package main

import (
	"flag"
	"fmt"
	"os"
	"path/filepath"
	"time"
)


var verbos = flag.Bool("v",false,"show verbose")

func main() {
	flag.Parse()
	roots := flag.Args()
	if len(roots) == 0 {
		roots = []string{"."}
	}

	fileSizes := make(chan int64)

	go func() {
		for _,root := range roots {
			WalkDir(root,fileSizes)
		}
		close(fileSizes)
	}()

	var tick <- chan time.Time

	if *verbos{
		tick = time.Tick(500 * time.Millisecond)
	}
	var nfiles,nbytes int64
loop:
	for {
		select {
		case size,ok := <- fileSizes:
			if !ok {
				break loop
			}
			nfiles++
			nbytes += size
		case <- tick:
			printDU(nfiles,nbytes)
		}
	}
}

func printDU(nfiles, nbytes int64) {
	fmt.Printf("%d files, %.1f GB\n",nfiles,float64(nbytes)/1e9)
}

func WalkDir(dir string, fileSizes chan <- int64) {
	for _, entry := range dirents(dir) {
		if entry.IsDir() {
			subdir := filepath.Join(dir,entry.Name())
			WalkDir(subdir,fileSizes)	
		} else {
			size,_ := entry.Info()
			fileSizes <- size.Size()
		}
	}
}

func dirents(dir string) []os.DirEntry{
	entries, err := os.ReadDir(dir)
	if err != nil {
		fmt.Fprintf(os.Stderr,"du1: %v\n",err)
		return  nil
	}
	return entries
}