Introduced templating and views

templating/engine.go

@@ -0,0 +1,148 @@
+package templating
+
+import (
+	"html/template"
+	"io"
+	"io/fs"
+	"sync"
+)
+
+const (
+	ASSETS_URL_PREFIX = "/assets"
+)
+
+type Engine struct {
+	// NOTE: LayoutRegistry and TemplateRegistry have their own syncronization & cache and do not require a mutex here
+	LayoutRegistry   *LayoutRegistry
+	TemplateRegistry *TemplateRegistry
+
+	mu         *sync.Mutex
+	FuncMap    template.FuncMap
+	GlobalData map[string]interface{}
+}
+
+// INFO: We pass the app here to be able to access the config and other data for functions
+// which also means we must reload the engine if the app changes
+func NewEngine(layouts, templates *fs.FS) *Engine {
+	e := Engine{
+		mu:               &sync.Mutex{},
+		LayoutRegistry:   NewLayoutRegistry(*layouts),
+		TemplateRegistry: NewTemplateRegistry(*templates),
+		FuncMap:          make(template.FuncMap),
+	}
+	e.funcs()
+	return &e
+}
+
+func (e *Engine) funcs() error {
+	e.mu.Lock()
+	e.mu.Unlock()
+	return nil
+}
+
+func (e *Engine) Globals(data map[string]interface{}) {
+	e.mu.Lock()
+	defer e.mu.Unlock()
+	if e.GlobalData == nil {
+		e.GlobalData = data
+	} else {
+		for k, v := range data {
+			(e.GlobalData)[k] = v
+		}
+	}
+}
+
+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) Reload() error {
+	wg := sync.WaitGroup{}
+	wg.Add(2)
+
+	go func() {
+		defer wg.Done()
+		e.LayoutRegistry.Reset()
+	}()
+
+	go func() {
+		defer wg.Done()
+		e.TemplateRegistry.Reset()
+	}()
+
+	wg.Wait()
+	return nil
+}
+
+// INFO: fn is a function that returns either one value or two values, the second one being an error
+func (e *Engine) AddFunc(name string, fn interface{}) {
+	e.mu.Lock()
+	defer e.mu.Unlock()
+	e.FuncMap[name] = fn
+}
+
+func (e *Engine) AddFuncs(funcs map[string]interface{}) {
+	e.mu.Lock()
+	defer e.mu.Unlock()
+	for k, v := range funcs {
+		e.FuncMap[k] = v
+	}
+}
+
+func (e *Engine) Render(out io.Writer, path string, ld map[string]interface{}, layout ...string) error {
+	// TODO: check if a reload is needed if files on disk have changed
+	gd := e.GlobalData
+	if e.GlobalData != nil {
+		for k, v := range ld {
+			gd[k] = v
+		}
+	}
+
+	e.mu.Lock()
+	defer e.mu.Unlock()
+	var l *template.Template
+	if layout == nil || len(layout) == 0 {
+		lay, err := e.LayoutRegistry.Default(&e.FuncMap)
+		if err != nil {
+			return err
+		}
+		l = lay
+	} else {
+		lay, err := e.LayoutRegistry.Layout(layout[0], &e.FuncMap)
+		if err != nil {
+			return err
+		}
+		l = lay
+	}
+
+	lay, err := l.Clone()
+	if err != nil {
+		return err
+	}
+
+	err = e.TemplateRegistry.Add(path, lay, &e.FuncMap)
+	if err != nil {
+		return err
+	}
+
+	err = lay.Execute(out, gd)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}