/*
 *  Licensed to the Apache Software Foundation (ASF) under one
 *  or more contributor license agreements.  See the NOTICE file
 *  distributed with this work for additional information
 *  regarding copyright ownership.  The ASF licenses this file
 *  to you under the Apache License, Version 2.0 (the
 *  "License"); you may not use this file except in compliance
 *  with the License.  You may obtain a copy of the License at
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing,
 *  software distributed under the License is distributed on an
 *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 *  KIND, either express or implied.  See the License for the
 *  specific language governing permissions and limitations
 *  under the License.
 */

/**
 * @author Jorge Bay Gondra
 */
'use strict';

const EventEmitter = require('events');
const Stream = require('stream');
const WebSocket = require('ws');
const util = require('util');
const utils = require('../utils');
const serializer = require('../structure/io/graph-serializer');
const { graphBinaryReader, graphBinaryWriter } = require('../structure/io/binary/GraphBinary');
const ResultSet = require('./result-set');
const ResponseError = require('./response-error');

const responseStatusCode = {
  success: 200,
  noContent: 204,
  partialContent: 206,
  authenticationChallenge: 407,
};

const defaultMimeType = 'application/vnd.gremlin-v3.0+json';
const graphSON2MimeType = 'application/vnd.gremlin-v2.0+json';
const graphBinaryMimeType = 'application/vnd.graphbinary-v1.0';

const pingIntervalDelay = 60 * 1000;
const pongTimeoutDelay = 30 * 1000;

/**
 * Represents a single connection to a Gremlin Server.
 */
class Connection extends EventEmitter {
  /**
   * Creates a new instance of {@link Connection}.
   * @param {String} url The resource uri.
   * @param {Object} [options] The connection options.
   * @param {Array} [options.ca] Trusted certificates.
   * @param {String|Array|Buffer} [options.cert] The certificate key.
   * @param {String} [options.mimeType] The mime type to use.
   * @param {String|Buffer} [options.pfx] The private key, certificate, and CA certs.
   * @param {GraphSONReader} [options.reader] The reader to use.
   * @param {Boolean} [options.rejectUnauthorized] Determines whether to verify or not the server certificate.
   * @param {String} [options.traversalSource] The traversal source. Defaults to: 'g'.
   * @param {GraphSONWriter} [options.writer] The writer to use.
   * @param {Authenticator} [options.authenticator] The authentication handler to use.
   * @param {Object} [options.headers] An associative array containing the additional header key/values for the initial request.
   * @param {Boolean} [options.enableUserAgentOnConnect] Determines if a user agent will be sent during connection handshake. Defaults to: true
   * @param {Boolean} [options.pingEnabled] Setup ping interval. Defaults to: true.
   * @param {Number} [options.pingInterval] Ping request interval in ms if ping enabled. Defaults to: 60000.
   * @param {Number} [options.pongTimeout] Timeout of pong response in ms after sending a ping. Defaults to: 30000.
   * @constructor
   */
  constructor(url, options) {
    super();

    this.url = url;
    this.options = options = options || {};

    /**
     * Gets the MIME type.
     * @type {String}
     */
    this.mimeType = options.mimeType || defaultMimeType;

    // A map containing the request id and the handler. The id should be in lower case to prevent string comparison issues.
    this._responseHandlers = {};
    this._reader = options.reader || this._getDefaultReader(this.mimeType);
    this._writer = options.writer || this._getDefaultWriter(this.mimeType);
    this._openPromise = null;
    this._openCallback = null;
    this._closePromise = null;
    this._closeCallback = null;
    this._pingInterval = null;
    this._pongTimeout = null;

    this._header = String.fromCharCode(this.mimeType.length) + this.mimeType; // TODO: what if mimeType.length > 255
    this._header_buf = Buffer.from(this._header);
    this.isOpen = false;
    this.traversalSource = options.traversalSource || 'g';
    this._authenticator = options.authenticator;
    this._enableUserAgentOnConnect = options.enableUserAgentOnConnect !== false;

    this._pingEnabled = this.options.pingEnabled === false ? false : true;
    this._pingIntervalDelay = this.options.pingInterval || pingIntervalDelay;
    this._pongTimeoutDelay = this.options.pongTimeout || pongTimeoutDelay;
  }

