import { TeacherError } from './config-client';

export interface TeacherSuggestions {
  intro: string;
  questions: string[];
}

/** Validate model output before it can become interactive student questions. */
export function parseTeacherSuggestions(response: string): TeacherSuggestions {
  const invalid = () => new TeacherError(
    502,
    'teacher_suggestions_invalid',
    '老师这次没能整理好可以讨论的问题，请再试一次，或直接告诉老师你的想法。'
  );
  const text = response.trim();
  const fenced = text.match(/^```(?:json)?\s*\n([\s\S]*?)\n```$/i);
  let parsed: unknown;
  try {
    parsed = JSON.parse(fenced ? fenced[1] : text);
  } catch {
    throw invalid();
  }
  if (!parsed || typeof parsed !== 'object' || Array.isArray(parsed)) throw invalid();
  const { intro, questions } = parsed as Record<string, unknown>;
  if (
    typeof intro !== 'string' || !intro.trim() || intro.trim().length > 400 ||
    !Array.isArray(questions) || questions.length < 2 || questions.length > 3 ||
    questions.some((question) => typeof question !== 'string' || !question.trim() || question.trim().length > 120)
  ) throw invalid();
  const uniqueQuestions = [...new Set(questions.map((question: string) => question.trim()))];
  if (uniqueQuestions.length < 2) throw invalid();
  return { intro: intro.trim(), questions: uniqueQuestions };
}