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