core/renderer/renderer.go

package renderer

import (
	"encoding/json"
	"fmt"
	"html/template"
	"net/http"
	"path"
	"path/filepath"
	"reflect"
	"strings"
)

type Renderer interface {
	Render(http.ResponseWriter, *http.Request, interface{}, ...string) error
}

type JSONRenderer struct{}

var (
	currRenderer Renderer
	Render       map[string]func(http.ResponseWriter, *http.Request, interface{}, ...string)
)

func init() {
	htmlRenderer, err := NewHTMLRenderer("templates/")
	if err != nil {
		panic(err)
	}
	Render = make(map[string]func(http.ResponseWriter, *http.Request, interface{}, ...string))

	Render["html"] = func(w http.ResponseWriter, r *http.Request, data interface{}, options ...string) {
		htmlRenderer.Render(w, r, data, options...)
	}
}

// FIXME: Not safe. We should check if it responds to the error interface instead.
func isErrorType(data interface{}) bool {
	return strings.Contains(strings.ToLower(reflect.TypeOf(data).String()), "error")
}

func NewJSONRenderer() *JSONRenderer {
	return &JSONRenderer{}
}

func (r *JSONRenderer) Render(w http.ResponseWriter, layout string, name string, data interface{}) error {
	w.Header().Set("Content-Type", "application/json; charset=utf-8")
	j, err := json.Marshal(data)
	if err != nil {
		return err
	}
	w.Write(j)
	return nil
}

type HTMLRenderer struct {
	TemplatePath string

	templates map[string]*template.Template
}

func NewHTMLRenderer(templatePath string) (*HTMLRenderer, error) {
	r := &HTMLRenderer{
		TemplatePath: templatePath,
		templates:    make(map[string]*template.Template),
	}
	fns, err := filepath.Glob(filepath.Join(templatePath, "*.tpl"))
	if err != nil {
		panic(err)
	}
	lfns, err := filepath.Glob(filepath.Join(templatePath, "layout", "*.tpl"))
	if err != nil {
		panic(err)
	}

	for _, fn := range fns {
		tplName := filepath.Base(fn)
		tplName = strings.TrimSuffix(tplName, path.Ext(tplName))
		tplName = strings.TrimSuffix(tplName, path.Ext(tplName))

		files := append(lfns, fn)
		if err != nil {
			return nil, err
		}
		r.templates[tplName] = template.Must(r.templates[tplName].ParseFiles(files...))
		if err != nil {
			return nil, err
		}

	}

	return r, nil
}

func Use(r Renderer) {
	currRenderer = r
}

func (rend *HTMLRenderer) writeError(w http.ResponseWriter, r *http.Request, err error) {
	t, ok := rend.templates["error"]
	if !ok {
		panic(fmt.Errorf("Error template not found! Can't proceed, sorry."))
	}

	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	e := t.ExecuteTemplate(w, "base", err)
	if e != nil {
		panic(e)
	}
}

func (rend *HTMLRenderer) Render(w http.ResponseWriter, r *http.Request, data interface{}, options ...string) {
	if isErrorType(data) {
		rend.writeError(w, r, data.(error))
	} else {

		t, ok := rend.templates[options[1]]
		if !ok {
			rend.writeError(w, r, fmt.Errorf("Template %s not found", options[1]))
		}
		w.Header().Set("Content-Type", "text/html; charset=utf-8")
		err := t.ExecuteTemplate(w, options[0], data)
		if err != nil {
			rend.writeError(w, r, err)
		}
	}
}