From 641e4cd8464d51d37842b26ec829aa027aed2f89 Mon Sep 17 00:00:00 2001
From: gcemaj <gcemaj@bloomberg.net>
Date: Tue, 5 Apr 2022 12:43:25 -0400
Subject: [PATCH] Add semver checks

Signed-off-by: gcemaj <gcemaj@bloomberg.net>
---
 build.go      | 27 ++++++++++++++++++++-------
 build_test.go |  2 +-
 go.mod        |  3 ++-
 go.sum        |  6 ++++--
 4 files changed, 27 insertions(+), 11 deletions(-)

diff --git a/build.go b/build.go
index 61eed5c..3c0297c 100644
--- a/build.go
+++ b/build.go
@@ -25,6 +25,7 @@ import (
 	"strings"
 
 	"github.com/BurntSushi/toml"
+	"github.com/Masterminds/semver/v3"
 
 	"github.com/buildpacks/libcnb/internal"
 	"github.com/buildpacks/libcnb/poet"
@@ -89,6 +90,12 @@ type BOM struct {
 	Entries []BOMEntry
 }
 
+// Constants to track minimum and maximum supported Buildpack API versions
+const (
+	MinSupportedBPVersion = "0.5"
+	MaxSupportedBPVersion = "0.8"
+)
+
 // NewBuildResult creates a new BuildResult instance, initializing empty fields.
 func NewBuildResult() BuildResult {
 	return BuildResult{
@@ -170,9 +177,15 @@ func Build(builder Builder, options ...Option) {
 	}
 	logger.Debugf("Buildpack: %+v", ctx.Buildpack)
 
-	API := strings.TrimSpace(ctx.Buildpack.API)
-	if API != "0.5" && API != "0.6" && API != "0.7" && API != "0.8" {
-		config.exitHandler.Error(errors.New("this version of libcnb is only compatible with buildpack APIs 0.5, 0.6, 0.7 and 0.8"))
+	API, err := semver.NewVersion(ctx.Buildpack.API)
+	if err != nil {
+		config.exitHandler.Error(errors.New("version cannot be parsed"))
+		return
+	}
+
+	compatVersionCheck, _ := semver.NewConstraint(fmt.Sprintf(">= %s, <= %s", MinSupportedBPVersion, MaxSupportedBPVersion))
+	if !compatVersionCheck.Check(API) {
+		config.exitHandler.Error(fmt.Errorf("this version of libcnb is only compatible with buildpack APIs >= %s, <= %s", MinSupportedBPVersion, MaxSupportedBPVersion))
 		return
 	}
 
@@ -279,7 +292,7 @@ func Build(builder Builder, options ...Option) {
 		file = filepath.Join(ctx.Layers.Path, fmt.Sprintf("%s.toml", layer.Name))
 		logger.Debugf("Writing layer metadata: %s <= %+v", file, layer)
 		var toWrite interface{} = layer
-		if API == "0.5" {
+		if API.Equal(semver.MustParse("0.5")) {
 			toWrite = internal.LayerAPI5{
 				Build:    layer.LayerTypes.Build,
 				Cache:    layer.LayerTypes.Cache,
@@ -307,7 +320,7 @@ func Build(builder Builder, options ...Option) {
 		}
 	}
 
-	if API != "0.5" && API != "0.6" {
+	if API.GreaterThan(semver.MustParse("0.7")) || API.Equal(semver.MustParse("0.7")) {
 		if err := validateSBOMFormats(ctx.Layers.Path, ctx.Buildpack.Info.SBOMFormats); err != nil {
 			config.exitHandler.Error(fmt.Errorf("unable to validate SBOM\n%w", err))
 			return
@@ -338,7 +351,7 @@ func Build(builder Builder, options ...Option) {
 		file = filepath.Join(ctx.Layers.Path, "launch.toml")
 		logger.Debugf("Writing application metadata: %s <= %+v", file, launch)
 
-		if API == "0.5" {
+		if API.LessThan(semver.MustParse("0.6")) {
 			for _, process := range launch.Processes {
 				if process.Default {
 					logger.Info("WARNING: Launch layer is setting default=true, but that is not supported until API version 0.6. This setting will be ignored.")
@@ -346,7 +359,7 @@ func Build(builder Builder, options ...Option) {
 			}
 		}
 
-		if API != "0.8" {
+		if API.LessThan(semver.MustParse("0.8")) {
 			for i, process := range launch.Processes {
 				if process.WorkingDirectory != "" {
 					logger.Infof("WARNING: Launch layer is setting working-directory=%s, but that is not supported until API version 0.8. This setting will be ignored.", process.WorkingDirectory)
diff --git a/build_test.go b/build_test.go
index 137c147..1c5a05b 100644
--- a/build_test.go
+++ b/build_test.go
@@ -204,7 +204,7 @@ version = "1.1.1"
 			)
 
 			Expect(exitHandler.Calls[0].Arguments.Get(0)).To(MatchError(
-				"this version of libcnb is only compatible with buildpack APIs 0.5, 0.6, 0.7 and 0.8",
+				"this version of libcnb is only compatible with buildpack APIs >= 0.5, <= 0.8",
 			))
 		})
 	})
diff --git a/go.mod b/go.mod
index ea8c208..494a338 100644
--- a/go.mod
+++ b/go.mod
@@ -3,7 +3,8 @@ module github.com/buildpacks/libcnb
 go 1.17
 
 require (
-	github.com/BurntSushi/toml v1.1.0
+	github.com/BurntSushi/toml v1.0.0
+	github.com/Masterminds/semver/v3 v3.1.1
 	github.com/onsi/gomega v1.19.0
 	github.com/sclevine/spec v1.4.0
 	github.com/stretchr/testify v1.7.1
diff --git a/go.sum b/go.sum
index 438a353..762acbb 100644
--- a/go.sum
+++ b/go.sum
@@ -1,5 +1,7 @@
-github.com/BurntSushi/toml v1.1.0 h1:ksErzDEI1khOiGPgpwuI7x2ebx/uXQNw7xJpn9Eq1+I=
-github.com/BurntSushi/toml v1.1.0/go.mod h1:CxXYINrC8qIiEnFrOxCa7Jy5BFHlXnUU2pbicEuybxQ=
+github.com/BurntSushi/toml v1.0.0 h1:dtDWrepsVPfW9H/4y7dDgFc2MBUSeJhlaDtK13CxFlU=
+github.com/BurntSushi/toml v1.0.0/go.mod h1:CxXYINrC8qIiEnFrOxCa7Jy5BFHlXnUU2pbicEuybxQ=
+github.com/Masterminds/semver/v3 v3.1.1 h1:hLg3sBzpNErnxhQtUy/mmLR2I9foDujNK030IGemrRc=
+github.com/Masterminds/semver/v3 v3.1.1/go.mod h1:VPu/7SZ7ePZ3QOrcuXROw5FAcLl4a0cBrbBpGY/8hQs=
 github.com/chzyer/logex v1.1.10/go.mod h1:+Ywpsq7O8HXn0nuIou7OrIPyXbp3wmkHB+jjWRnGsAI=
 github.com/chzyer/readline v0.0.0-20180603132655-2972be24d48e/go.mod h1:nSuG5e5PlCu98SY8svDHJxuZscDgtXS6KTTbou5AhLI=
 github.com/chzyer/test v0.0.0-20180213035817-a1ea475d72b1/go.mod h1:Q3SI9o4m/ZMnBNeIyt5eFwwo7qiLfzFZmjNmxjkiQlU=