Add postSync configuration as part of DeploymentConfiguration (#2792)

**What this PR does / why we need it**:

**Which issue(s) this PR fixes**:

Fixes #

**Does this PR introduce a user-facing change?**:
<!--
If no, just write "NONE" in the release-note block below.
-->
```release-note
NONE
```

This PR was merged by Kapetanios.

pkg/config/deployment.go

@@ -41,6 +41,8 @@ type GenericDeploymentSpec struct {
 	TriggerPaths []string `json:"triggerPaths,omitempty"`
 	// The trigger configuration use to determine trigger logic.
 	Trigger Trigger `json:"trigger"`
+	// Configuration to be used once the deployment is triggered successfully.
+	PostSync *PostSync `json:"postSync"`
 	// The maximum length of time to execute deployment before giving up.
 	// Default is 6h.
 	Timeout Duration `json:"timeout,omitempty" default:"6h"`
@@ -106,6 +108,12 @@ func (s *GenericDeploymentSpec) Validate() error {
 		}
 	}
 
+	if ps := s.PostSync; ps != nil {
+		if err := ps.Validate(); err != nil {
+			return err
+		}
+	}
+
 	if e := s.Encryption; e != nil {
 		if err := e.Validate(); err != nil {
 			return err
@@ -524,3 +532,78 @@ func (n *NotificationMention) Validate() error {
 	}
 	return fmt.Errorf("event %q is incorrect as NotificationEventType", n.Event)
 }
+
+// PostSync provides all configurations to be used once the current deployment
+// is triggered successfully.
+type PostSync struct {
+	DeploymentChain *DeploymentChain `json:"chain"`
+}
+
+func (p *PostSync) Validate() error {
+	if dc := p.DeploymentChain; dc != nil {
+		return dc.Validate()
+	}
+	return nil
+}
+
+// DeploymentChain provides all configurations used to trigger a chain of deployments.
+type DeploymentChain struct {
+	// Nodes provides list of DeploymentChainNodes which contain filters to be used
+	// to find applications to deploy as chain node. It's required to not empty.
+	Nodes []*DeploymentChainNode `json:"applications"`
+	// Conditions provides configuration used to determine should the piped in charge in
+	// the first applications in the chain trigger a whole new deployment chain or not.
+	// If this field is not set, always trigger a whole new deployment chain when the current
+	// application is triggered.
+	// TODO: Add conditions to deployment chain configuration.
+	// Conditions *DeploymentChainTriggerCondition `json:"conditions,omitempty"`
+}
+
+func (dc *DeploymentChain) Validate() error {
+	if len(dc.Nodes) == 0 {
+		return fmt.Errorf("missing specified applications that will be triggered on this chain of deployment")
+	}
+
+	for _, n := range dc.Nodes {
+		if err := n.Validate(); err != nil {
+			return err
+		}
+	}
+
+	// if cc := dc.Conditions; cc != nil {
+	// 	if err := cc.Validate(); err != nil {
+	// 		return err
+	// 	}
+	// }
+
+	return nil
+}
+
+// DeploymentChainNode provides filters used to find the right applications to trigger
+// as a part of the deployment chain.
+type DeploymentChainNode struct {
+	AppName   string            `json:"name"`
+	AppKind   string            `json:"kind"`
+	AppLabels map[string]string `json:"labels"`
+}
+
+func (n *DeploymentChainNode) Validate() error {
+	hasFilterCond := n.AppName != "" || n.AppKind != "" || len(n.AppLabels) != 0
+
+	if !hasFilterCond {
+		return fmt.Errorf("at least one of \"name\", \"kind\" or \"labels\" must be set to find applications to deploy")
+	}
+	return nil
+}
+
+type DeploymentChainTriggerCondition struct {
+	CommitPrefix string `json:"commitPrefix"`
+}
+
+func (c *DeploymentChainTriggerCondition) Validate() error {
+	hasCond := c.CommitPrefix != ""
+	if !hasCond {
+		return fmt.Errorf("missing commitPrefix configration as deployment chain trigger condition")
+	}
+	return nil
+}

pkg/config/deployment_test.go

@@ -383,3 +383,63 @@ func TestTrueByDefaultBoolConfiguration(t *testing.T) {
 		})
 	}
 }
+
+func TestGenericPostSyncConfiguration(t *testing.T) {
+	testcases := []struct {
+		fileName           string
+		expectedKind       Kind
+		expectedAPIVersion string
+		expectedSpec       interface{}
+		expectedError      error
+	}{
+		{
+			fileName:           "testdata/application/generic-postsync.yaml",
+			expectedKind:       KindKubernetesApp,
+			expectedAPIVersion: "pipecd.dev/v1beta1",
+			expectedSpec: &KubernetesDeploymentSpec{
+				GenericDeploymentSpec: GenericDeploymentSpec{
+					Timeout: Duration(6 * time.Hour),
+					Trigger: Trigger{
+						OnOutOfSync: OnOutOfSync{
+							Disabled:  newBoolPointer(true),
+							MinWindow: Duration(5 * time.Minute),
+						},
+					},
+					PostSync: &PostSync{
+						DeploymentChain: &DeploymentChain{
+							Nodes: []*DeploymentChainNode{
+								{
+									AppName: "app-1",
+								},
+								{
+									AppLabels: map[string]string{
+										"env": "staging",
+										"foo": "bar",
+									},
+								},
+								{
+									AppKind: "ECSApp",
+								},
+							},
+						},
+					},
+				},
+				Input: KubernetesDeploymentInput{
+					AutoRollback: newBoolPointer(true),
+				},
+			},
+			expectedError: nil,
+		},
+	}
+	for _, tc := range testcases {
+		t.Run(tc.fileName, func(t *testing.T) {
+			cfg, err := LoadFromYAML(tc.fileName)
+			require.Equal(t, tc.expectedError, err)
+			if err == nil {
+				assert.Equal(t, tc.expectedKind, cfg.Kind)
+				assert.Equal(t, tc.expectedAPIVersion, cfg.APIVersion)
+				assert.Equal(t, tc.expectedSpec, cfg.spec)
+			}
+		})
+	}
+}

pkg/config/testdata/application/generic-postsync.yaml

@@ -0,0 +1,11 @@
+apiVersion: pipecd.dev/v1beta1
+kind: KubernetesApp
+spec:
+  postSync:
+    chain:
+      applications:
+        - name: app-1
+        - labels:
+            env: staging
+            foo: bar
+        - kind: ECSApp