// Package version provides machinery for versioning file names

// with a timestamp-based version string

package version

import (

"path"

"regexp"

"strings"

"time"

)

const versionFormat = "-v2006-01-02-150405.000"

var versionRegexp = regexp.MustCompile(`-v\d{4}-\d{2}-\d{2}-\d{6}-\d{3}`)

// Split fileName into base and extension so that base + ext == fileName

func splitExt(fileName string) (base, ext string) {

ext = path.Ext(fileName)

base = fileName[:len(fileName)-len(ext)]

// .file splits to base == "", ext == ".file"

// so swap ext and base in this case

if ext != "" && base == "" {

base, ext = ext, base

}

return base, ext

}

// Add returns fileName modified to include t as the version

func Add(fileName string, t time.Time) string {

base, ext := splitExt(fileName)

s := t.Format(versionFormat)

// Replace the '.' with a '-'

s = strings.ReplaceAll(s, ".", "-")

return base + s + ext

}

// Remove returns a modified fileName without the version string and the time it represented

// If the fileName did not have a version then time.Time{} is returned along with an unmodified fileName

func Remove(fileName string) (t time.Time, fileNameWithoutVersion string) {

fileNameWithoutVersion = fileName

base, ext := splitExt(fileName)

if len(base) < len(versionFormat) {

return

}

versionStart := len(base) - len(versionFormat)

// Check it ends in -xxx

if base[len(base)-4] != '-' {

return

}

// Replace with .xxx for parsing

base = base[:len(base)-4] + "." + base[len(base)-3:]

newT, err := time.Parse(versionFormat, base[versionStart:])

if err != nil {

return

}

return newT, base[:versionStart] + ext

}

// Match returns true if the fileName has a version string

func Match(fileName string) bool {

return versionRegexp.MatchString(fileName)

}