template/html: refactor template loading

Allow customization of the template loading process by providing a
Loader implementation.

Allow auto-reloading of templates in development mode.

template/html/loader.go

@@ -0,0 +1,56 @@
+package html
+
+import (
+	"io/ioutil"
+	"path/filepath"
+)
+
+type Loader interface {
+	Load(*TemplateService) error
+}
+
+type DirectoryLoader struct {
+	rootDir string
+}
+
+func (l *DirectoryLoader) Load(srv *TemplateService) error {
+	blockFiles, err := filepath.Glob(filepath.Join(l.rootDir, "blocks", "*.tmpl"))
+	if err != nil {
+		return err
+	}
+
+	for _, f := range blockFiles {
+		blockContent, err := ioutil.ReadFile(f)
+		if err != nil {
+			return err
+		}
+
+		blockName := filepath.Base(f)
+		srv.AddBlock(blockName, string(blockContent))
+	}
+
+	layoutFiles, err := filepath.Glob(filepath.Join(l.rootDir, "layouts", "*.tmpl"))
+	if err != nil {
+		return err
+	}
+
+	// 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 := srv.LoadLayout(templateName, string(templateData)); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func NewDirectoryLoader(rootDir string) *DirectoryLoader {
+	return &DirectoryLoader{rootDir}
+}

template/html/option.go

@@ -6,6 +6,7 @@ import "html/template"
 type Options struct {
 	Helpers  template.FuncMap
 	PoolSize int
+	DevMode  bool
 }
 
 // OptionFunc configures options for the template service
@@ -48,6 +49,14 @@ func WithPoolSize(size int) OptionFunc {
 	}
 }
 
+// WithDevMode configures the template service
+// to use the development mode (auto reload of templates).
+func WithDevMode(enabled bool) OptionFunc {
+	return func(opts *Options) {
+		opts.DevMode = enabled
+	}
+}
+
 func defaultOptions() *Options {
 	options := &Options{}
 	funcs := []OptionFunc{

template/html/provider.go

@@ -4,9 +4,9 @@ import "gitlab.com/wpetit/goweb/service"
 
 // ServiceProvider returns a service.Provider for the
 // the HTML template service implementation
-func ServiceProvider(templateDir string, funcs ...OptionFunc) service.Provider {
-	templateService := NewTemplateService(funcs...)
-	err := templateService.LoadTemplatesDir(templateDir)
+func ServiceProvider(loader Loader, funcs ...OptionFunc) service.Provider {
+	templateService := NewTemplateService(loader, funcs...)
+	err := templateService.Load()
 	return func(container *service.Container) (interface{}, error) {
 		if err != nil {
 			return nil, err

template/html/service.go

@@ -1,91 +1,79 @@
 package html
 
 import (
-	"fmt"
+	"errors"
 	"html/template"
 	"io"
-	"io/ioutil"
 	"net/http"
-	"path/filepath"
+	"sync"
 
 	"github.com/oxtoacart/bpool"
 )
 
+var (
+	ErrLayoutNotFound = errors.New("layout not found")
+)
+
 // TemplateService is a template/html based templating service
 type TemplateService struct {
-	templates map[string]*template.Template
-	pool      *bpool.BufferPool
-	helpers   template.FuncMap
+	mutex   sync.RWMutex
+	blocks  map[string]string
+	layouts map[string]*template.Template
+	loader  Loader
+	pool    *bpool.BufferPool
+	helpers template.FuncMap
+	devMode bool
+}
+
+func (t *TemplateService) AddBlock(name string, blockContent string) {
+	t.mutex.Lock()
+	defer t.mutex.Unlock()
+
+	t.blocks[name] = blockContent
 }
 
-func (t *TemplateService) LoadLayout(name string, layout string, blocks []string) error {
+func (t *TemplateService) LoadLayout(name string, layoutContent string) error {
 	tmpl := template.New(name)
 	tmpl.Funcs(t.helpers)
 
-	for _, b := range blocks {
+	t.mutex.RLock()
+	for _, b := range t.blocks {
 		if _, err := tmpl.Parse(b); err != nil {
+			t.mutex.RUnlock()
 			return err
 		}
 	}
+	t.mutex.RUnlock()
 
-	tmpl, err := tmpl.Parse(layout)
+	tmpl, err := tmpl.Parse(layoutContent)
 	if err != nil {
 		return err
 	}
 
-	t.templates[name] = tmpl
+	t.mutex.Lock()
+	t.layouts[name] = tmpl
+	t.mutex.Unlock()
 
 	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
-
+// Load parses templates via the configured template loader.
+func (t *TemplateService) Load() error {
+	return t.loader.Load(t)
 }
 
 // RenderPage renders a template to the given http.ResponseWriter
 func (t *TemplateService) RenderPage(w http.ResponseWriter, templateName string, data interface{}) error {
+	if t.devMode {
+		if err := t.loader.Load(t); err != nil {
+			return err
+		}
+	}
 
 	// Ensure the template exists in the map.
-	tmpl, ok := t.templates[templateName]
+	tmpl, ok := t.layouts[templateName]
 	if !ok {
-		return fmt.Errorf("the template '%s' does not exist", templateName)
+		return ErrLayoutNotFound
 	}
 
 	// Create a buffer to temporarily write to and check if any errors were encountered.
@@ -103,20 +91,25 @@ func (t *TemplateService) RenderPage(w http.ResponseWriter, templateName string,
 
 }
 
-// Render renders a template to the given io.Writer
-func (t *TemplateService) Render(w io.Writer, templateName string, data interface{}) error {
+// Render renders a layout to the given io.Writer.
+func (t *TemplateService) Render(w io.Writer, layoutName string, data interface{}) error {
+	if t.devMode {
+		if err := t.loader.Load(t); err != nil {
+			return err
+		}
+	}
 
 	// Ensure the template exists in the map.
-	tmpl, ok := t.templates[templateName]
+	tmpl, ok := t.layouts[layoutName]
 	if !ok {
-		return fmt.Errorf("the template '%s' does not exist", templateName)
+		return ErrLayoutNotFound
 	}
 
 	// 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 {
+	if err := tmpl.ExecuteTemplate(buf, layoutName, data); err != nil {
 		return err
 	}
 
@@ -126,14 +119,17 @@ func (t *TemplateService) Render(w io.Writer, templateName string, data interfac
 }
 
 // NewTemplateService returns a new Service
-func NewTemplateService(funcs ...OptionFunc) *TemplateService {
+func NewTemplateService(loader Loader, 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,
+		blocks:  make(map[string]string),
+		layouts: make(map[string]*template.Template),
+		pool:    bpool.NewBufferPool(options.PoolSize),
+		helpers: options.Helpers,
+		loader:  loader,
+		devMode: options.DevMode,
 	}
 }