// Global logging toggles
// const fileLogging = false;
const consoleLogging = true;


// Imports
// const fs = require('fs');
const http = require('http');
const express = require('express');


// Global server setup
const app = express();
const clientPath = __dirname+'/../html';
console.log('Serving static from ' + clientPath);
app.use(express.json());
app.use(express.static(clientPath));
const server = http.createServer(app);


// Check if string is already in array
function isStringUnique(arr, str) {
    let match = true;
    for (const s of arr)
        if (s === str) {
            match = false;
            break;
        }
    return match;
}

// Generate the partial ID after username
function generatePartialID() {
    return Math.floor(Math.random()*10000).toString().padStart(4, '0');
}

// Check if input is a user
function isUser(user, other) {
    // Check by full name
    if ('full' in other)
        return `${user.name}#${user.id}` === other.full;
    // Check by unique id
    else if ('id' in other && 'name' in other)
        return other.id === user.id && other.name === user.name;
    // Not applicable
    else return false;
}

// Check for user inactivity and delete accordingly
function userInactivity(name, id) {
    for (let i = 0; i < users.length; i++)
        if (isUser(users[i], {name, id}) && new Date() - users[i].seen > 86400000) {
            // User with ID 'name#id' was inactive for longer than a day.

            if (consoleLogging)
                console.log(`Deleting user with ID '${name}#${id}' because of inactivity.`);

            users.splice(i, 1);
            break;
        }
}


// User and chat data
const users = [], chats = [];
// Incoming user connection
app.post('/connect', (req, res) => {
    // Retrieve username
    const { name } = req.body;

    // Generate id in unique pattern 'name#id'
    let id = generatePartialID();
    const name_id = users.map(u => `${u.name}#${u.id}`);
    while (!isStringUnique(name_id, `${name}#${id}`))
        id = generatePartialID();

    // Save user data
    users.push({
        deletion: setInterval(
            ()=>userInactivity(name, id),
            3600000),
        seen: new Date(),
        event: null,
        chats: {},
        name,
        id
    });

    // Log connection
    if (consoleLogging)
        console.log(`User with ID '${name}#${id}' connected.`);

    // Respond with id
    res.status(200).json({ id });
});

// User has disconnected
app.post('/disconnect', (req, res) => {
    // Retrieve user data
    const { name, id } = req.body;

    // Search for user in data
    for (let i = 0; i < users.length; i++)
        // If user was found, delete all of their data
        if (isUser(users[i], {name, id})) {
            // Log disconnect
            if (consoleLogging)
                console.log(`User with ID '${name}#${id}' disconnected.`);

            // Delete user
            users.splice(i, 1);
            break;
        }

    // Respond with id as confirmation
    res.status(200).send();
});

// User wants to measure ping
app.get('/ping', (req, res) => {
    res.status(200).send();
});

// User wants to change name
app.post('/nickname', (req, res) => {
    // Retrieve user data and old name
    const { oldName, name, id } = req.body;

    // Check if unique pattern 'name#id' is valid, generate new one
    const name_id = users.map(u => `${u.name}#${u.id}`);
    let currentID = id;
    while (!isStringUnique(name_id, `${name}#${currentID}`))
        currentID = generatePartialID();

    // Find specified user
    for (const u of users)
        if (isUser(u, {name: oldName, id})) {
            // Log renaming
            if (consoleLogging)
                console.log(`(Re-)named user with ID '${oldName}#${id}'.`);

            // Save new name
            u.name = name;
            u.id = currentID;
            u.seen = new Date();
            break;
        }

    // Respond with confirmation
    res.status(200).json({ id: currentID });
});

// User is pulling messages
app.get('/getChat', (req, res) => {
    res.setHeader('Content-Type', 'text/event-stream');
    res.setHeader('Cache-Control', 'no-cache');
    res.setHeader('Connection', 'keep-alive');

    // Save user activity
    let full = req.query.full, found = false;
    for (const u of users)
        if (isUser(u, {full})) {
            found = true;
            u.event = res;
            u.seen = new Date();
            break;
        }
    if (!found) {
        res.write('data: {"message":"Invalid user provided."}');
        res.end();
        return;
    }

    // Log if messages were delivered
    if (consoleLogging)
        console.log(`New message event listener opened by user with ID '${full}'.`);

