import { EventTarget } from "./event-target";
import { messageFrom,Message, TypeMessage } from "./message";
import { RPCError } from "./rpc-error";
import SockJS from 'sockjs-client';

const EventTypeMessage = "message";

export class Client extends EventTarget {

  _conn: any
  _rpcID: number
  _pendingRPC: {}
  _queue: Message[]
  _reconnectionDelay: number
  _autoReconnect: boolean
  debug: boolean

  constructor(autoReconnect = true) {
    super();
    this._conn = null;
    this._onConnectionClose = this._onConnectionClose.bind(this);
    this._onConnectionMessage = this._onConnectionMessage.bind(this);
    this._handleRPCResponse = this._handleRPCResponse.bind(this);
    this._rpcID = 0;
    this._pendingRPC = {};
    this._queue = [];
    this._reconnectionDelay = 250;
    this._autoReconnect = autoReconnect;

    this.debug = false;
    
    this.connect = this.connect.bind(this);
    this.disconnect = this.disconnect.bind(this);
    this.rpc = this.rpc.bind(this);
    this.send = this.send.bind(this);
    this.upload = this.upload.bind(this);

    this.addEventListener("message", this._handleRPCResponse);
  }

  connect(token = "") {
    return new Promise((resolve, reject) => {
      const url = `//${document.location.host}/edge/sock?token=${token}`;
      this._log("opening connection to", url);
      const conn: any = new SockJS(url);

      const onOpen = () => {
        this._log('client connected');
        resetHandlers();
        conn.onclose = this._onConnectionClose;
        conn.onmessage = this._onConnectionMessage;
        this._conn = conn;
        this._sendQueued();
        setTimeout(() => {
          this._dispatchConnect();
        }, 0);
        return resolve(this);
      };

      const onError = (evt) => {
        resetHandlers();
        this._scheduleReconnection();
        return reject(evt);
      };

      const resetHandlers = () => {
        conn.removeEventListener('open', onOpen);
        conn.removeEventListener('close', onError);
        conn.removeEventListener('error', onError);
      };
      
      conn.addEventListener('open', onOpen);
      conn.addEventListener('error', onError);
      conn.addEventListener('close', onError);
    });
  }

  disconnect() {
    this._cleanupConnection();
  }

  _onConnectionMessage(evt) {
    const rawMessage = JSON.parse(evt.data);
    const message = messageFrom(rawMessage);
    const event = new CustomEvent(message.getType(), {
      cancelable: true,
      detail: message.getPayload()
    });
    this.dispatchEvent(event);
  }

  _handleRPCResponse(evt) {
    const { jsonrpc, id, error, result } = evt.detail;
    
    if (jsonrpc !== '2.0' || id === undefined) return;

    // Prevent additional handlers to catch this event
    evt.stopImmediatePropagation();

    const pending = this._pendingRPC[id];
    if (!pending) return;

    delete this._pendingRPC[id];

    if (error) {
      pending.reject(new RPCError(error.code, error.message, error.data));
      return;
    }

    pending.resolve(result);
  }

  _onConnectionClose(evt) {
    this._log('client disconnected');
    this._dispatchDisconnect();
    this._cleanupConnection();
    this._scheduleReconnection();
  }

  _dispatchDisconnect() {
    const event = new CustomEvent('disconnect');
    this.dispatchEvent(event);
  }

  _dispatchConnect() {
    const event = new CustomEvent('connect');
    this.dispatchEvent(event);
  }

  _scheduleReconnection() {
    if (!this._autoReconnect) return;

    this._reconnectionDelay = this._reconnectionDelay * 2 + Math.random();
    this._log('client will try to reconnect in %dms', this._reconnectionDelay);
    setTimeout(this.connect.bind(this), this._reconnectionDelay);
  }

  _cleanupConnection() {
    if (!this._conn) return;
    this._conn.onopen = null;
    this._conn.onerror = null;
    this._conn.onclose = null;
    this._conn.onmessage = null;
    this._conn.close();
    this._conn = null;
  }

  _send(message) {
    if (!this._conn) return false;
    this._log('sending message', message);
    this._conn.send(JSON.stringify(message));
    return true;
  }

  _sendQueued() {
    this._log("sending queued messages", this._queue.length);
    let msg = this._queue.shift();
    while (msg) {
      const sent = this._send(msg);
      if (!sent) return;
      msg = this._queue.shift();
    }
  }

  _log(...args) {
    if (!this.debug) return;
    console.log(...args);
  }

  _sendOrQueue(msg) {
    if (this.isConnected()) {
      this._sendQueued();
      this._send(msg);
    } else {
      this._log('queuing message', msg);
      this._queue.push(msg);
    }
  }

  send(data) {
    const msg = new Message("message", data);
    this._sendOrQueue(msg);
  }

  rpc(method, params) {
    return new Promise((resolve, reject) => {
      const id = this._rpcID++;
      const rpc = new Message(TypeMessage, {
        jsonrpc: '2.0',
        id, method, params
      });
      this._sendOrQueue(rpc);
      this._pendingRPC[id.toString()] = { resolve, reject };
    });
  }

  isConnected() {
    return this._conn !== null;
  }

  upload(blob: string|Blob, metadata: any) {
    return new Promise((resolve, reject) => {
      const formData = new FormData();
      formData.set("file", blob);
      
      if (metadata) {
        try {
          formData.set("metadata", JSON.stringify(metadata));
        } catch(err) {
          return reject(err);
        }
      }
      const xhr = new XMLHttpRequest();
        
      const result = {
        onProgress: null,
        abort: () => xhr.abort(),
        result: () => {
          return new Promise((resolve, reject) => {
            xhr.onload = () => {
              let data;
              try {
                data = JSON.parse(xhr.responseText);
              } catch(err) {
                reject(err);
                return;
              }
              resolve(data);
            };
            xhr.onerror = reject;
            xhr.onabort = reject;
          });
        }
      };

      xhr.upload.onprogress = evt => {
        if (typeof result.onProgress !== 'function') return;
        (result as any).onProgress(evt.loaded, evt.total);
      };
      xhr.onabort = reject;
      xhr.onerror = reject;

      xhr.open('POST', `/edge/api/v1/upload`);
      xhr.send(formData);

      resolve(result);
    });
  }

  blobUrl(bucket: string, blobId: string) {
    return `/edge/api/v1/download/${bucket}/${blobId}`;
  }
}