cistern / packages / producer / client.ts

import { produceRequirements } from "@cistern/shared";
import { encryptText } from "@cistern/crypto";
import type {
  ProducerOptions,
  ProducerParams,
  PublicKeyOption,
} from "./types.ts";
import { type Did, parse, type ResourceUri } from "@atcute/lexicons";
import type { Client } from "@atcute/client";
import { now } from "@atcute/tid";
import { type AppCisternMemo, AppCisternPubkey } from "@cistern/lexicon";

/**
 * Creates a `Producer` instance with all necessary requirements. This is the recommended way to construct a `Producer`.
 *
 * @description Resolves the user's DID using Slingshot, instantiates an `@atcute/client` instance, creates an initial session, and returns a new `Producer`. If a pubkey record key is provided, it will be resolved and set as the active key.
 * @param {ProducerOptions} options - Information for constructing the underlying XRPC client
 * @returns {Promise<Producer>} A Cistern producer client with an authorized session
 */
export async function createProducer(
  { publicKey: rkey, ...opts }: ProducerOptions,
): Promise<Producer> {
  const reqs = await produceRequirements(opts);

  let publicKey: PublicKeyOption | undefined;
  if (rkey) {
    const res = await reqs.rpc.get("com.atproto.repo.getRecord", {
      params: {
        repo: reqs.miniDoc.did,
        rkey,
        collection: "app.cistern.pubkey",
      },
    });

    if (!res.ok) {
      throw new Error(
        `invalid public key record ID ${publicKey}, got: ${res.status} ${res.data.error}`,
      );
    }

    const record = parse(AppCisternPubkey.mainSchema, res.data.value);

    publicKey = {
      uri: res.data.uri,
      name: record.name,
      content: record.content.$bytes,
    };
  }

  return new Producer({
    ...reqs,
    publicKey,
  });
}

/**
 * A client for encrypting and creating Cistern memos.
 */
export class Producer {
  /** DID of the user this producer acts on behalf of */
  did: Did;

  /** `@atcute/client` instance with credential manager */
  rpc: Client;

  /** Partial public key record, used for encrypting items */
  publicKey?: PublicKeyOption;

  constructor(params: ProducerParams) {
    this.did = params.miniDoc.did;
    this.rpc = params.rpc;
    this.publicKey = params.publicKey;
  }

  /**
   * Creates a memo and saves it as a record in the user's PDS.
   * @param {string} text - The contents of the memo you wish to create
   */
  async createMemo(text: string): Promise<ResourceUri> {
    if (!this.publicKey) {
      throw new Error(
        "no public key set; select a public key before creating a memo",
      );
    }

    const payload = encryptText(
      Uint8Array.fromBase64(this.publicKey.content),
      text,
    );
    const record: AppCisternMemo.Main = {
      $type: "app.cistern.memo",
      tid: now(),
      algorithm: "x_wing-xchacha20_poly1305-sha3_512",
      ciphertext: { $bytes: payload.cipherText },
      contentHash: { $bytes: payload.hash },
      contentLength: payload.length,
      nonce: { $bytes: payload.nonce },
      payload: { $bytes: payload.content },
      pubkey: this.publicKey.uri,
    };

    const res = await this.rpc.post("com.atproto.repo.createRecord", {
      input: {
        collection: "app.cistern.memo",
        repo: this.did,
        record,
      },
    });

    if (!res.ok) {
      throw new Error(
        `failed to create new memo: ${res.status} ${res.data.error}`,
      );
    }

    return res.data.uri;
  }

  /**
   * Lists public keys registered in the user's PDS
   */
  async *listPublicKeys(): AsyncGenerator<
    PublicKeyOption,
    void,
    void
  > {
    let cursor: string | undefined;

    while (true) {
      const res = await this.rpc.get("com.atproto.repo.listRecords", {
        params: {
          collection: "app.cistern.pubkey",
          repo: this.did,
          cursor,
        },
      });

      if (!res.ok) {
        throw new Error(
          `failed to list public keys: ${res.status} ${res.data.error}`,
        );
      }

      cursor = res.data.cursor;

      for (const record of res.data.records) {
        const memo = parse(AppCisternPubkey.mainSchema, record.value);

        yield {
          uri: record.uri,
          content: memo.content.$bytes,
          name: memo.name,
        };
      }

      if (!cursor) return;
    }
  }

  /**
   * Sets a public key as the main encryption key. This is not necessary to use if you instantiated the client with a public key.
   * @param {PublicKeyOption} key - The key you want to use for encryption
   */
  selectPublicKey(key: PublicKeyOption) {
    this.publicKey = key;
  }
}