Keep/keep-notes/lib/ai/services/title-suggestion.service.ts

/**
 * Title Suggestion Service
 * Generates intelligent title suggestions based on note content
 */

import { createOpenAI } from '@ai-sdk/openai'
import { generateText } from 'ai'
import { LanguageDetectionService } from './language-detection.service'

// Helper to get AI model for text generation
function getTextGenerationModel() {
  const apiKey = process.env.OPENAI_API_KEY
  if (!apiKey) {
    throw new Error('OPENAI_API_KEY not configured for title generation')
  }

  const openai = createOpenAI({ apiKey })
  return openai('gpt-4o-mini')
}

export interface TitleSuggestion {
  title: string
  confidence: number // 0-100
  reasoning?: string // Why this title was suggested
}

export class TitleSuggestionService {
  private languageDetection: LanguageDetectionService

  constructor() {
    this.languageDetection = new LanguageDetectionService()
  }

  /**
   * Generate 3 title suggestions for a note
   * Uses interface language (from user settings) for prompts
   */
  async generateSuggestions(noteContent: string): Promise<TitleSuggestion[]> {
    // Detect language of the note content
    const { language: contentLanguage } = await this.languageDetection.detectLanguage(noteContent)

    try {
      const model = getTextGenerationModel()

      // System prompt - explains what to do
      const systemPrompt = `You are an expert title generator for a note-taking application.
Your task is to generate 3 distinct, engaging titles that capture the essence of the user's note.

Requirements:
- Generate EXACTLY 3 titles
- Each title should be 3-8 words
- Titles should be concise but descriptive
- Each title should have a different style:
  1. Direct/Summary style - What the note is about
  2. Question style - Posing a question the note addresses
  3. Creative/Metaphorical style - Using imagery or analogy
- Return titles in the SAME LANGUAGE as the user's note
- Be helpful and avoid generic titles like "My Note" or "Untitled"

Output Format (JSON):
{
  "suggestions": [
    { "title": "...", "confidence": 85, "reasoning": "..." },
    { "title": "...", "confidence": 80, "reasoning": "..." },
    { "title": "...", "confidence": 75, "reasoning": "..." }
  ]
}`

      // User prompt with language context
      const userPrompt = `Generate 3 title suggestions for this note:

${noteContent}

Note language detected: ${contentLanguage}
Respond with titles in ${contentLanguage} (same language as the note).`

      const { text } = await generateText({
        model,
        system: systemPrompt,
        prompt: userPrompt,
        temperature: 0.7
      })

      // Parse JSON response
      const response = JSON.parse(text)

      if (!response.suggestions || !Array.isArray(response.suggestions)) {
        throw new Error('Invalid response format')
      }

      // Validate and limit to exactly 3 suggestions
      const suggestions = response.suggestions
        .slice(0, 3)
        .filter((s: any) => s.title && typeof s.title === 'string')
        .map((s: any) => ({
          title: s.title.trim(),
          confidence: Math.min(100, Math.max(0, s.confidence || 75)),
          reasoning: s.reasoning || ''
        }))

      // Ensure we always return exactly 3 suggestions
      while (suggestions.length < 3) {
        suggestions.push({
          title: this.generateFallbackTitle(noteContent, contentLanguage),
          confidence: 60,
          reasoning: 'Generated fallback title'
        })
      }

      return suggestions
    } catch (error) {
      console.error('Error generating title suggestions:', error)

      // Fallback to simple extraction
      return this.generateFallbackSuggestions(noteContent, contentLanguage)
    }
  }

  /**
   * Generate fallback title from first few meaningful words
   */
  private generateFallbackTitle(content: string, language: string): string {
    const words = content.split(/\s+/).filter(w => w.length > 3)

    if (words.length === 0) {
      return language === 'fr' ? 'Note sans titre' : 'Untitled Note'
    }

    // Take first 3-5 meaningful words
    const titleWords = words.slice(0, Math.min(5, words.length))
    return titleWords.join(' ').charAt(0).toUpperCase() + titleWords.join(' ').slice(1)
  }

  /**
   * Generate fallback suggestions when AI fails
   */
  private generateFallbackSuggestions(content: string, language: string): TitleSuggestion[] {
    const baseTitle = this.generateFallbackTitle(content, language)

    return [
      {
        title: baseTitle,
        confidence: 70,
        reasoning: 'Extracted from note content'
      },
      {
        title: language === 'fr'
          ? `Réflexions sur ${baseTitle.toLowerCase()}`
          : `Thoughts on ${baseTitle.toLowerCase()}`,
        confidence: 65,
        reasoning: 'Contextual variation'
      },
      {
        title: language === 'fr'
          ? `${baseTitle}: Points clés`
          : `${baseTitle}: Key Points`,
        confidence: 60,
        reasoning: 'Summary style'
      }
    ]
  }

  /**
   * Save selected title to note metadata
   */
  async recordFeedback(
    noteId: string,
    selectedTitle: string,
    allSuggestions: TitleSuggestion[]
  ): Promise<void> {
    // This will be implemented in Phase 3 when we add feedback collection
    // For now, we just log it

    // TODO: In Phase 3, save to AiFeedback table for:
    // - Improving future suggestions
    // - Building user preference model
    // - Computing confidence scores
  }
}

// Singleton instance
export const titleSuggestionService = new TitleSuggestionService()