Alerting: Move alertRuleInfo and tests to new files (#83854)

Move ruleinfo and tests to new files

pkg/services/ngalert/schedule/alert_rule.go

@@ -0,0 +1,60 @@
+package schedule
+
+import (
+	context "context"
+
+	"github.com/grafana/grafana/pkg/util"
+)
+
+type alertRuleInfo struct {
+	evalCh   chan *evaluation
+	updateCh chan ruleVersionAndPauseStatus
+	ctx      context.Context
+	stop     func(reason error)
+}
+
+func newAlertRuleInfo(parent context.Context) *alertRuleInfo {
+	ctx, stop := util.WithCancelCause(parent)
+	return &alertRuleInfo{evalCh: make(chan *evaluation), updateCh: make(chan ruleVersionAndPauseStatus), ctx: ctx, stop: stop}
+}
+
+// eval signals the rule evaluation routine to perform the evaluation of the rule. Does nothing if the loop is stopped.
+// Before sending a message into the channel, it does non-blocking read to make sure that there is no concurrent send operation.
+// Returns a tuple where first element is
+//   - true when message was sent
+//   - false when the send operation is stopped
+//
+// the second element contains a dropped message that was sent by a concurrent sender.
+func (a *alertRuleInfo) eval(eval *evaluation) (bool, *evaluation) {
+	// read the channel in unblocking manner to make sure that there is no concurrent send operation.
+	var droppedMsg *evaluation
+	select {
+	case droppedMsg = <-a.evalCh:
+	default:
+	}
+
+	select {
+	case a.evalCh <- eval:
+		return true, droppedMsg
+	case <-a.ctx.Done():
+		return false, droppedMsg
+	}
+}
+
+// update sends an instruction to the rule evaluation routine to update the scheduled rule to the specified version. The specified version must be later than the current version, otherwise no update will happen.
+func (a *alertRuleInfo) update(lastVersion ruleVersionAndPauseStatus) bool {
+	// check if the channel is not empty.
+	select {
+	case <-a.updateCh:
+	case <-a.ctx.Done():
+		return false
+	default:
+	}
+
+	select {
+	case a.updateCh <- lastVersion:
+		return true
+	case <-a.ctx.Done():
+		return false
+	}
+}