sqlite3-worker1-promiser.js

/*
  2022-08-24

  The author disclaims copyright to this source code.  In place of a
  legal notice, here is a blessing:

  *   May you do good and not evil.
  *   May you find forgiveness for yourself and forgive others.
  *   May you share freely, never taking more than you give.

  ***********************************************************************

  This file implements a Promise-based proxy for the sqlite3 Worker
  API #1. It is intended to be included either from the main thread or
  a Worker, but only if (A) the environment supports nested Workers
  and (B) it's _not_ a Worker which loads the sqlite3 WASM/JS
  module. This file's features will load that module and provide a
  slightly simpler client-side interface than the slightly-lower-level
  Worker API does.

  This script necessarily exposes one global symbol, but clients may
  freely `delete` that symbol after calling it.
*/
'use strict';

globalThis.sqlite3Worker1Promiser = function callee(
  config = callee.defaultConfig,
) {
  if (1 === arguments.length && 'function' === typeof arguments[0]) {
    const f = config;
    config = Object.assign(Object.create(null), callee.defaultConfig);
    config.onready = f;
  } else {
    config = Object.assign(Object.create(null), callee.defaultConfig, config);
  }
  const handlerMap = Object.create(null);
  const noop = function () {};
  const err = config.onerror || noop;
  const debug = config.debug || noop;
  const idTypeMap = config.generateMessageId ? undefined : Object.create(null);
  const genMsgId =
    config.generateMessageId ||
    function (msg) {
      return (
        msg.type + '#' + (idTypeMap[msg.type] = (idTypeMap[msg.type] || 0) + 1)
      );
    };
  const toss = (...args) => {
    throw new Error(args.join(' '));
  };
  if (!config.worker) config.worker = callee.defaultConfig.worker;
  if ('function' === typeof config.worker) config.worker = config.worker();
  let dbId;
  let promiserFunc;
  config.worker.onmessage = function (ev) {
    ev = ev.data;
    debug('worker1.onmessage', ev);
    let msgHandler = handlerMap[ev.messageId];
    if (!msgHandler) {
      if (ev && 'sqlite3-api' === ev.type && 'worker1-ready' === ev.result) {
        if (config.onready) config.onready(promiserFunc);
        return;
      }
      msgHandler = handlerMap[ev.type];
      if (msgHandler && msgHandler.onrow) {
        msgHandler.onrow(ev);
        return;
      }
      if (config.onunhandled) config.onunhandled(arguments[0]);
      else err('sqlite3Worker1Promiser() unhandled worker message:', ev);
      return;
    }
    delete handlerMap[ev.messageId];
    switch (ev.type) {
      case 'error':
        msgHandler.reject(ev);
        return;
      case 'open':
        if (!dbId) dbId = ev.dbId;
        break;
      case 'close':
        if (ev.dbId === dbId) dbId = undefined;
        break;
      default:
        break;
    }
    try {
      msgHandler.resolve(ev);
    } catch (e) {
      msgHandler.reject(e);
    }
  };
  return (promiserFunc = function () {
    let msg;
    if (1 === arguments.length) {
      msg = arguments[0];
    } else if (2 === arguments.length) {
      msg = Object.create(null);
      msg.type = arguments[0];
      msg.args = arguments[1];
      msg.dbId = msg.args.dbId;
    } else {
      toss('Invalid arguments for sqlite3Worker1Promiser()-created factory.');
    }
    if (!msg.dbId && msg.type !== 'open') msg.dbId = dbId;
    msg.messageId = genMsgId(msg);
    msg.departureTime = performance.now();
    const proxy = Object.create(null);
    proxy.message = msg;
    let rowCallbackId;
    if ('exec' === msg.type && msg.args) {
      if ('function' === typeof msg.args.callback) {
        rowCallbackId = msg.messageId + ':row';
        proxy.onrow = msg.args.callback;
        msg.args.callback = rowCallbackId;
        handlerMap[rowCallbackId] = proxy;
      } else if ('string' === typeof msg.args.callback) {
        toss(
          'exec callback may not be a string when using the Promise interface.',
        );
      }
    }

    let p = new Promise(function (resolve, reject) {
      proxy.resolve = resolve;
      proxy.reject = reject;
      handlerMap[msg.messageId] = proxy;
      debug(
        'Posting',
        msg.type,
        'message to Worker dbId=' + (dbId || 'default') + ':',
        msg,
      );
      config.worker.postMessage(msg);
    });
    if (rowCallbackId) p = p.finally(() => delete handlerMap[rowCallbackId]);
    return p;
  });
};

globalThis.sqlite3Worker1Promiser.defaultConfig = {
  worker: function () {
    let theJs = 'sqlite3-worker1.js';
    if (this.currentScript) {
      const src = this.currentScript.src.split('/');
      src.pop();
      theJs = src.join('/') + '/' + theJs;
    } else if (globalThis.location) {
      const urlParams = new URL(globalThis.location.href).searchParams;
      if (urlParams.has('sqlite3.dir')) {
        theJs = urlParams.get('sqlite3.dir') + '/' + theJs;
      }
    }
    return new Worker(theJs + globalThis.location.search);
  }.bind({
    currentScript: globalThis?.document?.currentScript,
  }),
  onerror: (...args) => console.error('worker1 promiser error', ...args),
};

sqlite3Worker1Promiser.v2 = function (config) {
  let oldFunc;
  if ('function' == typeof config) {
    oldFunc = config;
    config = {};
  } else if ('function' === typeof config?.onready) {
    oldFunc = config.onready;
    delete config.onready;
  }
  const promiseProxy = Object.create(null);
  config = Object.assign(config || Object.create(null), {
    onready: async function (func) {
      try {
        if (oldFunc) await oldFunc(func);
        promiseProxy.resolve(func);
      } catch (e) {
        promiseProxy.reject(e);
      }
    },
  });
  const p = new Promise(function (resolve, reject) {
    promiseProxy.resolve = resolve;
    promiseProxy.reject = reject;
  });
  try {
    this.original(config);
  } catch (e) {
    promiseProxy.reject(e);
  }
  return p;
}.bind({
  original: sqlite3Worker1Promiser,
});