matcher and some utilities

Signed-off-by: Avi Deitcher <[email protected]>

pkg/v1/match/match.go

@@ -0,0 +1,71 @@
+// Copyright 2020 Google LLC All Rights Reserved.
+//
+// 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 match
+
+import (
+	v1 "github.com/google/go-containerregistry/pkg/v1"
+	imagespec "github.com/opencontainers/image-spec/specs-go/v1"
+)
+
+// Matcher function that is given a v1.Descriptor, and returns whether or
+// not it matches a given rule. Can match on anything it wants in the Descriptor.
+type Matcher func(desc v1.Descriptor) bool
+
+// Name returns a match.Matcher that matches on the name tag in
+// github.com/opencontainers/image-spec/specs-go/v1.AnnotationRefName
+func Name(name string) Matcher {
+	return Annotation(imagespec.AnnotationRefName, name)
+}
+
+// Annotation returns a match.Matcher that matches based on the provided annotation
+func Annotation(key, value string) Matcher {
+	return func(desc v1.Descriptor) bool {
+		if desc.Annotations == nil {
+			return false
+		}
+		if aValue, ok := desc.Annotations[key]; ok && aValue == value {
+			return true
+		}
+		return false
+	}
+}
+
+// Platform returns a match.Matcher that matches on the provided platform.
+// Ignores any descriptors that do not have a platform.
+func Platform(platform v1.Platform) Matcher {
+	return func(desc v1.Descriptor) bool {
+		if desc.Platform == nil {
+			return false
+		}
+		return desc.Platform.Equals(platform)
+	}
+}
+
+// MediaTypes returns a match.Matcher that matches at least one of the provided media types
+func MediaTypes(mediaTypes []string) Matcher {
+	mts := map[string]bool{}
+	for _, media := range mediaTypes {
+		mts[media] = true
+	}
+	return func(desc v1.Descriptor) bool {
+		if desc.MediaType == "" {
+			return false
+		}
+		if _, ok := mts[string(desc.MediaType)]; ok {
+			return true
+		}
+		return false
+	}
+}

pkg/v1/platform.go

@@ -23,3 +23,23 @@ type Platform struct {
 	Variant      string   `json:"variant,omitempty"`
 	Features     []string `json:"features,omitempty"`
 }
+
+// Equal return if another platform is equivalent to this one. It must have all of the fields be the same
+func (p Platform) Equals(o Platform) bool {
+	// ignoring the Platform.Features and Platform.OSFeatures for now
+	return p.OS == o.OS && p.Architecture == o.Architecture && p.Variant == o.Variant && p.OSVersion == o.OSVersion &&
+		stringSliceEqual(p.OSFeatures, o.OSFeatures) && stringSliceEqual(p.Features, o.Features)
+}
+
+// stringSliceEqual compares 2 string slices and returns if their contents are identical.
+func stringSliceEqual(a, b []string) bool {
+	if len(a) != len(b) {
+		return false
+	}
+	for i, elm := range a {
+		if elm != b[i] {
+			return false
+		}
+	}
+	return true
+}