import { NextRequest } from 'next/server';
import { GoogleGenerativeAI } from '@google/generative-ai';

export async function POST(req: NextRequest) {
  try {
    const { messages } = await req.json();

    if (!process.env.GEMINI_API_KEY) {
      return new Response(JSON.stringify({ error: 'Gemini API key not configured' }), { 
        status: 500,
        headers: { 'Content-Type': 'application/json' }
      });
    }

    const genAI = new GoogleGenerativeAI(process.env.GEMINI_API_KEY);
    const model = genAI.getGenerativeModel({ model: 'gemini-pro' });

    // Convert messages to Gemini format
    const history = messages.slice(0, -1).map((msg: any) => ({
      role: msg.role === 'assistant' ? 'model' : 'user',
      parts: [{ text: msg.content }],
    }));

    const userMessage = messages[messages.length - 1].content;

    const chat = model.startChat({
      history: history,
      generationConfig: {
        temperature: 0.7,
        maxOutputTokens: 1000,
      },
    });

    const result = await chat.sendMessageStream(userMessage);

    const encoder = new TextEncoder();
    const stream = new ReadableStream({
      async start(controller) {
        try {
          for await (const chunk of result.stream) {
            const text = chunk.text();
            controller.enqueue(encoder.encode(`data: ${JSON.stringify({ text })}\n\n`));
          }
          controller.enqueue(encoder.encode('data: [DONE]\n\n'));
          controller.close();
        } catch (error) {
          controller.error(error);
        }
      },
    });

    return new Response(stream, {
      headers: {
        'Content-Type': 'text/event-stream',
        'Cache-Control': 'no-cache',
        'Connection': 'keep-alive',
      },
    });
  } catch (error: any) {
    console.error('Error in chat API:', error);
    return new Response(JSON.stringify({ error: error.message }), {
      status: 500,
      headers: { 'Content-Type': 'application/json' },
    });
  }
}