package cli

import (
	"errors"
	"fmt"
	"io"
	"runtime/debug"
	"strings"

	"github.com/spf13/cobra"
)

// ErrNoBuildInfo is returned by `sutil info` when the binary carries no
// Go build information, which only happens for binaries not built with
// module support.
var ErrNoBuildInfo = errors.New("sutil: no build information in this binary")

// noConfigFile is what `sutil info` prints when no config file was loaded.
const noConfigFile = "(none)"

// newInfoCommand returns `sutil info`, which prints the build version, the
// Go toolchain version, the module path, the configuration file in use,
// and the VCS metadata recorded by the Go toolchain at build time.
func newInfoCommand(a *app) *cobra.Command {
	return &cobra.Command{
		Use:   "info",
		Short: "Print build information",
		Args:  cobra.NoArgs,
		RunE: func(cmd *cobra.Command, _ []string) error {
			return writeBuildInfo(
				cmd.OutOrStdout(), a.params.Version, a.configFileUsed(),
			)
		},
	}
}

// writeBuildInfo writes one "key: value" line per fact to w.
func writeBuildInfo(w io.Writer, version, configFile string) error {
	info, ok := debug.ReadBuildInfo()
	if !ok {
		return ErrNoBuildInfo
	}

	if configFile == "" {
		configFile = noConfigFile
	}

	lines := []string{
		"version: " + version,
		"go: " + info.GoVersion,
		"module: " + info.Main.Path,
		"config: " + configFile,
	}

	for _, setting := range info.Settings {
		if strings.HasPrefix(setting.Key, "vcs.") {
			lines = append(lines, setting.Key+": "+setting.Value)
		}
	}

	_, err := fmt.Fprintln(w, strings.Join(lines, "\n"))

	return err
}