import { S3Client, PutObjectCommand, GetObjectCommand, ListObjectsV2Command, DeleteObjectCommand } from '@aws-sdk/client-s3';
import { getSignedUrl } from '@aws-sdk/s3-request-presigner';

export function getS3Client() {
  const endpoint = process.env.S3_ENDPOINT; // e.g. http://<VPS_IP>:9000
  const region = process.env.S3_REGION || 'us-east-1';
  const accessKeyId = process.env.S3_ACCESS_KEY || '';
  const secretAccessKey = process.env.S3_SECRET_KEY || '';

  if (!endpoint || !accessKeyId || !secretAccessKey) {
    throw new Error('Missing S3 config: S3_ENDPOINT, S3_ACCESS_KEY, S3_SECRET_KEY');
  }
  return new S3Client({
    region,
    endpoint,
    forcePathStyle: true,
    credentials: { accessKeyId, secretAccessKey },
  });
}

export async function getPresignedUrl(params: { bucket: string; key: string; expiresInSeconds?: number }): Promise<string> {
  const s3 = getS3Client();
  const cmd = new GetObjectCommand({ Bucket: params.bucket, Key: params.key });
  const expiresIn = typeof params.expiresInSeconds === 'number' ? params.expiresInSeconds : 60 * 60 * 24 * 7; // 7 days
  return await getSignedUrl(s3, cmd, { expiresIn });
}

export function getPublicUrlForKey(key: string): string | null {
  const base = process.env.PUBLIC_MEDIA_BASE_URL;
  if (!base) return null;
  return `${base.replace(/\/$/, '')}/${key}`;
}

export async function listObjects(params: { bucket: string; prefix?: string; maxKeys?: number }) {
  const s3 = getS3Client();
  const cmd = new ListObjectsV2Command({
    Bucket: params.bucket,
    Prefix: params.prefix,
    MaxKeys: params.maxKeys || 100,
  });
  const res = await s3.send(cmd);
  const items = (res.Contents || []).map(obj => ({
    key: obj.Key || '',
    size: obj.Size || 0,
    lastModified: obj.LastModified?.toISOString() || null,
  })).filter(i => i.key);
  return { items, isTruncated: !!res.IsTruncated, nextContinuationToken: res.NextContinuationToken };
}

export async function deleteObject(params: { bucket: string; key: string }) {
  const s3 = getS3Client();
  await s3.send(new DeleteObjectCommand({ Bucket: params.bucket, Key: params.key }));
  return { success: true };
}

export async function uploadBuffer(params: {
  bucket: string;
  key: string;
  body: Buffer;
  contentType?: string;
}) {
  const s3 = getS3Client();
  console.log('[S3] Upload start', {
    bucket: params.bucket,
    key: params.key,
    bytes: params.body?.length ?? 0,
    contentType: params.contentType || 'application/octet-stream',
  });
  const cmd = new PutObjectCommand({
    Bucket: params.bucket,
    Key: params.key,
    Body: params.body,
    ContentType: params.contentType || 'application/octet-stream',
  });
  await s3.send(cmd);
  console.log('[S3] Upload done', { bucket: params.bucket, key: params.key });
  return { bucket: params.bucket, key: params.key };
}

export async function downloadObject(params: { bucket: string; key: string }): Promise<{ buffer: Buffer; contentType: string }> {
  const s3 = getS3Client();
  console.log('[S3] Download start', { bucket: params.bucket, key: params.key });
  const cmd = new GetObjectCommand({ Bucket: params.bucket, Key: params.key });
  const res = await s3.send(cmd);
  const contentType = res.ContentType || 'application/octet-stream';
  const body = res.Body as unknown as NodeJS.ReadableStream;
  const chunks: Buffer[] = [];
  await new Promise<void>((resolve, reject) => {
    body.on('data', (c: Buffer) => chunks.push(c));
    body.on('end', resolve);
    body.on('error', reject);
  });
  const buffer = Buffer.concat(chunks);
  console.log('[S3] Download done', { bucket: params.bucket, key: params.key, bytes: buffer.length, contentType });
  return { buffer, contentType };
}