<?php
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namespace app\api\service\bargain;
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class Amount
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{
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/**
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* 砍价金额
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*/
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protected $amount;
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/**
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* 砍价人数
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*/
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protected $num;
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/**
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* 砍价的最小金额
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*/
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protected $coupon_min;
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/**
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* 砍价分配结果
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*/
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protected $items = [];
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/**
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* 初始化
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* @param float $amount 砍价金额（单位：元）最多保留2位小数
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* @param int $num 砍价个数
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* @param float $coupon_min 每个至少领取的砍价金额
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*/
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public function __construct($amount, $num = 1, $coupon_min = 0.01)
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{
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$this->amount = $amount;
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$this->num = $num;
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$this->coupon_min = $coupon_min;
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}
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/**
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* 处理返回
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*/
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public function handle()
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{
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// 验证
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if ($this->amount < $validAmount = $this->coupon_min * $this->num) {
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throw new \Exception('砍价总金额必须≥' . $validAmount . '元');
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}
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// 分配砍价
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$this->apportion();
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return [
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'items' => $this->items,
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];
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}
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/**
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* 分配砍价
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*/
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protected function apportion()
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{
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$num = $this->num; // 剩余可分配的砍价个数
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$amount = $this->amount; //剩余可领取的砍价金额
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while ($num >= 1) {
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// 剩余一个的时候，直接取剩余砍价
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if ($num == 1) {
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$coupon_amount = $this->decimal_number($amount);
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} else {
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$avg_amount = $this->decimal_number($amount / $num); // 剩余的砍价的平均金额
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$coupon_amount = $this->decimal_number(
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$this->calcCouponAmount($avg_amount, $amount, $num)
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);
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}
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$this->items[] = $coupon_amount; // 追加分配
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$amount -= $coupon_amount;
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--$num;
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}
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shuffle($this->items); // 随机打乱
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}
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/**
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* 计算分配的砍价金额
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* @param float $avg_amount 每次计算的平均金额
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* @param float $amount 剩余可领取金额
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* @param int $num 剩余可领取的砍价个数
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*
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* @return float
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*/
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protected function calcCouponAmount($avg_amount, $amount, $num)
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{
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// 如果平均金额小于等于最低金额，则直接返回最低金额
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if ($avg_amount <= $this->coupon_min) {
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return $this->coupon_min;
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}
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// 浮动计算
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$coupon_amount = $this->decimal_number($avg_amount * (1 + $this->apportionRandRatio()));
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// 如果低于最低金额或超过可领取的最大金额，则重新获取
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if ($coupon_amount < $this->coupon_min
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|| $coupon_amount > $this->calcCouponAmountMax($amount, $num)
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) {
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return $this->calcCouponAmount($avg_amount, $amount, $num);
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}
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return $coupon_amount;
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}
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/**
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* 计算分配的砍价金额-可领取的最大金额
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*/
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protected function calcCouponAmountMax($amount, $num)
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{
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return $this->coupon_min + $amount - $num * $this->coupon_min;
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}
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/**
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* 砍价金额浮动比例
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*/
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protected function apportionRandRatio()
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{
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// 60%机率获取剩余平均值的大幅度砍价（可能正数、可能负数）
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if (rand(1, 100) <= 60) {
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return rand(-70, 70) / 100; // 上下幅度70%
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}
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return rand(-30, 30) / 100; // 其他情况，上下浮动30%；
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}
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/**
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* 格式化金额，保留2位
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*/
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protected function decimal_number($amount)
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{
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return sprintf('%01.2f', round($amount, 2));
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}
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}
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