'use strict';

var ngModule = angular.module('woUtil');
ngModule.service('connectionDoctor', ConnectionDoctor);
module.exports = ConnectionDoctor;

var TCPSocket = require('tcp-socket'),
    ImapClient = require('imap-client'),
    SmtpClient = require('wo-smtpclient');

/**
 * The connection doctor can check your connection. In essence, it reconstructs what happens when
 * the app goes online in an abbreviated way. You need to configure() the instance with the IMAP/SMTP
 * credentials before running check()!
 *
 * @constructor
 */
function ConnectionDoctor(appConfig) {
    this._appConfig = appConfig;
    this._workerPath = appConfig.config.workerPath + '/tcp-socket-tls-worker.min.js';
}

//
// Error codes
//

var OFFLINE = ConnectionDoctor.OFFLINE = 42;
var TLS_WRONG_CERT = ConnectionDoctor.TLS_WRONG_CERT = 43;
var HOST_UNREACHABLE = ConnectionDoctor.HOST_UNREACHABLE = 44;
var HOST_TIMEOUT = ConnectionDoctor.HOST_TIMEOUT = 45;
var AUTH_REJECTED = ConnectionDoctor.AUTH_REJECTED = 46;
var NO_INBOX = ConnectionDoctor.NO_INBOX = 47;
var GENERIC_ERROR = ConnectionDoctor.GENERIC_ERROR = 48;

//
// Public API
//

/**
 * Configures the connection doctor
 *
 * @param {Object} credentials.imap IMAP configuration (host:string, port:number, secure:boolean, ignoreTLS:boolean)
 * @param {Object} credentials.smtp SMTP configuration (host:string, port:number, secure:boolean, ignoreTLS:boolean)
 * @param {String} credentials.username
 * @param {String} credentials.password
 */
ConnectionDoctor.prototype.configure = function(credentials) {
    this.credentials = credentials;

    // internal members
    this._imap = new ImapClient({
        host: this.credentials.imap.host,
        port: this.credentials.imap.port,
        secure: this.credentials.imap.secure,
        ignoreTLS: this.credentials.imap.ignoreTLS,
        ca: this.credentials.imap.ca,
        tlsWorkerPath: this._workerPath,
        auth: {
            user: this.credentials.username,
            pass: this.credentials.password,
            xoauth2: this.credentials.xoauth2
        }
    });

    this._smtp = new SmtpClient(this.credentials.smtp.host, this.credentials.smtp.port, {
        useSecureTransport: this.credentials.smtp.secure,
        ignoreTLS: this.credentials.smtp.ignoreTLS,
        ca: this.credentials.smtp.ca,
        tlsWorkerPath: this._workerPath,
        auth: {
            user: this.credentials.username,
            pass: this.credentials.password,
            xoauth2: this.credentials.xoauth2
        }
    });
};

/**
 * It conducts the following tests for IMAP and SMTP, respectively:
 * 1) Check if browser is online
 * 2) Connect to host:port via TCP/TLS
 * 3) Login to the server
 * 4) Perform some basic commands (e.g. list folders)
 * 5) Exposes error codes
 */
ConnectionDoctor.prototype.check = function() {
    var self = this;
    return new Promise(function(resolve) {
        if (!self.credentials) {
            throw new Error('You need to configure() the connection doctor first!');
        } else {
            resolve();
        }
    }).then(function() {
        return self._checkOnline();
    }).then(function() {
        return self._checkReachable(self.credentials.imap);
    }).then(function() {
        return self._checkReachable(self.credentials.smtp);
    }).then(function() {
        return self._checkImap();
    }).then(function() {
        return self._checkSmtp();
    });
};


//
// Internal API
//

/**
 * Checks if the browser is online
 */
ConnectionDoctor.prototype._checkOnline = function() {
    var self = this;
    return new Promise(function(resolve) {
        if (navigator.onLine) {
            resolve();
        } else {
            throw createError(OFFLINE, self._appConfig.string.connDocOffline);
        }
    });
};