  /**
   * Opens the connection, if its not already opened.
   * @returns {Promise}
   */
  open() {
    if (this.isOpen) {
      return Promise.resolve();
    }
    if (this._openPromise) {
      return this._openPromise;
    }

    this.emit('log', 'ws open');
    let headers = this.options.headers;
    if (this._enableUserAgentOnConnect) {
      if (!headers) {
        headers = [];
      }
      headers[utils.getUserAgentHeader()] = utils.getUserAgent();
    }

    this._ws = new WebSocket(this.url, {
      headers: headers,
      ca: this.options.ca,
      cert: this.options.cert,
      pfx: this.options.pfx,
      rejectUnauthorized: this.options.rejectUnauthorized,
    });

    this._ws.on('message', (data) => this._handleMessage(data));
    this._ws.on('close', (code, message) => this._handleClose(code, message));

    this._ws.on('pong', () => {
      this.emit('log', 'ws pong received');
      if (this._pongTimeout) {
        clearTimeout(this._pongTimeout);
        this._pongTimeout = null;
      }
    });
    this._ws.on('ping', () => {
      this.emit('log', 'ws ping received');
      this._ws.pong();
    });

    return (this._openPromise = new Promise((resolve, reject) => {
      this._ws.on('open', () => {
        this.isOpen = true;
        if (this._pingEnabled) {
          this._pingHeartbeat();
        }
        resolve();
      });
      this._ws.on('error', (err) => {
        this._handleError(err);
        reject(err);
      });
    }));
  }

  /** @override */
  submit(processor, op, args, requestId) {
    // TINKERPOP-2847: Use lower case to prevent string comparison issues.
    const rid = (requestId || utils.getUuid()).toLowerCase();
    return this.open().then(
      () =>
        new Promise((resolve, reject) => {
          if (op !== 'authentication') {
            this._responseHandlers[rid] = {
              callback: (err, result) => (err ? reject(err) : resolve(result)),
              result: null,
            };
          }

          const request = {
            requestId: rid,
            op: op || 'bytecode',
            // if using op eval need to ensure processor stays unset if caller didn't set it.
            processor: !processor && op !== 'eval' ? 'traversal' : processor,
            args: args || {},
          };

          const request_buf = this._writer.writeRequest(request);
          const message = Buffer.concat([this._header_buf, request_buf]);
          this._ws.send(message);
        }),
    );
  }

  /** @override */
  stream(processor, op, args, requestId) {
    // TINKERPOP-2847: Use lower case to prevent string comparison issues.
    const rid = (requestId || utils.getUuid()).toLowerCase();

    const readableStream = new Stream.Readable({
      objectMode: true,
      read() {},
    });

    this._responseHandlers[rid] = {
      callback: (err) => (err ? readableStream.destroy(err) : readableStream.push(null)),
      result: readableStream,
    };

    this.open()
      .then(() => {
        const request = {
          requestId: rid,
          op: op || 'bytecode',
          // if using op eval need to ensure processor stays unset if caller didn't set it.
          processor: !processor && op !== 'eval' ? 'traversal' : processor,
          args: args || {},
        };

        const request_buf = this._writer.writeRequest(request);
        const message = Buffer.concat([this._header_buf, request_buf]);
        this._ws.send(message);
      })
      .catch((err) => readableStream.destroy(err));

    return readableStream;
  }

  _getDefaultReader(mimeType) {
    if (mimeType === graphBinaryMimeType) {
      return graphBinaryReader;
    }

    return mimeType === graphSON2MimeType ? new serializer.GraphSON2Reader() : new serializer.GraphSONReader();
  }

  _getDefaultWriter(mimeType) {
    if (mimeType === graphBinaryMimeType) {
      return graphBinaryWriter;
    }

    return mimeType === graphSON2MimeType ? new serializer.GraphSON2Writer() : new serializer.GraphSONWriter();
  }

  _pingHeartbeat() {
    if (this._pingInterval) {
      clearInterval(this._pingInterval);
      this._pingInterval = null;
    }

    this._pingInterval = setInterval(() => {
      if (this.isOpen === false) {
        // in case of if not open..
        if (this._pingInterval) {
          clearInterval(this._pingInterval);
          this._pingInterval = null;
        }
      }

      this._pongTimeout = setTimeout(() => {
        this._ws.terminate();
      }, this._pongTimeoutDelay);

      this._ws.ping();
    }, this._pingIntervalDelay);
  }

  _handleError(err) {
    this.emit('log', `ws error ${err}`);
    this._cleanupWebsocket(err);
    this.emit('socketError', err);
  }

  _handleClose(code, message) {
    this.emit('log', `ws close code=${code} message=${message}`);
    this._cleanupWebsocket();
    if (this._closeCallback) {
      this._closeCallback();
    }
    this.emit('close', code, message);
  }

