import { getSystemConfig } from '@/lib/config'
import { getChatProvider } from '@/lib/ai/factory'

export type FlashcardStyle = 'qa' | 'cloze' | 'concept'

export interface GeneratedFlashcard {
  front: string
  back: string
  type: FlashcardStyle
}

const STYLE_HINTS: Record<FlashcardStyle, string> = {
  qa: 'question/answer pairs — front is a clear question, back is a concise answer',
  cloze: 'fill-in-the-blank — front uses ___ for the missing word(s), back is the complete sentence',
  concept: 'term/definition — front is a term or concept name, back is its definition',
}

function parseFlashcardsJson(raw: string, style: FlashcardStyle): GeneratedFlashcard[] {
  const trimmed = raw.trim()
  const arrayMatch = trimmed.match(/\[[\s\S]*\]/)
  if (!arrayMatch) return []
  try {
    const parsed = JSON.parse(arrayMatch[0]) as unknown
    if (!Array.isArray(parsed)) return []
    return parsed
      .map((item) => {
        if (!item || typeof item !== 'object') return null
        const obj = item as Record<string, unknown>
        const front = typeof obj.front === 'string' ? obj.front.trim() : ''
        const back = typeof obj.back === 'string' ? obj.back.trim() : ''
        const type = (typeof obj.type === 'string' ? obj.type : style) as FlashcardStyle
        if (!front || !back) return null
        return {
          front: front.slice(0, 500),
          back: back.slice(0, 800),
          type: ['qa', 'cloze', 'concept'].includes(type) ? type : style,
        }
      })
      .filter((c): c is GeneratedFlashcard => c !== null)
  } catch {
    return []
  }
}

export async function generateFlashcardsFromNote(params: {
  title: string
  textContent: string
  count: number
  style: FlashcardStyle
  language?: string
}): Promise<GeneratedFlashcard[]> {
  const count = Math.min(20, Math.max(5, params.count))
  const excerpt = params.textContent.slice(0, 8000)
  const lang = params.language && params.language !== 'auto' ? params.language : 'same as source'

  const config = await getSystemConfig()
  const provider = getChatProvider(config)

  const prompt = `You create study flashcards from personal notes for spaced repetition.

Note title: ${params.title || 'Untitled'}
Language: ${lang}
Style: ${params.style} — ${STYLE_HINTS[params.style]}

Source content:
${excerpt}

Generate exactly ${count} flashcards. Use the same language as the source.
Respond with ONLY a JSON array (no markdown):
[
  { "front": "...", "back": "...", "type": "${params.style}" }
]

Rules:
- Each card tests one distinct fact from the note
- Front and back must be self-contained
- No duplicate cards
- Cloze cards must include ___ on the front`

  const raw = await provider.generateText(prompt)
  const cards = parseFlashcardsJson(raw, params.style)
  if (cards.length === 0) {
    throw new Error('Could not parse flashcards from AI response')
  }
  return cards.slice(0, count)
}