chore: refactor basic CPE functionality to its own package (#1436)

syft/cpe/by_specificity.go

@@ -0,0 +1,60 @@
+package cpe
+
+import (
+	"sort"
+
+	"github.com/facebookincubator/nvdtools/wfn"
+)
+
+var _ sort.Interface = (*BySpecificity)(nil)
+
+type BySpecificity []wfn.Attributes
+
+func (c BySpecificity) Len() int { return len(c) }
+
+func (c BySpecificity) Swap(i, j int) { c[i], c[j] = c[j], c[i] }
+
+func (c BySpecificity) Less(i, j int) bool {
+	iScore := weightedCountForSpecifiedFields(c[i])
+	jScore := weightedCountForSpecifiedFields(c[j])
+
+	// check weighted sort first
+	if iScore != jScore {
+		return iScore > jScore
+	}
+
+	// sort longer fields to top
+	if countFieldLength(c[i]) != countFieldLength(c[j]) {
+		return countFieldLength(c[i]) > countFieldLength(c[j])
+	}
+
+	// if score and length are equal then text sort
+	// note that we are not using String from the syft pkg
+	// as we are not encoding/decoding this CPE string so we don't
+	// need the proper quoted version of the CPE.
+	return c[i].BindToFmtString() < c[j].BindToFmtString()
+}
+
+func countFieldLength(cpe wfn.Attributes) int {
+	return len(cpe.Part + cpe.Vendor + cpe.Product + cpe.Version + cpe.TargetSW)
+}
+
+func weightedCountForSpecifiedFields(cpe wfn.Attributes) int {
+	checksForSpecifiedField := []func(cpe wfn.Attributes) (bool, int){
+		func(cpe wfn.Attributes) (bool, int) { return cpe.Part != "", 2 },
+		func(cpe wfn.Attributes) (bool, int) { return cpe.Vendor != "", 3 },
+		func(cpe wfn.Attributes) (bool, int) { return cpe.Product != "", 4 },
+		func(cpe wfn.Attributes) (bool, int) { return cpe.Version != "", 1 },
+		func(cpe wfn.Attributes) (bool, int) { return cpe.TargetSW != "", 1 },
+	}
+
+	weightedCount := 0
+	for _, fieldIsSpecified := range checksForSpecifiedField {
+		isSpecified, weight := fieldIsSpecified(cpe)
+		if isSpecified {
+			weightedCount += weight
+		}
+	}
+
+	return weightedCount
+}