// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.

/// <reference path="../../core/internal.d.ts" />

import { core, primordials } from "ext:core/mod.js";

import * as webidl from "ext:deno_webidl/00_webidl.js";
import { createFilteredInspectProxy } from "ext:deno_console/01_console.js";
import { URL } from "ext:deno_url/00_url.js";
import DOMException from "ext:deno_web/01_dom_exception.js";
import {
  defineEventHandler,
  EventTarget,
  setIsTrusted,
} from "ext:deno_web/02_event.js";
import { TransformStream } from "ext:deno_web/06_streams.js";
import { TextDecoderStream } from "ext:deno_web/08_text_encoding.js";
import { getLocationHref } from "ext:deno_web/12_location.js";
import { newInnerRequest } from "ext:deno_fetch/23_request.js";
import { mainFetch } from "ext:deno_fetch/26_fetch.js";

const {
  ArrayPrototypeFind,
  Number,
  NumberIsFinite,
  NumberIsNaN,
  ObjectDefineProperties,
  ObjectPrototypeIsPrototypeOf,
  Promise,
  StringPrototypeEndsWith,
  StringPrototypeIncludes,
  StringPrototypeIndexOf,
  StringPrototypeSlice,
  StringPrototypeSplit,
  StringPrototypeStartsWith,
  StringPrototypeToLowerCase,
  Symbol,
  SymbolFor,
} = primordials;

// Copied from https://github.com/denoland/deno_std/blob/e0753abe0c8602552862a568348c046996709521/streams/text_line_stream.ts#L20-L74
export class TextLineStream extends TransformStream {
  #allowCR;
  #buf = "";

  constructor(options) {
    super({
      transform: (chunk, controller) => this.#handle(chunk, controller),
      flush: (controller) => {
        if (this.#buf.length > 0) {
          if (
            this.#allowCR &&
            this.#buf[this.#buf.length - 1] === "\r"
          ) controller.enqueue(StringPrototypeSlice(this.#buf, 0, -1));
          else controller.enqueue(this.#buf);
        }
      },
    });
    this.#allowCR = options?.allowCR ?? false;
  }

  #handle(chunk, controller) {
    chunk = this.#buf + chunk;

    for (;;) {
      const lfIndex = StringPrototypeIndexOf(chunk, "\n");

      if (this.#allowCR) {
        const crIndex = StringPrototypeIndexOf(chunk, "\r");

        if (
          crIndex !== -1 && crIndex !== (chunk.length - 1) &&
          (lfIndex === -1 || (lfIndex - 1) > crIndex)
        ) {
          controller.enqueue(StringPrototypeSlice(chunk, 0, crIndex));
          chunk = StringPrototypeSlice(chunk, crIndex + 1);
          continue;
        }
      }

      if (lfIndex !== -1) {
        let crOrLfIndex = lfIndex;
        if (chunk[lfIndex - 1] === "\r") {
          crOrLfIndex--;
        }
        controller.enqueue(StringPrototypeSlice(chunk, 0, crOrLfIndex));
        chunk = StringPrototypeSlice(chunk, lfIndex + 1);
        continue;
      }

      break;
    }

    this.#buf = chunk;
  }
}

const CONNECTING = 0;
const OPEN = 1;
const CLOSED = 2;

const _url = Symbol("[[url]]");
const _withCredentials = Symbol("[[withCredentials]]");
const _readyState = Symbol("[[readyState]]");
const _reconnectionTime = Symbol("[[reconnectionTime]]");
const _lastEventID = Symbol("[[lastEventID]]");
const _abortController = Symbol("[[abortController]]");
const _loop = Symbol("[[loop]]");

class EventSource extends EventTarget {
  /** @type {AbortController} */
  [_abortController] = new AbortController();

  /** @type {number} */
  [_reconnectionTime] = 5000;

  /** @type {string} */
  [_lastEventID] = "";

  /** @type {number} */
  [_readyState] = CONNECTING;
  get readyState() {
    webidl.assertBranded(this, EventSourcePrototype);
    return this[_readyState];
  }

  get CONNECTING() {
    webidl.assertBranded(this, EventSourcePrototype);
    return CONNECTING;
  }
  get OPEN() {
    webidl.assertBranded(this, EventSourcePrototype);
    return OPEN;
  }
  get CLOSED() {
    webidl.assertBranded(this, EventSourcePrototype);
    return CLOSED;
  }

  /** @type {string} */
  [_url];
  get url() {
    webidl.assertBranded(this, EventSourcePrototype);
    return this[_url];
  }

  /** @type {boolean} */
  [_withCredentials];
  get withCredentials() {
    webidl.assertBranded(this, EventSourcePrototype);
    return this[_withCredentials];
  }

  constructor(url, eventSourceInitDict = {}) {
    super();
    this[webidl.brand] = webidl.brand;
    const prefix = "Failed to construct 'EventSource'";
    webidl.requiredArguments(arguments.length, 1, {
      prefix,
    });
    url = webidl.converters.USVString(url, {
      prefix,
      context: "Argument 1",
    });
    eventSourceInitDict = webidl.converters.EventSourceInit(
      eventSourceInitDict,
      {
        prefix,
        context: "Argument 2",
      },
    );

    try {
      url = new URL(url, getLocationHref()).href;
    } catch (e) {
      throw new DOMException(e.message, "SyntaxError");
    }

    this[_url] = url;
    this[_withCredentials] = eventSourceInitDict.withCredentials;

