labstack echo template inheritance recipe

templates.go

package bla

import (
	"io"
	"html/template"
	"path/filepath"
	"strings"
)

// folder structure

// views/layouts/base.hbs
// -----------------------
// [[define "layout"]] [[block "content" . ]] default content [[end]] [[end]]

// views/pages/contact.hbs
// -----------------------
// [[define "content"]] contact me [[block "ad" .]] [[end]] [[end]]

// views/pages/home.hbs
// -----------------------
// [[define "content"]] welcome [[block "ad" .]] [[end]]  [[end]]

// views/shared/ad.hbs
// [[define "ad"]] buy stuff [[end]]

// init:
// var EchoTemplate = &Template{}
// echo_inst.SetRenderer(EchoTemplate)
// ReloadTemplates onStart and while developing viewstuff in handler for example
//

// useage in handler
// func H_Start(c *echo.Context) error {
//	return c.Render(200, "base:home", nil)
// }

var templates map[string]*template.Template

type Template struct {
	templates *template.Template // this will never be used
}

func (t *Template) Render(w io.Writer, name string, data interface{}) error {
	tmpl, ok := templates[name]
	if !ok {
		err := errors.New2("template: name not found ->" +name, "template")
		LogErrorNoContext(&err, nil)
		return err
	}
	return tmpl.ExecuteTemplate(w, "layout", data) // layout -> defined in each layout template
}


// Load templates on program initialisation
func ReloadTemplates() {
	old_maintenance_state := MAINTENANCE
	MAINTENANCE = true
	if templates == nil {
		templates = make(map[string]*template.Template)
	}

	layouts, err := filepath.Glob("./views/layouts/*.hbs")
	if err != nil {
		err =  errors.Wrap(err, "template")
		LogErrorNoContext(&err, nil)
	}

	pages, err := filepath.Glob("./views/pages/*.hbs")
	if err != nil {
		err =  errors.Wrap(err, "template")
		LogErrorNoContext(&err, nil)
	}

	global_shared, err := filepath.Glob("./views/shared/*.hbs")
	if err != nil {
		err =  errors.Wrap(err, "template")
		LogErrorNoContext(&err, nil)
	}

	// todo: var crawl_folder = func(){}

	// Generate our templates map from our layouts/ and includes/ directories
	for _, layout := range layouts {
		for _, page := range pages {
			files := append(global_shared, layout, page)
			// todo - crawl_folder func call if include is folder
			layout_base :=filepath.Base(layout)
			layout_short := layout_base[0:strings.LastIndex(layout_base,".")]
			page_base :=filepath.Base(page)
			page_short := page_base[0:strings.LastIndex(page_base,".")]
			templates[layout_short+":"+ page_short] = template.Must(template.New(page_short).Delims("[[", "]]").ParseFiles(files...))
		}
	}
	MAINTENANCE = old_maintenance_state
}