re-add GetBOMChecksumAlgorithm function

bom.go

@@ -1,6 +1,8 @@
 package packit
 
 import (
+	"fmt"
+	"strings"
 	"time"
 )
 
@@ -48,6 +50,21 @@ func (a algorithm) alg() algorithm {
 	return a
 }
 
+// GetBOMChecksumAlgorithm takes in an algorithm string, and reasonably tries
+// to figure out the equivalent CycloneDX-supported algorithm field name.
+// It returns an error if no reasonable supported format is found.
+// Supported formats:
+// { 'MD5'| 'SHA-1'| 'SHA-256'| 'SHA-384'| 'SHA-512'| 'SHA3-256'| 'SHA3-384'| 'SHA3-512'| 'BLAKE2b-256'| 'BLAKE2b-384'| 'BLAKE2b-512'| 'BLAKE3'}
+func GetBOMChecksumAlgorithm(alg string) (algorithm, error) {
+	for _, a := range []algorithm{SHA256, SHA1, SHA384, SHA512, SHA3256, SHA3384, SHA3512, BLAKE2B256, BLAKE2B384, BLAKE2B512, BLAKE3, MD5} {
+		if strings.EqualFold(string(a), alg) || strings.EqualFold(strings.ReplaceAll(string(a), "-", ""), alg) {
+			return a, nil
+		}
+	}
+
+	return "", fmt.Errorf("failed to get supported BOM checksum algorithm: %s is not valid", alg)
+}
+
 const (
 	SHA256     algorithm = "SHA-256"
 	SHA1       algorithm = "SHA-1"

build_test.go

@@ -327,6 +327,9 @@ cache = true
 
 	context("when there are bom entries in the build metadata", func() {
 		it("persists a build.toml", func() {
+			algorithm512, err := packit.GetBOMChecksumAlgorithm("sha512")
+			Expect(err).ToNot(HaveOccurred())
+
 			packit.Build(func(ctx packit.BuildContext) (packit.BuildResult, error) {
 				return packit.BuildResult{
 					Build: packit.BuildMetadata{
@@ -344,7 +347,7 @@ cache = true
 									},
 									Source: packit.BOMSource{
 										Checksum: packit.BOMChecksum{
-											Algorithm: packit.SHA512,
+											Algorithm: algorithm512,
 											Hash:      "some-source-sha",
 										},
 									},
@@ -1067,5 +1070,11 @@ api = "0.4"
 				})
 			})
 		})
+		context("when the attempted BOM checksum algorithm is not supported", func() {
+			it("persists a build.toml", func() {
+				_, err := packit.GetBOMChecksumAlgorithm("RANDOM-ALG")
+				Expect(err).To(MatchError("failed to get supported BOM checksum algorithm: RANDOM-ALG is not valid"))
+			})
+		})
 	})
 }