package version

import (
	"fmt"
	"regexp"
	"runtime"
	"strconv"
	"strings"
)

// Info : data structure for program version information
type info struct {
	Major      int
	Minor      int
	Patch      int
	Prerelease []string
	BuildMeta  []string
}

// gitDescribe : Git's "git describe --always --dirty" output
var gitDescribe = ""

// GoVersion : The go version used to compile this binary
var GoVersion = runtime.Version()

// OsArch : The OS and archetcture used for this binary
var OsArch = fmt.Sprintf("%s (%s)", runtime.GOOS, runtime.GOARCH)

// Version : the complete version data
var Version = parseGitDescribe(gitDescribe)

// Equal compares two Info structs for equality
func (i info) Equal(o info) bool {
	if i.Major != o.Major || i.Minor != o.Minor || i.Patch != o.Patch {
		return false
	}
	if len(i.Prerelease) != len(o.Prerelease) || len(i.BuildMeta) != len(o.BuildMeta) {
		return false
	}
	for j := 0; j < len(i.Prerelease); j++ {
		if i.Prerelease[j] != o.Prerelease[j] {
			return false
		}
	}
	for j := 0; j < len(i.BuildMeta); j++ {
		if i.BuildMeta[j] != o.BuildMeta[j] {
			return false
		}
	}
	return true
}

// String returns a human friendly version string
func (i info) String() string {
	var b strings.Builder
	fmt.Fprintf(&b, "v%d.%d.%d", i.Major, i.Minor, i.Patch)
	if len(i.Prerelease) > 0 {
		fmt.Fprintf(&b, "-%s", strings.Join(i.Prerelease, "."))
	}
	if len(i.BuildMeta) > 0 {
		fmt.Fprintf(&b, "+%s", strings.Join(i.BuildMeta, "."))
	}
	return b.String()
}

/* reStr is a regular expression string to parse the output of git describe
Match groups:

1. version number (without "v")
2. major version
3. minor version
4. patch version
5. prerelease identifier
6. commit count
7. git short hash
8. "-dirty" if dirty, else ""
*/
const reStr = `^(?:v(([0-9]+)(?:\.([0-9]+)(?:\.([0-9]+))?)?))?(?:-((?:alpha|beta|rc|dev)(?:\.[a-zA-Z0-9]+)*))?(?:-([0-9]+)-g)?([a-f0-9A-F]+)?(?:(-dirty))?$`

var re = regexp.MustCompile(reStr)

func parseGitDescribe(input string) info {
	matches := re.FindStringSubmatch(input)
	if matches == nil || matches[0] == "" {
		return info{0, 0, 0, []string{"dev"}, []string{"unknown"}}
	}

	info := info{}
	if matches[2] != "" {
		num, _ := strconv.Atoi(matches[2])
		info.Major = num
	}
	if matches[3] != "" {
		num, _ := strconv.Atoi(matches[3])
		info.Minor = num
	}
	if matches[4] != "" {
		num, _ := strconv.Atoi(matches[4])
		info.Patch = num
	}
	if matches[5] != "" {
		info.Prerelease = strings.Split(matches[5], ".")
	}
	if matches[6] != "" || matches[7] != "" || matches[8] != "" {
		info.BuildMeta = append(info.BuildMeta, "git")
		if matches[6] != "" {
			info.BuildMeta = append(info.BuildMeta, matches[6])
		}
		if matches[7] != "" {
			info.BuildMeta = append(info.BuildMeta, matches[7])
		}
		if matches[8] != "" {
			info.BuildMeta = append(info.BuildMeta, "dirty")
		}
	}

	return info
}