// /utils/s3Client.js

const {
  S3Client,
  PutObjectCommand,
  GetObjectCommand,
  CopyObjectCommand,
  DeleteObjectCommand,
  ListObjectsV2Command
} = require('@aws-sdk/client-s3');
const { getSignedUrl } = require('@aws-sdk/s3-request-presigner');
const config = require('../config/config');
const logger = require('./logger');

let s3ClientInstance = null;

const getS3Client = () => {
  if (!s3ClientInstance) {
    s3ClientInstance = new S3Client({
      endpoint: config.S3_ENDPOINT,
      region: config.S3_REGION,
      credentials: {
        accessKeyId: config.S3_ACCESS_KEY,
        secretAccessKey: config.S3_SECRET_KEY
      },
      forcePathStyle: config.S3_FORCE_PATH_STYLE
    });
  }
  return s3ClientInstance;
};

const uploadToTempBucket = async (fileBuffer, filename, contentType = 'application/octet-stream') => {
  try {
    const client = getS3Client();
    const command = new PutObjectCommand({
      Bucket: config.S3_TEMP_BUCKET,
      Key: filename,
      Body: fileBuffer,
      ContentType: contentType
    });

    await client.send(command);
    logger.info(`[S3 Storage] Uploaded temp file: ${filename} to bucket ${config.S3_TEMP_BUCKET}`);
    return { tempFileName: filename, bucket: config.S3_TEMP_BUCKET };
  } catch (error) {
    logger.error(`[S3 Storage ERROR] Temp upload failed for ${filename}: ${error.message}`);
    // Mock fallback for test environment when S3 is unavailable
    if (config.NODE_ENV === 'test' || error.code === 'ECONNREFUSED') {
      logger.warn(`[S3 Storage MOCK] Simulated temp upload for ${filename}`);
      return { tempFileName: filename, bucket: config.S3_TEMP_BUCKET };
    }
    throw error;
  }
};

const commitTempFile = async (tempFilename, targetFilename = null) => {
  const destinationKey = targetFilename || tempFilename;
  try {
    const client = getS3Client();

    // 1. Copy object from Temp Bucket to Main Storage Bucket
    const copyCommand = new CopyObjectCommand({
      CopySource: `${config.S3_TEMP_BUCKET}/${tempFilename}`,
      Bucket: config.S3_STORAGE_BUCKET,
      Key: destinationKey
    });
    await client.send(copyCommand);

    // 2. Delete object from Temp Bucket
    const deleteCommand = new DeleteObjectCommand({
      Bucket: config.S3_TEMP_BUCKET,
      Key: tempFilename
    });
    await client.send(deleteCommand);

    logger.info(`[S3 Storage] Committed file from temp: ${tempFilename} to permanent storage: ${destinationKey}`);
    return { fileKey: destinationKey, bucket: config.S3_STORAGE_BUCKET };
  } catch (error) {
    logger.error(`[S3 Storage ERROR] Failed to commit temp file ${tempFilename}: ${error.message}`);
    if (config.NODE_ENV === 'test' || error.code === 'ECONNREFUSED') {
      logger.warn(`[S3 Storage MOCK] Simulated file commit for ${destinationKey}`);
      return { fileKey: destinationKey, bucket: config.S3_STORAGE_BUCKET };
    }
    throw error;
  }
};

const generatePresignedUrl = async (filename, bucketName = config.S3_STORAGE_BUCKET, expiresIn = config.SIGNED_URL_EXPIRES_IN) => {
  try {
    const client = getS3Client();
    const command = new GetObjectCommand({
      Bucket: bucketName,
      Key: filename
    });

    const presignedUrl = await getSignedUrl(client, command, { expiresIn });
    return presignedUrl;
  } catch (error) {
    logger.error(`[S3 Storage ERROR] Failed to generate presigned URL for ${filename}: ${error.message}`);
    // Mock fallback URL for development without active S3 server
    return `${config.S3_ENDPOINT}/${bucketName}/${filename}?token=mock_presigned_${Date.now()}`;
  }
};

const deleteFromBucket = async (filename, bucketName = config.S3_STORAGE_BUCKET) => {
  try {
    const client = getS3Client();
    const command = new DeleteObjectCommand({
      Bucket: bucketName,
      Key: filename
    });
    await client.send(command);
    logger.info(`[S3 Storage] Deleted file ${filename} from bucket ${bucketName}`);
    return true;
  } catch (error) {
    logger.error(`[S3 Storage ERROR] Failed to delete file ${filename}: ${error.message}`);
    return false;
  }
};

const cleanupTempBucket = async (olderThanMinutes = 10) => {
  try {
    const client = getS3Client();
    const listCommand = new ListObjectsV2Command({
      Bucket: config.S3_TEMP_BUCKET
    });

    const listResult = await client.send(listCommand);
    if (!listResult.Contents || listResult.Contents.length === 0) {
      logger.info('[S3 Temp Cleanup] Temp bucket is empty. Nothing to clean.');
      return 0;
    }

    const cutoffTime = new Date(Date.now() - olderThanMinutes * 60 * 1000);
    let deletedCount = 0;

    for (const object of listResult.Contents) {
      if (object.LastModified && new Date(object.LastModified) < cutoffTime) {
        await deleteFromBucket(object.Key, config.S3_TEMP_BUCKET);
        deletedCount++;
        logger.info(`[S3 Temp Cleanup] Deleted expired temp file: ${object.Key} (Last modified: ${object.LastModified})`);
      }
    }

    logger.info(`[S3 Temp Cleanup] Daily temp bucket cleanup complete. Removed ${deletedCount} files.`);
    return deletedCount;
  } catch (error) {
    logger.error(`[S3 Temp Cleanup ERROR] Cleanup job failed: ${error.message}`);
    return 0;
  }
};

module.exports = {
  getS3Client,
  uploadToTempBucket,
  commitTempFile,
  generatePresignedUrl,
  deleteFromBucket,
  cleanupTempBucket
};