Merge pull request #4 from Kuadrant/json-patch

New example JSON patch merge strategy

examples/json_patch/color_policy.go

@@ -0,0 +1,143 @@
+package json_patch
+
+import (
+	"encoding/json"
+
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	gwapi "sigs.k8s.io/gateway-api/apis/v1alpha2"
+
+	jsonpatch "github.com/evanphx/json-patch"
+	"github.com/kuadrant/policy-machinery/machinery"
+)
+
+type ColorPolicy struct {
+	metav1.TypeMeta   `json:",inline"`
+	metav1.ObjectMeta `json:"metadata,omitempty"`
+
+	Spec ColorSpec `json:"spec"`
+}
+
+var _ machinery.Policy = &ColorPolicy{}
+
+func (p *ColorPolicy) GetURL() string {
+	return machinery.UrlFromObject(p)
+}
+
+func (p *ColorPolicy) GetTargetRefs() []machinery.PolicyTargetReference {
+	return []machinery.PolicyTargetReference{
+		machinery.LocalPolicyTargetReferenceWithSectionName{
+			LocalPolicyTargetReferenceWithSectionName: p.Spec.TargetRef,
+			PolicyNamespace: p.Namespace,
+		},
+	}
+}
+
+func (p *ColorPolicy) GetMergeStrategy() machinery.MergeStrategy {
+	return func(parent, child machinery.Policy) machinery.Policy {
+		colorParent, okSource := parent.(*ColorPolicy)
+		colorChild, okTarget := child.(*ColorPolicy)
+
+		if !okSource || !okTarget {
+			return nil
+		}
+
+		parentSpecJSON, err := json.Marshal(colorParent.Spec.Proper())
+		if err != nil {
+			return nil
+		}
+
+		childSpecJSON, err := json.Marshal(colorChild.Spec.Proper())
+		if err != nil {
+			return nil
+		}
+
+		var resultSpecJSON []byte
+
+		if overrides := colorParent.Spec.Overrides; overrides != nil {
+			resultSpecJSON, err = jsonpatch.MergePatch(childSpecJSON, parentSpecJSON)
+		} else {
+			resultSpecJSON, err = jsonpatch.MergePatch(parentSpecJSON, childSpecJSON)
+		}
+
+		if err != nil {
+			return nil
+		}
+
+		result := ColorSpecProper{}
+		if err := json.Unmarshal(resultSpecJSON, &result); err != nil {
+			return nil
+		}
+
+		return &ColorPolicy{
+			TypeMeta:   colorChild.TypeMeta,
+			ObjectMeta: colorChild.ObjectMeta,
+			Spec: ColorSpec{
+				TargetRef:       colorChild.Spec.TargetRef,
+				ColorSpecProper: result,
+			},
+		}
+	}
+}
+
+func (p *ColorPolicy) Merge(policy machinery.Policy) machinery.Policy {
+	source := policy.(*ColorPolicy)
+	return source.GetMergeStrategy()(source, p)
+}
+
+func (p *ColorPolicy) DeepCopy() *ColorPolicy {
+	spec := p.Spec.DeepCopy()
+	return &ColorPolicy{
+		TypeMeta:   p.TypeMeta,
+		ObjectMeta: p.ObjectMeta,
+		Spec:       *spec,
+	}
+}
+
+type ColorSpec struct {
+	TargetRef gwapi.LocalPolicyTargetReferenceWithSectionName `json:"targetRef"`
+
+	Defaults  *ColorSpecProper `json:"defaults,omitempty"`
+	Overrides *ColorSpecProper `json:"overrides,omitempty"`
+
+	ColorSpecProper `json:""`
+}
+
+func (s *ColorSpec) Proper() *ColorSpecProper {
+	if s.Defaults != nil {
+		return s.Defaults
+	}
+	if s.Overrides != nil {
+		return s.Overrides
+	}
+	return &s.ColorSpecProper
+}
+
+func (s *ColorSpec) DeepCopy() *ColorSpec {
+	rules := make(map[string]ColorValue, len(s.Proper().Rules))
+	for k, v := range s.Proper().Rules {
+		rules[k] = v
+	}
+	return &ColorSpec{
+		TargetRef: s.TargetRef,
+		ColorSpecProper: ColorSpecProper{
+			Rules: rules,
+		},
+	}
+}
+
+type ColorSpecProper struct {
+	Rules map[string]ColorValue `json:"rules,omitempty"`
+}
+
+type ColorValue string
+
+const (
+	Black  ColorValue = "black"
+	Blue   ColorValue = "blue"
+	Green  ColorValue = "green"
+	Orange ColorValue = "orange"
+	Purple ColorValue = "purple"
+	Red    ColorValue = "red"
+	White  ColorValue = "white"
+	Yellow ColorValue = "yellow"
+)

