import { EventEmitter2 } from "eventemitter2";

import { stringifyQuery } from "talk-common/utils";
import ensureNoEndSlash from "talk-common/utils/ensureNoEndSlash";
import urls from "talk-framework/helpers/urls";
import { ExternalConfig } from "talk-framework/lib/externalConfig";

import {
  Decorator,
  withAutoHeight,
  withClickEvent,
  withConfig,
  withEventEmitter,
  withIOSSafariWidthWorkaround,
  withPymStorage,
  withSetCommentID,
} from "./decorators";
import onIntersect, { OnIntersectCancellation } from "./onIntersect";
import PymControl, {
  defaultPymControlFactory,
  PymControlFactory,
} from "./PymControl";

export interface StreamEmbedConfig {
  storyID?: string;
  storyURL?: string;
  commentID?: string;
  autoRender?: boolean;
  title: string;
  eventEmitter: EventEmitter2;
  id: string;
  rootURL: string;
  authToken?: string;
}

export class StreamEmbed {
  private config: StreamEmbedConfig;
  private pymControl?: PymControl;
  private pymControlFactory: PymControlFactory;
  private ready = false;
  private cancelAutoRender: OnIntersectCancellation | null = null;

  constructor(
    config: StreamEmbedConfig,
    pymControlFactory = defaultPymControlFactory
  ) {
    this.config = config;
    this.pymControlFactory = pymControlFactory;
    if (config.commentID) {
      // Delay emit of `showPermalink` event to allow
      // user enough time to setup event listeners.
      setTimeout(() => config.eventEmitter.emit("showPermalink"), 0);
    }
    if (config.autoRender) {
      if (config.commentID) {
        this.render();
      } else {
        this.cancelAutoRender = onIntersect(
          document.getElementById(config.id)!,
          () => {
            this.cancelAutoRender = null;
            if (!this.rendered) {
              this.render();
            }
          }
        );
      }
    }
    config.eventEmitter.once("ready", () => {
      this.ready = true;
    });
  }

  private assertRendered() {
    if (!this.pymControl) {
      throw new Error("Stream Embed must be rendered first");
    }
  }

  public on(eventName: string, callback: (data: any) => void) {
    return this.config.eventEmitter.on(eventName, callback);
  }

  public off(eventName: string, callback: (data: any) => void) {
    return this.config.eventEmitter.off(eventName, callback);
  }

  public login(token: string) {
    if (!this.ready) {
      this.config.eventEmitter.once("ready", () => this.login(token));
      return;
    }
    this.pymControl!.sendMessage("login", token);
  }

  public logout() {
    if (!this.ready) {
      this.config.eventEmitter.once("ready", () => this.logout());
      return;
    }
    this.pymControl!.sendMessage("logout");
  }

  public remove() {
    // If lazy render was enabled, just cancel it.
    if (this.cancelAutoRender) {
      this.cancelAutoRender();
      this.cancelAutoRender = null;
      return;
    }
    this.assertRendered();
    this.pymControl!.remove();
    this.pymControl = undefined;
  }

  get rendered() {
    return !!this.pymControl;
  }

  public render() {
    if (this.pymControl) {
      throw new Error("Stream Embed already rendered");
    }

    const externalConfig: ExternalConfig = {
      authToken: this.config.authToken,
    };

    const streamDecorators: ReadonlyArray<Decorator> = [
      withIOSSafariWidthWorkaround,
      withAutoHeight,
      withClickEvent,
      withSetCommentID,
      withEventEmitter(this.config.eventEmitter),
      withPymStorage(localStorage, "localStorage"),
      withPymStorage(sessionStorage, "sessionStorage"),
      withConfig(externalConfig),
    ];

    const query = stringifyQuery({
      storyID: this.config.storyID,
      storyURL: this.config.storyURL,
      commentID: this.config.commentID,
    });

    const url = `${ensureNoEndSlash(this.config.rootURL)}${urls.embed.stream}${
      query ? `?${query}` : ""
    }`;
    this.pymControl = this.pymControlFactory({
      id: this.config.id,
      title: this.config.title,
      decorators: streamDecorators,
      url,
    });
  }
}

export default function createStreamEmbed(config: StreamEmbedConfig) {
  return new StreamEmbed(config);
}