// Copyright 2023 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.


// Package version provides operations on [Go versions]
// in [Go toolchain name syntax]: strings like
// "go1.20", "go1.21.0", "go1.22rc2", and "go1.23.4-bigcorp".
//
// [Go versions]: https://go.dev/doc/toolchain#version
// [Go toolchain name syntax]: https://go.dev/doc/toolchain#name
package version // import "go/version"

import (
	
	
)

// stripGo converts from a "go1.21-bigcorp" version to a "1.21" version.
// If v does not start with "go", stripGo returns the empty string (a known invalid version).
func stripGo( string) string {
	, _, _ = strings.Cut(, "-") // strip -bigcorp suffix.
	if len() < 2 || [:2] != "go" {
		return ""
	}
	return [2:]
}

// Lang returns the Go language version for version x.
// If x is not a valid version, Lang returns the empty string.
// For example:
//
//	Lang("go1.21rc2") = "go1.21"
//	Lang("go1.21.2") = "go1.21"
//	Lang("go1.21") = "go1.21"
//	Lang("go1") = "go1"
//	Lang("bad") = ""
//	Lang("1.21") = ""
func ( string) string {
	 := gover.Lang(stripGo())
	if  == "" {
		return ""
	}
	if strings.HasPrefix([2:], ) {
		return [:2+len()] // "go"+v without allocation
	} else {
		return "go" + 
	}
}

// Compare returns -1, 0, or +1 depending on whether
// x < y, x == y, or x > y, interpreted as Go versions.
// The versions x and y must begin with a "go" prefix: "go1.21" not "1.21".
// Invalid versions, including the empty string, compare less than
// valid versions and equal to each other.
// The language version "go1.21" compares less than the
// release candidate and eventual releases "go1.21rc1" and "go1.21.0".
func (,  string) int {
	return gover.Compare(stripGo(), stripGo())
}

// IsValid reports whether the version x is valid.
func ( string) bool {
	return gover.IsValid(stripGo())
}