package main

import (
	"bufio"
	"flag"
	"fmt"
	"log"
	"os"
	"sort"
	"strings"
)

var src string = ""
var dst string = ""
var trm bool = false

func init() {
	flag.StringVar(&src, "i", "", "Input File")
	flag.StringVar(&dst, "o", "", "Output File")
	flag.BoolVar(&trm, "t", false, "Trim all leading and trailing spaces of each line")
	flag.Parse()
}

func main() {
	if src == "" || dst == "" {
		flag.Usage()
		os.Exit(1)
	}
	fsi, err := os.Open(src)
	if err != nil {
		fmt.Printf("[ERR] %v\r\n", err)
		os.Exit(1)
	}
	defer fsi.Close()

	var lines []string
	scn := bufio.NewScanner(fsi)
	for scn.Scan() {
		if trm {
			lines = append(lines, strings.TrimSpace(scn.Text()))
			continue
		}
		lines = append(lines, scn.Text())
	}
	sort.Strings(lines)

	fso, err := os.OpenFile(dst, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0666)
	if err != nil {
		fmt.Printf("[ERR] %v\r\n", err)
	}
	defer fso.Close()

	for _, line := range lines {
		_, err = fso.WriteString(line + "\r\n")
		if err != nil {
			log.Printf("[ERR] %v\r\n", err)
			continue
		}
	}
	fso.Sync()
	fso.Close()
}