// xuchao: 数学每周检测——从已点亮数学课的题池 seeded 抽 10 题
import { and, eq } from "drizzle-orm";
import { db } from "@/db";
import { mathPoints, mathProgress, mathWeeklyTest } from "@/db/schema";
import { extractQuiz, type QuizQ } from "@/lib/quiz-parse";
import { todayStr, weekKey } from "@/lib/dates";

export const currentMathWeekKey = () => weekKey(todayStr());

// xuchao: 确定性随机(同 seed 每次得到相同组卷,渲染与判分一致)
function hashStr(s: string): number {
  let h = 5381;
  for (let i = 0; i < s.length; i++) h = ((h << 5) + h + s.charCodeAt(i)) >>> 0;
  return h >>> 0;
}
function mulberry32(a: number) {
  return () => {
    a |= 0;
    a = (a + 0x6d2b79f5) | 0;
    let t = Math.imul(a ^ (a >>> 15), 1 | a);
    t = (t + Math.imul(t ^ (t >>> 7), 61 | t)) ^ t;
    return ((t ^ (t >>> 14)) >>> 0) / 4294967296;
  };
}
function seededSample<T>(arr: T[], seed: string, n: number): T[] {
  const rnd = mulberry32(hashStr(seed));
  const pool = [...arr];
  for (let i = pool.length - 1; i > 0; i--) {
    const j = Math.floor(rnd() * (i + 1));
    [pool[i], pool[j]] = [pool[j], pool[i]];
  }
  return pool.slice(0, n);
}

// xuchao: 从已点亮数学课组卷;题池不足 5 题时用计算模块兜底
export async function buildMathWeeklyQuestions(childId: number, wk: string): Promise<QuizQ[]> {
  const lit = await db
    .select({ pointId: mathProgress.pointId })
    .from(mathProgress)
    .where(and(eq(mathProgress.childUserId, childId), eq(mathProgress.passed, true)));
  const litIds = new Set(lit.map((r) => r.pointId));

  const all = await db.select().from(mathPoints);
  let pool: QuizQ[] = [];
  for (const p of all) {
    if (litIds.has(p.pointId)) pool.push(...extractQuiz(p.md));
  }
  if (pool.length < 5) {
    for (const p of all) if (p.module === "calc") pool.push(...extractQuiz(p.md));
  }
  return seededSample(pool, `${childId}:math:${wk}`, 10);
}

export async function getMathWeeklyRecord(childId: number, wk: string) {
  const [row] = await db
    .select()
    .from(mathWeeklyTest)
    .where(and(eq(mathWeeklyTest.childUserId, childId), eq(mathWeeklyTest.weekKey, wk)))
    .limit(1);
  return row ?? null;
}