import { isBrowser, isNode } from 'browser-or-node';
import { Action, Scry, Thread } from '@urbit/api';
import { fetchEventSource, EventSourceMessage, EventStreamContentType } from '@microsoft/fetch-event-source';

import { AuthenticationInterface, SubscriptionInterface, CustomEventHandler, PokeInterface, SubscriptionRequestInterface, headers, UrbitInterface, SSEOptions, PokeHandlers, Message } from './types';
import { uncamelize, hexString } from './utils';

/**
 * A class for interacting with an urbit ship, given its URL and code
 */
export class Urbit implements UrbitInterface {
  /**
   * UID will be used for the channel: The current unix time plus a random hex string
   */
  uid: string = `${Math.floor(Date.now() / 1000)}-${hexString(6)}`;

  /**
   * Last Event ID is an auto-updated index of which events have been sent over this channel
   */
  lastEventId: number = 0;

  lastAcknowledgedEventId: number = 0;

  /**
   * SSE Client is null for now; we don't want to start polling until it the channel exists
   */
  sseClientInitialized: boolean = false;

  /**
   * Cookie gets set when we log in.
   */
  cookie?: string | undefined;

  /**
   * A registry of requestId to successFunc/failureFunc
   * 
   * These functions are registered during a +poke and are executed
   * in the onServerEvent()/onServerError() callbacks. Only one of
   * the functions will be called, and the outstanding poke will be
   * removed after calling the success or failure function.
   */

  outstandingPokes: Map<number, PokeHandlers> = new Map();

  /**
   * A registry of requestId to subscription functions.
   * 
   * These functions are registered during a +subscribe and are
   * executed in the onServerEvent()/onServerError() callbacks. The
   * event function will be called whenever a new piece of data on this
   * subscription is available, which may be 0, 1, or many times. The
   * disconnect function may be called exactly once.
   */

  outstandingSubscriptions: Map<number, SubscriptionRequestInterface> = new Map();

  /**
   * Ship can be set, in which case we can do some magic stuff like send chats
   */
  ship?: string | null;

  /**
   * If verbose, logs output eagerly.
   */
  verbose?: boolean;

  onError?: (error: any) => void = null;

  /** This is basic interpolation to get the channel URL of an instantiated Urbit connection. */
  get channelUrl(): string {
    return `${this.url}/~/channel/${this.uid}`;
  }

  get fetchOptions(): any {
    const headers: headers = {
      'Content-Type': 'application/json',
    };
    if (!isBrowser) {
      headers.Cookie = this.cookie;
    }
    return {
      credentials: 'include',
      accept: '*',
      headers
    };
  }

  /**
   * Constructs a new Urbit connection.
   *
   * @param url  The URL (with protocol and port) of the ship to be accessed
   * @param code The access code for the ship at that address
   */
  constructor(
    public url: string,
    public code: string
  ) {
    if (isBrowser) {
      window.addEventListener('beforeunload', this.delete);
    }
    return this;
  }

  /**
   * All-in-one hook-me-up.
   * 
   * Given a ship, url, and code, this returns an airlock connection
   * that is ready to go. It `|hi`s itself to create the channel,
   * then opens the channel via EventSource.
   * 
   * @param AuthenticationInterface
   */
  static async authenticate({ ship, url, code, verbose = false }: AuthenticationInterface) {
    const airlock = new Urbit(`http://${url}`, code);
    airlock.verbose = verbose;
    airlock.ship = ship;
    await airlock.connect();
    await airlock.poke({ app: 'hood', mark: 'helm-hi', json: 'opening airlock' });
    await airlock.eventSource();
    return airlock;
  }

  /**
   * Connects to the Urbit ship. Nothing can be done until this is called.
   * That's why we roll it into this.authenticate
   */
  async connect(): Promise<void> {
    if (this.verbose) {
      console.log(`password=${this.code} `, isBrowser ? "Connecting in browser context at " + `${this.url}/~/login` : "Connecting from node context");
    }
    return fetch(`${this.url}/~/login`, {
      method: 'post',
      body: `password=${this.code}`,
      credentials: 'include',
    }).then(response => {
      if (this.verbose) {
        console.log('Received authentication response', response);
      }
      const cookie = response.headers.get('set-cookie');
      if (!this.ship) {
        this.ship = new RegExp(/urbauth-~([\w-]+)/).exec(cookie)[1];
      }
      if (!isBrowser) {
        this.cookie = cookie;
      }
    });
  }
  

