blob-store.ts

import { GetObjectCommand, PutObjectCommand } from "@aws-sdk/client-s3";
import stableStringify from "fast-json-stable-stringify";
import forge from "node-forge";
import { createS3Client } from "./client-aws";
import { streamToString } from "./stream-ultils";

function get128BitHash(input: string): string {
  const messageDigest = forge.md.md5.create();
  messageDigest.update(input);
  return messageDigest.digest().toHex();
}

// S3-backed POJO dictionary
export class BlobStore<TKey, TItem> {
  constructor(private bucketName: string, private prefix: string) {}

  private getS3Key(key: TKey): string {
    const hashedItemKey = get128BitHash(stableStringify(key));
    const s3Key = this.prefix + hashedItemKey;
    return s3Key;
  }

  async set(key: TKey, item: TItem): Promise<void> {
    await createS3Client().send(
      new PutObjectCommand({
        Bucket: this.bucketName,
        Key: this.getS3Key(key),
        Body: JSON.stringify(item),
      })
    );
  }

  async get(key: TKey): Promise<TItem> {
    const item = await createS3Client().send(
      new GetObjectCommand({
        Bucket: this.bucketName,
        Key: this.getS3Key(key),
      })
    );
    const str = await streamToString(item.Body);
    return JSON.parse(str) as TItem;
  }
}