feat: add Instance lifecycle checkpoints

internal/domain/instance/instance.go

@@ -0,0 +1,101 @@
+/*
+Copyright 2026.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package instance
+
+import "errors"
+
+// Phase is a workflow checkpoint, never evidence of external resource state.
+type Phase string
+
+const (
+	PhasePending              Phase = "Pending"
+	PhaseValidating           Phase = "Validating"
+	PhaseInitializingRegistry Phase = "InitializingRegistry"
+	PhaseReady                Phase = "Ready"
+	PhaseDeleting             Phase = "Deleting"
+)
+
+type Readiness string
+
+const (
+	Unknown  Readiness = "Unknown"
+	Ready    Readiness = "Ready"
+	NotReady Readiness = "NotReady"
+)
+
+// Snapshot contains persisted observations only, without credentials or live evidence.
+// Failure detail mapping will be added with capability assessment, not intent transitions.
+type Snapshot struct {
+	Phase            Phase
+	ObservedRevision int64
+	Readiness        Readiness
+	ReportedVersion  string
+}
+
+// Instance protects registration state and pure lifecycle transitions.
+// Reconstitution does not establish live capability evidence, even for a Ready snapshot.
+// This initial slice deliberately exposes no operation that authorizes provisioning.
+type Instance struct {
+	target   ObservationTarget
+	snapshot Snapshot
+	deleting bool
+}
+
+func Reconstitute(target ObservationTarget, snapshot Snapshot, deleting bool) (*Instance, error) {
+	if err := target.Validate(); err != nil {
+		return nil, err
+	}
+	switch snapshot.Phase {
+	case PhasePending, PhaseValidating, PhaseInitializingRegistry, PhaseReady, PhaseDeleting:
+	default:
+		snapshot.Phase = PhasePending
+		snapshot.Readiness = Unknown
+	}
+	return &Instance{target: target, snapshot: snapshot, deleting: deleting}, nil
+}
+
+func (i *Instance) Target() ObservationTarget { return i.target }
+
+// Snapshot returns a detached value. Persisting it remains the application's job.
+func (i *Instance) Snapshot() Snapshot { return i.snapshot }
+
+// BeginValidation records intent only; it does not claim a concluded observation.
+func (i *Instance) BeginValidation() error {
+	if err := i.target.Validate(); err != nil {
+		return err
+	}
+	if i.deleting {
+		return errors.New("cannot begin validation after deletion was requested")
+	}
+	i.snapshot.Phase = PhaseValidating
+	i.snapshot.Readiness = Unknown
+	return nil
+}
+
+// BeginDeletion stops the lifecycle from accepting validation. It does not delete
+// resources, inspect Tenant references, close connections or modify finalizers.
+func (i *Instance) BeginDeletion() error {
+	if err := i.target.Validate(); err != nil {
+		return err
+	}
+	if !i.deleting {
+		return errors.New("cannot begin deletion without a deletion request")
+	}
+	i.snapshot.Phase = PhaseDeleting
+	i.snapshot.Readiness = Unknown
+	return nil
+}

