package buildinfo

import (
	"fmt"
	"io"
	"os"
	"path/filepath"
	"runtime/debug"
	"strings"
	"text/template"
)

var (
	Name      string = ""
	Version   string = ""
	Commit    string = ""
	BuildTime string = ""
	OS        string = ""
	Arch      string = ""
	ShowDeps  bool   = true

	dependencies = []Dep{}

	PrintFormat = `
{{- block "version" . -}}
	{{- if .Name -}} {{- .Name -}} {{- end }}
	{{- if .Version }} {{ .Version -}} {{- end }}
	{{- if and (.OS) (.Arch) }} {{ .OS -}} / {{- .Arch -}} {{- end }}
	{{- if (.BuildTime) }} (built at {{ .BuildTime -}}) {{- end }}

	{{- if and (not .Version) (.Commit) (not .BuildTime) }} (commit {{ .Commit -}}) {{- end }}
	{{- if and (not .Version) (.Commit) (.BuildTime) }} (commit {{ .Commit }} built at {{ .BuildTime -}}) {{- end }}
	{{- if and (not .Version) (not .Commit) (.BuildTime) }} (built at {{ .BuildTime -}}) {{- end }}
{{ end -}}

{{- block "deps" . -}}
	{{- if and (.ShowDeps) (len .Deps) -}}
		dependecies:
		{{- range .Deps }}
  {{ .Name }} {{ .Version -}}
		{{- end -}}
	{{- end -}}
{{- end }}
`
)

var (
	fmtTmpl = template.Must(template.New("print-format").Parse(PrintFormat))
)

func Print() {
	Fprint(os.Stdout)
}

func Fprint(w io.Writer) {
	if Name == "" {
		Name = filepath.Base(os.Args[0])
	}

	if OS == "" || Arch == "" || ShowDeps {
		fillDebugInfo()
	}

	b := new(strings.Builder)

	err := fmtTmpl.Execute(b, newBuildInfo())
	if err != nil {
		panic(err)
	}

	fmt.Fprintln(w, strings.TrimSpace(b.String()))
}

func overwriteValueIfEmpty(value *string, newValue string) {
	if *value == "" {
		*value = newValue
	}
}

func fillDebugInfo() {
	info, ok := debug.ReadBuildInfo()
	if !ok {
		return
	}

	for _, setting := range info.Settings {
		switch setting.Key {
		case "GOOS":
			overwriteValueIfEmpty(&OS, setting.Value)
		case "GOARCH":
			overwriteValueIfEmpty(&Arch, setting.Value)
		case "vcs.revision":
			overwriteValueIfEmpty(&Commit, setting.Value)
		}
	}

	for _, dep := range info.Deps {
		dependencies = append(dependencies, Dep{
			Name:    dep.Path,
			Version: dep.Version,
			Sum:     dep.Sum,
		})
	}
}