From 7e9dc068fb6ec78ebd2a144579edd9f014abf961 Mon Sep 17 00:00:00 2001
From: Makis Maropoulos <makis@ideopod.com>
Date: Tue, 28 Jun 2016 18:06:52 +0300
Subject: [PATCH] Extend the Handlebars support as requested here
 https://github.com/kataras/iris/issues/239#issuecomment-229020737

History, Books  & examples are updated.
---
 HISTORY.md                                    | 18 +++++-
 context.go                                    |  2 +-
 initiatory.go                                 |  1 +
 .../template/engine/handlebars/handlebars.go  | 56 ++++++++++++++++++-
 4 files changed, 72 insertions(+), 5 deletions(-)

diff --git a/HISTORY.md b/HISTORY.md
index 04e64c09..72f7baf3 100644
--- a/HISTORY.md
+++ b/HISTORY.md
@@ -1,9 +1,23 @@
 # History
 
-## 3.0.0-rc.2 -> 3.0.0-rc.3
-
 **How to upgrade**: remove your $GOPATH/src/github.com/kataras folder, open your command-line and run `go get -u github.com/kataras/iris/iris`.
 
+## 3.0.0-rc.3 -> 3.0.0-rc.4
+
+**NEW**: **Handlebars** template engine support with all Iris' view engine's functions/helpers support:
+- `iris.Config.Render.Template.Layout = "layouts/layout.html"`
+- `config.NoLayout`
+- **dynamic** optional layout on `context.Render`
+- **Party specific** layout
+- `iris.Config.Render.Template.Handlebars.Helpers["myhelper"] = func()...`
+- `{{ yield }} `
+- `{{ render }}`
+- `{{ url "myroute" myparams}}`
+- `{{ urlpath "myroute" myparams}}`
+
+For a complete example please navigate [here](https://github.com/iris-contrib/examples/tree/master/templates_handlebars/templates).
+
+## 3.0.0-rc.2 -> 3.0.0-rc.3
 
 **Breaking changes**
 - Move middleware & their configs to the  [iris-contrib/middleware](https://github.com/iris-contrib/middleware) repository
diff --git a/context.go b/context.go
index 80f521c7..cbcb5224 100644
--- a/context.go
+++ b/context.go
@@ -476,7 +476,7 @@ func (ctx *Context) Render(name string, binding interface{}, layout ...string) e
 func (ctx *Context) MustRender(name string, binding interface{}, layout ...string) {
 	if err := ctx.Render(name, binding, layout...); err != nil {
 		ctx.Panic()
-		ctx.framework.Logger.Dangerf("MustRender panics for client with IP: %s On template: %s", ctx.RemoteAddr(), name)
+		ctx.framework.Logger.Dangerf("MustRender panics for client with IP: %s On template: %s.Trace: %s\n", ctx.RemoteAddr(), name, err)
 	}
 }
 
diff --git a/initiatory.go b/initiatory.go
index 80d58495..56743fe3 100644
--- a/initiatory.go
+++ b/initiatory.go
@@ -38,6 +38,7 @@ func init() {
 
 const (
 	/* conversional */
+
 	// HTMLEngine conversion for config.HTMLEngine
 	HTMLEngine = config.HTMLEngine
 	// PongoEngine conversion for config.PongoEngine
diff --git a/render/template/engine/handlebars/handlebars.go b/render/template/engine/handlebars/handlebars.go
index 5e86dee5..4acf91e2 100644
--- a/render/template/engine/handlebars/handlebars.go
+++ b/render/template/engine/handlebars/handlebars.go
@@ -39,6 +39,17 @@ func (e *Engine) BuildTemplates() error {
 	if e.Config.Handlebars.Helpers != nil {
 		raymond.RegisterHelpers(e.Config.Handlebars.Helpers)
 	}
+
+	// the render works like {{ render "myfile.html" theContext.PartialContext}}
+	// instead of the html/template engine which works like {{ render "myfile.html"}} and accepts the parent binding, with handlebars we can't do that because of lack of runtime helpers (dublicate error)
+	raymond.RegisterHelper("render", func(partial string, binding interface{}) raymond.SafeString {
+		contents, err := e.executeTemplateBuf(partial, binding)
+		if err != nil {
+			return raymond.SafeString("Template with name: " + partial + " couldn't not be found.")
+		}
+		return raymond.SafeString(contents)
+	})
+
 	var templateErr error
 
 	dir := e.Config.Directory
@@ -84,6 +95,7 @@ func (e *Engine) BuildTemplates() error {
 		}
 		return nil
 	})
+
 	return templateErr
 
 }
@@ -98,13 +110,53 @@ func (e *Engine) fromCache(relativeName string) *raymond.Template {
 	return nil
 }
 
+func (e *Engine) executeTemplateBuf(name string, binding interface{}) (string, error) {
+	if tmpl := e.fromCache(name); tmpl != nil {
+		return tmpl.Exec(binding)
+	}
+	return "", nil
+}
+
 // ExecuteWriter executes a templates and write its results to the out writer
 func (e *Engine) ExecuteWriter(out io.Writer, name string, binding interface{}, layout string) error {
-	if tmpl := e.fromCache(name); tmpl != nil {
+
+	isLayout := false
+
+	renderFilename := name
+	if layout != "" && layout != config.NoLayout {
+		isLayout = true
+		renderFilename = layout // the render becomes the layout, and the name is the partial.
+	}
+
+	if tmpl := e.fromCache(renderFilename); tmpl != nil {
+		if isLayout {
+			var context map[string]interface{}
+			if m, is := binding.(map[string]interface{}); is { //handlebars accepts maps,
+				context = m
+			} else {
+				return fmt.Errorf("Please provide a map[string]interface{} type as the binding instead of the %#v", binding)
+			}
+
+			contents, err := e.executeTemplateBuf(name, binding)
+			if err != nil {
+				return err
+			}
+			if context == nil {
+				context = make(map[string]interface{}, 1)
+			}
+			// I'm implemented the {{ yield }} as with the rest of template engines, so this is not inneed for iris, but the user can do that manually if want
+			// there is no performanrce different: raymond.RegisterPartialTemplate(name, tmpl)
+			context["yield"] = raymond.SafeString(contents)
+		}
+
 		res, err := tmpl.Exec(binding)
+
+		if err != nil {
+			return err
+		}
 		_, err = fmt.Fprint(out, res)
 		return err
 	}
 
-	return fmt.Errorf("[IRIS TEMPLATES] Template with name %s doesn't exists in the dir %s", name, e.Config.Directory)
+	return fmt.Errorf("[IRIS TEMPLATES] Template with name %s[original name = %s] doesn't exists in the dir %s", renderFilename, name, e.Config.Directory)
 }