package main

import "fmt"
import "io"
import "log"
import "os"
import "bufio"
import "strings"

var PUNCTUATION = []string{".", ",", "\"", "—", "-", "/"}

func longest(r io.Reader) string {
	lw := ""
	s := bufio.NewScanner(r)
	s.Split(bufio.ScanWords)
	for s.Scan() {
		word := s.Text()
		word = strings.ToLower(word)
		for _, c := range PUNCTUATION {
			word = strings.Replace(word, c, " ", -1)
		}
		for _, word := range strings.Fields(word) {
			if len(word) > len(lw) {
				lw = word
			}
		}
	}
	return lw
}

func openFile(path *string) *os.File {
	f, err := os.Open(os.Args[1])
	if err != nil {
		log.Fatalln(err)
	}
	return f
}
func main() {
	if len(os.Args) <= 1 {
		log.Fatalln("Missing file")
	}
	f := openFile(&os.Args[1])

	fmt.Println(longest(f))
}