Added template engine

templating/engine.go

@@ -0,0 +1,80 @@
+package templating
+
+import (
+	"html/template"
+	"io"
+	"io/fs"
+	"sync"
+)
+
+type Engine struct {
+	// NOTE: LayoutRegistry and TemplateRegistry have their own syncronization and do not require a mutex here
+	LayoutRegistry   *LayoutRegistry
+	TemplateRegistry *TemplateRegistry
+
+	mu      *sync.Mutex
+	FuncMap template.FuncMap
+}
+
+func NewEngine(layouts, templates *fs.FS) *Engine {
+	return &Engine{
+		mu:               &sync.Mutex{},
+		LayoutRegistry:   NewLayoutRegistry(*layouts),
+		TemplateRegistry: NewTemplateRegistry(*templates),
+		FuncMap:          template.FuncMap{},
+	}
+}
+
+func (e *Engine) Load() error {
+	wg := sync.WaitGroup{}
+	wg.Add(2)
+
+	go func() {
+		defer wg.Done()
+		e.LayoutRegistry.Load()
+	}()
+
+	go func() {
+		defer wg.Done()
+		e.TemplateRegistry.Load()
+	}()
+
+	wg.Wait()
+	return nil
+}
+
+func (e *Engine) Render(out io.Writer, path string, data interface{}, layout ...string) error {
+	// TODO: check if a reload is needed if files on disk have changed
+
+	var l *template.Template
+	if layout == nil || len(layout) == 0 {
+		lay, err := e.LayoutRegistry.Default()
+		if err != nil {
+			return err
+		}
+		l = lay
+	} else {
+		lay, err := e.LayoutRegistry.Layout(layout[0])
+		if err != nil {
+			return err
+		}
+		l = lay
+	}
+
+	lay, err := l.Clone()
+	if err != nil {
+		return err
+	}
+
+	err = e.TemplateRegistry.Add(path, lay)
+	if err != nil {
+		return err
+	}
+
+	err = lay.Execute(out, data)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}