132 lines
3.8 KiB
Go
132 lines
3.8 KiB
Go
package lotteryengine
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import (
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crand "crypto/rand"
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"errors"
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"math/big"
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"strings"
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)
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const (
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PrizeKindCoin = "coin"
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PrizeKindGift = "gift"
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PrizeKindProp = "prop"
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PrizeKindDress = "dress"
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)
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var (
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ErrNoCandidate = errors.New("lottery candidate is empty")
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ErrInvalidWeight = errors.New("lottery candidate weight is invalid")
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)
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// Candidate 是抽奖引擎唯一关心的奖档视图。
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// lucky-gift-service 在进入引擎前已经完成规则版本、单池水位和用户阶段过滤；
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// 引擎只负责不可预测的权重随机，不能再读取数据库或感知商户、房间、钱包等业务边界。
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type Candidate struct {
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ID string
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Weight int64
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PrizeKind string
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RTPValueCoins int64
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}
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// NormalizeCandidates 复制并清洗候选集，避免调用方的事务内规则快照被引擎兜底逻辑改写。
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// 全部候选权重为 0 时退化为等权随机，用于兼容旧配置；负权重直接拒绝，避免错误配置反向影响概率。
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func NormalizeCandidates(candidates []Candidate) ([]Candidate, error) {
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if len(candidates) == 0 {
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return nil, ErrNoCandidate
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}
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out := make([]Candidate, 0, len(candidates))
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var totalWeight int64
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for _, candidate := range candidates {
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if candidate.Weight < 0 {
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return nil, ErrInvalidWeight
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}
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candidate.PrizeKind = NormalizePrizeKind(candidate.PrizeKind)
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candidate.RTPValueCoins = NormalizeRTPValueCoins(candidate.PrizeKind, candidate.RTPValueCoins)
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if candidate.Weight > 0 {
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totalWeight += candidate.Weight
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out = append(out, candidate)
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}
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}
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if totalWeight > 0 {
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return out, nil
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}
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out = out[:0]
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for _, candidate := range candidates {
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candidate.PrizeKind = NormalizePrizeKind(candidate.PrizeKind)
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candidate.RTPValueCoins = NormalizeRTPValueCoins(candidate.PrizeKind, candidate.RTPValueCoins)
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candidate.Weight = 1
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out = append(out, candidate)
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}
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return out, nil
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}
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// SelectWeighted 从归一化后的候选集中按权重抽一档。
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// 使用 crypto/rand 是为了让高价值奖档不可被时间种子、并发顺序或请求重放预测。
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func SelectWeighted(candidates []Candidate) (Candidate, error) {
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normalized, err := NormalizeCandidates(candidates)
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if err != nil {
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return Candidate{}, err
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}
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var totalWeight int64
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for _, candidate := range normalized {
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totalWeight += candidate.Weight
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}
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if totalWeight <= 0 {
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return Candidate{}, ErrNoCandidate
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}
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index, err := secureIndex(totalWeight)
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if err != nil {
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return Candidate{}, err
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}
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for _, candidate := range normalized {
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if index < candidate.Weight {
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return candidate, nil
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}
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index -= candidate.Weight
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}
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return normalized[len(normalized)-1], nil
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}
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// NormalizePrizeKind 把后台配置同义词收敛到引擎口径。
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// 装扮/道具类可以有展示价值，但不能进入现金化 RTP 分子，避免非金币权益误伤奖池结算。
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func NormalizePrizeKind(kind string) string {
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switch strings.ToLower(strings.TrimSpace(kind)) {
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case PrizeKindCoin:
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return PrizeKindCoin
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case PrizeKindGift:
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return PrizeKindGift
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case PrizeKindProp, "item", "decoration", "resource":
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return PrizeKindProp
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case PrizeKindDress, "dress_up", "costume":
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return PrizeKindDress
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default:
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return strings.ToLower(strings.TrimSpace(kind))
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}
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}
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// NormalizeRTPValueCoins 是所有幸运礼物奖档进入 RTP 的唯一计值口。
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// 金币和可折价礼物按配置值计入，装扮/道具固定归零，负数归零以阻断后台脏数据扩大池水。
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func NormalizeRTPValueCoins(kind string, value int64) int64 {
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if value < 0 {
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value = 0
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}
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switch NormalizePrizeKind(kind) {
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case PrizeKindProp, PrizeKindDress:
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return 0
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default:
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return value
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}
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}
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func secureIndex(totalWeight int64) (int64, error) {
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if totalWeight <= 0 {
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return 0, ErrNoCandidate
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}
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n, err := crand.Int(crand.Reader, big.NewInt(totalWeight))
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if err != nil {
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return 0, err
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}
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return n.Int64(), nil
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}
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