var util = require('./util');
var bodyParser = require('body-parser');
var WebSocketServer = require('ws').Server;
var url = require('url');

var app = exports = module.exports = {};

/** Initialize WebSocket server. */
app._initializeWSS = function(server) {
    var self = this;

    if (this.mountpath instanceof Array) {
        throw new Error("This app can only be mounted on a single path");
    }

    var path = this.mountpath;
    var path = path + (path[path.length - 1] != '/' ? '/' : '') + 'peerjs';

    // Create WebSocket server as well.
    this._wss = new WebSocketServer({ path: path, server: server});

    this._wss.on('connection', function(socket) {
        var query = url.parse(socket.upgradeReq.url, true).query;
        var id = query.id;
        var token = query.token;
        var key = query.key;
        var ip = socket.upgradeReq.socket.remoteAddress;

        if (!id || !token || !key) {
            socket.send(JSON.stringify({ type: 'ERROR', payload: { msg: 'No id, token, or key supplied to websocket server' } }));
            socket.close();
            return;
        }

        if (!self._clients[key] || !self._clients[key][id]) {
            self._checkKey(key, ip, function(err) {
                if (!err) {
                    if (!self._clients[key][id]) {
                        self._clients[key][id] = { token: token, ip: ip };
                        self._ips[ip]++;
                        socket.send(JSON.stringify({ type: 'OPEN' }));
                    }
                    self._configureWS(socket, key, id, token);
                } else {
                    socket.send(JSON.stringify({ type: 'ERROR', payload: { msg: err } }));
                }
            });
        } else {
            self._configureWS(socket, key, id, token);
        }
    });
};

app._configureWS = function(socket, key, id, token) {

    var self = this;
    var client = this._clients[key][id];

    if (token === client.token) {
        // res 'close' event will delete client.res for us
        client.socket = socket;
        // Client already exists
        if (client.res) {
            client.res.end();
        }
    } else {
        // ID-taken, invalid token
        socket.send(JSON.stringify({ type: 'ID-TAKEN', payload: { msg: 'ID is taken' } }));
        socket.close();
        return;
    }

    this._processOutstanding(key, id);

    // Cleanup after a socket closes.
    socket.on('close', function() {
        util.log('Socket closed:', id);
        if (client.socket == socket) {
            self._removePeer(key, id);
        }
    });

    // Handle messages from peers.
    socket.on('message', function(data) {
        try {
            var message = JSON.parse(data);

            if (['LEAVE', 'CANDIDATE', 'OFFER', 'ANSWER'].indexOf(message.type) !== -1) {
                self._handleTransmission(key, {
                    type: message.type,
                    src: id,
                    dst: message.dst,
                    payload: message.payload
                });
            } else {
                util.prettyError('Message unrecognized');
            }
        } catch(e) {
            util.log('Invalid message', data);
            throw e;
        }
    });

    // We're going to emit here, because for XHR we don't *know* when someone
    // disconnects.
    this.emit('connection', id);
};

app._checkAllowsDiscovery = function(key, cb) {
    cb(this.options.allow_discovery);
};

app._checkKey = function(key, ip, cb) {
    if (key == this.options.key) {
        if (!this._clients[key]) {
            this._clients[key] = {};
        }
        if (!this._outstanding[key]) {
            this._outstanding[key] = {};
        }
        if (!this._ips[ip]) {
            this._ips[ip] = 0;
        }
        // Check concurrent limit
        if (Object.keys(this._clients[key]).length >= this.options.concurrent_limit) {
            cb('Server has reached its concurrent user limit');
            return;
        }
        if (this._ips[ip] >= this.options.ip_limit) {
            cb(ip + ' has reached its concurrent user limit');
            return;
        }
        cb(null);
    } else {
        cb('Invalid key provided');
    }
};

/** Initialize HTTP server routes. */
app._initializeHTTP = function() {
    var self = this;

    this.use(util.allowCrossDomain);

    // Retrieve guaranteed random ID.
    this.get('/:key/id', function(req, res, next) {
        res.contentType = 'text/html';
        res.send(self._generateClientId(req.params.key));
    });

    // Server sets up HTTP streaming when you get post an ID.
    this.post('/:key/:id/:token/id', function(req, res, next) {
        var id = req.params.id;
        var token = req.params.token;
        var key = req.params.key;
        var ip = req.connection.remoteAddress;

        if (!self._clients[key] || !self._clients[key][id]) {
            self._checkKey(key, ip, function(err) {
                if (!err && !self._clients[key][id]) {
                    self._clients[key][id] = { token: token, ip: ip };
                    self._ips[ip]++;
                    self._startStreaming(res, key, id, token, true);
                } else {
                    res.send(JSON.stringify({ type: 'HTTP-ERROR' }));
                }
            });
        } else {
            self._startStreaming(res, key, id, token);
        }
    });

    // Get a list of all peers for a key, enabled by the `allowDiscovery` flag.
    this.get('/:key/peers', function(req, res, next) {
        var key = req.params.key;
        if (self._clients[key]) {
            self._checkAllowsDiscovery(key, function(isAllowed) {
                if (isAllowed) {
                    res.send(Object.keys(self._clients[key]));
                } else {
                    res.send(401);
                }
            });
        } else {
            res.send(404);
        }
    });

    var handle = function(req, res, next) {
        var key = req.params.key;
        var id = req.params.id;

        var client;
        if (!self._clients[key] || !(client = self._clients[key][id])) {
            if (req.params.retry) {
                res.send(401);
            } else {
                // Retry this request
                req.params.retry = true;
                setTimeout(handle, 25, req, res);
                return;
            }
        }

