// Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.

const core = globalThis.Deno.core;
const ops = core.ops;
const primordials = globalThis.__bootstrap.primordials;
const {
  Error,
  ObjectPrototypeIsPrototypeOf,
  StringPrototypeStartsWith,
  String,
  SymbolIterator,
  SymbolToStringTag,
} = primordials;
import * as webidl from "internal:ext/webidl/00_webidl.js";
import { URL } from "internal:ext/url/00_url.js";
import { getLocationHref } from "internal:ext/web/12_location.js";
import { serializePermissions } from "internal:runtime/js/10_permissions.js";
import { log } from "internal:runtime/js/06_util.js";
import {
  defineEventHandler,
  ErrorEvent,
  EventTarget,
  MessageEvent,
} from "internal:ext/web/02_event.js";
import {
  deserializeJsMessageData,
  MessagePortPrototype,
  serializeJsMessageData,
} from "internal:ext/web/13_message_port.js";

function createWorker(
  specifier,
  hasSourceCode,
  sourceCode,
  permissions,
  name,
  workerType,
) {
  return ops.op_create_worker({
    hasSourceCode,
    name,
    permissions: serializePermissions(permissions),
    sourceCode,
    specifier,
    workerType,
  });
}

function hostTerminateWorker(id) {
  ops.op_host_terminate_worker(id);
}

function hostPostMessage(id, data) {
  ops.op_host_post_message(id, data);
}

function hostRecvCtrl(id) {
  return core.opAsync("op_host_recv_ctrl", id);
}

function hostRecvMessage(id) {
  return core.opAsync("op_host_recv_message", id);
}

class Worker extends EventTarget {
  #id = 0;
  #name = "";

  // "RUNNING" | "CLOSED" | "TERMINATED"
  // "TERMINATED" means that any controls or messages received will be
  // discarded. "CLOSED" means that we have received a control
  // indicating that the worker is no longer running, but there might
  // still be messages left to receive.
  #status = "RUNNING";

  constructor(specifier, options = {}) {
    super();
    specifier = String(specifier);
    const {
      deno,
      name,
      type = "classic",
    } = options;

    const workerType = webidl.converters["WorkerType"](type);

    if (
      StringPrototypeStartsWith(specifier, "./") ||
      StringPrototypeStartsWith(specifier, "../") ||
      StringPrototypeStartsWith(specifier, "/") || workerType === "classic"
    ) {
      const baseUrl = getLocationHref();
      if (baseUrl != null) {
        specifier = new URL(specifier, baseUrl).href;
      }
    }

    this.#name = name;
    let hasSourceCode, sourceCode;
    if (workerType === "classic") {
      hasSourceCode = true;
      sourceCode = `importScripts("#");`;
    } else {
      hasSourceCode = false;
      sourceCode = "";
    }

    const id = createWorker(
      specifier,
      hasSourceCode,
      sourceCode,
      deno?.permissions,
      name,
      workerType,
    );
    this.#id = id;
    this.#pollControl();
    this.#pollMessages();
  }

  #handleError(e) {
    const event = new ErrorEvent("error", {
      cancelable: true,
      message: e.message,
      lineno: e.lineNumber ? e.lineNumber : undefined,
      colno: e.columnNumber ? e.columnNumber : undefined,
      filename: e.fileName,
      error: null,
    });

    this.dispatchEvent(event);
    // Don't bubble error event to window for loader errors (`!e.fileName`).
    // TODO(nayeemrmn): It's not correct to use `e.fileName` to detect user
    // errors. It won't be there for non-awaited async ops for example.
    if (e.fileName && !event.defaultPrevented) {
      globalThis.dispatchEvent(event);
    }

    return event.defaultPrevented;
  }

  #pollControl = async () => {
    while (this.#status === "RUNNING") {
      const { 0: type, 1: data } = await hostRecvCtrl(this.#id);

      // If terminate was called then we ignore all messages
      if (this.#status === "TERMINATED") {
        return;
      }

      switch (type) {
        case 1: { // TerminalError
          this.#status = "CLOSED";
        } /* falls through */
        case 2: { // Error
          if (!this.#handleError(data)) {
            throw new Error("Unhandled error in child worker.");
          }
          break;
        }
        case 3: { // Close
          log(`Host got "close" message from worker: ${this.#name}`);
          this.#status = "CLOSED";
          return;
        }
        default: {
          throw new Error(`Unknown worker event: "${type}"`);
        }
      }
    }
  };

  #pollMessages = async () => {
    while (this.#status !== "TERMINATED") {
      const data = await hostRecvMessage(this.#id);
      if (this.#status === "TERMINATED" || data === null) {
        return;
      }
      let message, transferables;
      try {
        const v = deserializeJsMessageData(data);
        message = v[0];
        transferables = v[1];
      } catch (err) {
        const event = new MessageEvent("messageerror", {
          cancelable: false,
          data: err,
        });
        this.dispatchEvent(event);
        return;
      }
      const event = new MessageEvent("message", {
        cancelable: false,
        data: message,
        ports: transferables.filter((t) =>
          ObjectPrototypeIsPrototypeOf(MessagePortPrototype, t)
        ),
      });
      this.dispatchEvent(event);
    }
  };

  postMessage(message, transferOrOptions = {}) {
    const prefix = "Failed to execute 'postMessage' on 'MessagePort'";
    webidl.requiredArguments(arguments.length, 1, { prefix });
    message = webidl.converters.any(message);
    let options;
    if (
      webidl.type(transferOrOptions) === "Object" &&
      transferOrOptions !== undefined &&
      transferOrOptions[SymbolIterator] !== undefined
    ) {
      const transfer = webidl.converters["sequence<object>"](
        transferOrOptions,
        { prefix, context: "Argument 2" },
      );
      options = { transfer };
    } else {
      options = webidl.converters.StructuredSerializeOptions(
        transferOrOptions,
        {
          prefix,
          context: "Argument 2",
        },
      );
    }
    const { transfer } = options;
    const data = serializeJsMessageData(message, transfer);
    if (this.#status === "RUNNING") {
      hostPostMessage(this.#id, data);
    }
  }

  terminate() {
    if (this.#status !== "TERMINATED") {
      this.#status = "TERMINATED";
      hostTerminateWorker(this.#id);
    }
  }

  [SymbolToStringTag] = "Worker";
}

defineEventHandler(Worker.prototype, "error");
defineEventHandler(Worker.prototype, "message");
defineEventHandler(Worker.prototype, "messageerror");

webidl.converters["WorkerType"] = webidl.createEnumConverter("WorkerType", [
  "classic",
  "module",
]);

export { Worker };