go-webserver-template/main.go

package main

import (
	"fmt"
	"html/template"
	"log"
	"net/http"
	"os"
	"path/filepath"

	"github.com/joho/godotenv"
)

func main() {
	// Load the .env file
	err := godotenv.Load()
	if err != nil {
		// Try to load the .env.example file
		fmt.Println("Error loading .env file, trying .env.example")
		err = godotenv.Load(".env.example")
		if err != nil {
			log.Fatal("Error loading .env.example file")
		}
	}
	http.HandleFunc("/", mainHandler)
	http.HandleFunc("/assets/", assetHandler)

	fmt.Println("Starting server on :3000 ...")
	log.Fatal(http.ListenAndServe(":3000", nil))
}

func mainHandler(w http.ResponseWriter, r *http.Request) {
	// Sanitize the path to prevent directory traversal attacks
	relPath := r.URL.Path
	if relPath == "/" {
		relPath = "/index"
	}

	// Check method
	switch r.Method {
	case http.MethodGet:
		getHandler(relPath, w, r)
	case http.MethodPost:
		postHandler(relPath, w, r)
	default:
		errorPage(405, w, r)

	}

}

func getHandler(relPath string, w http.ResponseWriter, r *http.Request) {
	tmplPath := filepath.Join("templates", filepath.Clean(relPath)+".html")

	// Get message from Env
	message := os.Getenv("MESSAGE")

	// Parse the template
	tmpl, err := template.ParseFiles(tmplPath)
	if err != nil {
		errorPage(404, w, r)
		return
	}

	// Create a map to hold the data
	requestData := map[string]interface{}{"envMessage": message}

	// Execute the template
	err = tmpl.Execute(w, requestData)
	if err != nil {
		http.Error(w, "Error rendering template", http.StatusInternalServerError)
	}
}

func postHandler(relPath string, w http.ResponseWriter, r *http.Request) {
	switch relPath {
	case "/index":
		indexPostHandler(w, r)
	default:
		errorPage(405, w, r)
	}
}

func indexPostHandler(w http.ResponseWriter, r *http.Request) {
	// Parse the form data
	err := r.ParseForm()
	if err != nil {
		errorPage(500, w, r)
		return
	}

	// Get the form data
	message := r.FormValue("message")

	// Print the message to the console
	log.Printf("Message: %s", message)

	// Create a map to hold the data
	requestData := map[string]interface{}{
		"message": message,
	}

	// Return a page with message
	tmpl, err := template.ParseFiles("templates/index.html")
	if err != nil {
		errorPage(500, w, r)
		return
	}

	err = tmpl.Execute(w, requestData)

}

func errorPage(errorCode int, w http.ResponseWriter, r *http.Request) {
	w.WriteHeader(errorCode)
	tmpl, err := template.ParseFiles("templates/error.html")
	if err != nil {
		log.Printf("Error loading error page template: %v", err)
		http.Error(w, "Error loading error page", http.StatusInternalServerError)
		return
	}

	errorMsgs := map[int]string{
		404: "Page not found for " + r.URL.Path,
		405: "Method not allowed",
		500: "Internal server error",
	}

	// Check if errorcode isn't in the map
	if _, ok := errorMsgs[errorCode]; !ok {
		errorCode = 500
	}

	// Correcting the initialization of the errorData map
	errorData := map[string]interface{}{
		"short": errorCode,
		"long":  errorMsgs[errorCode],
	}

	err = tmpl.Execute(w, errorData)
	if err != nil {
		log.Printf("Error executing error page template: %v", err)
		http.Error(w, "Error rendering error page", http.StatusInternalServerError)
	}
}

func assetHandler(w http.ResponseWriter, r *http.Request) {
	// Serve static files from templates/assets
	http.ServeFile(w, r, filepath.Join("templates", filepath.Clean(r.URL.Path)))
}