    // Handle close-event for when client is no longer listening
    res.on('close', () => {
        for (const u of users)
            if (isUser(u, {full}))
                u.event = null;
    });
});

// User sent new message
app.post('/message', (req, res) => {
    // Retrieve user data, their message and where to deliver it to
    const { name, id, to, message } = req.body;

    // Search for sender
    for (const u of users)
        if (isUser(u, {name, id})) {
            // Go through every recipient
            for (const recipient of to) {
                // Save message for recipient
                for (const o of users)
                    if (isUser(o, {full: recipient}) && o.event !== null)
                        o.event.write(`data: ${JSON.stringify({from: `${name}#${id}`, message})}\n\n`);
            }
            // Save user activity
            u.seen = new Date();
            break;
        }

    // Log users' message
    if (consoleLogging)
        console.log(`User with ID '${name}#${id}' sent message '${message}' to '${to}'.`);

    // Confirm process
    res.status(200).send();
});

// User requesting all names
app.get('/getNames', (req, res) => {
    // Log request
    if (consoleLogging)
        console.log('Some user requested all usernames + IDs.');

    // Respond with unique patterns 'name#id'
    res.status(200).json(users.map(u => {
        return {
            name: u.name,
            id: u.id
        };
    }));
});

// User sends activity notification
app.post('/activity', (req, res) => {
    // Retrieve user data
    const { name, id } = req.body;

    // Save activity
    for (const u of users)
        if (isUser(u, {name, id})) {
            // Log activity
            if (consoleLogging)
                console.log(`User with ID '${name}#${id}' is online.`);

            u.seen = new Date();
            break;
        }

    // Confirm process
    res.status(200).send();
});

// User asks if their data exists
app.post('/login', (req, res) => {
    // Retrieve user data
    const { name, id } = req.body;

    // Log login
    if (consoleLogging)
        console.log(`Some user requested existence of '${name}#${id}'.`);

    // Go through users, success if user exists
    let success = false;
    for (const u of users)
        if (isUser(u, {name, id})) {
            success = true;
            // Save activity
            u.seen = new Date();
            break;
        }

    // Respond with status
    res.status(200).json({success});
});

// User wants to join chat
app.post('/chatInit', (req, res) => {
    // Retrieve user data and chat name
    const { name, id, chat } = req.body;

    // Save user activity
    for (const u of users)
        if (isUser(u, {name, id})) {
            u.seen = new Date();
            break;
        }

    // Check if chats already exist
    const fullName = `${name}#${id}`;
    let existance = chat.map(e => [e, false]);
    // Go through chats
    for (const c of chats)
        // Go through provided names
        for (const n of existance) {
            // If name is this chat
            if (n[0] === c.name) {
                // Chat exists, add user to it
                n[1] = true;
                if (!c.users.includes(fullName))
                    c.users.push(fullName);
                break;
            }
        }

    // Go through provided names
    for (const n of existance) {
        // Chat didn't exist
        if (!n[1])
            // Create it and save user in it
            chats.push({
                users: [fullName],
                name: n[0]
            });
    }

    // Log chat initialization
    if (consoleLogging)
        console.log(`User with ID '${name}#${id}' joined chat '${chat}'.`);

    // Confirm process
    res.status(200).send();
});

// User sends a message in chat
app.post('/sendGroup', (req, res) => {
    // Retrieve user data and chat name and message
    const { name, id, message, chat } = req.body;

    // Save user activity
    for (const u of users)
        if (isUser(u, {name, id})) {
            u.seen = new Date();
            break;
        }

    // Find provided chat
    const fullName = `${name}#${id}`;
    for (const c of chats)
        if (chat.includes(c.name)) {
            // Go through users in chat
            for (const u of c.users)
                if (u !== fullName) {
                    // Send message to recipient
                    for (const o of users)
                        if (isUser(o, {full: u}) && o.event !== null)
                            o.event.write(`data: ${JSON.stringify({from: fullName, message})}\n\n`);
                }
        }

    // Log users' message
    if (consoleLogging)
        console.log(`User with ID '${name}#${id}' sent message '${message}' in '${chat}'.`);

    // Confirm process
    res.status(200).send();
});

// Internal server error
server.on('error', err => {
    console.error('Internal server error', err);
});

// Server has closed
server.on('close', () => {
    console.log('Shutting down server ...');
});

// Listen on port 3000 for webserver connection
server.listen(3000, () => {
    console.log('Server running on port 3000');
});