/**
 * aptitudeClient.ts
 * ------------------
 * Fetches Aptitude topic data from the Go backend which
 * reads it from the MongoDB collections dynamically.
 */

const API_BASE = '';

export interface AptitudeTopic {
  id: string;
  chapter_no: number;
  chapter_name: string;
}

export interface AptitudeTopicContent extends AptitudeTopic {
  content: string;
}

/**
 * Fetches all topics for a given aptitude category.
 */
export async function fetchAptitudeTopics(category: string): Promise<AptitudeTopic[]> {
  const res = await fetch(`${API_BASE}/api/aptitude/topics?category=${category}`, {
    method: 'GET',
    headers: { 'Content-Type': 'application/json' },
  });

  if (!res.ok) {
    throw new Error(`API error ${res.status}: ${res.statusText}`);
  }

  const data = await res.json() as { topics: AptitudeTopic[] };
  return data.topics ?? [];
}

/**
 * Fetches full content for a specific aptitude topic in a category.
 */
export async function fetchAptitudeTopicContent(category: string, topicNo: number): Promise<AptitudeTopicContent> {
  const res = await fetch(`${API_BASE}/api/aptitude/topics/${topicNo}?category=${category}`, {
    method: 'GET',
    headers: { 'Content-Type': 'application/json' },
  });

  if (!res.ok) {
    throw new Error(`API error ${res.status}: ${res.statusText}`);
  }

  return await res.json() as AptitudeTopicContent;
}

export interface ExplainRequest {
  question: string;
  options: string;
  answer: string;
  topic: string;
}

/**
 * Calls the AI backend to generate a structured step-by-step explanation
 * for an aptitude question whose explanation is missing from the database.
 */
export async function generateAptitudeExplanation(req: ExplainRequest): Promise<string> {
  const res = await fetch(`${API_BASE}/api/ai/explain`, {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify(req),
  });

  if (!res.ok) {
    const err = await res.json().catch(() => ({})) as { error?: string };
    throw new Error(err?.error ?? `API error ${res.status}`);
  }

  const data = await res.json() as { explanation: string };
  return data.explanation ?? '';
}