/** 
 * @file Initialise et configure le serveur Express sur lequel tourne le back.
 * 
 * La configuration inclut tout le _middleware_ définissant les API et les services
 * nécessaire utilisés, comme `express-session`, GraphiQL, GraphQL Voyager.
 * 
 * @todo changer cette description... ^
 * @todo qu'arrive-t-il aux requetes avec un cookie expire? elles ne sont traitees ni par passport.session() ni par passport.authenticate('ldapauth')...
 * 
 * @author manifold, kadabra
 */
import dotenv from 'dotenv';
dotenv.config();
import express from 'express';
import bodyParser from 'body-parser';
// packages pour graphql
import { express as graphqlVoyager } from 'graphql-voyager/middleware';
// replacement of express-graphql, which hasn't been updated in 6 months 
import { ApolloServer } from 'apollo-server-express';
// typeDefs and resolvers
import schema from './graphql/schema';
// packages pour adminview
import { ensureLoggedIn } from 'connect-ensure-login';
import flash from 'connect-flash';
import router from './routing/admin.router';
// packages pour l'authentification
import passport from 'passport';
import session from 'express-session';
import cookieParser from 'cookie-parser';
import cors from 'cors';
// packages divers
import favicon from 'serve-favicon';
import morgan from 'morgan';
// packages pour pouvoir importer depuis des fichiers de config
import path from 'path';

import { ldapConfig, credentialsConfig } from './ldap/config';

const { dn, passwd } = credentialsConfig;

// "The app object conventionally denotes the Express application" 
// see https://expressjs.com/en/4x/api.html#app
const app = express(); 

// Parse incoming HTTP request bodies, available under the req.body property. cf www.npmjs.com/package/body-parser
app.use(bodyParser.json()); //parses bodies of media type "application/json"
app.use(bodyParser.urlencoded({ //parses bodies of media type "application/x-www-form-urlencoded"
    extended: true //use qs library (quoi que ca veuille dire o.O)
}));
//parses Cookie header and populate req.cookies with an object keyed by the cookie names. was necessary for express-session before its v1.5.0. on peut probablement l'enlever desormais.
app.use(cookieParser());

// cache le fait que l'application tourne sous Express dans le header HTTP.
app.disable('x-powered-by');
app.use(morgan('dev'));
app.use(favicon(path.resolve('./', 'assets', 'favicon.ico')));
// specifies path to static assets. ......je comprends pas ce que c'est. TODO
app.use('/assets', express.static(path.resolve('./', 'assets')));

/**
 * @desc AUTHENTIFICATION POUR LES REQUETES POSSEDANT UN COOKIE ET PROVENANT D'UN UTILISATEUR DEJA AUTHENTIFIE
 * Remarque: introduit aussi les middlewares session et passport, 
 * qui sont aussi utiles pour l'authentification dans les autres cas.
 */

/**
 * WTF??? why is sessionSecret in ldap_config.json? it has nothing to do with ldap.
 * @todo FIX
 */

/**
/* defines parameters for *session store*. (adds field req.session and do some magic stuff)
 * basically, searches for a session matching the received cookie and, if found, adds field req.blasomethingbla containing serialized
 * object representing user (i.e. similar to what passport.serializeUser() could produce)
 * @todo do this right, express-session docs warns that isn't for prod!
 * it is important to configure this right!!! please check out https://www.npmjs.com/package/express-session 
 * and make sure you understand the way session is stored. (en vrai c'est vraiment important...)
 */
app.use(session({
    secret: ldapConfig.sessionSecret,
    resave: true,
    saveUninitialized: false,
}));

app.use(passport.initialize());

//GHETTO
//initialize Passport. (adds hidden field req._passport and do some magic stuff)
//app.use(passport.session()); //this is equivalent to app.use(passport.authenticate('session'))
//this is equivalent to app.use(passport.authenticate('session'))
app.use(passport.session(), (req, res, next)=>{
    const user = req.user ? req.user.uid : "none";
    console.log(
        `passport.session: found user: ${user}, authenticated: ${req.isAuthenticated()}`);
    next();
}); 
// *aucun* effet sur les requetes n'ayant pas ete reconnues par app.use(session(...)) (e.g. les requetes sans cookie ou les requetes avec cookie expired). source: lecture directe du code passport/lib/strategies/session.js sur github... :/

// connect-flash is middleware for flashing messages, used in adminview
app.use(flash());

/**
 * @desc SETUP DE ADMINVIEW
 */
// setting up view engine for pug, for adminview
console.log("Running at", __dirname);
let viewpath = path.resolve(__dirname, 'views');
app.set('views', viewpath);
app.set('view engine', 'pug');



/**
 * @desc AUTHENTIFICATION POUR LES REQUETES DE CONNEXION VIA LDAP VENANT DU FRONT
 * i.e. endpoint for *frontend's* authentication requests (login through adminview/avlogin are caught by the router in admin_router.js)
 * i.e. quand l'utilisateur submit le formulaire de login avec ses identifiants/mdp dans le front
 * Remarque: configure aussi passport pour l'authentification ldap, ce qui est aussi utile pour les requetes de connexion via ldap venant de adminview
 */
const FRONTEND_SERVER_URL = process.env.FRONTEND_SERVER_URL || 'http://localhost:8888';

