const express = require('express');
const { createProxyMiddleware, fixRequestBody } = require('http-proxy-middleware');
const fs = require('fs');
const path = require('path');

const app = express();
const proxyCache = {}; 

// 1. GLOBAL CORS INTERCEPTOR
// This stops SillyTavern/JanitorAI preflight requests from reaching NIM and getting rejected.
app.use((req, res, next) => {
    res.setHeader('Access-Control-Allow-Origin', '*');
    res.setHeader('Access-Control-Allow-Methods', 'GET, POST, OPTIONS, PUT, PATCH, DELETE');
    res.setHeader('Access-Control-Allow-Headers', 'Content-Type, Authorization');
    
    if (req.method === 'OPTIONS') {
        return res.sendStatus(200); // Instantly approve all preflights
    }
    next();
});

// Parse incoming bodies (required to inject NIM's thinking parameters)
app.use(express.json({ limit: '50mb' }));

// Load Endpoints
let endpoints = {};
try {
    endpoints = JSON.parse(fs.readFileSync(path.join(__dirname, 'endpoints.json'), 'utf8'));
    console.log("✔ Loaded Endpoints:", Object.keys(endpoints).join(', '));
} catch (e) {
    console.error("✘ Error: endpoints.json missing or invalid.");
}

app.use(express.static(path.join(__dirname, 'public')));
app.get('/api/endpoints', (req, res) => res.json(endpoints));

// 2. THE SMART PROXY
app.use('/:nick', (req, res, next) => {
    const { nick } = req.params;

    // Ignore internal or invalid routes
    if (nick === 'api' || !endpoints[nick]) return next();

    if (!proxyCache[nick]) {
        const target = endpoints[nick].url;
        console.log(`[Setup] Routing /${nick} -> ${target}`);

        // Logic to inject GLM 5.1 Thinking Parameters
        const handleProxyReq = (proxyReq, req, res) => {
            if (req.method === 'POST' && req.body) {
                if (nick === 'nim') {
                    req.body.chat_template_kwargs = {
                        enable_thinking: true,
                        clear_thinking: false
                    };
                    
                    // Map unsupported roles
                    if (req.body.messages && Array.isArray(req.body.messages)) {
                        req.body.messages.forEach(msg => {
                            if (msg.role === 'developer') msg.role = 'system';
                        });
                    }
                }
                // Safely repackage the modified JSON body
                fixRequestBody(proxyReq, req);
            }
        };

        const handleError = (err, req, res) => {
            console.error(`[Error: ${nick}]`, err.message);
            if (!res.headersSent) {
                res.status(502).json({ error: "Provider Offline or Connection Timeout." });
            }
        };

        proxyCache[nick] = createProxyMiddleware({
            target: target,
            changeOrigin: true,
            pathRewrite: { [`^/${nick}`]: '' },
            
            // 3. DUAL-COMPATIBILITY HOOKS
            // Guarantees fixRequestBody fires regardless of the middleware version installed
            
            // --- Legacy v2 Syntax ---
            onProxyReq: handleProxyReq,
            onError: handleError,
            
            // --- Modern v3 Syntax ---
            on: {
                proxyReq: handleProxyReq,
                error: handleError
            }
        });
    }

    return proxyCache[nick](req, res, next);
});

const PORT = 7860;
app.listen(PORT, '0.0.0.0', () => console.log(`🚀 Hub active on port ${PORT}`));