add package to parse upgrade files

internal/helm/upgrade/upgrade.go

@@ -0,0 +1,80 @@
+package upgrade
+
+import (
+	semver "github.com/Masterminds/semver/v3"
+	"sigs.k8s.io/yaml"
+)
+
+// UpgradeFile is a collection of upgrade notes between specific versions
+type UpgradeFile struct {
+	UpgradeNotes []*UpgradeNote `yaml:"upgrade_notes"`
+}
+
+// UpgradeNote is a single note for upgrading between a previous version and
+// a target version.
+type UpgradeNote struct {
+	PreviousVersion string `yaml:"previous"`
+	TargetVersion   string `yaml:"target"`
+	Note            string `yaml:"note"`
+}
+
+// ParseUpgradeFileFromBytes parses the raw bytes of an upgrade file and returns an
+// UpgradeFile object. sigs.k8s.io/yaml parser is used.
+func ParseUpgradeFileFromBytes(upgradeNotes []byte) (*UpgradeFile, error) {
+	// parse bytes into object
+	res := &UpgradeFile{}
+
+	err := yaml.Unmarshal(bytes, form)
+
+	if err != nil {
+		return nil, err
+	}
+
+	return res, err
+}
+
+// GetUpgradeFileBetweenVersions gets the set of upgrade notes that are applicable to an upgrade
+// between a previous and target version.
+func (u *UpgradeFile) GetUpgradeFileBetweenVersions(prev, target string) (*UpgradeFile, error) {
+	prevVersion, err := semver.NewVersion(prev)
+
+	if err != nil {
+		return nil, err
+	}
+
+	targetVersion, err := semver.NewVersion(target)
+
+	if err != nil {
+		return nil, err
+	}
+
+	// for each upgrade note, determine if it's geq than the previous version, leq the target
+	// version
+	resNotes := make([]*UpgradeNote, 0)
+
+	for _, note := range u.UpgradeNotes {
+		notePrevVersion, err := semver.NewVersion(note.PreviousVersion)
+
+		if err != nil {
+			return nil, err
+		}
+
+		noteTargetVersion, err := semver.NewVersion(note.PreviousVersion)
+
+		if err != nil {
+			return nil, err
+		}
+
+		// check that the previous version is not smaller than the note previous version
+		if comp := prevVersion.Compare(notePrevVersion); comp != -1 {
+			// check that the target version is not larger than the note target version
+			if comp := targetVersion.Compare(noteTargetVersion); comp != 1 {
+				resNotes := append(resNotes, note)
+			}
+		}
+	}
+
+	return &UpgradeFile{
+		UpgradeNotes: resNotes,
+	}, nil
+}