town/cmd/launcher/main.go

package main

import (
	"fmt"
	"io/ioutil"
	"os"
	"os/exec"
	"os/user"
	"path/filepath"
	"strings"

	"github.com/spf13/cobra"
	"gopkg.in/yaml.v3"
)

const binroot = "/town/commands"

var rootCmd = &cobra.Command{
	Use:   "town",
	Short: "Run commands unique to tilde.town",
}

var adminCmd = &cobra.Command{
	Use:   "admin",
	Short: "Run administrative commands",
}

func isAdmin() (bool, error) {
	u, err := user.Current()
	if err != nil {
		return false, fmt.Errorf("failed to get information about current user: %w", err)
	}

	adminGroup, err := user.LookupGroup("admin")
	if err != nil {
		return false, fmt.Errorf("failed to get admin group info: %w", err)
	}

	groupIds, err := u.GroupIds()
	if err != nil {
		return false, fmt.Errorf("failed to get groups info: %w", err)
	}

	for _, groupId := range groupIds {
		if groupId == adminGroup.Gid {
			return true, nil
		}
	}

	return false, nil
}

func parseCommands(targetCmd *cobra.Command, path string) error {
	binPath := filepath.Join(binroot, path)
	files, err := ioutil.ReadDir(binPath)
	if err != nil {
		return fmt.Errorf("failed to list directory %s: %s", binPath, err)
	}

	for _, file := range files {
		if strings.HasSuffix(file.Name(), "yml") {
			parseCommand(targetCmd, filepath.Join(binPath, file.Name()))
		}
	}

	return nil
}

type commandDoc struct {
	ShortDesc  string `yaml:"shortDesc"`
	LongDesc   string `yaml:"longDesc"`
	Examples   string
	Maintainer string
}

func parseCommand(targetCmd *cobra.Command, yamlPath string) {
	executablePath := strings.TrimSuffix(yamlPath, ".yml")

	// TODO handle when files lack executable bit
	_, err := os.Stat(executablePath)

	if err != nil {
		fmt.Fprintf(os.Stderr, "could not find matching executable for %s; skipping...\n", yamlPath)
		return
	}

	yamlBytes, err := ioutil.ReadFile(yamlPath)
	if err != nil {
		fmt.Fprintf(os.Stderr, "could not read %s; skipping...\n", yamlPath)
		return
	}

	doc := commandDoc{}
	err = yaml.Unmarshal(yamlBytes, &doc)
	if err != nil {
		fmt.Fprintf(os.Stderr, "could not parse %s; skipping...\n", yamlPath)
		return
	}

	if doc.Maintainer == "" {
		fmt.Fprintf(os.Stderr, "%s is missing maintainer field; skipping...\n", yamlPath)
		return
	}

	parsedCmd := &cobra.Command{
		Use:                filepath.Base(executablePath),
		RunE:               execWrapper(executablePath),
		DisableFlagParsing: true,
	}
	if doc.ShortDesc != "" {
		parsedCmd.Short = doc.ShortDesc
	}

	if doc.LongDesc != "" {
		parsedCmd.Long = doc.LongDesc
	}

	parsedCmd.Long += fmt.Sprintf("\nMaintained by %s; reach out to them via mail or chat with questions", doc.Maintainer)

	if doc.Examples != "" {
		parsedCmd.Example = doc.Examples
	}

	targetCmd.AddCommand(parsedCmd)
}

func execWrapper(executablePath string) func(*cobra.Command, []string) error {
	return func(cmd *cobra.Command, args []string) error {
		execCmd := exec.Command(executablePath, args...)
		execCmd.Stderr = os.Stderr
		execCmd.Stdout = os.Stdout
		execCmd.Stdin = os.Stdin
		return execCmd.Run()
	}
}

func cli() int {
	err := parseCommands(rootCmd, "core")
	if err != nil {
		fmt.Fprintf(os.Stderr, "failed to parse core commands: %s", err)
		return 1
	}

	err = parseCommands(rootCmd, "contrib")
	if err != nil {
		fmt.Fprintf(os.Stderr, "failed to parse contrib commands: %s", err)
		return 1
	}

	admin, err := isAdmin()
	if err != nil {
		fmt.Fprintf(os.Stderr, "failed to check admin status: %s", err)
		return 2
	}

	if admin {
		rootCmd.AddCommand(adminCmd)
		err = parseCommands(adminCmd, "admin")
		if err != nil {
			fmt.Fprintf(os.Stderr, "failed to parse admin commands: %s", err)
			return 1
		}
	}

	// I feel like the example/documentation yaml can be frontmatter for non-binary files. to start
	// i'll just do the accompanying yaml file.
	rootCmd.Execute()

	return 0
}

func main() {
	os.Exit(cli())
}