require('dotenv').config();
const fs = require('fs');
const path = require('path');
const cron = require('node-cron');
const { google } = require('googleapis');

const TOKENS_DIR = path.join(__dirname, 'tokens');
const CREDENTIALS_PATH = path.join(__dirname, 'credentials.json');

function getCredentials() {
    if (!fs.existsSync(CREDENTIALS_PATH) || fs.statSync(CREDENTIALS_PATH).isDirectory()) {
        throw new Error('Google OAuth credentials.json is missing. Please create the gmail-agent-auth Kubernetes Secret with your Google Cloud OAuth credentials.');
    }
    return JSON.parse(fs.readFileSync(CREDENTIALS_PATH));
}

const GEMINI_API_KEY = process.env.GEMINI_API_KEY || 'AIzaSyDKYcgVPN2oJirwzf_td3sBYMnXHWfVphU';
const WHATSAPP_GATEWAY_URL = process.env.WHATSAPP_GATEWAY_URL || 'http://whatsapp-gateway.ai-agents.svc.cluster.local:5001/api/send-message';
const WHATSAPP_TO = process.env.WHATSAPP_TO;

let baseOAuth2Client;
let accounts = [];

function loadAuth() {
    try {
        if (!fs.existsSync(CREDENTIALS_PATH) || fs.statSync(CREDENTIALS_PATH).isDirectory()) {
            console.warn('⚠️ Missing credentials.json. Gmail Agent will not be able to process emails or authenticate new accounts until this file is provided.');
            return;
        }
        if (!fs.existsSync(TOKENS_DIR)) {
            fs.mkdirSync(TOKENS_DIR, { recursive: true });
            console.log('Created empty tokens directory.');
        }
        
        const creds = getCredentials();
        const {client_secret, client_id, redirect_uris} = creds.installed || creds.web;
        baseOAuth2Client = { client_id, client_secret, redirect_uri: redirect_uris[0] || 'urn:ietf:wg:oauth:2.0:oob' };
        
        const tokenFiles = fs.readdirSync(TOKENS_DIR).filter(file => file.endsWith('.json'));
        if (tokenFiles.length === 0) {
            console.log('ℹ️ No token files found in tokens/. Waiting for accounts to be added via UI.');
            return;
        }
        
        for (const file of tokenFiles) {
            const accountName = file.replace('.json', '');
            const tokenContent = JSON.parse(fs.readFileSync(path.join(TOKENS_DIR, file)));
            
            const client = new google.auth.OAuth2(baseOAuth2Client.client_id, baseOAuth2Client.client_secret, baseOAuth2Client.redirect_uri);
            client.setCredentials(tokenContent);
            
            accounts.push({ name: accountName, client });
            console.log(`✅ Loaded credentials for account: ${accountName}`);
        }
    } catch (err) {
        console.error('❌ Error loading auth files:', err.message);
    }
}

async function ensureAgentReadLabel(account) {
    const gmail = google.gmail({ version: 'v1', auth: account.client });
    const res = await gmail.users.labels.list({ userId: 'me' });
    const labels = res.data.labels || [];
    let agentReadLabel = labels.find(l => l.name === 'AGENT_READ');
    
    if (!agentReadLabel) {
        console.log(`Creating AGENT_READ label for account ${account.name}...`);
        const createRes = await gmail.users.labels.create({
            userId: 'me',
            requestBody: {
                name: 'AGENT_READ',
                labelListVisibility: 'labelShow',
                messageListVisibility: 'show'
            }
        });
        agentReadLabel = createRes.data;
    }
    return agentReadLabel.id;
}

async function getUnreadEmails(account) {
    const gmail = google.gmail({ version: 'v1', auth: account.client });
    const res = await gmail.users.messages.list({
        userId: 'me',
        q: '-label:AGENT_READ newer_than:2d',
        maxResults: 10
    });
    
    const messages = res.data.messages || [];
    const emails = [];
    
    for (const msg of messages) {
        const fullMsg = await gmail.users.messages.get({ userId: 'me', id: msg.id, format: 'full' });
        const headers = fullMsg.data.payload.headers;
        const subject = headers.find(h => h.name === 'Subject')?.value || 'No Subject';
        const from = headers.find(h => h.name === 'From')?.value || 'Unknown';
        
        let body = '';
        if (fullMsg.data.payload.parts) {
            const part = fullMsg.data.payload.parts.find(p => p.mimeType === 'text/plain');
            if (part && part.body.data) {
                body = Buffer.from(part.body.data, 'base64').toString('utf8');
            }
        } else if (fullMsg.data.payload.body && fullMsg.data.payload.body.data) {
            body = Buffer.from(fullMsg.data.payload.body.data, 'base64').toString('utf8');
        }
        
        emails.push({ id: msg.id, subject, from, body: body.substring(0, 1000), accountName: account.name, client: account.client });
    }
    return emails;
}

async function markAsAgentRead(email, labelId) {
    const gmail = google.gmail({ version: 'v1', auth: email.client });
    await gmail.users.messages.modify({
        userId: 'me',
        id: email.id,
        requestBody: { addLabelIds: [labelId] }
    });
}

async function analyzeWithGemini(email) {
    const prompt = `You are a strict AI assistant. Your ONLY job is to filter emails to send to WhatsApp.
    
CRITICAL RULES:
1. STRICTLY IGNORE ALL promotional emails, newsletters, daily updates, market recaps, deals, marketing, product updates, surveys, or general spam. If it looks like a mass email or newsletter, it is NOT important.
2. ONLY flag truly personal messages, urgent requests from real people, travel updates, direct security alerts, or specific receipts.

