/**
 * utils/http.js —— 唯一的网络出口（只有 services 调它；视图层不直接 fetch）。
 * 只带公开的 App ID；任何凭据都不进前端。
 */
export const request = (...args) => fetch(...args);

export class HttpError extends Error {
  constructor(status, body, url) {
    super(`HTTP ${status}${body ? ` · ${body}` : ''}`);
    this.name = 'HttpError';
    this.status = status;
    this.url = url;
  }
}

export function createHttp({ base, appId, fetchImpl = (...a) => fetch(...a) }) {
  const headers = () => ({ 'X-Parse-Application-Id': appId, Accept: 'application/json' });

  async function call(path, { method = 'GET', body, timeoutMs = 20000, retries = 1 } = {}) {
    const url = base + path;
    let lastErr;
    for (let i = 0; i <= retries; i++) {
      const ctrl = new AbortController();
      const t = setTimeout(() => ctrl.abort(), timeoutMs);
      try {
        const res = await fetchImpl(url, {
          method,
          headers: { ...headers(), ...(body ? { 'Content-Type': 'application/json' } : {}) },
          body: body ? JSON.stringify(body) : undefined,
          cache: 'no-store',
          signal: ctrl.signal,
        });
        const text = await res.text();
        let json = null;
        try { json = text ? JSON.parse(text) : {}; } catch { json = null; }
        if (!res.ok) throw new HttpError(res.status, json?.error || text.slice(0, 200), path);
        if (json == null) throw new HttpError(res.status, '返回的不是 JSON', path);
        return json;
      } catch (err) {
        lastErr = err;
        // 4xx 不重试（重试也没用）；网络错误 / 5xx 重试一次
        if (err instanceof HttpError && err.status < 500) break;
        if (i < retries) await new Promise((r) => setTimeout(r, 400 * (i + 1)));
      } finally {
        clearTimeout(t);
      }
    }
    throw lastErr;
  }

  return {
    get: (path, opts) => call(path, opts),
    post: (path, body, opts) => call(path, { ...opts, method: 'POST', body }),
    put: (path, body, opts) => call(path, { ...opts, method: 'PUT', body }),
  };
}

/**
 * 分页拉全表：每页 limit 条（Parse 单次上限 1000），直到不足一页。
 * 翻了 50 页仍满页 → 标记 truncated，UI 明确提示「数据被截断」，不悄悄少显示。
 */
export async function fetchAll(http, className, { limit = 1000, order = 'createdAt' } = {}) {
  const rows = [];
  let skip = 0;
  for (let guard = 0; guard < 50; guard++) {
    const json = await http.get(`/classes/${encodeURIComponent(className)}?limit=${limit}&skip=${skip}&order=${order}`);
    const batch = Array.isArray(json.results) ? json.results : [];
    rows.push(...batch);
    if (batch.length < limit) return { rows, truncated: false };
    skip += limit;
  }
  return { rows, truncated: true };
}