const express = require('express');
const fetch = require('node-fetch');
const cors = require('cors');
const rateLimit = require('express-rate-limit');
require('dotenv').config();

const app = express();

// --- 1. SECURITY: TRUST PROXY ---
// Required for Hugging Face to see the Real IP for rate limiting
app.set('trust proxy', 1); 

// --- 2. SECURITY: RATE LIMITING ---
// Limit each IP to 100 requests per 15 minutes
const limiter = rateLimit({
    windowMs: 15 * 60 * 1000, 
    max: 100, 
    standardHeaders: true,
    legacyHeaders: false,
    message: { error: "Too many requests, please try again later." }
});
app.use(limiter);

// --- 3. SECURITY: STRICT CORS ---
const allowedOrigins = process.env.ALLOWED_ORIGINS ? process.env.ALLOWED_ORIGINS.split(',') : [];

app.use(cors({
    origin: function (origin, callback) {
        // Open Mode: If list is empty or origin is null (tools/mobile), allow it.
        if (!origin || allowedOrigins.length === 0) return callback(null, true);
        
        if (allowedOrigins.indexOf(origin) !== -1) {
            callback(null, true);
        } else {
            callback(new Error('Not allowed by CORS'));
        }
    }
}));

app.use(express.json());

// --- 4. MULTI-INSTANCE CONFIGURATION ---
let INSTANCES = [];
try {
    // Example Secret: [{"url":"https://my-flowise.com","key":"tr-123"}, {"url":"https://open-flowise.com","key":""}]
    INSTANCES = JSON.parse(process.env.FLOWISE_INSTANCES || '[]');
} catch (e) {
    console.error("CRITICAL ERROR: Could not parse FLOWISE_INSTANCES JSON", e);
}

// Master Cache: Maps "bot-name" -> { flowId, instanceUrl, apiKey }
let flowDirectory = {};
let lastCacheUpdate = 0;

// --- 5. DYNAMIC DISCOVERY ---
async function refreshFlowDirectory() {
    // Cache valid for 60 seconds
    if (Date.now() - lastCacheUpdate < 60000 && Object.keys(flowDirectory).length > 0) return;

    console.log(`[System] Scanning ${INSTANCES.length} Flowise Instances...`);
    const newDirectory = {};

    // Run all fetches in parallel
    const promises = INSTANCES.map(async (inst) => {
        try {
            // Smart Auth: Only add header if key exists
            const headers = {};
            if (inst.key && inst.key.length > 0) {
                headers['Authorization'] = `Bearer ${inst.key}`;
            }

            const res = await fetch(`${inst.url}/api/v1/chatflows`, { headers });
            
            if(!res.ok) throw new Error(`Status ${res.status}`);
            const flows = await res.json();
            
            flows.forEach(flow => {
                const alias = flow.name.toLowerCase().replace(/\s+/g, '-');
                newDirectory[alias] = {
                    id: flow.id,
                    host: inst.url,
                    key: inst.key
                };
            });
        } catch (err) {
            console.error(`[Error] Failed to fetch from ${inst.url}:`, err.message);
        }
    });

    await Promise.allSettled(promises);
    
    flowDirectory = newDirectory;
    lastCacheUpdate = Date.now();
    console.log(`[System] Directory Updated. Serving ${Object.keys(flowDirectory).length} bots.`);
}

// --- 6. THE ROUTE ---
app.post('/api/v1/prediction/:botName', async (req, res) => {
    const botName = req.params.botName.toLowerCase();
    
    await refreshFlowDirectory();

    const target = flowDirectory[botName];

    if (!target) {
        lastCacheUpdate = 0; 
        await refreshFlowDirectory();
        if (!flowDirectory[botName]) {
            return res.status(404).json({ error: `Bot '${botName}' not found.` });
        }
    }

    const finalTarget = flowDirectory[botName];

    try {
        // Construct Headers for forwarding
        const forwardHeaders = {
            'Content-Type': 'application/json',
            'HTTP-Referer': req.headers.origin || 'https://huggingface.co', 
            'X-Title': 'FederatedProxy'
        };

        // Smart Auth: Only add Bearer if key exists
        if (finalTarget.key && finalTarget.key.length > 0) {
            forwardHeaders['Authorization'] = `Bearer ${finalTarget.key}`;
        }

        const flowiseResponse = await fetch(`${finalTarget.host}/api/v1/prediction/${finalTarget.id}`, {
            method: 'POST',
            headers: forwardHeaders,
            body: JSON.stringify(req.body)
        });

        const data = await flowiseResponse.json();
        res.status(flowiseResponse.status).json(data);

    } catch (error) {
        console.error("Proxy Forwarding Error:", error);
        res.status(500).json({ error: 'Proxy forwarding failed.' });
    }
});

app.get('/', (req, res) => res.send('Federated Proxy Active'));

app.listen(7860, '0.0.0.0', () => console.log('Federated Proxy running on port 7860'));