邹方成
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109 lines
3.3 KiB
Go
109 lines
3.3 KiB
Go
package strategy
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import (
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"bindbox-game/internal/repository/mysql/dao"
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"context"
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"crypto/hmac"
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"crypto/rand"
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"crypto/sha256"
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"encoding/binary"
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"errors"
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"fmt"
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)
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type defaultStrategy struct {
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read *dao.Query
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write *dao.Query
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}
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func NewDefault(read *dao.Query, write *dao.Query) ActivityDrawStrategy {
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return &defaultStrategy{read: read, write: write}
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}
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func (s *defaultStrategy) PreChecks(ctx context.Context, activityID int64, issueID int64, userID int64) error {
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issue, err := s.read.ActivityIssues.WithContext(ctx).Where(s.read.ActivityIssues.ID.Eq(issueID), s.read.ActivityIssues.ActivityID.Eq(activityID)).First()
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if err != nil || issue == nil {
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return errors.New("issue not found")
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}
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return nil
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}
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func (s *defaultStrategy) SelectItem(ctx context.Context, activityID int64, issueID int64, userID int64) (int64, map[string]any, error) {
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rewards, err := s.read.ActivityRewardSettings.WithContext(ctx).ReadDB().Where(s.read.ActivityRewardSettings.IssueID.Eq(issueID)).Find()
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if err != nil || len(rewards) == 0 {
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return 0, nil, errors.New("no rewards")
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}
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var total int64
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for _, r := range rewards {
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if r.Quantity != 0 {
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total += int64(r.Weight)
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}
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}
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if total <= 0 {
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return 0, nil, errors.New("no weight")
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}
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// Determine seed key: use Activity Commitment (REQUIRED)
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act, _ := s.read.Activities.WithContext(ctx).Where(s.read.Activities.ID.Eq(activityID)).First()
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if act == nil || len(act.CommitmentSeedMaster) == 0 {
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return 0, nil, errors.New("活动尚未生成承诺，无法抽奖")
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}
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seedKey := act.CommitmentSeedMaster
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// To ensure uniqueness per draw when using a fixed CommitmentSeedMaster, mix in a random salt
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salt := make([]byte, 16)
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if _, err := rand.Read(salt); err != nil {
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return 0, nil, errors.New("crypto rand salt failed")
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}
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// Use HMAC-SHA256 to generate random number derived from seed + context + salt
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mac := hmac.New(sha256.New, seedKey)
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mac.Write([]byte(fmt.Sprintf("draw:issue:%d|user:%d|salt:%x", issueID, userID, salt)))
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sum := mac.Sum(nil)
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rnd := int64(binary.BigEndian.Uint64(sum[:8]) % uint64(total))
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var acc int64
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var picked int64
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for _, r := range rewards {
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if r.Quantity == 0 {
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continue
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}
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acc += int64(r.Weight)
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if rnd < acc {
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picked = r.ID
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break
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}
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}
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if picked == 0 {
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return 0, nil, errors.New("pick failed")
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}
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proof := map[string]any{
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"weights_total": total,
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"rand": rnd,
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"seed_hash": fmt.Sprintf("%x", sha256.Sum256(seedKey)),
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"salt": fmt.Sprintf("%x", salt),
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"seed_type": "commitment",
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}
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return picked, proof, nil
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}
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func (s *defaultStrategy) GrantReward(ctx context.Context, userID int64, rewardID int64) error {
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// 【使用乐观锁扣减库存】直接用 Quantity > 0 作为更新条件，避免并发超卖
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result, err := s.write.ActivityRewardSettings.WithContext(ctx).Where(
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s.write.ActivityRewardSettings.ID.Eq(rewardID),
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s.write.ActivityRewardSettings.Quantity.Gt(0), // 乐观锁：只有库存>0才能扣减
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).UpdateSimple(s.write.ActivityRewardSettings.Quantity.Add(-1))
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if err != nil {
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return err
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}
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if result.RowsAffected == 0 {
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return errors.New("sold out or reward not found")
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}
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return nil
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}
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func (s *defaultStrategy) PostEffects(ctx context.Context, userID int64, activityID int64, issueID int64, rewardID int64) error {
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return nil
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}
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