// /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 BUCKETS = {
  temp: () => config.S3_TEMP_BUCKET,
  certificates: () => config.S3_CERTIFICATES_BUCKET,
  documents: () => config.S3_DOCUMENTS_BUCKET,
  storage: () => config.S3_STORAGE_BUCKET
};

const resolveBucket = (bucketNameOrKind) => {
  if (!bucketNameOrKind) return config.S3_CERTIFICATES_BUCKET;
  if (BUCKETS[bucketNameOrKind]) return BUCKETS[bucketNameOrKind]();
  return bucketNameOrKind;
};

const isBucketPublic = (bucketName) => {
  const name = resolveBucket(bucketName);
  if (name === config.S3_CERTIFICATES_BUCKET) return config.S3_CERTIFICATES_PUBLIC;
  if (name === config.S3_DOCUMENTS_BUCKET) return config.S3_DOCUMENTS_PUBLIC;
  return false;
};

const buildPublicUrl = (bucketName, fileKey) => {
  if (!isBucketPublic(bucketName) || !fileKey) return null;
  const base = (config.S3_PUBLIC_BASE_URL || config.S3_ENDPOINT || '').replace(/\/$/, '');
  if (!base) return null;
  return `${base}/${resolveBucket(bucketName)}/${fileKey}`;
};

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}`);
    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;
  }
};

/**
 * Copy a temp object into a target private/public bucket, then remove the temp object.
 * @param {string} tempFilename
 * @param {string} destinationKey
 * @param {string} [targetBucketKind='certificates'] - 'certificates' | 'documents' | bucket name
 */
const commitTempFile = async (tempFilename, destinationKey = null, targetBucketKind = 'certificates') => {
  const targetKey = destinationKey || tempFilename;
  const targetBucket = resolveBucket(targetBucketKind);

  try {
    const client = getS3Client();

    const copyCommand = new CopyObjectCommand({
      CopySource: `${config.S3_TEMP_BUCKET}/${tempFilename}`,
      Bucket: targetBucket,
      Key: targetKey
    });
    await client.send(copyCommand);

    const deleteCommand = new DeleteObjectCommand({
      Bucket: config.S3_TEMP_BUCKET,
      Key: tempFilename
    });
    await client.send(deleteCommand);

    const fileUrl = buildPublicUrl(targetBucket, targetKey);
    logger.info(`[S3 Storage] Committed ${tempFilename} → ${targetBucket}/${targetKey}`);
    return { fileKey: targetKey, bucket: targetBucket, fileUrl };
  } 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 ${targetKey}`);
      return {
        fileKey: targetKey,
        bucket: targetBucket,
        fileUrl: buildPublicUrl(targetBucket, targetKey)
      };
    }
    throw error;
  }
};

const generatePresignedUrl = async (
  filename,
  bucketName = config.S3_CERTIFICATES_BUCKET,
  expiresIn = config.SIGNED_URL_EXPIRES_IN
) => {
  const bucket = resolveBucket(bucketName);
  try {
    const client = getS3Client();
    const command = new GetObjectCommand({
      Bucket: bucket,
      Key: filename
    });

    return await getSignedUrl(client, command, { expiresIn });
  } catch (error) {
    logger.error(`[S3 Storage ERROR] Failed to generate presigned URL for ${filename}: ${error.message}`);
    return `${config.S3_ENDPOINT}/${bucket}/${filename}?token=mock_presigned_${Date.now()}`;
  }
};

const deleteFromBucket = async (filename, bucketName = config.S3_CERTIFICATES_BUCKET) => {
  const bucket = resolveBucket(bucketName);
  try {
    const client = getS3Client();
    const command = new DeleteObjectCommand({
      Bucket: bucket,
      Key: filename
    });
    await client.send(command);
    logger.info(`[S3 Storage] Deleted file ${filename} from bucket ${bucket}`);
    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}`);
      }
    }

    logger.info(`[S3 Temp Cleanup] Removed ${deletedCount} expired temp 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,
  resolveBucket,
  isBucketPublic,
  buildPublicUrl,
  BUCKETS
};