package main

import (
  "fmt"
  "io/fs"
  "path/filepath"
  "flag"
)

type Opts struct {
  Recurse bool
  Paths []string
}

func ParseOpts() Opts {
  var opts Opts

  flag.BoolVar(&opts.Recurse, "R", false, "recursive listing")
  flag.Parse()

  opts.Paths = flag.Args()

  if len(opts.Paths) == 0 {
    opts.Paths = append(opts.Paths, ".")
  }

  return opts
}

func main() {
  opts := ParseOpts()

  for _, what := range opts.Paths {
    if flag.NArg() > 1 {
      fmt.Printf("\n%s:\n", what)
    }

    filepath.WalkDir(what, func (path string, d fs.DirEntry, err error) error {
      if path == what { return nil }

      if d.IsDir() && opts.Recurse {
        fmt.Printf("\n%s:\n", path)
      } else if d.IsDir() {
        fmt.Printf("%s\n", filepath.Base(path))
        return fs.SkipDir
      } else {
        fmt.Printf("%s\n", filepath.Base(path))
      }

      return nil
    })
  }
}