/** Express app factory for @geepers/chat server mode */

import express from 'express';
import path from 'node:path';
import { fileURLToPath } from 'node:url';
import type { ServerConfig } from './types.js';
import { getHtml } from './html.js';
import { streamChat } from './providers.js';
import { proxyToGateway } from './gateway.js';
import { resolveApiKey } from './detect.js';

const __filename = fileURLToPath(import.meta.url);
const __dirname = path.dirname(__filename);

export function createServer(config: ServerConfig): express.Express {
  const app = express();
  app.use(express.json());

  // Serve the IIFE bundle from the dist/ directory (same dir as cli.js)
  app.get('/dist/index.iife.global.js', (_req, res) => {
    const iifePath = path.join(__dirname, 'index.iife.global.js');
    res.sendFile(iifePath);
  });

  // Landing page with ChatUI
  app.get('/', (_req, res) => {
    res.type('html').send(getHtml(config.providers, config.mode));
  });

  // Provider list
  app.get('/providers', (_req, res) => {
    res.json(config.providers.map(p => ({
      name: p.name,
      label: p.label,
      model: p.model,
    })));
  });

  // Health check
  app.get('/health', (_req, res) => {
    res.json({
      status: 'ok',
      mode: config.mode,
      providers: config.providers.map(p => p.name),
    });
  });

  // SSE streaming chat endpoint — matches what SSEChat client expects
  app.post('/llm/chat', async (req, res) => {
    const { provider, model, messages } = req.body;

    if (config.mode === 'gateway') {
      return proxyToGateway(req, res, config.gatewayUrl);
    }

    // Direct mode
    res.setHeader('Content-Type', 'text/event-stream');
    res.setHeader('Cache-Control', 'no-cache');
    res.setHeader('Connection', 'keep-alive');

    const apiKey = resolveApiKey(provider);
    if (!apiKey && provider !== 'ollama') {
      res.write(`data: ${JSON.stringify({ error: `No API key found for ${provider}` })}\n\n`);
      res.end();
      return;
    }

    try {
      for await (const chunk of streamChat(provider, model, messages, apiKey)) {
        res.write(`data: ${JSON.stringify({ content: chunk })}\n\n`);
      }
      res.write(`data: ${JSON.stringify({ done: true })}\n\n`);
    } catch (error) {
      const msg = error instanceof Error ? error.message : String(error);
      res.write(`data: ${JSON.stringify({ error: msg })}\n\n`);
    }
    res.end();
  });

  return app;
}