examples/json_patch/color_policy_test.go

@@ -0,0 +1,180 @@
+//go:build unit
+
+package json_patch
+
+import (
+	"testing"
+
+	"github.com/kuadrant/policy-machinery/machinery"
+)
+
+func TestMerge(t *testing.T) {
+	testCases := []struct {
+		name     string
+		source   machinery.Policy
+		target   machinery.Policy
+		expected map[string]ColorValue
+	}{
+		{
+			name: "JSON patch defaults into empty policy",
+			source: &ColorPolicy{
+				Spec: ColorSpec{
+					Defaults: &ColorSpecProper{
+						Rules: map[string]ColorValue{
+							"rule-1": Blue,
+							"rule-2": Red,
+						},
+					},
+				},
+			},
+			target: &ColorPolicy{},
+			expected: map[string]ColorValue{
+				"rule-1": Blue,
+				"rule-2": Red,
+			},
+		},
+		{
+			name: "JSON patch defaults into policy without conflicting rules",
+			source: &ColorPolicy{
+				Spec: ColorSpec{
+					Defaults: &ColorSpecProper{
+						Rules: map[string]ColorValue{
+							"rule-1": Blue,
+							"rule-2": Red,
+						},
+					},
+				},
+			},
+			target: &ColorPolicy{
+				Spec: ColorSpec{
+					ColorSpecProper: ColorSpecProper{
+						Rules: map[string]ColorValue{
+							"rule-3": Green,
+						},
+					},
+				},
+			},
+			expected: map[string]ColorValue{
+				"rule-1": Blue,
+				"rule-2": Red,
+				"rule-3": Green,
+			},
+		},
+		{
+			name: "JSON patch defaults into policy with conflicting rules",
+			source: &ColorPolicy{
+				Spec: ColorSpec{
+					Defaults: &ColorSpecProper{
+						Rules: map[string]ColorValue{
+							"rule-1": Blue,
+							"rule-2": Red,
+						},
+					},
+				},
+			},
+			target: &ColorPolicy{
+				Spec: ColorSpec{
+					ColorSpecProper: ColorSpecProper{
+						Rules: map[string]ColorValue{
+							"rule-1": Yellow,
+							"rule-3": Green,
+						},
+					},
+				},
+			},
+			expected: map[string]ColorValue{
+				"rule-1": Yellow,
+				"rule-2": Red,
+				"rule-3": Green,
+			},
+		},
+		{
+			name: "JSON patch overrides into empty policy",
+			source: &ColorPolicy{
+				Spec: ColorSpec{
+					Overrides: &ColorSpecProper{
+						Rules: map[string]ColorValue{
+							"rule-1": Blue,
+							"rule-2": Red,
+						},
+					},
+				},
+			},
+			target: &ColorPolicy{},
+			expected: map[string]ColorValue{
+				"rule-1": Blue,
+				"rule-2": Red,
+			},
+		},
+		{
+			name: "JSON patch overrides into policy without conflicting rules",
+			source: &ColorPolicy{
+				Spec: ColorSpec{
+					Overrides: &ColorSpecProper{
+						Rules: map[string]ColorValue{
+							"rule-1": Blue,
+							"rule-2": Red,
+						},
+					},
+				},
+			},
+			target: &ColorPolicy{
+				Spec: ColorSpec{
+					ColorSpecProper: ColorSpecProper{
+						Rules: map[string]ColorValue{
+							"rule-3": Green,
+						},
+					},
+				},
+			},
+			expected: map[string]ColorValue{
+				"rule-1": Blue,
+				"rule-2": Red,
+				"rule-3": Green,
+			},
+		},
+		{
+			name: "JSON patch overrides into policy with conflicting rules",
+			source: &ColorPolicy{
+				Spec: ColorSpec{
+					Overrides: &ColorSpecProper{
+						Rules: map[string]ColorValue{
+							"rule-1": Blue,
+							"rule-2": Red,
+						},
+					},
+				},
+			},
+			target: &ColorPolicy{
+				Spec: ColorSpec{
+					ColorSpecProper: ColorSpecProper{
+						Rules: map[string]ColorValue{
+							"rule-1": Yellow,
+							"rule-3": Green,
+						},
+					},
+				},
+			},
+			expected: map[string]ColorValue{
+				"rule-1": Blue,
+				"rule-2": Red,
+				"rule-3": Green,
+			},
+		},
+	}
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			merged := tc.target.Merge(tc.source)
+			mergedColorPolicy := merged.(*ColorPolicy)
+			mergedRules := mergedColorPolicy.Spec.Proper().Rules
+			if len(mergedRules) != len(tc.expected) {
+				t.Errorf("Expected %d rules, but got %d", len(tc.expected), len(mergedRules))
+			}
+			for id, color := range mergedRules {
+				if tc.expected[id] != color {
+					t.Errorf("Expected rule %s to have color %s, but got %s", id, tc.expected[id], color)
+				}
+			}
+		})
+	}
+}