  _handleMessage(data) {
    const response = this._reader.readResponse(data);
    if (response.requestId === null || response.requestId === undefined) {
      // There was a serialization issue on the server that prevented the parsing of the request id
      // We invoke any of the pending handlers with an error
      Object.keys(this._responseHandlers).forEach((requestId) => {
        const handler = this._responseHandlers[requestId];
        this._clearHandler(requestId);
        if (response.status !== undefined && response.status.message) {
          return handler.callback(
            // TINKERPOP-2285: keep the old server error message in case folks are parsing that - fix in a future breaking version
            new ResponseError(
              util.format(
                'Server error (no request information): %s (%d)',
                response.status.message,
                response.status.code,
              ),
              response.status,
            ),
          );
        }
        // TINKERPOP-2285: keep the old server error message in case folks are parsing that - fix in a future breaking version
        return handler.callback(
          new ResponseError(util.format('Server error (no request information): %j', response), response.status),
        );
      });
      return;
    }

    // TINKERPOP-2847: Use lower case to prevent string comparison issues.
    response.requestId = response.requestId.toLowerCase();
    const handler = this._responseHandlers[response.requestId];

    if (!handler) {
      // The handler for a given request id was not found
      // It was probably invoked earlier due to a serialization issue.
      return;
    }

    if (response.status.code === responseStatusCode.authenticationChallenge && this._authenticator) {
      this._authenticator
        .evaluateChallenge(response.result.data)
        .then((res) => this.submit(undefined, 'authentication', res, response.requestId))
        .catch(handler.callback);

      return;
    } else if (response.status.code >= 400) {
      // callback in error
      return handler.callback(
        // TINKERPOP-2285: keep the old server error message in case folks are parsing that - fix in a future breaking version
        new ResponseError(
          util.format('Server error: %s (%d)', response.status.message, response.status.code),
          response.status,
        ),
      );
    }

    const isStreamingResponse = handler.result instanceof Stream.Readable;

    switch (response.status.code) {
      case responseStatusCode.noContent:
        this._clearHandler(response.requestId);
        if (isStreamingResponse) {
          handler.result.push(new ResultSet(utils.emptyArray, response.status.attributes));
          return handler.callback(null);
        }
        return handler.callback(null, new ResultSet(utils.emptyArray, response.status.attributes));
      case responseStatusCode.partialContent:
        if (isStreamingResponse) {
          handler.result.push(new ResultSet(response.result.data, response.status.attributes));
          break;
        }
        handler.result = handler.result || [];
        handler.result.push.apply(handler.result, response.result.data);
        break;
      default:
        if (isStreamingResponse) {
          handler.result.push(new ResultSet(response.result.data, response.status.attributes));
          return handler.callback(null);
        }
        if (handler.result) {
          handler.result.push.apply(handler.result, response.result.data);
        } else {
          handler.result = response.result.data;
        }
        this._clearHandler(response.requestId);
        return handler.callback(null, new ResultSet(handler.result, response.status.attributes));
    }
  }

  /**
   * clean websocket context
   */
  _cleanupWebsocket(err) {
    if (this._pingInterval) {
      clearInterval(this._pingInterval);
    }
    this._pingInterval = null;
    if (this._pongTimeout) {
      clearTimeout(this._pongTimeout);
    }
    this._pongTimeout = null;

    // Invoke waiting callbacks to complete Promises when closing the websocket
    Object.keys(this._responseHandlers).forEach((requestId) => {
      const handler = this._responseHandlers[requestId];
      const isStreamingResponse = handler.result instanceof Stream.Readable;
      if (isStreamingResponse) {
        handler.callback(null);
      } else {
        const cause = err ? err : new Error('Connection has been closed.');
        handler.callback(cause);
      }
    });
    this._ws.removeAllListeners();
    this._openPromise = null;
    this._closePromise = null;
    this.isOpen = false;
  }

  /**
   * Clears the internal state containing the callback and result buffer of a given request.
   * @param requestId
   * @private
   */
  _clearHandler(requestId) {
    delete this._responseHandlers[requestId];
  }

  /**
   * Closes the Connection.
   * @return {Promise}
   */
  close() {
    if (this.isOpen === false) {
      return Promise.resolve();
    }
    if (!this._closePromise) {
      this._closePromise = new Promise((resolve) => {
        this._closeCallback = resolve;
        this._ws.close();
      });
    }
    return this._closePromise;
  }
}

module.exports = Connection;
