var _           = require('lodash'),
    Promise     = require('bluebird'),
    logging     = require('../logging'),
    errors      = require('../errors'),
    api         = require('../api'),
    loader      = require('./loader'),
    i18n        = require('../i18n'),
    config      = require('../config'),
    // Holds the available apps
    availableApps = {};

function getInstalledApps() {
    return api.settings.read({context: {internal: true}, key: 'installed_apps'}).then(function (response) {
        var installed = response.settings[0];

        installed.value = installed.value || '[]';

        try {
            installed = JSON.parse(installed.value);
        } catch (e) {
            return Promise.reject(e);
        }

        return installed.concat(config.get('apps:internal'));
    });
}

function saveInstalledApps(installedApps) {
    return getInstalledApps().then(function (currentInstalledApps) {
        var updatedAppsInstalled = _.difference(_.uniq(installedApps.concat(currentInstalledApps)), config.get('apps:internal'));

        return api.settings.edit({settings: [{key: 'installed_apps', value: updatedAppsInstalled}]}, {context: {internal: true}});
    });
}

module.exports = {
    init: function () {
        var appsToLoad;

        try {
            // We have to parse the value because it's a string
            api.settings.read({context: {internal: true}, key: 'active_apps'}).then(function (response) {
                var aApps = response.settings[0];

                appsToLoad = JSON.parse(aApps.value) || [];

                appsToLoad = appsToLoad.concat(config.get('apps:internal'));
            });
        } catch (err) {
            logging.error(new errors.GhostError({
                err: err,
                context: i18n.t('errors.apps.failedToParseActiveAppsSettings.context'),
                help: i18n.t('errors.apps.failedToParseActiveAppsSettings.help')
            }));

            return Promise.resolve();
        }

        // Grab all installed apps, install any not already installed that are in appsToLoad.
        return getInstalledApps().then(function (installedApps) {
            var loadedApps = {},
                recordLoadedApp = function (name, loadedApp) {
                    // After loading the app, add it to our hash of loaded apps
                    loadedApps[name] = loadedApp;

                    return Promise.resolve(loadedApp);
                },
                loadPromises = _.map(appsToLoad, function (app) {
                    // If already installed, just activate the app
                    if (_.includes(installedApps, app)) {
                        return loader.activateAppByName(app).then(function (loadedApp) {
                            return recordLoadedApp(app, loadedApp);
                        });
                    }

                    // Install, then activate the app
                    return loader.installAppByName(app).then(function () {
                        return loader.activateAppByName(app);
                    }).then(function (loadedApp) {
                        return recordLoadedApp(app, loadedApp);
                    });
                });

            return Promise.all(loadPromises).then(function () {
                // Save our installed apps to settings
                return saveInstalledApps(_.keys(loadedApps));
            }).then(function () {
                // Extend the loadedApps onto the available apps
                _.extend(availableApps, loadedApps);
            }).catch(function (err) {
                logging.error(new errors.GhostError({
                    err: err,
                    context: i18n.t('errors.apps.appWillNotBeLoaded.error'),
                    help: i18n.t('errors.apps.appWillNotBeLoaded.help')
                }));
            });
        });
    },
    availableApps: availableApps
};