<?php

namespace App\Support;

use Illuminate\Support\Facades\DB;

/**
 * 会员受众：区分正式数据和模拟数据（users.user_type = 2 的后台模拟会员）。
 * 默认 REAL：所有列表和统计都看不到模拟会员；SIMULATED：只看模拟会员，仅 /admin/simulation/* 通过 simulated() 进入。
 * 游客（users.from = 2 且不是模拟会员）是否参与由调用方决定，这里只管模拟会员。
 */
final class MemberAudience
{
    public const REAL = 'real';
    public const SIMULATED = 'simulated';
    public const TYPE_SIMULATED = 2;

    private static string $mode = self::REAL;
    private static ?\WeakMap $enabled = null;
    private static ?\WeakMap $memo = null;

    public static function isSimulated(): bool
    {
        return self::$mode === self::SIMULATED;
    }

    /** 在“仅模拟会员”口径下执行 $fn，结束后一定还原。 */
    public static function simulated(callable $fn)
    {
        $previous = self::$mode;
        self::$mode = self::SIMULATED;
        try {
            return $fn();
        } finally {
            self::$mode = $previous;
        }
    }

    /** users.user_type 存在才区分（迁移执行前不过滤）。按数据库连接缓存。 */
    public static function enabled(): bool
    {
        self::$enabled ??= new \WeakMap();
        $connection = DB::connection();
        return self::$enabled[$connection] ??= DB::getSchemaBuilder()->hasColumn('users', 'user_type');
    }

    /** 模拟会员的某一列（member_id / user_id / id）子查询。 */
    public static function simulatedMembers(string $column = 'member_id')
    {
        return DB::table('users')->select($column)->where('user_type', self::TYPE_SIMULATED)->whereNotNull($column);
    }

    /** 查询里已有 users 表（或别名）时：REAL 排除模拟会员，SIMULATED 只留模拟会员。 */
    public static function visibleUsers($query, string $alias = 'users')
    {
        if (!self::enabled()) return self::isSimulated() ? $query->whereRaw('1 = 0') : $query;
        return $query->where($alias . '.user_type', self::isSimulated() ? '=' : '<>', self::TYPE_SIMULATED);
    }

    /** 查询里没有 users 表时，按会员列过滤。$userColumn 是 $column 对应的 users 列。$column 为空的行在 REAL 口径下保留。 */
    public static function visibleMembers($query, string $column = 'member_id', string $userColumn = 'member_id')
    {
        if (!self::enabled()) return self::isSimulated() ? $query->whereRaw('1 = 0') : $query;
        if (self::isSimulated()) return $query->whereIn($column, self::simulatedMembers($userColumn));
        return $query->where(fn ($q) => $q->whereNull($column)->orWhereNotIn($column, self::simulatedMembers($userColumn)));
    }

    /** 原生 SQL 用：users 别名为 $alias 时追加的条件（以 AND 开头）。 */
    public static function rawVisibleUsers(string $alias = 'u'): string
    {
        if (!self::enabled()) return self::isSimulated() ? ' AND 1 = 0' : '';
        return " AND {$alias}.user_type " . (self::isSimulated() ? '=' : '<>') . ' ' . self::TYPE_SIMULATED;
    }

    /** 某个 member_id 是否是模拟会员（同一连接内缓存；用户类型创建后不会变）。 */
    public static function isSimulatedMember($memberId): bool
    {
        if ($memberId === null || $memberId === '' || !self::enabled()) return false;
        self::$memo ??= new \WeakMap();
        $connection = DB::connection();
        $known = self::$memo[$connection] ?? [];
        $key = (string) $memberId;
        if (!isset($known[$key])) {
            $known[$key] = DB::table('users')->where('member_id', $key)->where('user_type', self::TYPE_SIMULATED)->exists();
            self::$memo[$connection] = $known;
        }
        return $known[$key];
    }

    /** 新建模拟会员后登记，免得同一请求里缓存了“不是模拟会员”。 */
    public static function remember($memberId): void
    {
        self::$memo ??= new \WeakMap();
        $connection = DB::connection();
        $known = self::$memo[$connection] ?? [];
        $known[(string) $memberId] = true;
        self::$memo[$connection] = $known;
    }
}