  /**
   * Initializes the SSE pipe for the appropriate channel.
   */
  eventSource(): void {
    if (!this.sseClientInitialized) {
      const sseOptions: SSEOptions = {
        headers: {}
      };
      if (isBrowser) {
        sseOptions.withCredentials = true;
      } else if (isNode) {
        sseOptions.headers.Cookie = this.cookie;
      }
      if (this.lastEventId === 0) {
        // Can't receive events until the channel is open
        this.poke({ app: 'hood', mark: 'helm-hi', json: 'Opening API channel' });
      }
      fetchEventSource(this.channelUrl, {
        ...this.fetchOptions,
        openWhenHidden: true,
        onopen: async (response) => {
          if (this.verbose) {
            console.log('Opened eventsource', response);
          }
          if (response.ok && response.headers.get('content-type') === EventStreamContentType) {
            return; // everything's good
          } else if (response.status >= 400 && response.status < 500 && response.status !== 429) {
            if (this.onError) {
              this.onError(response.statusText);
            } else {
              throw new Error();
            }
          } else {
            if (this.onError) {
              this.onError(response.statusText);
            } else {
              throw new Error();
            }
          }
        },
        onmessage: (event: EventSourceMessage) => {
          if (this.verbose) {
            console.log('Received SSE: ', event);
          }
          if (!event.id) return;
          this.ack(Number(event.id));
          if (event.data && JSON.parse(event.data)) {
            
            const data: any = JSON.parse(event.data);

            if (data.response === 'diff') {
              this.clearQueue();
            }

            if (data.response === 'poke' && this.outstandingPokes.has(data.id)) {
              const funcs = this.outstandingPokes.get(data.id);
              if (data.hasOwnProperty('ok')) {
                funcs.onSuccess();
              } else if (data.hasOwnProperty('err')) {
                funcs.onError(data.err);
              } else {
                console.error('Invalid poke response', data);
              }
              this.outstandingPokes.delete(data.id);
            } else if (data.response === 'subscribe' || 
              (data.response === 'poke' && this.outstandingSubscriptions.has(data.id))) {
              const funcs = this.outstandingSubscriptions.get(data.id);
              if (data.hasOwnProperty('err')) {
                funcs.err(data.err);
                this.outstandingSubscriptions.delete(data.id);
              }
            } else if (data.response === 'diff' && this.outstandingSubscriptions.has(data.id)) {
              const funcs = this.outstandingSubscriptions.get(data.id);
              funcs.event(data.json);
            } else if (data.response === 'quit' && this.outstandingSubscriptions.has(data.id)) {
              const funcs = this.outstandingSubscriptions.get(data.id);
              funcs.quit(data);
              this.outstandingSubscriptions.delete(data.id);
            } else {
              console.log('Unrecognized response', data);
            }
          }
        },
        onerror: (error) => {
          if (this.onError) {
            this.onError(error);
          } else {
            throw error;
          }
        }
      });
      this.sseClientInitialized = true;
    }
    return;
  }

  /**
   * Autoincrements the next event ID for the appropriate channel.
   */
  getEventId(): number {
    this.lastEventId = Number(this.lastEventId) + 1;
    return this.lastEventId;
  }

  /**
   * Acknowledges an event.
   *
   * @param eventId The event to acknowledge.
   */
  async ack(eventId: number): Promise<number | void> {
    const message: Message = {
      action: 'ack',
      'event-id': eventId
    };
    await this.sendJSONtoChannel(message);
    return eventId;
  }

  /**
   * This is a wrapper method that can be used to send any action with data.
   *
   * Every message sent has some common parameters, like method, headers, and data
   * structure, so this method exists to prevent duplication.
   *
   * @param action The action to send
   * @param data The data to send with the action
   * 
   * @returns void | number If successful, returns the number of the message that was sent
   */
  // async sendMessage(action: Action, data?: object): Promise<number | void> {
  //   const id = this.getEventId();
  //   if (this.verbose) {
  //     console.log(`Sending message ${id}:`, action, data,);
  //   }
  //   const message: Message = { id, action, ...data };
  //   await this.sendJSONtoChannel(message);
  //   return id;
  // }

  outstandingJSON: Message[] = [];

  debounceTimer: any = null;
  debounceInterval = 500;
  calm = true;

  sendJSONtoChannel(json: Message): Promise<boolean | void> {
    this.outstandingJSON.push(json);
    return this.processQueue();
  }

  processQueue(): Promise<boolean | void> {
    return new Promise(async (resolve, reject) => {
      const process = async () => {
        if (this.calm) {
          if (this.outstandingJSON.length === 0) resolve(true);
          this.calm = false; // We are now occupied
          const json = this.outstandingJSON;
          const body = JSON.stringify(json);
          this.outstandingJSON = [];
          if (body === '[]') {
            this.calm = true;
            return resolve(false);
          }
          try {
            await fetch(this.channelUrl, {
              ...this.fetchOptions,
              method: 'PUT',
              body
            });
          } catch (error) {
            json.forEach(failed => this.outstandingJSON.push(failed));
            if (this.onError) {
              this.onError(error);
            } else {
              throw error;
            }
          }
          this.calm = true;
          if (!this.sseClientInitialized) {
            this.eventSource(); // We can open the channel for subscriptions once we've sent data over it
          }
          resolve(true);
        } else {
          clearTimeout(this.debounceTimer);
          this.debounceTimer = setTimeout(process, this.debounceInterval);
          resolve(false);
        }
      }
  
      this.debounceTimer = setTimeout(process, this.debounceInterval);

