<?php

namespace app\common\helper;

class WxPayHelper
{
    /**
     * 根据权重随机获取一个商户
     * 
     * @param array $merchants 商户数组
     * @return array|null 随机选择的商户信息
     */
    public static function getRandomMerchant(array $merchants)
    {
        if (empty($merchants)) {
            return null;
        }
        
        // 只有一个商户，直接返回
        if (count($merchants) === 1) {
            return $merchants[0];
        }
        
        // 计算总权重
        $totalWeight = 0;
        foreach ($merchants as $merchant) {
            $totalWeight += isset($merchant['weight']) ? (int)$merchant['weight'] : 1;
        }
        
        // 生成随机数
        $randomWeight = mt_rand(1, $totalWeight);
        
        // 根据权重选择商户
        $currentWeight = 0;
        foreach ($merchants as $merchant) {
            $weight = isset($merchant['weight']) ? (int)$merchant['weight'] : 1;
            $currentWeight += $weight;
            
            if ($randomWeight <= $currentWeight) {
                return $merchant;
            }
        }
        
        // 默认返回第一个商户
        return $merchants[0];
    }
    
    /**
     * 获取微信支付配置
     * 
     * @return array 包含随机选择的商户信息和appid
     */
    public static function getWxPayConfig()
    {
        $wechat_setting = getConfig('wechat_setting');
        $weixinpay_setting = getConfig('weixinpay_setting');
        
        // 选择一个随机商户
        $merchant = null;
        if (!empty($weixinpay_setting) && !empty($weixinpay_setting['merchants'])) {
            $merchant = self::getRandomMerchant($weixinpay_setting['merchants']);
        } else {
            // 兼容旧配置
            $old_config = getConfig('weixinpay');
            if (!empty($old_config)) {
                $merchant = [
                    'name' => '默认商户',
                    'mch_id' => $old_config['mch_id'],
                    'keys' => $old_config['keys'],
                    'order_prefix' => $old_config['order_prefix'] ?? 'MYH',
                    'weight' => 1
                ];
            }
        }
        
        // 获取微信AppID
        $appid = '';
        if (!empty($wechat_setting) && !empty($wechat_setting['appid'])) {
            $appid = $wechat_setting['appid'];
        } else if (!empty($old_config) && !empty($old_config['appid'])) {
            $appid = $old_config['appid'];
        }
        
        return [
            'merchant' => $merchant,
            'appid' => $appid
        ];
    }
    
    /**
     * 获取固定的微信支付配置（基于订单前缀）
     * 
     * @param string $order_prefix 订单前缀，如果提供则返回对应前缀的商户信息
     * @return array 包含固定商户信息和appid
     */
    public static function getFixedWxPayConfig($order_prefix = '')
    {
        $wechat_setting = getConfig('wechat_setting');
        $weixinpay_setting = getConfig('weixinpay_setting');
        
        // 尝试查找与订单前缀匹配的商户
        $merchant = null;
        if (!empty($order_prefix) && !empty($weixinpay_setting) && !empty($weixinpay_setting['merchants'])) {
            foreach ($weixinpay_setting['merchants'] as $m) {
                if (!empty($m['order_prefix']) && $m['order_prefix'] === $order_prefix) {
                    $merchant = $m;
                    break;
                }
            }
        }
        
        // 如果没有找到匹配的商户，则使用随机选择
        if (empty($merchant)) {
            return self::getWxPayConfig();
        }
        
        // 获取微信AppID
        $appid = '';
        if (!empty($wechat_setting) && !empty($wechat_setting['appid'])) {
            $appid = $wechat_setting['appid'];
        } else {
            $old_config = getConfig('weixinpay');
            if (!empty($old_config) && !empty($old_config['appid'])) {
                $appid = $old_config['appid'];
            }
        }
        
        return [
            'merchant' => $merchant,
            'appid' => $appid
        ];
    }
    
    /**
     * 从订单号中提取商户前缀
     * 
     * @param string $order_no 订单号（格式如 MH_ABC20240529...)
     * @return string|null 商户前缀，如果无法提取则返回null
     */
    public static function extractOrderPrefix($order_no)
    {
        if (strpos($order_no, 'MH_') === 0) {
            // 尝试提取MH_后的3个字符作为商户前缀
            $prefix = substr($order_no, 3, 3);
            if (!empty($prefix) && strlen($prefix) === 3) {
                return $prefix;
            }
        }
        return null;
    }
}