package main

import (
	"bytes"
	"flag"
	"fmt"
	"io"
	"os"
)

func byteCounter(f *os.File) {
	fileInfo, err := f.Stat()
	if err != nil {
		fmt.Fprintf(os.Stderr, "error: %v\n", err)
		os.Exit(1)
	}
	fmt.Println(fileInfo.Size())
}

func lineCounter(f io.Reader) {
	buf := make([]byte, 32*1024)
	count := 0
	lineSep := []byte{'\n'}

	for {
		c, err := f.Read(buf)
		count += bytes.Count(buf[:c], lineSep)

		switch {
		case err == io.EOF:
			fmt.Println(count)
			return

		case err != nil:
			fmt.Fprintf(os.Stderr, "error: %v\n", err)
			os.Exit(1)
		}
	}
}

func main() {

	cFlag := flag.Bool("c", false, "print the byte counts")
	lFlag := flag.Bool("l", false, "print the line counts")
	flag.Parse()
	fileName := flag.Arg(0)

	if len(fileName) == 0 {
		fmt.Fprintf(os.Stderr, "gowc [flags] filename\n")
		flag.Usage()
		os.Exit(1)
	}

	f, err := os.Open(fileName)
	if err != nil {
		fmt.Fprintf(os.Stderr, "error: %v\n", err)
		os.Exit(1)
	}
	defer f.Close()

	switch {
	case *cFlag:
		byteCounter(f)
	case *lFlag:
		lineCounter(f)
	}
}