Add platform filtering support to mapping.yml (#167)

* chore!: rename package config -> mapping
* feat: add platform filtering support to mapping.yml

mapping/match.go

@@ -0,0 +1,80 @@
+package mapping
+
+import (
+	"fmt"
+
+	v1 "github.com/google/go-containerregistry/pkg/v1"
+)
+
+type matchType string
+
+const (
+	MatchTypePolicy        matchType = "policy"
+	MatchTypeMatchNoPolicy matchType = "match_no_policy"
+	MatchTypeNoMatch       matchType = "no_match"
+)
+
+type PolicyMatch struct {
+	MatchType   matchType
+	Policy      *PolicyMapping
+	Rule        *PolicyRule
+	MatchedName string
+}
+
+func (mappings *PolicyMappings) FindPolicyMatch(imageName string, platform *v1.Platform) (*PolicyMatch, error) {
+	if mappings == nil {
+		return &PolicyMatch{MatchType: MatchTypeNoMatch, MatchedName: imageName}, nil
+	}
+	return mappings.findPolicyMatchImpl(imageName, platform, make(map[*PolicyRule]bool))
+}
+
+func (mappings *PolicyMappings) findPolicyMatchImpl(imageName string, platform *v1.Platform, matched map[*PolicyRule]bool) (*PolicyMatch, error) {
+	for _, rule := range mappings.Rules {
+		if !rule.matchesPlatform(platform) {
+			continue
+		}
+		if rule.Pattern.MatchString(imageName) {
+			switch {
+			case rule.PolicyID == "" && rule.Replacement == "":
+				return nil, fmt.Errorf("rule %s has neither policy-id nor rewrite", rule.Pattern)
+			case rule.PolicyID != "" && rule.Replacement != "":
+				return nil, fmt.Errorf("rule %s has both policy-id and rewrite", rule.Pattern)
+			case rule.PolicyID != "":
+				policy := mappings.Policies[rule.PolicyID]
+				if policy != nil {
+					return &PolicyMatch{
+						MatchType:   MatchTypePolicy,
+						Policy:      policy,
+						Rule:        rule,
+						MatchedName: imageName,
+					}, nil
+				}
+				return &PolicyMatch{
+					MatchType:   MatchTypeMatchNoPolicy,
+					Rule:        rule,
+					MatchedName: imageName,
+				}, nil
+			case rule.Replacement != "":
+				if matched[rule] {
+					return nil, fmt.Errorf("rewrite loop detected")
+				}
+				matched[rule] = true
+				imageName = rule.Pattern.ReplaceAllString(imageName, rule.Replacement)
+				return mappings.findPolicyMatchImpl(imageName, platform, matched)
+			}
+		}
+	}
+	return &PolicyMatch{MatchType: MatchTypeNoMatch}, nil
+}
+
+func (rule *PolicyRule) matchesPlatform(platform *v1.Platform) bool {
+	if len(rule.Platforms) == 0 {
+		return true
+	}
+	for i := range rule.Platforms {
+		if rule.Platforms[i].Equals(*platform) {
+			return true
+		}
+	}
+	return false
+}