internal/domain/instance/instance_test.go

@@ -0,0 +1,134 @@
+/*
+Copyright 2026.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package instance_test
+
+import (
+	"testing"
+
+	"git.ddupan.top/panxiao81/postgresql-tenant-operator/internal/domain/instance"
+)
+
+func lifecycleInstance(t *testing.T, snapshot instance.Snapshot, deleting bool) *instance.Instance {
+	t.Helper()
+	identity, revision, definition := targetParts(t)
+	target, err := instance.NewObservationTarget(identity, revision, definition)
+	if err != nil {
+		t.Fatal(err)
+	}
+	value, err := instance.Reconstitute(target, snapshot, deleting)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return value
+}
+
+// Acceptance: docs/domain-instance.md §3, checkpoint reconstruction and intent-only transitions.
+func TestReconstituteCheckpoints(t *testing.T) {
+	for _, phase := range []instance.Phase{
+		instance.PhasePending, instance.PhaseValidating, instance.PhaseInitializingRegistry,
+		instance.PhaseReady, instance.PhaseDeleting,
+	} {
+		snapshot := instance.Snapshot{Phase: phase, ObservedRevision: 1, Readiness: instance.Ready, ReportedVersion: "17"}
+		value := lifecycleInstance(t, snapshot, false)
+		if value.Snapshot() != snapshot {
+			t.Fatal("known checkpoint was not preserved")
+		}
+		// A snapshot is detached; it is not a setter on the aggregate.
+		copy := value.Snapshot()
+		copy.Phase = instance.PhasePending
+		copy.ReportedVersion = "changed"
+		if value.Snapshot() != snapshot {
+			t.Fatal("snapshot mutation changed aggregate")
+		}
+	}
+	for _, phase := range []instance.Phase{"", "unknown"} {
+		value := lifecycleInstance(t, instance.Snapshot{Phase: phase, Readiness: instance.Ready}, false)
+		if value.Snapshot().Phase != instance.PhasePending || value.Snapshot().Readiness != instance.Unknown {
+			t.Fatal("missing or unknown checkpoint did not restart conservatively")
+		}
+	}
+	if value, err := instance.Reconstitute(instance.ObservationTarget{}, instance.Snapshot{}, false); err == nil || value != nil {
+		t.Fatal("invalid target reconstructed an aggregate")
+	}
+}
+
+func TestBeginValidationPreservesObservedRevision(t *testing.T) {
+	snapshot := instance.Snapshot{
+		Phase: instance.PhaseReady, ObservedRevision: 0, Readiness: instance.Ready, ReportedVersion: "17",
+	}
+	value := lifecycleInstance(t, snapshot, false)
+	target := value.Target()
+	for range 2 {
+		if err := value.BeginValidation(); err != nil {
+			t.Fatal(err)
+		}
+		got := value.Snapshot()
+		if got.Phase != instance.PhaseValidating || got.Readiness != instance.Unknown ||
+			got.ObservedRevision != snapshot.ObservedRevision || got.ReportedVersion != snapshot.ReportedVersion {
+			t.Fatal("recording validation intent claimed a completed observation or erased diagnostic version")
+		}
+	}
+	if value.Target() != target {
+		t.Fatal("lifecycle action mutated identity or configuration")
+	}
+}
+
+func TestDeletionRequiresRequestAndPreventsValidation(t *testing.T) {
+	snapshot := instance.Snapshot{Phase: instance.PhaseReady, Readiness: instance.Ready, ObservedRevision: 1}
+	active := lifecycleInstance(t, snapshot, false)
+	if err := active.BeginDeletion(); err == nil {
+		t.Fatal("deletion without a request accepted")
+	}
+	if active.Snapshot() != snapshot {
+		t.Fatal("rejected deletion mutated state")
+	}
+	for _, phase := range []instance.Phase{
+		instance.PhasePending, instance.PhaseValidating, instance.PhaseInitializingRegistry,
+		instance.PhaseReady, instance.PhaseDeleting,
+	} {
+		snapshot.Phase = phase
+		value := lifecycleInstance(t, snapshot, true)
+		if err := value.BeginValidation(); err == nil {
+			t.Fatal("validation accepted after deletion request")
+		}
+		if value.Snapshot() != snapshot {
+			t.Fatal("rejected validation mutated state")
+		}
+		for range 2 {
+			if err := value.BeginDeletion(); err != nil {
+				t.Fatal(err)
+			}
+			if got := value.Snapshot(); got.Phase != instance.PhaseDeleting || got.Readiness != instance.Unknown ||
+				got.ObservedRevision != snapshot.ObservedRevision {
+				t.Fatal("incorrect deletion checkpoint")
+			}
+		}
+	}
+}
+
+func TestZeroInstanceCannotTransition(t *testing.T) {
+	var value instance.Instance
+	if err := value.BeginValidation(); err == nil {
+		t.Fatal("zero instance started validation")
+	}
+	if err := value.BeginDeletion(); err == nil {
+		t.Fatal("zero instance started deletion")
+	}
+	if value.Snapshot() != (instance.Snapshot{}) {
+		t.Fatal("invalid transition changed zero instance")
+	}
+}