Initial commit

renderer.go

@@ -0,0 +1,102 @@
+package rndr
+
+import (
+	"html/template"
+	"io/fs"
+	"net/http"
+	"path/filepath"
+	"reflect"
+	"strings"
+	"unicode"
+
+	log "gitlab.com/gdulai/simpleloglvl"
+)
+
+// ComponentRenderer handles the associations between templates and models, and renders the template files with the appropriate backing model.
+type ComponentRenderer struct {
+	templates *template.Template
+}
+
+// NewRenderer creates returns the pointer of newly created ComponentRenderer, or an error.
+func NewRenderer(root string) (*ComponentRenderer, error) {
+	templates, err := loadTemplates(root)
+	if err != nil {
+		return nil, err
+	}
+	return &ComponentRenderer{templates: templates}, nil
+}
+
+// Render, renders a template html file with a backing model.
+// The template file name is derived from the model type via reflection.
+func (renderer *ComponentRenderer) Render(w http.ResponseWriter, r *http.Request, model any) {
+	requestId := r.Context().Value("requestId")
+	modelTyp := reflect.TypeOf(model)
+	for modelTyp.Kind() == reflect.Pointer {
+		modelTyp = modelTyp.Elem()
+	}
+
+	if modelTyp == nil {
+		log.LogError("Could not determine model type for %s (%s)", model, requestId)
+		return
+	}
+	templateName := toKebabCase(modelTyp.Name()) + ".html"
+
+	w.Header().Set("Content-Type", "text/html")
+	err := renderer.templates.ExecuteTemplate(w, templateName, model)
+
+	if err != nil {
+		log.LogError("Error while serving html teplate: %s (%s)", err, requestId)
+		http.Error(w, "Component render error", http.StatusInternalServerError)
+	}
+
+}
+
+// RenderLayout, renders layout template file, without any backing model
+func (renderer *ComponentRenderer) RenderLayout(w http.ResponseWriter, r *http.Request, templateName string) {
+	requestId := r.Context().Value("requestId")
+	err := renderer.templates.ExecuteTemplate(w, templateName, nil)
+
+	if err != nil {
+		log.LogError("Error while serving html teplate: %s (%s)", err, requestId)
+		http.Error(w, "Component render error", http.StatusInternalServerError)
+	}
+}
+
+func loadTemplates(root string) (*template.Template, error) {
+	var files []string
+
+	err := filepath.WalkDir(root, func(path string, d fs.DirEntry, err error) error {
+		if err != nil {
+			return err
+		}
+
+		if !d.IsDir() && filepath.Ext(path) == ".html" {
+			files = append(files, path)
+		}
+
+		return nil
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	return template.ParseFiles(files...)
+}
+
+func toKebabCase(s string) string {
+	var b strings.Builder
+
+	for i, r := range s {
+		if i > 0 && unicode.IsUpper(r) {
+			prev := rune(s[i-1])
+			if unicode.IsLower(prev) ||
+				(i+1 < len(s) && unicode.IsLower(rune(s[i+1]))) {
+				b.WriteByte('-')
+			}
+		}
+
+		b.WriteRune(unicode.ToLower(r))
+	}
+
+	return b.String()
+}