From cf00c7a3fa5b5611df2a27ba196a5ac2ddbd5294 Mon Sep 17 00:00:00 2001
From: Yanislav Igonin <yanislavdabest@gmail.com>
Date: Tue, 11 Jan 2022 11:49:39 +0200
Subject: [PATCH] feat: add css renamer for production (#8)

---
 build/css-renamer.go | 104 +++++++++++++++++++++++++++++++++++++++++++
 main.go              |   5 +++
 2 files changed, 109 insertions(+)
 create mode 100644 build/css-renamer.go

diff --git a/build/css-renamer.go b/build/css-renamer.go
new file mode 100644
index 0000000..d13c9e1
--- /dev/null
+++ b/build/css-renamer.go
@@ -0,0 +1,104 @@
+package build
+
+import (
+	"io/ioutil"
+	"math/rand"
+	"os"
+	"strings"
+)
+
+// Returns all html templates paths from ../templates folder.
+func getHtmlTemplatePaths() []string {
+	var paths []string
+	files, err := ioutil.ReadDir("templates")
+	if err != nil {
+		panic(err)
+	}
+	for _, file := range files {
+		paths = append(paths, "templates/"+file.Name())
+	}
+	return paths
+}
+
+// Returns all css files paths in ../static/styles folder.
+func getCssFilesPaths() []string {
+	var paths []string
+	files, err := ioutil.ReadDir("static/styles")
+	if err != nil {
+		panic(err)
+	}
+	for _, file := range files {
+		paths = append(paths, "/static/styles/"+file.Name())
+	}
+	return paths
+}
+
+// Creates map of css file names to their new names.
+func createCssMap() map[string]string {
+	var cssMap = make(map[string]string)
+	origPaths := getCssFilesPaths()
+	for _, origPath := range origPaths {
+		newPath := "/static/styles/" + randomString(10) + ".css"
+		cssMap[origPath] = newPath
+	}
+
+	return cssMap
+}
+
+// Renames file by paths.
+func renameFile(oldPath, newPath string) {
+	// rename the file
+	err := os.Rename(removeFirstChar(oldPath), removeFirstChar(newPath))
+	if err != nil {
+		panic(err)
+	}
+}
+
+// Removes first character from string.
+func removeFirstChar(s string) string {
+	return s[1:]
+}
+
+// Generates a random string.
+func randomString(length int) string {
+	// create a slice of characters to use
+	letters := []rune("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ")
+
+	// create a new slice to hold the random string
+	b := make([]rune, length)
+
+	// loop through the length of the string
+	for i := range b {
+		// get a random number
+		b[i] = letters[rand.Intn(len(letters))]
+	}
+
+	// return the string
+	return string(b)
+}
+
+// Renames css files to prevent caching old files on production.
+func RenameCss() {
+	cssMap := createCssMap()
+	htmlTemplatePaths := getHtmlTemplatePaths()
+
+	for origPath, newPath := range cssMap {
+		renameFile(origPath, newPath)
+	}
+
+	for _, htmlTemplatePath := range htmlTemplatePaths {
+		htmlTemplate, err := ioutil.ReadFile(htmlTemplatePath)
+		if err != nil {
+			panic(err)
+		}
+		// walk through css map and replace all occurencies of css origName with newName
+		for origPath, newPath := range cssMap {
+			htmlTemplate = []byte(strings.Replace(string(htmlTemplate), origPath, newPath, -1))
+		}
+		// write html template to file
+		err = ioutil.WriteFile(htmlTemplatePath, htmlTemplate, 0644)
+		if err != nil {
+			panic(err)
+		}
+	}
+}
diff --git a/main.go b/main.go
index d943847..4e67f2f 100644
--- a/main.go
+++ b/main.go
@@ -12,6 +12,7 @@ import (
 	mgin "github.com/ulule/limiter/v3/drivers/middleware/gin"
 	memory "github.com/ulule/limiter/v3/drivers/store/memory"
 
+	Build "micrach/build"
 	Config "micrach/config"
 	Controllers "micrach/controllers"
 	Db "micrach/db"
@@ -29,6 +30,10 @@ func main() {
 		Repositories.Seed()
 	}
 
+	if Config.App.Env == "release" {
+		Build.RenameCss()
+	}
+
 	err := Utils.CreateUploadsFolder()
 	if err != nil {
 		log.Panicln(err)