/**
 * 云函数：proxyHub（LLM 代理中心）
 * 替代：POST /api/llm/chat → action=llmChat
 *      POST /api/llm/gemini → action=geminiChat
 *      流式聊天：action=llmChatStream（SSE 透传，需要 fmode 平台 dispatcher 支持 chunked response）
 * 注意：/api/video-proxy 不迁（二进制大流量不适合云函数）
 */
const LLM_BASE_URL = 'http://server.fmode.cn:9999';
const LLM_API_KEY = 'sk-MFBOnsAtZiqlwwMgMLKCFmPy55pMohQEGMqsIw3aJrIgvoEO';

async function handler(request, response) {
  try {
    const action = pickParam(request, 'action');

    // ============ 流式聊天（SSE 透传） ============
    if (action === 'llmChatStream') {
      const body = pickParam(request, 'payload', 'data') || request.body || {};
      const { model, messages, temperature, max_tokens, ...rest } = body;
      if (!Array.isArray(messages) || messages.length === 0) {
        return response.json({ code: 400, success: false, error: '缺少 messages' });
      }
      const upstream = await fetch(`${LLM_BASE_URL}/v1/chat/completions`, {
        method: 'POST',
        headers: {
          'Content-Type': 'application/json',
          'Authorization': `Bearer ${LLM_API_KEY}`
        },
        body: JSON.stringify({
          model: model || 'gpt-4o',
          messages,
          temperature: temperature ?? 0.7,
          max_tokens: max_tokens ?? 4096,
          ...rest,
          stream: true
        })
      });
      if (!upstream.ok) {
        const errText = await upstream.text();
        return response.json({ code: upstream.status, success: false, error: errText || `upstream ${upstream.status}` });
      }

      // 把上游 SSE 原样透传给客户端
      // 注意：fmode 平台 dispatcher 必须放行 chunked response，否则客户端会一次性收到全部内容
      try {
        if (typeof response.setHeader === 'function') {
          response.setHeader('Content-Type', 'text/event-stream; charset=utf-8');
          response.setHeader('Cache-Control', 'no-cache, no-transform');
          response.setHeader('Connection', 'keep-alive');
          response.setHeader('X-Accel-Buffering', 'no');
        }
        if (typeof response.flushHeaders === 'function') response.flushHeaders();
      } catch (_) {}

      const reader = upstream.body.getReader();
      try {
        while (true) {
          const { value, done } = await reader.read();
          if (done) break;
          if (value && typeof response.write === 'function') {
            response.write(Buffer.from(value));
          }
        }
      } finally {
        try { reader.cancel(); } catch (_) {}
        if (typeof response.end === 'function') response.end();
      }
      return;
    }

    if (action === 'llmChat') {
      const body = pickParam(request, 'payload', 'data') || request.body || {};
      const { model, messages, temperature, max_tokens, ...rest } = body;
      if (!Array.isArray(messages)) {
        return response.json({ code: 400, success: false, error: '缺少 messages' });
      }
      const r = await fetch(`${LLM_BASE_URL}/v1/chat/completions`, {
        method: 'POST',
        headers: {
          'Content-Type': 'application/json',
          'Authorization': `Bearer ${LLM_API_KEY}`
        },
        body: JSON.stringify({
          model: model || 'gpt-4o',
          messages,
          temperature: temperature ?? 0.7,
          max_tokens: max_tokens ?? 4096,
          stream: false,
          ...rest
        })
      });
      const data = await r.json();
      response.json({ code: r.ok ? 200 : 500, success: r.ok, data });
      return;
    }

    if (action === 'geminiChat') {
      const body = pickParam(request, 'payload', 'data') || request.body || {};
      const { model, contents, generationConfig, safetySettings, systemInstruction } = body;
      if (!contents) {
        return response.json({ code: 400, success: false, error: '缺少 contents' });
      }
      const r = await fetch(`${LLM_BASE_URL}/v1beta/models/${model || 'gemini-2.0-flash'}:generateContent`, {
        method: 'POST',
        headers: {
          'Content-Type': 'application/json',
          'Authorization': `Bearer ${LLM_API_KEY}`
        },
        body: JSON.stringify({ contents, generationConfig, safetySettings, systemInstruction })
      });
      const data = await r.json();
      response.json({ code: r.ok ? 200 : 500, success: r.ok, data });
      return;
    }

    response.json({ code: 400, success: false, error: `未知 action: ${action}` });
  } catch (error) {
    console.error('❌ proxyHub 失败:', error.message);
    response.json({ code: 500, success: false, error: error.message });
  }
}

function pickParam(request, ...names) {
  const sources = [request.params, request.body, request];
  for (const src of sources) {
    if (!src || typeof src !== 'object') continue;
    for (const n of names) {
      const v = src[n];
      if (v !== undefined && v !== null && v !== '') return v;
    }
  }
  return null;
}