压缩历史至 95081aff

internal/apps/redenvelope/utils.go

@@ -0,0 +1,73 @@
+/*
+Copyright 2025 linux.do
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package redenvelope
+
+import (
+	"math/rand"
+
+	"github.com/shopspring/decimal"
+)
+
+// calculateRandomAmount 二倍均值算法计算随机红包金额
+func calculateRandomAmount(remaining decimal.Decimal, count int) decimal.Decimal {
+	// 如果是最后一个红包，返回所有剩余金额（避免舍入误差）
+	if count == 1 {
+		return remaining
+	}
+
+	minAmount := decimal.NewFromFloat(0.01)
+
+	// 确保剩余金额足够分配给所有人至少0.01
+	minRequired := minAmount.Mul(decimal.NewFromInt(int64(count)))
+	if remaining.LessThanOrEqual(minRequired) {
+		// 如果剩余金额刚好或不足，每人分配0.01（确保不会出现0 LDC的情况）
+		return minAmount
+	}
+
+	// 二倍均值算法：金额范围 [0.01, min(剩余金额/剩余人数*2, 剩余金额-其他人最小金额)]
+	avg := remaining.Div(decimal.NewFromInt(int64(count)))
+	maxAmount := avg.Mul(decimal.NewFromInt(2))
+
+	// 确保给其他人留下足够的金额（每人至少0.01）
+	maxPossible := remaining.Sub(minAmount.Mul(decimal.NewFromInt(int64(count - 1))))
+	if maxAmount.GreaterThan(maxPossible) {
+		maxAmount = maxPossible
+	}
+
+	// 确保maxAmount不小于minAmount
+	if maxAmount.LessThan(minAmount) {
+		maxAmount = minAmount
+	}
+
+	// 生成随机金额 [minAmount, maxAmount]
+	diff := maxAmount.Sub(minAmount)
+	if diff.LessThanOrEqual(decimal.Zero) {
+		return minAmount
+	}
+
+	// 生成随机数：转换为分（cents）来处理，避免精度问题
+	diffCents := diff.Mul(decimal.NewFromInt(100)).IntPart()
+	if diffCents <= 0 {
+		return minAmount
+	}
+
+	randCents := rand.Int63n(diffCents + 1) // [0, diffCents]
+	randAmount := decimal.NewFromInt(randCents).Div(decimal.NewFromInt(100))
+	amount := minAmount.Add(randAmount)
+
+	return amount.Round(2)
+}