goweb/template/html/service.go

package html

import (
	"fmt"
	"html/template"
	"io"
	"io/ioutil"
	"net/http"
	"path/filepath"

	"github.com/oxtoacart/bpool"
)

// TemplateService is a template/html based templating service
type TemplateService struct {
	templates map[string]*template.Template
	pool      *bpool.BufferPool
	helpers   template.FuncMap
}

func (t *TemplateService) LoadLayout(name string, layout string, blocks []string) error {
	tmpl := template.New(name)
	tmpl.Funcs(t.helpers)

	for _, b := range blocks {
		if _, err := tmpl.Parse(b); err != nil {
			return err
		}
	}

	tmpl, err := tmpl.Parse(layout)
	if err != nil {
		return err
	}

	t.templates[name] = tmpl

	return nil
}

// LoadTemplatesDir loads the templates used by the service
func (t *TemplateService) LoadTemplatesDir(templatesDir string) error {
	layoutFiles, err := filepath.Glob(filepath.Join(templatesDir, "layouts", "*.tmpl"))
	if err != nil {
		return err
	}

	blockFiles, err := filepath.Glob(filepath.Join(templatesDir, "blocks", "*.tmpl"))
	if err != nil {
		return err
	}

	blockTemplates := make([]string, 0, len(blockFiles))

	for _, f := range blockFiles {
		templateData, err := ioutil.ReadFile(f)
		if err != nil {
			return err
		}

		blockTemplates = append(blockTemplates, string(templateData))
	}

	// Generate our templates map from our layouts/ and blocks/ directories
	for _, f := range layoutFiles {
		templateData, err := ioutil.ReadFile(f)
		if err != nil {
			return err
		}

		templateName := filepath.Base(f)

		if err := t.LoadLayout(templateName, string(templateData), blockTemplates); err != nil {
			return err
		}
	}

	return nil

}

// RenderPage renders a template to the given http.ResponseWriter
func (t *TemplateService) RenderPage(w http.ResponseWriter, templateName string, data interface{}) error {

	// Ensure the template exists in the map.
	tmpl, ok := t.templates[templateName]
	if !ok {
		return fmt.Errorf("the template '%s' does not exist", templateName)
	}

	// Create a buffer to temporarily write to and check if any errors were encountered.
	buf := t.pool.Get()
	defer t.pool.Put(buf)

	if err := tmpl.ExecuteTemplate(buf, templateName, data); err != nil {
		return err
	}

	// Set the header and write the buffer to the http.ResponseWriter
	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	_, err := buf.WriteTo(w)
	return err

}

// Render renders a template to the given io.Writer
func (t *TemplateService) Render(w io.Writer, templateName string, data interface{}) error {

	// Ensure the template exists in the map.
	tmpl, ok := t.templates[templateName]
	if !ok {
		return fmt.Errorf("the template '%s' does not exist", templateName)
	}

	// Create a buffer to temporarily write to and check if any errors were encountered.
	buf := t.pool.Get()
	defer t.pool.Put(buf)

	if err := tmpl.ExecuteTemplate(buf, templateName, data); err != nil {
		return err
	}

	_, err := buf.WriteTo(w)

	return err
}

// NewTemplateService returns a new Service
func NewTemplateService(funcs ...OptionFunc) *TemplateService {
	options := defaultOptions()
	for _, f := range funcs {
		f(options)
	}
	return &TemplateService{
		templates: make(map[string]*template.Template),
		pool:      bpool.NewBufferPool(options.PoolSize),
		helpers:   options.Helpers,
	}
}