    this[_loop]();
  }

  close() {
    webidl.assertBranded(this, EventSourcePrototype);
    this[_abortController].abort();
    this[_readyState] = CLOSED;
  }

  async [_loop]() {
    let lastEventIDValue = "";
    while (this[_readyState] !== CLOSED) {
      const lastEventIDValueCopy = lastEventIDValue;
      lastEventIDValue = "";
      const req = newInnerRequest(
        "GET",
        this[_url],
        () =>
          lastEventIDValueCopy === ""
            ? [
              ["accept", "text/event-stream"],
            ]
            : [
              ["accept", "text/event-stream"],
              [
                "Last-Event-Id",
                core.ops.op_utf8_to_byte_string(lastEventIDValueCopy),
              ],
            ],
        null,
        false,
      );
      /** @type {InnerResponse} */
      const res = await mainFetch(req, true, this[_abortController].signal);

      const contentType = ArrayPrototypeFind(
        res.headerList,
        (header) => StringPrototypeToLowerCase(header[0]) === "content-type",
      );
      if (res.type === "error") {
        if (res.aborted) {
          this[_readyState] = CLOSED;
          this.dispatchEvent(new Event("error"));
          break;
        } else {
          if (this[_readyState] === CLOSED) {
            this[_abortController].abort();
            break;
          }
          this[_readyState] = CONNECTING;
          this.dispatchEvent(new Event("error"));
          await new Promise((res) => setTimeout(res, this[_reconnectionTime]));
          if (this[_readyState] !== CONNECTING) {
            continue;
          }

          if (this[_lastEventID] !== "") {
            lastEventIDValue = this[_lastEventID];
          }
          continue;
        }
      } else if (
        res.status !== 200 ||
        !StringPrototypeIncludes(
          contentType?.[1].toLowerCase(),
          "text/event-stream",
        )
      ) {
        this[_readyState] = CLOSED;
        this.dispatchEvent(new Event("error"));
        break;
      }

      if (this[_readyState] !== CLOSED) {
        this[_readyState] = OPEN;
        this.dispatchEvent(new Event("open"));

        let data = "";
        let eventType = "";
        let lastEventID = this[_lastEventID];

        for await (
          // deno-lint-ignore prefer-primordials
          const chunk of res.body.stream
            .pipeThrough(new TextDecoderStream())
            .pipeThrough(new TextLineStream({ allowCR: true }))
        ) {
          if (chunk === "") {
            this[_lastEventID] = lastEventID;
            if (data === "") {
              eventType = "";
              continue;
            }
            if (StringPrototypeEndsWith(data, "\n")) {
              data = StringPrototypeSlice(data, 0, -1);
            }
            const event = new MessageEvent(eventType || "message", {
              data,
              origin: res.url(),
              lastEventId: this[_lastEventID],
            });
            setIsTrusted(event, true);
            data = "";
            eventType = "";
            if (this[_readyState] !== CLOSED) {
              this.dispatchEvent(event);
            }
          } else if (StringPrototypeStartsWith(chunk, ":")) {
            continue;
          } else {
            let field = chunk;
            let value = "";
            if (StringPrototypeIncludes(chunk, ":")) {
              ({ 0: field, 1: value } = StringPrototypeSplit(chunk, ":"));
              if (StringPrototypeStartsWith(value, " ")) {
                value = StringPrototypeSlice(value, 1);
              }
            }

            switch (field) {
              case "event": {
                eventType = value;
                break;
              }
              case "data": {
                data += value + "\n";
                break;
              }
              case "id": {
                if (!StringPrototypeIncludes(value, "\0")) {
                  lastEventID = value;
                }
                break;
              }
              case "retry": {
                const reconnectionTime = Number(value);
                if (
                  !NumberIsNaN(reconnectionTime) &&
                  NumberIsFinite(reconnectionTime)
                ) {
                  this[_reconnectionTime] = reconnectionTime;
                }
                break;
              }
            }
          }

          if (this[_abortController].signal.aborted) {
            break;
          }
        }
        if (this[_readyState] === CLOSED) {
          this[_abortController].abort();
          break;
        }
        this[_readyState] = CONNECTING;
        this.dispatchEvent(new Event("error"));
        await new Promise((res) => setTimeout(res, this[_reconnectionTime]));
        if (this[_readyState] !== CONNECTING) {
          continue;
        }

        if (this[_lastEventID] !== "") {
          lastEventIDValue = this[_lastEventID];
        }
      }
    }
  }

  [SymbolFor("Deno.privateCustomInspect")](inspect, inspectOptions) {
    return inspect(
      createFilteredInspectProxy({
        object: this,
        evaluate: ObjectPrototypeIsPrototypeOf(EventSourcePrototype, this),
        keys: [
          "readyState",
          "url",
          "withCredentials",
          "onopen",
          "onmessage",
          "onerror",
        ],
      }),
      inspectOptions,
    );
  }
}

const EventSourcePrototype = EventSource.prototype;

ObjectDefineProperties(EventSource, {
  CONNECTING: {
    value: 0,
  },
  OPEN: {
    value: 1,
  },
  CLOSED: {
    value: 2,
  },
});

defineEventHandler(EventSource.prototype, "open");
defineEventHandler(EventSource.prototype, "message");
defineEventHandler(EventSource.prototype, "error");

webidl.converters.EventSourceInit = webidl.createDictionaryConverter(
  "EventSourceInit",
  [
    {
      key: "withCredentials",
      defaultValue: false,
      converter: webidl.converters.boolean,
    },
  ],
);

export { EventSource };