add possibility to sort TrustChains

pkg/metadata_resolver.go

@@ -50,11 +50,11 @@ func (LocalMetadataResolver) resolveResponsePayloadWithoutTrustMarks(
 		Types:          req.EntityTypes,
 	}
 	chains := tr.ResolveToValidChains()
-	chains = chains.Filter(TrustChainsFilterMinPathLength)
 	if len(chains) == 0 {
 		err = errors.New("no trust chain found")
 		return
 	}
+	chains = chains.SortAsc(TrustChainScoringPathLen)
 	for _, chain = range chains {
 		m, err := chain.Metadata()
 		if err == nil {

pkg/trustchainfilter.go

@@ -1,5 +1,9 @@
 package pkg
 
+import (
+	"sort"
+)
+
 // TrustChains is a slice of multiple TrustChain
 type TrustChains []TrustChain
 
@@ -14,6 +18,45 @@ func (c TrustChains) Filter(filter ...TrustChainsFilter) TrustChains {
 	return c
 }
 
+// SortAsc sorts multiple TrustChains ascending by using the passed TrustChainScoringFnc
+func (c TrustChains) SortAsc(scorer TrustChainScoringFnc) TrustChains {
+	scores := make([]int, len(c))
+	for i, tc := range c {
+		scores[i] = scorer(tc)
+	}
+
+	sort.Slice(
+		c, func(i, j int) bool {
+			return scores[i] < scores[j]
+		},
+	)
+	return c
+}
+
+// SortDesc sorts multiple TrustChains descending by using the passed TrustChainScoringFnc
+func (c TrustChains) SortDesc(scorer TrustChainScoringFnc) TrustChains {
+	scores := make([]int, len(c))
+	for i, tc := range c {
+		scores[i] = scorer(tc)
+	}
+
+	sort.Slice(
+		c, func(i, j int) bool {
+			return scores[i] > scores[j]
+		},
+	)
+	return c
+}
+
+// TrustChainScoringFnc a function type that takes a TrustChain and calculates a score for the chain.
+// This score then can be used to sort TrustChains
+type TrustChainScoringFnc func(c TrustChain) int
+
+// TrustChainScoringPathLen is a TrustChainScoringFnc that uses the chain's path len
+func TrustChainScoringPathLen(c TrustChain) int {
+	return c.PathLen()
+}
+
 // TrustChainChecker can check a single TrustChain to determine if it should be included or not,
 // i.e. in a TrustChainsFilter
 type TrustChainChecker interface {