Add hot tempalte reloading, WIP pos

httputils/handler.go

@@ -3,25 +3,68 @@ package httputils
 import (
 	"fmt"
 	"net/http"
+	"os"
+	"path/filepath"
+	"strings"
 	"text/template"
+	"time"
 )
 
 type Handler = func(http.ResponseWriter, *http.Request)
 
+const templateFolder = "templates"
+
+var templatePaths, templateModTimes, _ = getTemplates()
+var templates *template.Template = template.Must(template.ParseFiles(templatePaths...))
+
+func getTemplates() ([]string, map[string]time.Time, error) {
+	var modTimes map[string]time.Time = make(map[string]time.Time)
+	err := filepath.Walk(templateFolder, func(path string, info os.FileInfo, err error) error {
+		if err != nil {
+			return err
+		}
+		if !info.IsDir() && strings.HasSuffix(path, ".html") {
+			modTimes[path] = info.ModTime()
+		}
+		return nil
+	})
+	paths := make([]string, len(modTimes))
+	i := 0
+	for path := range modTimes {
+		paths[i] = path
+		i++
+	}
+	return paths, modTimes, err
+}
+
+func reloadTemplateIfModified(path string) {
+	fileInfo, _ := os.Stat(path)
+	modTime := fileInfo.ModTime()
+	if modTime.After(templateModTimes[path]) {
+		fmt.Printf("Reloading template %s...\n", path)
+		templates.ParseFiles(path)
+		templateModTimes[path] = modTime
+	}
+}
+
+func reloadTemplatesIfModified() {
+	for _, path := range templatePaths {
+		reloadTemplateIfModified(path)
+	}
+}
+
+const reloadTemplates = true
+
 func GenerateHandler(
 	file string,
 	handler func(http.ResponseWriter, *http.Request) bool,
 	data func(http.ResponseWriter, *http.Request) any,
 	methods []string,
 ) Handler {
-	var tmpl *template.Template
-	//if file != "" {
-	//	tmpl = template.Must(template.ParseFiles(fmt.Sprintf("templates/%s", file)))
-	//}
 	return func(w http.ResponseWriter, r *http.Request) {
-		// Remove in production, enables live template reloading
-		if file != "" {
-			tmpl = template.Must(template.ParseFiles(fmt.Sprintf("templates/%s", file)))
+		// All templates must be reloaded in case of dependencies
+		if reloadTemplates {
+			reloadTemplatesIfModified()
 		}
 		for _, method := range methods {
 			if method == r.Method {
@@ -32,9 +75,9 @@ func GenerateHandler(
 		return
 	ok:
 		renderTemplate := handler(w, r)
-		if renderTemplate && tmpl != nil {
+		if renderTemplate && file != "" {
 			w.Header().Set("Content-Type", "text/html; charset=utf-8")
-			tmpl.Execute(w, data(w, r))
+			templates.ExecuteTemplate(w, file, data(w, r))
 		}
 	}
 }