import { NextResponse } from "next/server";
import prisma from "@/lib/prisma";
import { getUserIdFromRequest } from "@/lib/auth";

function toYmdUTC(d: Date): string {
  const yy = d.getUTCFullYear();
  const mm = String(d.getUTCMonth() + 1).padStart(2, "0");
  const dd = String(d.getUTCDate()).padStart(2, "0");
  return `${yy}-${mm}-${dd}`;
}

export async function GET(req: Request) {
  const userId = getUserIdFromRequest(req);
  if (!userId) return NextResponse.json({ total: 0, currentStreak: 0, maxStreak: 0 });

  // 총 출석일
  const total = await prisma.attendance.count({ where: { userId } });

  // 모든 출석일(UTC 자정 기준) 가져와서 streak 계산
  const rows = await prisma.attendance.findMany({
    where: { userId },
    select: { date: true },
    orderBy: { date: "asc" },
  });
  const days = Array.from(new Set(rows.map((r) => toYmdUTC(new Date(r.date))))); // unique, asc

  // 현재 연속 출석
  let currentStreak = 0;
  if (days.length > 0) {
    const set = new Set(days);
    const now = new Date();
    let cursor = new Date(Date.UTC(now.getUTCFullYear(), now.getUTCMonth(), now.getUTCDate(), 0, 0, 0, 0));
    while (true) {
      const ymd = toYmdUTC(cursor);
      if (set.has(ymd)) {
        currentStreak += 1;
        cursor.setUTCDate(cursor.getUTCDate() - 1);
      } else {
        break;
      }
    }
  }

  // 최대 연속 출석
  let maxStreak = 0;
  if (days.length > 0) {
    // scan through sorted list
    let localMax = 1;
    for (let i = 1; i < days.length; i++) {
      const prev = new Date(days[i - 1] + "T00:00:00.000Z");
      const cur = new Date(days[i] + "T00:00:00.000Z");
      const diff = (cur.getTime() - prev.getTime()) / (24 * 60 * 60 * 1000);
      if (diff === 1) {
        localMax += 1;
      } else if (diff > 1) {
        if (localMax > maxStreak) maxStreak = localMax;
        localMax = 1;
      }
    }
    if (localMax > maxStreak) maxStreak = localMax;
  }

  return NextResponse.json({ total, currentStreak, maxStreak });
}