add version package

parse.go

@@ -0,0 +1,92 @@
+package version
+
+import (
+	"strconv"
+	"strings"
+)
+
+const (
+	sectionMajor     = 0
+	sectionMinor     = 1
+	sectionPatch     = 2
+	sectionExtension = 3
+)
+
+func MustParse(str string) *Version {
+	v, err := Parse(str)
+	if err != nil {
+		panic(err)
+	}
+	return v
+}
+
+func Parse(str string) (*Version, error) {
+	v := &Version{Text: string(str)}
+
+	if len(str) == 0 {
+		return nil, ErrInvalidVersion
+	}
+
+	section := sectionMajor
+	chars := []byte{}
+
+	commit := func() error {
+		if len(chars) == 0 {
+			return ErrInvalidVersion
+		}
+
+		if section < sectionExtension {
+			n, err := strconv.Atoi(string(chars))
+			if err != nil {
+				return ErrInvalidVersion
+			}
+
+			switch section {
+			case sectionMajor:
+				v.Major = n
+			case sectionMinor:
+				v.Minor = n
+			case sectionPatch:
+				v.Patch = n
+			}
+		} else {
+			v.Extension = string(chars)
+		}
+
+		chars = []byte{}
+		return nil
+	}
+
+	for i := 0; i < len(str); i++ {
+		c := str[i]
+
+		if i == 0 && strings.IndexByte("vV", c) > -1 {
+			continue
+		}
+
+		if section < sectionExtension {
+			if strings.IndexByte("0123456789", c) > -1 {
+				chars = append(chars, c)
+			} else {
+				if err := commit(); err != nil {
+					return nil, err
+				}
+				if c == '.' {
+					section++
+				} else {
+					section = sectionExtension
+					chars = append(chars, c)
+				}
+			}
+		} else {
+			chars = append(chars, c)
+		}
+	}
+	if len(chars) > 0 {
+		if err := commit(); err != nil {
+			return nil, err
+		}
+	}
+
+	return v, nil
+}