src/app/api/generate-article/route.ts

import { openai } from '@ai-sdk/openai';
import { generateText } from 'ai';
import { langfuse } from '@/lib/langfuse';
import { AI_CONFIG } from '@/config/ai';

export async function POST(req: Request) {
  try {
    const { 
      grade, 
      unit, 
      textbookVocab, 
      additionalVocab, 
      grammar, 
      topic, 
      inputArticle 
    } = await req.json();

    // Get the prompt from Langfuse (FREE - no cost for prompt management)
    const langfusePrompt = await langfuse.prompt.get('article/generation');
    
    // Replace placeholders with actual values
    const prompt = langfusePrompt.prompt
      .replace(/\{\{grade_values\}\}/g, grade.join(', '))
      .replace(/\{\{unit_values\}\}/g, unit.join(', '))
      .replace(/\{\{textbook_vocab_values\}\}/g, textbookVocab)
      .replace(/\{\{additional_vocab_values\}\}/g, additionalVocab)
      .replace(/\{\{grammar_values\}\}/g, grammar.join(', '))
      .replace(/\{\{topic_values\}\}/g, topic.join(', '));

    const result = await generateText({
      model: openai(AI_CONFIG.model),
      prompt: prompt,
    });

    return Response.json({
      article: result.text,
      createdAt: new Date().toISOString(),
    });

  } catch (error) {
    console.error('Error generating article:', error);
    return Response.json(
      { error: 'Failed to generate article' },
      { status: 500 }
    );
  }
}