version.go

package main

import (
	"bytes"
	"fmt"
	"strings"
)

// semanticAlphabet
const semanticAlphabet = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz-"

// These constants define the application version and follow the semantic versioning 2.0.0 spec (http://semver.org/).
const (
	appMajor uint = 0
	appMinor uint = 1
	appPatch uint = 3
	// appPreRelease MUST only contain characters from semanticAlphabet per the semantic versioning spec.
	appPreRelease = "alpha"
)

// appBuild is defined as a variable so it can be overridden during the build process with '-ldflags "-X main.appBuild foo' if needed.  It MUST only contain characters from semanticAlphabet per the semantic versioning spec.
var appBuild string

// version returns the application version as a properly formed string per the semantic versioning 2.0.0 spec (http://semver.org/).
func version() string {
	// Start with the major, minor, and patch versions.
	version := fmt.Sprintf("%d.%d.%d", appMajor, appMinor, appPatch)
	// Append pre-release version if there is one.  The hyphen called for by the semantic versioning spec is automatically appended and should not be contained in the pre-release string.  The pre-release version is not appended if it contains invalid characters.
	preRelease := normalizeVerString(appPreRelease)
	if preRelease != "" {
		version = fmt.Sprintf("%s-%s", version, preRelease)
	}
	// Append build metadata if there is any.  The plus called for by the semantic versioning spec is automatically appended and should not be contained in the build metadata string.  The build metadata string is not appended if it contains invalid characters.
	build := normalizeVerString(appBuild)
	if build != "" {
		version = fmt.Sprintf("%s+%s", version, build)
	}
	return version
}

// normalizeVerString returns the passed string stripped of all characters which are not valid according to the semantic versioning guidelines for pre-release version and build metadata strings.  In particular they MUST only contain characters in semanticAlphabet.
func normalizeVerString(str string) string {
	var result bytes.Buffer
	for _, r := range str {
		if strings.ContainsRune(semanticAlphabet, r) {
			result.WriteRune(r)
		}
	}
	return result.String()
}