      
    });
  }

  

  // resetDebounceTimer() {
  //   if (this.debounceTimer) {
  //     clearTimeout(this.debounceTimer);
  //     this.debounceTimer = null;
  //   }
  //   this.calm = false;
  //   this.debounceTimer = setTimeout(() => {
  //     this.calm = true;
  //   }, this.debounceInterval);
  // }

  clearQueue() {
    clearTimeout(this.debounceTimer);
    this.debounceTimer = null;
  }

  /**
   * Pokes a ship with data.
   *
   * @param app The app to poke
   * @param mark The mark of the data being sent
   * @param json The data to send
   */
  poke<T>(params: PokeInterface<T>): Promise<number> {
    const {
      app,
      mark,
      json,
      ship,
      onSuccess,
      onError
    } = {
      onSuccess: () => { },
      onError: () => { },
      ship: this.ship,
      ...params
    };
    return new Promise((resolve, reject) => {
      const message: Message = {
        id: this.getEventId(),
        action: 'poke',
        ship,
        app,
        mark,
        json
      };
      this.outstandingPokes.set(message.id, {
        onSuccess: () => {
          onSuccess();
          resolve(message.id);
        },
        onError: (event) => {
          onError(event);
          reject(event.err);
        }
      });
      this.sendJSONtoChannel(message).then(() => {
        resolve(message.id);
      });
    });
  }

  /**
   * Subscribes to a path on an app on a ship.
   *
   * @param app The app to subsribe to
   * @param path The path to which to subscribe
   * @param handlers Handlers to deal with various events of the subscription
   */
  async subscribe(params: SubscriptionRequestInterface): Promise<number> {
    const {
      app,
      path,
      ship,
      err,
      event,
      quit
    } = {
      err: () => { },
      event: () => { },
      quit: () => { },
      ship: this.ship,
      ...params
    };

    const message: Message = {
      id: this.getEventId(),
      action: 'subscribe',
      ship,
      app,
      path
    };

    this.outstandingSubscriptions.set(message.id, {
      app, path, err, event, quit
    });

    await this.sendJSONtoChannel(message);
    
    return message.id;
  }

  /**
   * Unsubscribes to a given subscription.
   *
   * @param subscription
   */
  async unsubscribe(subscription: number) {
    return this.sendJSONtoChannel({
      id: this.getEventId(),
      action: 'unsubscribe',
      subscription
    }).then(() => {
      this.outstandingSubscriptions.delete(subscription);
    });
  }

  /**
   * Deletes the connection to a channel.
   */
  delete() {
    if (isBrowser) {
      navigator.sendBeacon(this.channelUrl, JSON.stringify([{
        action: 'delete'
      }]));
    } else {
      // TODO
      // this.sendMessage('delete');
    }
  }

  /**
   * 
   * @param app   The app into which to scry
   * @param path  The path at which to scry
   */
  async scry(params: Scry): Promise<void | any> {
    const { app, path } = params;
    const response = await fetch(`${this.url}/~/scry/${app}${path}.json`, this.fetchOptions);
    return await response.json();
  }

  /**
   * 
   * @param inputMark   The mark of the data being sent
   * @param outputMark  The mark of the data being returned
   * @param threadName  The thread to run
   * @param body        The data to send to the thread
   */
  async thread<T>(params: Thread<T>): Promise<T> {
    const { inputMark, outputMark, threadName, body } = params;
    const res = await fetch(`${this.url}/spider/${inputMark}/${threadName}/${outputMark}.json`, {
      ...this.fetchOptions,
      method: 'POST',
      body: JSON.stringify(body)
    });

    return res.json();
  }

  /**
   * Utility function to connect to a ship that has its *.arvo.network domain configured.
   *
   * @param name Name of the ship e.g. zod
   * @param code Code to log in
   */
  static async onArvoNetwork(ship: string, code: string): Promise<Urbit> {
    const url = `https://${ship}.arvo.network`;
    return await Urbit.authenticate({ ship, url, code });
  }
}



export default Urbit;