import type { FastifyRequest } from 'fastify'
import { readData } from '../data/store.js'
import { dataFiles } from '../data/files.js'
import { ApiError } from '../errors.js'
import type { Question } from '../schemas/entities.js'
import type { z } from 'zod'
import { AiExplainBodySchema } from '../schemas/api.js'

/**
 * AI 讲解：返回结构化的讲解结果。
 * TODO 任务11：组装题目上下文调用 OpenAI 兼容接口，超时或未配置 Token 时回退到题库解析。
 * 当前固定返回题库解析回退结果，保证接口契约与前端可以先联调。
 */
export async function explainQuestion(request: FastifyRequest) {
  const body = request.body as z.infer<typeof AiExplainBodySchema>
  const questions = await readData<Question[]>(dataFiles.questions, [])
  const question = questions.find((q) => q.id === body.questionId)
  if (!question) throw ApiError.notFound('题目不存在')

  return {
    source: 'fallback' as const,
    summary: `AI 讲解尚未接入，已回退到题库标准解析（用户答案：${body.userAnswer}）`,
    steps: [question.analysis],
    knowledgePoints: question.tags,
    commonMistakes: [],
    answer: question.answer
  }
}