Go application to version JavaScript resources in web page

jsver.go

/*
Copyright (c) 2019, Saleem Mirza
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
    * Redistributions of source code must retain the above copyright
      notice, this list of conditions and the following disclaimer.
    * Redistributions in binary form must reproduce the above copyright
      notice, this list of conditions and the following disclaimer in the
      documentation and/or other materials provided with the distribution.
    * Neither the name of the <organization> nor the
      names of its contributors may be used to endorse or promote products
      derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL <COPYRIGHT HOLDER> BE LIABLE FOR ANY
DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

package main

import (
	"flag"
	"fmt"
	"io/ioutil"
	"log"
	"os"
	"path"
	"path/filepath"
	"regexp"
	"strings"
	"time"
)

var (
	homeDirectory string
	workDirectory string
	filter        string
	rxString      = `(?msi)<script[^>]+?src=\"~?\/(.+?)(\?.+?)?\".*?<\/script>`
	rx            = regexp.MustCompile(rxString)
	scriptInfoMap = make(map[string]int64)
	extensionsMap = make(map[string]bool)
)

func init() {
	currentDirectory, _ := os.Getwd()
	flag.StringVar(&homeDirectory, "homeDirectory", currentDirectory, "set home directory")
	flag.StringVar(&workDirectory, "workDirectory", currentDirectory, "set working directory")
	flag.StringVar(&filter, "filter", ".html", "file types to apply changes.")
}

func main() {
	var logoText = `
               oo oo  oo oo 
              oo oo oo oo ooo 
          ooooo            ooooooo 
        ooooo               ooooooo 
       ooooo                  ooooo 
       oooo                    ooo
        oo                      ooo 
        o                        oooo 
       oo     ooo      oo        ooooooo 
       o     oooo     ooooo      oooooo o 
       o    ooooo    oooooooo    oooooo  o 
       oo  ooooo      ooooooo   ooooooo   o 
        o  ooo          oooo   ooooooooo   o 
        oo                    oooooooooo   ooo 
        ooo     oooooo       ooooooooooo   oooo 
        ooooo   oooooo     ooooooooooooo  oooooo 
        ooooooo         ooooooooooooooo  oooooooo 
        oooooooo  ooo   ooooooooooooooo ooooooooo 
         oooooooooooo  oooooooooooooooooooooooooo 
         ooooooooooooooooooooooooooooo oooooooooo 
         ooooooooo ooooooo ooooooooooo oooooooo 
       ooooooooooo         ooooooooooo ooooo 
       oooooooooo         ooooooooooo 
        ooooooo         oooooooooooo 
                        ooooooooooo 
                        oooooooooo     
`

	fmt.Println(logoText)
	flag.Usage = func() {
		fmt.Println("\nUsage:")

		flag.PrintDefaults()
		fmt.Println()
	}
	flag.Parse()

	for _, v := range strings.Split(filter, ";") {
		extensionsMap[v] = true
	}

	fileCounter := 0
	var startTime = time.Now()

	err := filepath.Walk(workDirectory, func(path string, info os.FileInfo, err error) error {
		if err != nil {
			return err
		}

		if info.IsDir() {
			return nil
		}

		fileExt := filepath.Ext(info.Name())
		if _, ok := extensionsMap[fileExt]; ok == true {
			fileCounter++
			_ = processFile(path)
		}

		return nil
	})

	fmt.Printf("\n\n%d files processed in %0.3f seconds\n", fileCounter, time.Since(startTime).Seconds())

	if err != nil {
		println(err)
	}
}

func processFile(filePath string) error {
	data, e := ioutil.ReadFile(filePath)
	if e == nil {
		fileContents := string(data)

		matchIndices := rx.FindAllStringSubmatchIndex(fileContents, -1)
		if matchIndices != nil {
			file, err := os.OpenFile(filePath, os.O_TRUNC|os.O_WRONLY, 0777)
			if err != nil {
				log.Println(err)
				return err
			}

			defer file.Close()
			_ = file.Truncate(0)

			lastIndex := 0
			for _, v := range matchIndices {
				_, _ = file.WriteString(fileContents[lastIndex:v[2]])

				script := fileContents[v[2]:v[3]]
				scriptPath := path.Join(homeDirectory, script)

				fileInfo, err := os.Stat(scriptPath)
				if err == nil {
					_, _ = file.WriteString(fmt.Sprintf("%s?v=%v", script, fileInfo.ModTime().Unix()))
				} else {
					log.Printf("[ NOT FOUND: %s ] %s\n", script, filePath)
					_, _ = file.WriteString(script)
				}

				if v[5] < 1 {
					lastIndex = v[3]
				} else {
					lastIndex = v[5]
				}

			}
			_, _ = file.WriteString(fileContents[lastIndex:])
		}
		return nil
	} else {
		return e
	}
}