/**
 * Checks if a host is reachable via TCP
 *
 * @param {String} options.host
 * @param {Number} options.port
 * @param {Boolean} options.secure
 */
ConnectionDoctor.prototype._checkReachable = function(options) {
    var self = this;
    return new Promise(function(resolve, reject) {
        var socket,
            error, // remember the error message
            timeout, // remember the timeout object
            host = options.host + ':' + options.port,
            hasTimedOut = false, // prevents multiple callbacks
            cfg = self._appConfig.config,
            str = self._appConfig.string;

        timeout = setTimeout(function() {
            hasTimedOut = true;
            reject(createError(HOST_TIMEOUT, str.connDocHostTimeout.replace('{0}', host).replace('{1}', cfg.connDocTimeout)));
        }, cfg.connDocTimeout);

        socket = TCPSocket.open(options.host, options.port, {
            binaryType: 'arraybuffer',
            useSecureTransport: options.secure,
            ca: options.ca,
            tlsWorkerPath: self._workerPath
        });

        socket.ondata = function() {}; // we don't actually care about the data

        // [WO-625] Mozilla forbids extensions to the TCPSocket object,
        // throws an exception when assigned unexpected callback functions.
        // The exception can be safely ignored since we need the callback
        // for the other shims
        try {
            socket.oncert = function() {
                if (options.ca) {
                    // the certificate we already have is outdated
                    error = createError(TLS_WRONG_CERT, str.connDocTlsWrongCert.replace('{0}', host));
                }
            };
        } catch (e) {}

        socket.onerror = function(e) {
            if (!error) {
                error = createError(HOST_UNREACHABLE, str.connDocHostUnreachable.replace('{0}', host), e.data);
            }
        };

        socket.onopen = function() {
            socket.close();
        };

        socket.onclose = function() {
            if (!hasTimedOut) {
                clearTimeout(timeout);
                if (error) {
                    reject(error);
                } else {
                    resolve();
                }
            }
        };
    });
};

/**
 * Checks if an IMAP server is reachable, accepts the credentials, can list folders and has an inbox and logs out.
 * Adds the certificate to the IMAP settings if not provided.
 */
ConnectionDoctor.prototype._checkImap = function() {
    var self = this;
    return new Promise(function(resolve, reject) {
        var loggedIn = false,
            host = self.credentials.imap.host + ':' + self.credentials.imap.port,
            str = self._appConfig.string;

        self._imap.onCert = function(pemEncodedCert) {
            if (!self.credentials.imap.ca) {
                self.credentials.imap.ca = pemEncodedCert;
            }
        };

        // login and logout do not use error objects in the callback, but rather invoke
        // the global onError handler, so we need to track if login was successful
        self._imap.onError = function(error) {
            if (!loggedIn) {
                reject(createError(AUTH_REJECTED, str.connDocAuthRejected.replace('{0}', host), error));
            } else {
                reject(createError(GENERIC_ERROR, str.connDocGenericError.replace('{0}', host).replace('{1}', error.message), error));
            }
        };

        self._imap.login(function() {
            loggedIn = true;

            self._imap.listWellKnownFolders(function(error, wellKnownFolders) {
                if (error) {
                    reject(createError(GENERIC_ERROR, str.connDocGenericError.replace('{0}', host).replace('{1}', error.message), error));
                    return;
                }

                if (wellKnownFolders.Inbox.length === 0) {
                    // the client needs at least an inbox folder to work properly
                    reject(createError(NO_INBOX, str.connDocNoInbox.replace('{0}', host)));
                    return;
                }

                self._imap.logout(function() {
                    resolve();
                });
            });
        });
    });
};

/**
 * Checks if an SMTP server is reachable and accepts the credentials and logs out.
 * Adds the certificate to the SMTP settings if not provided.
 */
ConnectionDoctor.prototype._checkSmtp = function() {
    var self = this;
    return new Promise(function(resolve, reject) {
        var host = self.credentials.smtp.host + ':' + self.credentials.smtp.port,
            errored = false, // tracks if we need to invoke the callback at onclose or not
            str = self._appConfig.string;

        self._smtp.oncert = function(pemEncodedCert) {
            if (!self.credentials.smtp.ca) {
                self.credentials.smtp.ca = pemEncodedCert;
            }
        };

        self._smtp.onerror = function(error) {
            if (error) {
                errored = true;
                reject(createError(AUTH_REJECTED, str.connDocAuthRejected.replace('{0}', host), error));
            }
        };

        self._smtp.onidle = function() {
            self._smtp.quit();
        };

        self._smtp.onclose = function() {
            if (!errored) {
                resolve();
            }
        };

        self._smtp.connect();
    });
};


//
// Helper Functions
//

function createError(code, message, underlyingError) {
    var error = new Error(message);
    error.code = code;
    error.underlyingError = underlyingError;

    return error;
}