NK-31: Added missed file

webhooks/patches.go

@@ -0,0 +1,85 @@
+package webhooks
+
+import (
+	"encoding/json"
+	"errors"
+
+	jsonpatch "github.com/evanphx/json-patch"
+	types "github.com/nirmata/kube-policy/pkg/apis/policy/v1alpha1"
+)
+
+type PatchingSets uint8
+
+const (
+	PatchingSetsStopOnError             PatchingSets = 0
+	PatchingSetsContinueOnRemoveFailure PatchingSets = 1
+	PatchingSetsContinueAlways          PatchingSets = 255
+
+	PatchingSetsDefault PatchingSets = PatchingSetsContinueOnRemoveFailure
+)
+
+type PatchBytes []byte
+
+// Test patches on given document according to given sets.
+// Returns array from separate patches that can be applied to the document
+func ProcessPatches(patches []types.PolicyPatch, originalDocument []byte, sets PatchingSets) ([]PatchBytes, error) {
+	if len(originalDocument) == 0 {
+		return nil, errors.New("Source document for patching is empty")
+	}
+
+	var appliedPatches []PatchBytes
+	patchedDocument := originalDocument
+	for _, patch := range patches {
+		patchBytes, err := json.Marshal(patch)
+		if err != nil && sets == PatchingSetsStopOnError {
+			return nil, err
+		}
+
+		patchedDocument, err = CheckPatch(patchedDocument, patchBytes)
+		if err != nil { // Ignore errors on "remove" operations
+			if sets == PatchingSetsContinueOnRemoveFailure && patch.Operation == "remove" {
+				continue
+			} else if sets != PatchingSetsContinueAlways {
+				return nil, err
+			}
+		} else { // In any case we should collect only valid patches
+			appliedPatches = append(appliedPatches, patchBytes)
+		}
+	}
+	return appliedPatches, nil
+}
+
+// Joins array of serialized JSON patches to the single JSONPatch array
+func JoinPatches(patches []PatchBytes) PatchBytes {
+	var result PatchBytes
+	if len(patches) == 0 {
+		return result
+	}
+
+	result = append(result, []byte("[\n")...)
+	for index, patch := range patches {
+		result = append(result, patch...)
+		if index != (len(patches) - 1) {
+			result = append(result, []byte(",\n")...)
+		}
+	}
+	result = append(result, []byte("\n]")...)
+	return result
+}
+
+// Checks patch for document, returns patched document.
+// On error returns original document and error.
+func CheckPatch(document []byte, patchRaw []byte) (PatchBytes, error) {
+	patchRaw = append([]byte{'['}, patchRaw...) // push [ forward
+	patchRaw = append(patchRaw, ']')            // push ] back
+	patch, err := jsonpatch.DecodePatch(patchRaw)
+	if err != nil {
+		return document, err
+	}
+
+	patchedDocument, err := patch.Apply(document)
+	if err != nil {
+		return document, err
+	}
+	return patchedDocument, err
+}