// Options de configuration pour le _middleware_ `cors`.
// CORS = Cross Origin Resource Sharing
const corsOptions = {
    origin: FRONTEND_SERVER_URL, // Configures the Access-Control-Allow-Origin CORS header. i.e. specifies that sigma-back wants to make resources accessible to this site (and this site only)
    credentials: true // Configures the Access-Control-Allow-Credentials CORS header. i.e. allows cookies to be included on cross-origin requests
};
app.use(cors(corsOptions));
 
//GHETTO
// Config de passport pour l'authentification ldap. Ne fait que *configurer* passport (aucun passport.authenticate() n'est appele, par exemple)
import './config_passport';

//with custom callback:
//http://www.passportjs.org/docs/authenticate/#custom-callback
// http://toon.io/understanding-passportjs-authentication-flow/
app.post('/login', (req, res, next) => {
    console.log("Received an authentication request to /login");
    passport.authenticate('ldapauth', (err, user, info) => {
        console.log("| Entering passport.authenticate('ldapauth', - ) callback");
        // If an exception occurred
        if (err) {
            console.log("| Error when trying to passport.authenticate with ldapauth");
            console.log(err);
            return res.status(err.status).json({
                message: "Exception raised in backend process during authentication: " + err,
                authSucceeded: false
            });
            // return next(err); // handle error? or drop request and answer with res.json()?
        }
        // If authentication failed, user will be set to false
        if (!user) {
            console.log("| Authentication failed, passport.authenticate did not return a user. ");
            return res.status(401).json({
                message: "Authentication failed: " + info.message,
                authSucceeded: false
            });
        }

        req.login(user, (err) => {
            // If an exception occurred at login
            if (err) {
                console.log("| Error when trying to req.login in callback in passport.authenticate('ldapauth', - )");
                console.log(err);
                return res.status(err.status).json({
                    message: "Exception raised in backend process during login: " + err,
                    authSucceeded: false
                });
                // return next(err); // handle error? or drop request and answer with res.json()?
            }
            // If all went well
            console.log("| Authentication succeeded! :)");
            // passport.authenticate automatically includes a Set-Cookie HTTP header in 
            // the response. The JSON body is just to signal the frontend that all went well
            return res.status(200).json({
                message: 'Authentication succeeded',
                authSucceeded: true
            });
        });
    })(req, res, next);
});

//without custom callback:
/*
// http://toon.io/understanding-passportjs-authentication-flow/
app.post('/login',
    passport.authenticate('ldapauth'),
    function (req, res) {
        // If this function gets called, authentication was successful.
        // `req.user` contains the authenticated user.
        console.log("Frontend authentication succeeded");
        res.json({
            message: 'Authentication succeeded',
            authSucceeded: true
        }); 
    }
);
*/

/**
 * @desc API GraphQL
 */
const environment = process.env.NODE_ENV || 'development';

/**
 * @desc Define GraphQL request context object, through a callback, with authorization.
 * See: https://github.com/apollographql/apollo-server/blob/master/docs/source/best-practices/authentication.md
 * 
 */
const context = async ({ req }) => {
    let uid;
    let password;
    
    console.log("Responding to graphql request...");
    console.log(`
    | User: ${req.user ? req.user.uid : "none"}
    | Authorization: ${req.headers.authorization}
    | Authenticated: ${req.isAuthenticated()}
    `.trim());
    
    if(req.isAuthenticated()) {
        console.log("graphql API is receiving a request from an authenticated user! \\o/");
        try {
            uid = req.user.uid;
            password = "mythe";
        } catch (err) {
            console.log("Error: req is authenticated, but pb when trying to extract uid from req.user. Probably user was either not serialized or not deserialized properly");
            console.log(err);
        }
    } else {
        // FOR DEVELOPMENT ONLY. for production, replace with a "publicUser" or "notLoggedInUser" or something.
        uid = dn.split("=")[1].split(",")[0];
        password = passwd;
    }
    
    return {
        request: req,
        user: { uid, password }
    }
}

const server = new ApolloServer({
    ...schema,
    context,
    playground: {
        settings: {
            "editor.theme": "dark",
            "editor.cursorShape": 'line'
        }
    }
});

server.applyMiddleware({ app });

// GraphQL voyager affiche une représentation sous forme de graphe du schema GraphQL
// accessible depuis adminview
app.use('/voyager',
    /*ensureLoggedIn('/login'),*/
    graphqlVoyager({ endpointUrl: '/graphql' })
);

// on utilise un express.Router qui sert a creer un "sous-middleware stack".
app.use('/adminview', router); // catches and resolves HTTP requests to paths '/adminview/*'

app.use('/', (req, res) => {
    res.redirect('/adminview');
});

export default app;