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

export async function POST(request: NextRequest) {
  try {
    const { question, answer, role, difficulty } = await request.json();

    const headerApiKey = request.headers.get('x-gemini-api-key');
    const apiKey = headerApiKey || process.env.GEMINI_API_KEY;
    if (!apiKey) {
      return NextResponse.json(
        { error: 'GEMINI_API_KEY is not configured. Please add it in Settings or .env.local file.' },
        { status: 500 }
      );
    }

    const genAI = new GoogleGenerativeAI(apiKey);
    const model = genAI.getGenerativeModel({ model: 'gemini-2.0-flash' });

    const prompt = `You are an expert interview evaluator for a ${role} position (${difficulty} level).

QUESTION: "${question}"

CANDIDATE'S ANSWER: "${answer}"

Evaluate the candidate's answer thoroughly. Return ONLY a valid JSON object (no markdown, no code blocks) with these exact fields:
{
  "score": <overall score 0-10>,
  "relevance": <relevance to question 0-10>,
  "clarity": <clarity of explanation 0-10>,
  "technicalAccuracy": <technical correctness 0-10>,
  "confidence": <apparent confidence level 0-10>,
  "strengths": [<array of 2-3 specific strengths>],
  "weaknesses": [<array of 2-3 specific areas for improvement>],
  "suggestions": [<array of 2-3 actionable suggestions>],
  "sampleAnswer": "<a comprehensive ideal answer in 3-4 sentences>"
}

Be fair but rigorous. Provide constructive, actionable feedback. The sample answer should demonstrate what an excellent response looks like.`;

    const result = await model.generateContent(prompt);
    const responseText = result.response.text();

    // Parse JSON from the response
    const jsonMatch = responseText.match(/\{[\s\S]*\}/);
    if (!jsonMatch) {
      throw new Error('Failed to parse evaluation from AI response');
    }

    const evaluation = JSON.parse(jsonMatch[0]);

    return NextResponse.json({ evaluation });
  } catch (error) {
    console.error('Error evaluating answer:', error);
    return NextResponse.json(
      { error: 'Failed to evaluate answer. Please try again.' },
      { status: 500 }
    );
  }
}