// go run v5.go -- $PWD
// go run -race v5.go -- /usr/bin
package main

import (
	"bufio"
	"flag"
	"fmt"
	"os"
	"path/filepath"
	"sync"
)

// START global OMIT
type lcResult struct {
	lc   int
	path string
	err  error
}

var (
	lcC chan *lcResult // HLchan
	wg  sync.WaitGroup
)

// END global OMIT

func lineCount(path string) (int, error) {
	f, err := os.Open(path)
	if err != nil {
		return 0, err
	}
	defer f.Close()
	r := bufio.NewReader(f)
	var lc int
	for err == nil {
		_, err = r.ReadString('\n')
		if err == nil {
			lc++
		}
	}
	return lc, nil
}

func visit(path string, fi os.FileInfo, err error) error {
	if err != nil {
		return err
	}
	if !fi.Mode().IsRegular() {
		return nil
	}
	// START visit OMIT
	wg.Add(1)
	go func() {
		lc, err := lineCount(path)
		lcC <- &lcResult{lc, path, err} // HLchan
		wg.Done()
	}()
	// END visit OMIT
	return nil
}

// START main OMIT
func main() {
	lcC = make(chan *lcResult, 100) // HLchan
	flag.Parse()
	root := flag.Arg(0)
	err := filepath.Walk(root, visit)
	if err != nil {
		fmt.Errorf("%s", err)
	}
	go func() { wg.Wait(); close(lcC) }() // HLchan

	var globalLineCount int
	for lcr := range lcC { // HLchan
		if lcr.err != nil {
			fmt.Errorf("%s", lcr.err)
			err = lcr.err
		}
		globalLineCount += lcr.lc
		fmt.Printf("%d\t%s\n", lcr.lc, lcr.path)
	} // HLchan
	fmt.Printf("%d\ttotal\n", globalLineCount)
	if err != nil {
		os.Exit(1)
	}
}

// END main OMIT