import { Injectable } from '@nestjs/common';
import { ConfigService } from '@nestjs/config';
import { randomUUID } from 'crypto';
import {
  DeleteObjectCommand,
  GetObjectCommand,
  PutObjectCommand,
  S3Client,
} from '@aws-sdk/client-s3';
import { StorageProvider } from './storage-provider';

/// S3-compatible object storage (AWS S3, MinIO, etc.).
@Injectable()
export class S3StorageProvider implements StorageProvider {
  private readonly client: S3Client;
  private readonly bucket: string;

  constructor(config: ConfigService) {
    this.bucket = config.getOrThrow<string>('S3_BUCKET');
    this.client = new S3Client({
      region: config.get<string>('S3_REGION') ?? 'auto',
      endpoint: config.get<string>('S3_ENDPOINT'),
      forcePathStyle: config.get<string>('S3_FORCE_PATH_STYLE') === 'true',
      credentials: {
        accessKeyId: config.getOrThrow<string>('S3_ACCESS_KEY_ID'),
        secretAccessKey: config.getOrThrow<string>('S3_SECRET_ACCESS_KEY'),
      },
    });
  }

  async upload(kcId: string, filename: string, data: Buffer): Promise<string> {
    const storageKey = `${kcId}/${randomUUID()}-${filename}`;
    await this.client.send(
      new PutObjectCommand({ Bucket: this.bucket, Key: storageKey, Body: data }),
    );
    return storageKey;
  }

  async download(storageKey: string): Promise<Buffer> {
    const result = await this.client.send(
      new GetObjectCommand({ Bucket: this.bucket, Key: storageKey }),
    );
    const chunks: Uint8Array[] = [];
    for await (const chunk of result.Body as AsyncIterable<Uint8Array>) {
      chunks.push(chunk);
    }
    return Buffer.concat(chunks);
  }

  async delete(storageKey: string): Promise<void> {
    await this.client.send(new DeleteObjectCommand({ Bucket: this.bucket, Key: storageKey }));
  }
}