实现七月迭代公共技术基础

pkg/asynctask/state.go

@@ -0,0 +1,53 @@
+package asynctask
+
+import (
+	stderrors "errors"
+	"time"
+)
+
+// LeaseState 是业务任务持久化层应保存的最小状态与租约事实。
+type LeaseState struct {
+	Status         int
+	LeaseOwner     string
+	LeaseExpiresAt *time.Time
+}
+
+// ClaimResult 表示条件领取后的新事实。
+type ClaimResult struct {
+	State   LeaseState
+	Claimed bool
+}
+
+// Claim 按统一语义判断待处理或租约过期任务能否被领取。
+//
+// 业务持久化 Adapter 必须把同样的条件放进 PostgreSQL UPDATE 的 WHERE 中；
+// 本函数用于跨业务共享状态判定，不能替代数据库条件更新。
+func Claim(current LeaseState, owner string, now time.Time, leaseDuration time.Duration) (ClaimResult, error) {
+	if owner == "" || leaseDuration <= 0 {
+		return ClaimResult{}, stderrors.New("任务租约所有者和时长不能为空")
+	}
+	claimable := current.Status == StatusPending
+	if current.Status == StatusProcessing && current.LeaseExpiresAt != nil && !current.LeaseExpiresAt.After(now) {
+		claimable = true
+	}
+	if !claimable {
+		return ClaimResult{State: current}, nil
+	}
+	expiresAt := now.Add(leaseDuration)
+	return ClaimResult{
+		State:   LeaseState{Status: StatusProcessing, LeaseOwner: owner, LeaseExpiresAt: &expiresAt},
+		Claimed: true,
+	}, nil
+}
+
+// CanFinish 判断当前租约所有者能否从处理中进入终态。
+func CanFinish(current LeaseState, owner string, now time.Time) bool {
+	return current.Status == StatusProcessing &&
+		current.LeaseOwner == owner &&
+		current.LeaseExpiresAt != nil && current.LeaseExpiresAt.After(now)
+}
+
+// CanCancel 判断业务支持取消时是否可用预期状态条件更新。
+func CanCancel(status int) bool {
+	return status == StatusPending || status == StatusProcessing
+}