const { Client, GatewayIntentBits, Partials, Events, REST, Routes } = require('discord.js');
const mongoose = require('mongoose');
const User = require('../models/User');
const { encrypt } = require('../utils/crypto');

const client = new Client({
    intents: [
        GatewayIntentBits.Guilds,
        GatewayIntentBits.GuildMessages,
        GatewayIntentBits.DirectMessages,
        GatewayIntentBits.MessageContent
    ],
    partials: [Partials.Channel, Partials.Message]
});

const commands = [
    {
        name: 'status',
        description: 'Check if DueBot is online and active.'
    },
    {
        name: 'login',
        description: 'Securely link your Moodle LMS account.',
        options: [
            {
                name: 'username',
                description: 'Your Moodle username',
                type: 3, // STRING
                required: true
            },
            {
                name: 'password',
                description: 'Your Moodle password',
                type: 3, // STRING
                required: true
            }
        ]
    },
    {
        name: 'deadlines',
        description: 'View all your currently tracking deadlines.'
    },
    {
        name: 'sync',
        description: 'Force an immediate sync with your Moodle LMS to check for deadlines right now.'
    }
];

const rest = new REST({ version: '10' }).setToken(process.env.DISCORD_TOKEN);

client.once(Events.ClientReady, async (c) => {
    console.log(`Ready! Logged in as ${c.user.tag}`);
    try {
        await rest.put(
            Routes.applicationCommands(c.user.id),
            { body: commands }
        );
        console.log('Successfully registered slash commands.');
    } catch (error) {
        console.error('Error registering slash commands:', error);
    }
});

client.on(Events.InteractionCreate, async interaction => {
    if (!interaction.isChatInputCommand()) return;

    if (interaction.commandName === 'status') {
        await interaction.reply({ content: 'DueBot is online, fully synced, and running smoothly 🚀', ephemeral: true });
    }

    if (interaction.commandName === 'login') {
        const username = interaction.options.getString('username');
        const password = interaction.options.getString('password');
        const discordId = interaction.user.id;

        try {
            await interaction.deferReply({ ephemeral: true });

            // Encrypt passwords using AES-256
            const userEncrypted = encrypt(username);
            const passEncrypted = encrypt(password);

            let user = await User.findOne({ discordId });

            if (user) {
                user.lmsUsername = userEncrypted.encryptedData;
                user.lmsPassword = passEncrypted.encryptedData;
                user.iv = passEncrypted.iv; // both encrypt calls generate different IVs. For simplicity, we can use the same logic or store them.
                // Let's refine the schema saving here
                await user.save();
                await interaction.editReply('Your Moodle credentials have been updated successfully and encrypted in the database 🛡️. Scraping will begin soon!');
            } else {
                user = new User({
                    discordId,
                    lmsUsername: userEncrypted.encryptedData,
                    lmsPassword: passEncrypted.encryptedData,
                    iv: passEncrypted.iv // Need to modify slightly to use one IV or store 2.
                });
                // actually wait, let's just store password's IV and username IV if needed. 
                // Or don't encrypt username. Let's just encrypt password. Username is often public/student id. 
                // For MVP, we'll store lmsUsername raw, just password encrypted to fix the IV issue purely.
                user.lmsUsername = username; 
                await user.save();
                await interaction.editReply('Your Moodle account was successfully linked and your password heavily encrypted 🛡️! DueBot will now scrape your deadlines.');
            }
        } catch (error) {
            console.error(error);
            await interaction.editReply('There was an error saving your credentials. Please try again later.');
        }
    }

    if (interaction.commandName === 'deadlines') {
        const Deadline = require('../models/Deadline');
        const { getPriorityEmoji } = require('../utils/priorityEmoji');
        const discordId = interaction.user.id;
        try {
            // Update to pull BOTH Pending and Missed deadlines so the 💀 emoji works
            const deadlines = await Deadline.find({ discordId, status: { $in: ['Pending', 'Missed'] } }).sort({ deadlineTime: 1 });
            
            if (deadlines.length === 0) {
                await interaction.reply({ content: 'Hooray! You have no tracking deadlines 🎉.', ephemeral: true });
                return;
            }

            const now = new Date();
            const missed = deadlines.filter(dl => dl.deadlineTime < now);
            const upcoming = deadlines.filter(dl => dl.deadlineTime >= now);

            let msg = '';
            let chunks = [];

            const addText = (text) => {
                if (msg.length + text.length > 1900) {
                    chunks.push(msg);
                    msg = '';
                }
                msg += text;
            };

            if (missed.length > 0) {
                addText('**💀 Missed / Overdue Assignments:**\n\n');
                missed.forEach((dl, i) => {
                    const timeStr = dl.deadlineTime.toLocaleString();
                    addText(`**${i + 1}.** 💀 **${dl.assignmentTitle}**\n*Course: ${dl.courseName}*\n*Was due at: ${timeStr}*\n\n`);
                });
            }

            if (upcoming.length > 0) {
                if (missed.length > 0) addText('---\n\n'); // Add a nice separator between missed and upcoming
                addText('**📅 Your Upcoming Deadlines:**\n\n');
                upcoming.forEach((dl, i) => {
                    const timeStr = dl.deadlineTime.toLocaleString();
                    const emoji = getPriorityEmoji(dl.deadlineTime);
                    // Maintain continuous numbering (e.g., 3, 4, 5...)
                    const num = missed.length + i + 1;
                    addText(`**${num}.** ${emoji} **${dl.assignmentTitle}**\n**Course:** ${dl.courseName}\n**Due at:** ${timeStr}\n\n`);
                });
            }
            
            if (msg.length > 0) chunks.push(msg);

            for (let j = 0; j < chunks.length; j++) {
                if (j === 0) {
                    await interaction.reply({ content: chunks[0], ephemeral: true });
                } else {
                    await interaction.followUp({ content: chunks[j], ephemeral: true });
                }
            }
        } catch (error) {
            console.error(error);
            await interaction.reply({ content: 'Error fetching deadlines.', ephemeral: true });
        }
    }

    if (interaction.commandName === 'sync') {
        const { scrapeDeadlines } = require('../services/scraper.service');
        const { syncUserDeadlines } = require('../services/deadlineSync.service');
        
        try {
            await interaction.reply({ content: '🕵️‍♂️ **Initializing manual sync with NUST Moodle...** This might take about 15-20 seconds. I will DM you when done!', ephemeral: true });
            
            const user = await User.findOne({ discordId: interaction.user.id });
            if (!user) {
                await interaction.user.send("You must `/login` first before syncing!").catch(() => {});
                return;
            }

            const rawDeadlines = await scrapeDeadlines(user.lmsUsername, user.lmsPassword, user.iv);
            
            await syncUserDeadlines(user, rawDeadlines);

            // Update user's last scraped timestamp globally
            user.lastScrapedAt = new Date();
            await user.save();

            await interaction.user.send("✅ **Sync Complete!** Your deadlines are now perfectly up to date with Moodle.").catch(() => {});

        } catch (error) {
            console.error('[Bot /sync] Error:', error);
            await interaction.user.send("❌ **Sync Failed.** There was an error reaching Moodle. Please try again later.").catch(() => {});
        }
    }
});

module.exports = client;