/************************************************************************
 *  Copyright 2010-2015 Brian McKelvey.
 *
 *  Licensed 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.
 ***********************************************************************/

var utils = require('./utils');
var extend = utils.extend;
var util = require('util');
var EventEmitter = require('events').EventEmitter;
var http = require('http');
var https = require('https');
var url = require('url');
var crypto = require('crypto');
var WebSocketConnection = require('./WebSocketConnection');
var bufferAllocUnsafe = utils.bufferAllocUnsafe;

var protocolSeparators = [
    '(', ')', '<', '>', '@',
    ',', ';', ':', '\\', '\"',
    '/', '[', ']', '?', '=',
    '{', '}', ' ', String.fromCharCode(9)
];

var excludedTlsOptions = ['hostname','port','method','path','headers'];

function WebSocketClient(config) {
    // Superclass Constructor
    EventEmitter.call(this);

    // TODO: Implement extensions

    this.config = {
        // 1MiB max frame size.
        maxReceivedFrameSize: 0x100000,

        // 8MiB max message size, only applicable if
        // assembleFragments is true
        maxReceivedMessageSize: 0x800000,

        // Outgoing messages larger than fragmentationThreshold will be
        // split into multiple fragments.
        fragmentOutgoingMessages: true,

        // Outgoing frames are fragmented if they exceed this threshold.
        // Default is 16KiB
        fragmentationThreshold: 0x4000,

        // Which version of the protocol to use for this session.  This
        // option will be removed once the protocol is finalized by the IETF
        // It is only available to ease the transition through the
        // intermediate draft protocol versions.
        // At present, it only affects the name of the Origin header.
        webSocketVersion: 13,

        // If true, fragmented messages will be automatically assembled
        // and the full message will be emitted via a 'message' event.
        // If false, each frame will be emitted via a 'frame' event and
        // the application will be responsible for aggregating multiple
        // fragmented frames.  Single-frame messages will emit a 'message'
        // event in addition to the 'frame' event.
        // Most users will want to leave this set to 'true'
        assembleFragments: true,

        // The Nagle Algorithm makes more efficient use of network resources
        // by introducing a small delay before sending small packets so that
        // multiple messages can be batched together before going onto the
        // wire.  This however comes at the cost of latency, so the default
        // is to disable it.  If you don't need low latency and are streaming
        // lots of small messages, you can change this to 'false'
        disableNagleAlgorithm: true,

        // The number of milliseconds to wait after sending a close frame
        // for an acknowledgement to come back before giving up and just
        // closing the socket.
        closeTimeout: 5000,

        // Options to pass to https.connect if connecting via TLS
        tlsOptions: {}
    };

    if (config) {
        var tlsOptions;
        if (config.tlsOptions) {
          tlsOptions = config.tlsOptions;
          delete config.tlsOptions;
        }
        else {
          tlsOptions = {};
        }
        extend(this.config, config);
        extend(this.config.tlsOptions, tlsOptions);
    }

    this._req = null;
    
    switch (this.config.webSocketVersion) {
        case 8:
        case 13:
            break;
        default:
            throw new Error('Requested webSocketVersion is not supported. Allowed values are 8 and 13.');
    }
}

util.inherits(WebSocketClient, EventEmitter);

WebSocketClient.prototype.connect = function(requestUrl, protocols, origin, headers, extraRequestOptions) {
    var self = this;
    
    if (typeof(protocols) === 'string') {
        if (protocols.length > 0) {
            protocols = [protocols];
        }
        else {
            protocols = [];
        }
    }
    if (!(protocols instanceof Array)) {
        protocols = [];
    }
    this.protocols = protocols;
    this.origin = origin;

    if (typeof(requestUrl) === 'string') {
        this.url = url.parse(requestUrl);
    }
    else {
        this.url = requestUrl; // in case an already parsed url is passed in.
    }
    if (!this.url.protocol) {
        throw new Error('You must specify a full WebSocket URL, including protocol.');
    }
    if (!this.url.host) {
        throw new Error('You must specify a full WebSocket URL, including hostname. Relative URLs are not supported.');
    }

    this.secure = (this.url.protocol === 'wss:');

    // validate protocol characters:
    this.protocols.forEach(function(protocol) {
        for (var i=0; i < protocol.length; i ++) {
            var charCode = protocol.charCodeAt(i);
            var character = protocol.charAt(i);
            if (charCode < 0x0021 || charCode > 0x007E || protocolSeparators.indexOf(character) !== -1) {
                throw new Error('Protocol list contains invalid character "' + String.fromCharCode(charCode) + '"');
            }
        }
    });

    var defaultPorts = {
        'ws:': '80',
        'wss:': '443'
    };

    if (!this.url.port) {
        this.url.port = defaultPorts[this.url.protocol];
    }

    var nonce = bufferAllocUnsafe(16);
    for (var i=0; i < 16; i++) {
        nonce[i] = Math.round(Math.random()*0xFF);
    }
    this.base64nonce = nonce.toString('base64');

    var hostHeaderValue = this.url.hostname;
    if ((this.url.protocol === 'ws:' && this.url.port !== '80') ||
        (this.url.protocol === 'wss:' && this.url.port !== '443'))  {
        hostHeaderValue += (':' + this.url.port);
    }

