AlbinoGeek/number-place

// +build ignore

// This program generates git.go. It can be invoked by running `go generate`
package main

import (
    "fmt"
    "io/ioutil"
    "os"
    "os/exec"
    "path/filepath"
    "runtime"
    "strings"
    "text/template"
    "time"
)

var tmpl = template.Must(template.New("").Parse(`// Code generated by go generate; DO NOT EDIT.
// This file was generated at: {{.Timestamp}}
// This file is in sync with: {{.CommitSHA}}
package main

// PROGRAM is the human readable product name
const PROGRAM = "{{.Program}}"

// VERSION is the human readable product version
const VERSION = "{{.Version}}"
`))

func getCommitSHA() string {
    str, err := ioutil.ReadFile(".git/FETCH_HEAD")
    if err != nil {
        return "unknown-commit"
    }

    return strings.Split(string(str), "\t")[0]
}

func getPackageName() string {
    _, b, _, _ := runtime.Caller(0)
    return filepath.Base(filepath.Dir(b))
}

func getVersion() string {
    // If the `git` tool is available, we can get our version number reliably
    cmd := exec.Command("git", "describe", "--match", "v*", "--always", "--tags")

    // Should return a string like "v0.3.65-g3a407d2"
    // "v" tag "." commits_since_tag "-g" commit_sha
    out, err := cmd.CombinedOutput()

    // Otherwise, return the commit SHA of HEAD
    if err != nil {
        return fmt.Sprintf("git-%s", getCommitSHA())
    }

    return strings.Trim(string(out), " \t\r\n")
}

func main() {
    if len(os.Args) > 1 {
        if os.Args[1] == "PROGRAM" {
            fmt.Println(getPackageName())
        }
        if os.Args[1] == "VERSION" {
            fmt.Println(getVersion())
        }

        return
    }

    f, err := os.Create("version.go")
    if err != nil {
        panic(err)
    }

    tmpl.Execute(f, struct {
        CommitSHA string
        Program   string
        Timestamp string
        Version   string
    }{
        getCommitSHA(),
        getPackageName(),
        time.Now().String(),
        getVersion(),
    })

    if err := f.Close(); err != nil {
        panic(err)
    }
}