package main

import (
	"bufio"
	"fmt"
	"io"
	"os"
	"strconv"
	"strings"
	"time"
)

const filename = "ShipParameterRecord.csv"
const backuptemplate = "ShipParameterRecord-%d.csv"

var stdin = bufio.NewReader(os.Stdin)

func Exit(code int) {
	fmt.Println("Press enter to exit...")
	stdin.ReadBytes('\n')
	os.Exit(code)
}

func main() {
	if _, err := os.Stat(filename); os.IsNotExist(err) {
		fmt.Println("File", filename, "doesn't exist!")
		Exit(1)
	} else if err != nil {
		fmt.Println("Error open while stat file", filename, ":", err.Error())
		Exit(254)
	}

	now := time.Now().UnixNano()
	backupname := fmt.Sprintf(backuptemplate, now)
	for {
		if _, err := os.Stat(backupname); os.IsNotExist(err) {
			break
		}
		now = time.Now().UnixNano()
		backupname = fmt.Sprintf(backuptemplate, now)
	}
	original, err := os.Open(filename)
	if err != nil {
		fmt.Println("Can't open file for reading:", err.Error())
		Exit(1)
	}
	reader := bufio.NewReader(original)
	if err := os.Rename(filename, backupname); err != nil {
		fmt.Println("Can not rename file", filename, ":", err.Error())
		Exit(1)
	}
	fmt.Println("Old file is backuped at", backupname)
	modified, err := os.OpenFile(filename, os.O_WRONLY|os.O_CREATE|os.O_EXCL, 0666)
	defer modified.Close()
	if err != nil {
		fmt.Println("Can't open file for writing:", err.Error())
		Exit(1)
	}
	for i := 1; ; i++ {
		line, err := reader.ReadString('\n')
		if err != nil {
			if err == io.EOF {
				fmt.Printf("%d lines processed.\n", i-1)
				break
			} else {
				fmt.Println("Error read file:", err.Error())
				Exit(1)
			}
		} else {
			line = strings.TrimSpace(line)
		}
		csvparts := strings.Split(line, ",")
		if len(csvparts) != 36 {
			fmt.Printf("[Line #%d] CSV should contains 36 columns, leave this line untouched.\n", i)
			fmt.Fprintln(modified, line)
			continue
		}
		n, err := strconv.ParseInt(csvparts[0], 10, 0)
		if err != nil {
			fmt.Printf("[Line #%d] Ship ID is not a number, leave this line untouched.\n", i)
			fmt.Fprintln(modified, line)
			continue
		}
		f := false
		if n > 500 && n < 1000 && n != 503 && n != 508 {
			n += 1000
			f = true
			csvparts[0] = strconv.FormatInt(n, 10)
		}
		// Duplicate line, remove it.
		if n < 1500 || f {
			fmt.Printf("[Line #%d] Line patched.\n", i)
			line = strings.Join(csvparts, ",")
			fmt.Fprintln(modified, line)
		} else {
			fmt.Printf("[Line #%d] Duplicate line. Removed from output.\n", i)
		}
	}
	fmt.Println("Done!")
	Exit(0)
}