// /components/files/fileService.js

const fs = require('fs/promises');
const path = require('path');
const config = require('../../config/config');
const {
  uploadToTempBucket,
  commitTempFile,
  generatePresignedUrl,
  getObjectBuffer,
  deleteFromBucket
} = require('../../utils/s3Client');
const AppError = require('../../utils/AppError');

const unlinkQuietly = async (filePath) => {
  if (!filePath) return;
  try {
    await fs.unlink(filePath);
  } catch {
    // temp disk file may already be gone
  }
};

const uploadTempFile = async (file) => {
  const originalName = file?.originalname || file?.originalName;
  const mimeType = file?.mimetype || file?.mimeType || 'application/octet-stream';
  const source = file?.path || file?.buffer;

  if (!source || !originalName) {
    throw new AppError('FILE_REQUIRED');
  }

  const ext = path.extname(originalName);
  const uniquePrefix = `${Date.now()}-${Math.round(Math.random() * 1E9)}`;
  const tempFileName = `temp-${uniquePrefix}${ext}`;

  try {
    const result = await uploadToTempBucket(source, tempFileName, mimeType);
    return {
      tempFileName: result.tempFileName,
      originalName,
      mimeType,
      bucket: result.bucket
    };
  } finally {
    await unlinkQuietly(file.path);
  }
};

const getPresignedUrl = async (filename, bucket = null) => {
  if (!filename) {
    throw new AppError('VALIDATION_FAILED', null, 'Filename is required');
  }

  const targetBucket = bucket || config.S3_TEMP_BUCKET;
  const signedUrl = await generatePresignedUrl(filename, targetBucket);
  return {
    filename,
    bucket: targetBucket,
    presignedUrl: signedUrl,
    signedUrl,
    expiresInSeconds: config.SIGNED_URL_EXPIRES_IN
  };
};

const getFileContent = async (filename, bucket = null) => {
  if (!filename) {
    throw new AppError('VALIDATION_FAILED', null, 'Filename is required');
  }
  return getObjectBuffer(filename, bucket || config.S3_TEMP_BUCKET);
};

const commitFile = async (tempFileName, targetFileName = null, targetBucket = 'certificates') => {
  return commitTempFile(tempFileName, targetFileName, targetBucket);
};

const deleteFile = async (filename, bucket = null) => {
  return deleteFromBucket(filename, bucket || config.S3_TEMP_BUCKET);
};

module.exports = {
  uploadTempFile,
  getPresignedUrl,
  getFileContent,
  commitFile,
  deleteFile
};