Email Subject: ${email.subject}
Email From: ${email.from}
Email Body Preview:
${email.body}

Determine if this is an important email. Return a strict JSON response. Do not include markdown formatting.
Format:
{
  "isImportant": true or false,
  "summary": "1-sentence summary of what the user needs to know if true, otherwise leave empty"
}`;

    try {
        const res = await fetch(`https://generativelanguage.googleapis.com/v1beta/models/gemini-2.5-flash:generateContent?key=${GEMINI_API_KEY}`, {
            method: 'POST',
            headers: { 'Content-Type': 'application/json' },
            body: JSON.stringify({
                contents: [{ parts: [{ text: prompt }] }],
                generationConfig: {
                    temperature: 0.1,
                    responseMimeType: "application/json"
                }
            })
        });
        
        const data = await res.json();
        if (data.candidates && data.candidates.length > 0) {
            const text = data.candidates[0].content.parts[0].text;
            const parsed = JSON.parse(text);
            return { isImportant: parsed.isImportant, summary: parsed.summary || '' };
        }
        return { isImportant: false, summary: '' };
    } catch (err) {
        console.error('Gemini Error:', err.message);
        return { isImportant: false, summary: '' };
    }
}

async function sendWhatsAppNotification(email, summary) {
    const message = `📧 *[${email.accountName}] Important Email*\n*From:* ${email.from}\n*Subject:* ${email.subject}\n\n🤖 *Summary:* ${summary}`;
    
    try {
        await fetch(WHATSAPP_GATEWAY_URL, {
            method: 'POST',
            headers: { 
                'Content-Type': 'application/json',
                'x-app-name': 'Gmail Agent'
            },
            body: JSON.stringify({
                to: 'default',
                message: message
            })
        });
        console.log(`Notification sent for: [${email.accountName}] ${email.subject}`);
    } catch (err) {
        console.error('WhatsApp Gateway Error:', err.message);
    }
}

async function processEmails() {
    console.log(`[${new Date().toISOString()}] Checking for new emails across ${accounts.length} accounts...`);
    try {
        for (const account of accounts) {
            console.log(`Checking account: ${account.name}...`);
            if (!account.agentReadLabelId) {
                account.agentReadLabelId = await ensureAgentReadLabel(account);
            }
            
            const emails = await getUnreadEmails(account);
            if (emails.length === 0) {
                console.log(`No new emails for ${account.name}.`);
                continue;
            }
            
            console.log(`Found ${emails.length} unread emails for ${account.name}.`);
            
            for (const email of emails) {
                const analysis = await analyzeWithGemini(email);
                if (analysis.isImportant) {
                    await sendWhatsAppNotification(email, analysis.summary);
                } else {
                    console.log(`Skipped non-important email: ${email.subject}`);
                }
                // Mark as processed using our custom label
                await markAsAgentRead(email, account.agentReadLabelId);
            }
        }
    } catch (err) {
        console.error('Error processing emails:', err.message);
    }
}

// ─── Express Server for UI Integration ─────────────────────────────────────────
const express = require('express');
const cors = require('cors');
const app = express();
app.use(cors());
app.use(express.json());

// Get all connected accounts
app.get('/api/accounts', (req, res) => {
    res.json({
        success: true,
        accounts: accounts.map(a => ({ name: a.name }))
    });
});

// Generate Auth URL for a new account
app.post('/api/auth/url', (req, res) => {
    const { accountName } = req.body;
    if (!accountName) return res.status(400).json({ success: false, error: 'accountName is required' });
    
    try {
        const creds = getCredentials();
        const {client_secret, client_id, redirect_uris} = creds.installed || creds.web;
        const oAuth2Client = new google.auth.OAuth2(client_id, client_secret, redirect_uris[0] || 'urn:ietf:wg:oauth:2.0:oob');
        
        const SCOPES = ['https://www.googleapis.com/auth/gmail.readonly', 'https://www.googleapis.com/auth/gmail.modify'];
        const authUrl = oAuth2Client.generateAuthUrl({
            access_type: 'offline',
            prompt: 'consent',
            scope: SCOPES,
            state: accountName // pass the accountName in state so we don't lose it across redirects
        });
        
        res.json({ success: true, url: authUrl });
    } catch (e) {
        res.status(500).json({ success: false, error: e.message });
    }
});

// Verify token and hot-reload account
app.post('/api/auth/token', (req, res) => {
    const { accountName, code } = req.body;
    if (!accountName || !code) return res.status(400).json({ success: false, error: 'accountName and code are required' });
    
    try {
        const creds = getCredentials();
        const {client_secret, client_id, redirect_uris} = creds.installed || creds.web;
        const oAuth2Client = new google.auth.OAuth2(client_id, client_secret, redirect_uris[0] || 'urn:ietf:wg:oauth:2.0:oob');
        
        oAuth2Client.getToken(code, (err, token) => {
            if (err) return res.status(400).json({ success: false, error: err.message });
            
            const tokenPath = path.join(TOKENS_DIR, `${accountName}.json`);
            fs.writeFileSync(tokenPath, JSON.stringify(token));
            
            // Reload accounts list
            accounts = [];
            loadAuth();
            
            res.json({ success: true, message: `Account ${accountName} added successfully!` });
        });
    } catch (e) {
        res.status(500).json({ success: false, error: e.message });
    }
});

const PORT = process.env.PORT || 5002;
app.listen(PORT, '0.0.0.0', () => {
    console.log(`Express server listening on 0.0.0.0:${PORT}`);
});

// Start Application
try {
    loadAuth();
    console.log('Gmail Agent started successfully.');
    console.log(`Cron job scheduled to check every 15 minutes.`);
    
    // Check immediately on startup
    processEmails();
    
    // Schedule every 15 minutes
    cron.schedule('*/15 * * * *', () => {
        processEmails();
    });
} catch (e) {
    console.error('Failed to start:', e.message);
}