src/lib/services/title-generator.ts

import { generateText } from 'ai';
import { createOpenAI } from '@ai-sdk/openai';
import { Message } from '../types/models';

// Create OpenAI provider with custom API key
const openai = createOpenAI({
  apiKey: process.env.CZ_OPENAI_API_KEY || '',
});

/**
 * Generates a concise Traditional Chinese title for a conversation
 * based on provided messages (6-10 characters)
 * Caller determines which messages to include (typically first 15 messages)
 */
export async function generateConversationTitle(messages: Message[]): Promise<string> {
  if (messages.length === 0) {
    return '新對話';
  }

  // Use all provided messages (caller sends first 15 for best context)
  const recentMessages = messages;

  // Format messages for the prompt
  const conversationText = recentMessages
    .map(m => {
      const speaker = m.speaker === 'student' ? '學生' : '老師';
      return `${speaker}: ${m.content}`;
    })
    .join('\n');

  try {
    const { text } = await generateText({
      model: openai.responses(process.env.MODEL_NAME || 'gpt-5'),
      prompt: `根據以下對話內容，用6-10個繁體中文字產生一個簡潔的標題。標題應該概括對話的主題或情境。只回傳標題文字，不要有其他說明。

對話內容：
${conversationText}

標題：`,
    });

    // Clean up the response - remove quotes, extra whitespace, etc.
    const cleanedTitle = text.trim().replace(/^["「『]|["」』]$/g, '').slice(0, 15);

    return cleanedTitle || '新對話';
  } catch (error) {
    console.error('Error generating conversation title:', error);
    return '新對話';
  }
}