    var reqHeaders = {};
    if (this.secure && this.config.tlsOptions.hasOwnProperty('headers')) {
      // Allow for additional headers to be provided when connecting via HTTPS
      extend(reqHeaders, this.config.tlsOptions.headers);
    }
    if (headers) {
      // Explicitly provided headers take priority over any from tlsOptions
      extend(reqHeaders, headers);
    }
    extend(reqHeaders, {
        'Upgrade': 'websocket',
        'Connection': 'Upgrade',
        'Sec-WebSocket-Version': this.config.webSocketVersion.toString(10),
        'Sec-WebSocket-Key': this.base64nonce,
        'Host': reqHeaders.Host || hostHeaderValue
    });

    if (this.protocols.length > 0) {
        reqHeaders['Sec-WebSocket-Protocol'] = this.protocols.join(', ');
    }
    if (this.origin) {
        if (this.config.webSocketVersion === 13) {
            reqHeaders['Origin'] = this.origin;
        }
        else if (this.config.webSocketVersion === 8) {
            reqHeaders['Sec-WebSocket-Origin'] = this.origin;
        }
    }

    // TODO: Implement extensions

    var pathAndQuery;
    // Ensure it begins with '/'.
    if (this.url.pathname) {
        pathAndQuery = this.url.path;
    }
    else if (this.url.path) {
        pathAndQuery = '/' + this.url.path;
    }
    else {
        pathAndQuery = '/';
    }

    function handleRequestError(error) {
        self._req = null;
        self.emit('connectFailed', error);
    }

    var requestOptions = {
        agent: false
    };
    if (extraRequestOptions) {
        extend(requestOptions, extraRequestOptions);
    }
    // These options are always overridden by the library.  The user is not
    // allowed to specify these directly.
    extend(requestOptions, {
        hostname: this.url.hostname,
        port: this.url.port,
        method: 'GET',
        path: pathAndQuery,
        headers: reqHeaders
    });
    if (this.secure) {
        var tlsOptions = this.config.tlsOptions;
        for (var key in tlsOptions) {
            if (tlsOptions.hasOwnProperty(key) && excludedTlsOptions.indexOf(key) === -1) {
                requestOptions[key] = tlsOptions[key];
            }
        }
    }

    var req = this._req = (this.secure ? https : http).request(requestOptions);
    req.on('upgrade', function handleRequestUpgrade(response, socket, head) {
        self._req = null;
        req.removeListener('error', handleRequestError);
        self.socket = socket;
        self.response = response;
        self.firstDataChunk = head;
        self.validateHandshake();
    });
    req.on('error', handleRequestError);

    req.on('response', function(response) {
        self._req = null;
        if (utils.eventEmitterListenerCount(self, 'httpResponse') > 0) {
            self.emit('httpResponse', response, self);
            if (response.socket) {
                response.socket.end();
            }
        }
        else {
            var headerDumpParts = [];
            for (var headerName in response.headers) {
                headerDumpParts.push(headerName + ': ' + response.headers[headerName]);
            }
            self.failHandshake(
                'Server responded with a non-101 status: ' +
                response.statusCode + ' ' + response.statusMessage +
                '\nResponse Headers Follow:\n' +
                headerDumpParts.join('\n') + '\n'
            );
        }
    });
    req.end();
};

WebSocketClient.prototype.validateHandshake = function() {
    var headers = this.response.headers;

    if (this.protocols.length > 0) {
        this.protocol = headers['sec-websocket-protocol'];
        if (this.protocol) {
            if (this.protocols.indexOf(this.protocol) === -1) {
                this.failHandshake('Server did not respond with a requested protocol.');
                return;
            }
        }
        else {
            this.failHandshake('Expected a Sec-WebSocket-Protocol header.');
            return;
        }
    }

    if (!(headers['connection'] && headers['connection'].toLocaleLowerCase() === 'upgrade')) {
        this.failHandshake('Expected a Connection: Upgrade header from the server');
        return;
    }

    if (!(headers['upgrade'] && headers['upgrade'].toLocaleLowerCase() === 'websocket')) {
        this.failHandshake('Expected an Upgrade: websocket header from the server');
        return;
    }

    var sha1 = crypto.createHash('sha1');
    sha1.update(this.base64nonce + '258EAFA5-E914-47DA-95CA-C5AB0DC85B11');
    var expectedKey = sha1.digest('base64');

    if (!headers['sec-websocket-accept']) {
        this.failHandshake('Expected Sec-WebSocket-Accept header from server');
        return;
    }

    if (headers['sec-websocket-accept'] !== expectedKey) {
        this.failHandshake('Sec-WebSocket-Accept header from server didn\'t match expected value of ' + expectedKey);
        return;
    }

    // TODO: Support extensions

    this.succeedHandshake();
};

WebSocketClient.prototype.failHandshake = function(errorDescription) {
    if (this.socket && this.socket.writable) {
        this.socket.end();
    }
    this.emit('connectFailed', new Error(errorDescription));
};

WebSocketClient.prototype.succeedHandshake = function() {
    var connection = new WebSocketConnection(this.socket, [], this.protocol, true, this.config);

    connection.webSocketVersion = this.config.webSocketVersion;
    connection._addSocketEventListeners();

    this.emit('connect', connection);
    if (this.firstDataChunk.length > 0) {
        connection.handleSocketData(this.firstDataChunk);
    }
    this.firstDataChunk = null;
};

WebSocketClient.prototype.abort = function() {
    if (this._req) {
        this._req.abort();
    }
};

module.exports = WebSocketClient;