Stream S3 File object with Ts.ED

MediasController.ts

import { Controller } from "@tsed/common";
import { Inject, Injectable } from "@tsed/di";
import AWS from "aws-sdk";

@Controller("/medias")
export class MediasController {
  @Inject()
  protected s3: S3Client;

  @Get()
  async getImage(@QueryParams("id") imageKey: number, @Context() ctx: Context): Promise<Buffer> {
    try {
      const { object, metadata } = await this.s3.getObject(IMAGE_BUCKET, imageKey);
      const buffer = object.createReadStream();

      // buffer.res.set("Content-Type", mime.lookup(key));
      ctx.response.set("Content-Length", metadata.ContentLength); // maybe not necessary
      // use the last-modified header to use browser cache
      ctx.response.set("Last-Modified", metadata.LastModified);
      ctx.response.set("ETag", metadata.ETag);

      // Ts.ED will handle the buffer
      return buffer;
    } catch (err) {
      throw new BadRequest(`Unable to satisfy object request: ${imageKey}`);
    }
  }
}

S3Client.ts

import { Inject, Injectable } from "@tsed/di";
import AWS from "aws-sdk";

@Injectable()
class S3Client {
  protected s3 = new AWS.S3();

  /**
   * Grab an object from s3.
   * e.g. s3://my-bucket/path/to/file.txt
   * bucket: my-bucket, key: path/to/file.txt
   * @param bucket Bucket containing object.
   * @param key Key path to object.
   */
  async getObject(bucket: string, key: string) {
    const params = {
      Bucket: bucket,
      Key: key
    };

    const metadata = await this.s3.headObject(params).promise();

    return {
      metadata,
      object: this.s3.getObject(params)
    };
  }
}