// Allow streaming responses up to 30 seconds
export const maxDuration = 30;

export async function POST(req: Request) {
  try {
    const { messages, sessionId } = await req.json();
    
    // Transform assistant-ui message format to backend format
    const transformedMessages = messages.map((msg: { role: string; content: unknown }) => ({
      role: msg.role,
      content: Array.isArray(msg.content) 
        ? msg.content.map((part: { text?: string; content?: string }) => part.text || part.content || '').join('')
        : msg.content
    }));
    
    // Get session ID from multiple sources (priority order: body, header, generate new)
    const headerSessionId = req.headers.get('X-Session-ID');
    const effectiveSessionId = sessionId || headerSessionId || `session_${Date.now()}_${Math.random().toString(36).substring(2)}`;
    
    console.log(`Using session ID: ${effectiveSessionId}`);
    
    // Forward request to our Python backend with enhanced configuration 
    
    const apiUrl = process.env["NEXT_PUBLIC_API_URL"] || "http://localhost:8000/api";
    const backendResponse = await fetch(apiUrl+'/ai-sdk/chat', {
      method: 'POST',
      headers: {
        'Content-Type': 'application/json',
        'Accept': 'text/plain',
      },
      body: JSON.stringify({
        messages: transformedMessages,
        session_id: effectiveSessionId,
        // Add metadata for better assistant-ui integration
        metadata: {
          source: 'assistant-ui',
          version: '0.10.x',
          timestamp: new Date().toISOString(),
        },
      }),
    });

    if (!backendResponse.ok) {
      const errorText = await backendResponse.text();
      console.error(`Backend error (${backendResponse.status}):`, errorText);
      throw new Error(`Backend responded with status: ${backendResponse.status}`);
    }

    // Return the stream from our backend with proper Data Stream Protocol headers
    return new Response(backendResponse.body, {
      headers: {
        'Content-Type': 'text/plain; charset=utf-8',
        'Cache-Control': 'no-cache, no-store, must-revalidate',
        'Connection': 'keep-alive',
        'x-vercel-ai-data-stream': 'v1', // AI SDK compatibility
        'x-assistant-ui-stream': 'v1',   // assistant-ui compatibility
        'Access-Control-Allow-Origin': '*',
        'Access-Control-Allow-Methods': 'POST, GET, OPTIONS',
        'Access-Control-Allow-Headers': 'Content-Type, Accept',
      },
    });
  } catch (error) {
    console.error('Chat API error:', error);
    
    // Return error in Data Stream Protocol format
    return new Response(
      `3:${JSON.stringify(error instanceof Error ? error.message : 'Unknown error')}\n`,
      {
        status: 500,
        headers: {
          'Content-Type': 'text/plain; charset=utf-8',
          'x-vercel-ai-data-stream': 'v1',
        },
      }
    );
  }
}

// Handle preflight requests
export async function OPTIONS() {
  return new Response(null, {
    status: 200,
    headers: {
      'Access-Control-Allow-Origin': '*',
      'Access-Control-Allow-Methods': 'POST, GET, OPTIONS',
      'Access-Control-Allow-Headers': 'Content-Type, Accept',
    },
  });
}