package main

import "bufio"

//import "fmt"
import "io"
import "log"
import "os"
import "strings"

func splitWord(data []byte, atEOF bool) (advance int, token []byte, err error) {
	if atEOF && len(data) > 0 {
		//fmt.Print("EOF")
		return len(data), data, nil
	}
	splitAt := -1
	if len(data) > 0 {
		for i, c := range data {
			//fmt.Print(string(c))
			switch string(c) {
			case "\n":
				fallthrough
			case " ":
				fallthrough
			case "\t":
				if splitAt < 0 {
					splitAt = i
				}
			default:
				if splitAt > 0 {
					return i, data[:splitAt], nil
				}
			}
		}
		//fmt.Println()
	}
	return 0, nil, nil
}

func transform(in io.Reader, out io.Writer) {
	bufw := bufio.NewWriter(out)
	s := bufio.NewScanner(in)
	//s.Split(bufio.ScanWords)
	s.Split(splitWord)
	for s.Scan() {
		token := s.Text()
		//fmt.Println(token)
		if len(token) > 1 {
			bufw.WriteString(strings.ToUpper(string(token[0])) + token[1:] + " ")
		}
	}
	bufw.Flush()
}

func main() {
	if len(os.Args) < 2 {
		log.Fatalln("Usage upper-line <file>")
	}
	f, err := os.Open(os.Args[1])
	if err != nil {
		log.Fatalln("Error opening file", err)
	}
	defer f.Close()

	var w io.Writer
	if len(os.Args) >= 3 {
		fout, err := os.Create(os.Args[2])
		if err != nil {
			log.Fatalln("Error creating file", err)
		}
		defer fout.Close()
		w = fout
	} else {
		w = os.Stdout
	}

	transform(f, w)
}