process.env.STORAGE_BASE_PATH || path.join(process.cwd(), "storage");

/**
 * Ensure storage directory exists
 */
async function ensureStorageDir(dirPath: string) {
  try {
    await fs.mkdir(dirPath, { recursive: true });
  } catch (error) {
    console.error(`[LocalStorage] Failed to create directory ${dirPath}:`, error);
    throw error;
  }
}

/**
 * Generate a storage key with YYYY-MM prefix for organization
 */
export function generateStorageKey(userId: number, fileName: string): string {
  const now = new Date();
  const year = now.getFullYear();
  const month = String(now.getMonth() + 1).padStart(2, "0");
  const randomId = nanoid(8);
  
  // Format: YYYY-MM/userId-randomId-filename
  return `${year}-${month}/${userId}-${randomId}-${fileName}`;
}

/**
 * Store a file in local storage
 * @param fileKey - Storage key (e.g., "2025-01/1-abc123-invoice.pdf")
 * @param buffer - File content as Buffer
 * @param contentType - MIME type (optional, for metadata)
 * @returns Object with key and public URL
 */
export async function localStoragePut(
  fileKey: string,
  buffer: Buffer,
  _contentType?: string
): Promise<{ key: string; url: string }> {
  try {
    const fullPath = path.join(STORAGE_BASE_PATH, fileKey);
    const dirPath = path.dirname(fullPath);
    
    // Ensure directory exists
    await ensureStorageDir(dirPath);
    
    // Write file
    await fs.writeFile(fullPath, buffer);
    
    // Generate public URL (served by Express static middleware)
    const url = `/storage/${fileKey}`;
    
    console.log(`[LocalStorage] File stored: ${fileKey}`);
    
    return { key: fileKey, url };
  } catch (error) {
    console.error(`[LocalStorage] Failed to store file ${fileKey}:`, error);
    throw error;
  }
}

/**
 * Retrieve a file from local storage
 * @param fileKey - Storage key
 * @returns File content as Buffer
 */
export async function localStorageGet(fileKey: string): Promise<Buffer> {
  try {
    const fullPath = path.join(STORAGE_BASE_PATH, fileKey);
    const buffer = await fs.readFile(fullPath);
    return buffer;
  } catch (error) {
    console.error(`[LocalStorage] Failed to retrieve file ${fileKey}:`, error);
    throw error;
  }
}

/**
 * Delete a file from local storage
 * @param fileKey - Storage key
 */
export async function localStorageDelete(fileKey: string): Promise<void> {
  try {
    const fullPath = path.join(STORAGE_BASE_PATH, fileKey);
    await fs.unlink(fullPath);
    console.log(`[LocalStorage] File deleted: ${fileKey}`);
  } catch (error) {
    console.error(`[LocalStorage] Failed to delete file ${fileKey}:`, error);
    throw error;
  }
}

/**
 * Check if a file exists in storage
 * @param fileKey - Storage key
 * @returns true if file exists, false otherwise
 */
export async function localStorageExists(fileKey: string): Promise<boolean> {
  try {
    const fullPath = path.join(STORAGE_BASE_PATH, fileKey);
    await fs.access(fullPath);
    return true;
  } catch {
    return false;
  }
}