import "server-only";

import { toPublicUser } from "@/lib/auth";
import {
  getSettingsSnapshot,
  getUsageForUser,
  listUserSummaries,
} from "@/lib/db";
import { getCurrentPeriodKey } from "@/lib/quota-core";
import type { AdminSnapshot, QuotaSnapshot, UserRecord } from "@/lib/types";

type QuotaUser = Pick<UserRecord, "id" | "role" | "monthlyQuota">;

export function getQuotaSnapshotForUser(
  user: QuotaUser | null | undefined,
): QuotaSnapshot {
  const periodKey = getCurrentPeriodKey();

  if (!user || user.role === "admin") {
    return {
      periodKey,
      limit: null,
      used: user ? getUsageForUser(user.id, periodKey) : 0,
      remaining: null,
      isUnlimited: true,
    };
  }

  const settings = getSettingsSnapshot();
  const limit =
    user.monthlyQuota === null
      ? settings.defaultMonthlyQuota
      : user.monthlyQuota;
  const used = getUsageForUser(user.id, periodKey);

  return {
    periodKey,
    limit,
    used,
    remaining: Math.max(limit - used, 0),
    isUnlimited: false,
  };
}

export function assertCanGenerate(user: QuotaUser): QuotaSnapshot {
  const quotaSnapshot = getQuotaSnapshotForUser(user);
  const remaining = quotaSnapshot.remaining ?? 0;

  if (!quotaSnapshot.isUnlimited && remaining <= 0) {
    const error = new Error(
      "本月额度已用完，请联系管理员调整额度。",
    ) as Error & {
      statusCode?: number;
    };
    error.statusCode = 403;
    throw error;
  }

  return quotaSnapshot;
}

export function buildAdminQuotaSummaries(): AdminSnapshot {
  const settings = getSettingsSnapshot();
  const periodKey = getCurrentPeriodKey();
  const users = listUserSummaries(periodKey).map((user) => {
    const publicUser = toPublicUser(user);

    if (!publicUser) {
      throw new Error("Failed to sanitize user record.");
    }

    if (user.role === "admin") {
      return {
        ...publicUser,
        usedThisPeriod: user.usedThisPeriod,
        limit: null,
        remaining: null,
        isUnlimited: true,
      };
    }

    const limit =
      user.monthlyQuota === null
        ? settings.defaultMonthlyQuota
        : user.monthlyQuota;

    return {
      ...publicUser,
      usedThisPeriod: user.usedThisPeriod,
      limit,
      remaining: Math.max(limit - user.usedThisPeriod, 0),
      isUnlimited: false,
    };
  });

  return {
    settings,
    periodKey,
    users,
  };
}