From 67eca80d618c15693541e272d9be589878d9bd95 Mon Sep 17 00:00:00 2001
From: Kyle Fuller <inbox@kylefuller.co.uk>
Date: Sun, 26 Oct 2014 18:16:27 +0000
Subject: [PATCH] Provide simple API for tags

Closes #6
---
 README.md                       | 20 ++++++++++++++++++++
 Stencil/Node.swift              | 12 ++++++++++++
 Stencil/Parser.swift            |  6 ++++++
 StencilTests/StencilTests.swift | 12 ++++++++++++
 4 files changed, 50 insertions(+)

diff --git a/README.md b/README.md
index cf88dde..ca08ba6 100644
--- a/README.md
+++ b/README.md
@@ -125,6 +125,26 @@ A for loop allows you to iterate over an array found by variable lookup.
 {% endif %}
 ```
 
+#### Building custom tags
+
+You can build a custom template tag. There are a couple of APIs to allow
+you to write your own custom tags. The following is the simplest form:
+
+```swift
+template.parser.registerSimpleTag("custom") { context in
+  return .Success("Hello World")
+}
+```
+
+When your tag is used via `{% custom %}` it will execute the registered block
+of code allowing you to modify or retrieve a value from the context. Then
+return either a string rendered in your template, or an error.
+
+If you want to accept arguments or to capture different tokens between two sets
+of template tags. You will need to the `registerTag` API which accepts a
+closure to handle the parsing. You can find examples of the `now`, `if` and
+`for` tags found inside `Node.swift`.
+
 ### Comments
 
 To comment out part of your template you can use the following syntax:
diff --git a/Stencil/Node.swift b/Stencil/Node.swift
index 9f34ec2..7661ada 100644
--- a/Stencil/Node.swift
+++ b/Stencil/Node.swift
@@ -52,6 +52,18 @@ public func renderNodes(nodes:[Node], context:Context) -> Result {
     return .Success(result)
 }
 
+public class SimpleNode : Node {
+    let handler:(Context) -> (Result)
+
+    public init(handler:((Context) -> (Result))) {
+        self.handler = handler
+    }
+
+    public func render(context:Context) -> Result {
+        return handler(context)
+    }
+}
+
 public class TextNode : Node {
     public let text:String
 
diff --git a/Stencil/Parser.swift b/Stencil/Parser.swift
index c33e6c9..0f35bea 100644
--- a/Stencil/Parser.swift
+++ b/Stencil/Parser.swift
@@ -41,6 +41,12 @@ public class TokenParser {
         tags[name] = parser
     }
 
+    public func registerSimpleTag(name:String, handler:((Context) -> (Stencil.Result))) {
+        registerTag(name, parser: { (parser, token) -> TokenParser.Result in
+            return .Success(node:SimpleNode(handler: handler))
+        })
+    }
+
     public func parse() -> Results {
         return parse(nil)
     }
diff --git a/StencilTests/StencilTests.swift b/StencilTests/StencilTests.swift
index 0eb4b57..d913773 100644
--- a/StencilTests/StencilTests.swift
+++ b/StencilTests/StencilTests.swift
@@ -64,4 +64,16 @@ class StencilTests: XCTestCase {
         let result = template.render()
         XCTAssertEqual(result, Result.Success("Hello World"))
     }
+
+    func testSimpleCustomTag() {
+        let templateString = "{% custom %}"
+        let template = Template(templateString:templateString)
+
+        template.parser.registerSimpleTag("custom") { context in
+            return .Success("Hello World")
+        }
+
+        let result = template.render()
+        XCTAssertEqual(result, Result.Success("Hello World"))
+    }
 }