aws.ts

import { PutObjectCommand, S3Client, GetObjectCommand } from '@aws-sdk/client-s3'
import * as S3 from '@aws-sdk/s3-request-presigner'
import { v4 as uuid } from 'uuid'

import { RandomUtils } from '../lib/utils/random'

export interface IAWSSource {
  /**
   * Gets upload parameters for a file.
   */
  getFileUploadParameters(params: { extension?: string | null; contentType: string; folder: string }): Promise<{
    file_url: string
    file_key: string
    upload_url: string
  }>

  /**
   * Uploads a file to the S3 bucket.
   */
  uploadFile(params: { extension?: string | null; contentType: string; folder: string; file: Uint8Array }): Promise<{
    file_url: string
    file_key: string
  }>

  /**
   * Returns a key of the file from a given URL.
   */
  getFileKey(params: { fileURL: string }): string

  /**
   * Pulls a file from the S3 bucket if it exists.
   */
  getFile(params: { key: string }): Promise<{ file: Uint8Array; contentType: string } | null>
}

type AWSConfig = {
  accessKeyId: string
  secretAccessKey: string

  /**
   * Region identifier for the given bucket.
   */
  region: string
  /**
   * Base access URL of the AWS bucket (e.g. https://s3.eu-central-1.amazonaws.com/).
   */
  baseURL: string
  s3BucketName: string
}

/**
 * A utility class that helps with S3 communication.
 */
export class AWSSource implements IAWSSource {
  private readonly _client: S3Client

  private readonly _config: AWSConfig

  constructor(config: AWSConfig) {
    this._config = config
    this._client = new S3Client({
      credentials: {
        accessKeyId: config.accessKeyId,
        secretAccessKey: config.secretAccessKey,
      },
      region: config.region,
    })
  }

  /**
   * Get file and content type from AWS S3 bucket.
   */
  public async getFile({ key }: { key: string }): Promise<{
    file: Uint8Array
    contentType: string
  } | null> {
    const command = new GetObjectCommand({
      Bucket: this._config.s3BucketName,
      Key: key,
    })

    const response = await this._client.send(command)
    if (!response.Body) {
      return null
    }
    const file = await response.Body.transformToByteArray()
    return {
      file: file,
      contentType: response.ContentType as string,
    }
  }

  /**
   * Uploads a file to the AWS S3 bucket.
   */
  public async uploadFile({
    extension,
    contentType,
    folder,
    file,
  }: {
    extension?: string | null
    contentType: string
    folder: string
    file: Uint8Array
  }): Promise<{
    file_url: string
    file_key: string
  }> {
    const Key = this.generateS3Key({ folder, extension })

    const command = new PutObjectCommand({
      Bucket: this._config.s3BucketName,
      Key,
      ContentType: contentType,
      Body: file,
      ACL: 'public-read',
    })

    await this._client.send(command)

    const file_url = this.getFileURL({ fileKey: Key })

    return {
      file_url,
      file_key: Key,
    }
  }

  /**
   * Returns information that you need to upload a file to the AWS S3 bucket.
   */
  public async getFileUploadParameters({
    extension,
    contentType,
    folder,
  }: {
    extension?: string | null
    contentType: string
    folder: string
  }): Promise<{
    file_url: string
    file_key: string
    upload_url: string
  }> {
    const Key = this.generateS3Key({ folder, extension })

    const command = new PutObjectCommand({
      // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
      Bucket: process.env.AWS_S3_BUCKET!,
      Key,
      ContentType: contentType,
      ACL: 'public-read',
    })
    const upload_url = await S3.getSignedUrl(this._client, command, { expiresIn: 3600 })

    const file_url = this.getFileURL({ fileKey: Key })

    return {
      upload_url,
      file_url,
      file_key: Key,
    }
  }

  /**
   * Returns a file key from a file url.
   */
  public getFileKey({ fileURL }: { fileURL: string }): string {
    return fileURL.replace(this._config.baseURL, '').replace(`${this._config.s3BucketName}/`, '')
  }

  /**
   * Converts file key to a public URL.
   */
  private getFileURL({ fileKey }: { fileKey: string }): string {
    return this._config.baseURL + this._config.s3BucketName + `/` + fileKey
  }

  private generateS3Key({ folder, extension }: { folder: string; extension?: string | null }): string {
    // S3 performance is tied to the file prefix. By creating more prefixes,
    // we improve S3 performance (https://docs.aws.amazon.com/AmazonS3/latest/dev/optimizing-performance.html).
    const subfolder = RandomUtils.generateRandomAlphaNumericString(2)
    const id = uuid()

    let key = `${folder}/${subfolder}/${id}`
    if (extension) {
      key += '.' + extension
    }
    return key
  }
}