        // Auth the req
        if (req.params.token !== client.token) {
            res.send(401);
            return;
        } else {
            self._handleTransmission(key, {
                type: req.body.type,
                src: id,
                dst: req.body.dst,
                payload: req.body.payload
            });
            res.send(200);
        }
    };

    var jsonParser = bodyParser.json();

    this.post('/:key/:id/:token/offer', jsonParser, handle);

    this.post('/:key/:id/:token/candidate', jsonParser, handle);

    this.post('/:key/:id/:token/answer', jsonParser, handle);

    this.post('/:key/:id/:token/leave', jsonParser, handle);
};

/** Saves a streaming response and takes care of timeouts and headers. */
app._startStreaming = function(res, key, id, token, open) {
    var self = this;

    res.writeHead(200, {'Content-Type': 'application/octet-stream'});

    var pad = '00';
    for (var i = 0; i < 10; i++) {
        pad += pad;
    }
    res.write(pad + '\n');

    if (open) {
        res.write(JSON.stringify({ type: 'OPEN' }) + '\n');
    }

    var client = this._clients[key][id];

    if (token === client.token) {
        // Client already exists
        res.on('close', function() {
            if (client.res === res) {
                if (!client.socket) {
                    // No new request yet, peer dead
                    self._removePeer(key, id);
                    return;
                }
                delete client.res;
            }
        });
        client.res = res;
        this._processOutstanding(key, id);
    } else {
        // ID-taken, invalid token
        res.end(JSON.stringify({ type: 'HTTP-ERROR' }));
    }
};

app._pruneOutstanding = function() {
    var keys = Object.keys(this._outstanding);
    for (var k = 0, kk = keys.length; k < kk; k += 1) {
        var key = keys[k];
        var dsts = Object.keys(this._outstanding[key]);
        for (var i = 0, ii = dsts.length; i < ii; i += 1) {
            var offers = this._outstanding[key][dsts[i]];
            var seen = {};
            for (var j = 0, jj = offers.length; j < jj; j += 1) {
                var message = offers[j];
                if (!seen[message.src]) {
                    this._handleTransmission(key, { type: 'EXPIRE', src: message.dst, dst: message.src });
                    seen[message.src] = true;
                }
            }
        }
        this._outstanding[key] = {};
    }
};

/** Cleanup */
app._setCleanupIntervals = function() {
    var self = this;

    // Clean up ips every 10 minutes
    setInterval(function() {
        var keys = Object.keys(self._ips);
        for (var i = 0, ii = keys.length; i < ii; i += 1) {
            var key = keys[i];
            if (self._ips[key] === 0) {
                delete self._ips[key];
            }
        }
    }, 600000);

    // Clean up outstanding messages every 5 seconds
    setInterval(function() {
        self._pruneOutstanding();
    }, 5000);
};

/** Process outstanding peer offers. */
app._processOutstanding = function(key, id) {
    var offers = this._outstanding[key][id];
    if (!offers) {
        return;
    }
    for (var j = 0, jj = offers.length; j < jj; j += 1) {
        this._handleTransmission(key, offers[j]);
    }
    delete this._outstanding[key][id];
};

app._removePeer = function(key, id) {
    if (this._clients[key] && this._clients[key][id]) {
        this._ips[this._clients[key][id].ip]--;
        delete this._clients[key][id];
        this.emit('disconnect', id);
    }
};

/** Handles passing on a message. */
app._handleTransmission = function(key, message) {
    var type = message.type;
    var src = message.src;
    var dst = message.dst;
    var data = JSON.stringify(message);

    var destination = this._clients[key][dst];

    // User is connected!
    if (destination) {
        try {
            util.log(type, 'from', src, 'to', dst);
            if (destination.socket) {
                destination.socket.send(data);
            } else if (destination.res) {
                data += '\n';
                destination.res.write(data);
            } else {
                // Neither socket no res available. Peer dead?
                throw "Peer dead";
            }
        } catch (e) {
            // This happens when a peer disconnects without closing connections and
            // the associated WebSocket has not closed.
            util.prettyError(e);
            // Tell other side to stop trying.
            this._removePeer(key, dst);
            this._handleTransmission(key, {
                type: 'LEAVE',
                src: dst,
                dst: src
            });
        }
    } else {
        // Wait for this client to connect/reconnect (XHR) for important
        // messages.
        if (type !== 'LEAVE' && type !== 'EXPIRE' && dst) {
            var self = this;
            if (!this._outstanding[key][dst]) {
                this._outstanding[key][dst] = [];
            }
            this._outstanding[key][dst].push(message);
        } else if (type === 'LEAVE' && !dst) {
            this._removePeer(key, src);
        } else {
            // Unavailable destination specified with message LEAVE or EXPIRE
            // Ignore
        }
    }
};

app._generateClientId = function(key) {
    var clientId = util.randomId();
    if (!this._clients[key]) {
        return clientId;
    }
    while (!!this._clients[key][clientId]) {
        clientId = util.randomId();
    }
    return clientId;
};