Merge pull request #1 from waterlink/add-ability-to-register-template-outside-of-the-library

Add ability to register template engine outside the library

README.md

@@ -6,12 +6,14 @@ Generic templating interface for Crystal.
 
 Simplify developers' lives by abstracting template rendering for multiple template languages.
 
-## Supported
+## Supported out of the box
 
 | Language | File extensions | Required libraries |
 | -------- | --------------- | ------------------ |
 | ECR      | .ecr            | none (part of the stdlib) |
-| Slang    | .slang          | [slang](https://github.com/jeromegn/slang) |
+
+See also:
+[Registering your own template engine](#registering-your-own-template-engine).
 
 ## Installation
 
@@ -55,6 +57,26 @@ end
 puts str # => <compiled template>
 ```
 
+## Registering your own template engine
+
+Use `Kilt.register_template(extension, embed_command)` macro:
+
+```crystal
+require "kilt"
+
+module MyEngine
+  macro embed(filename, io_name)
+    # ....
+  end
+end
+
+Kilt.register_template("myeng", ::MyEngine.embed)
+```
+
+This can be part of your own `my-engine` library: in this case it should depend
+on `kilt` directly, or this could be a part of adapter library, like:
+`kilt-my-engine`, which will depend on both `kilt` and `my-engine`.
+
 ## Contributing
 
 Please contribute your own "adapter" if you create a template language for Crystal that's not yet supported here!

spec/spec_helper.cr

@@ -1,9 +1,11 @@
 require "spec"
 require "../src/kilt"
+
 require "slang"
+Kilt.register_template("slang", embed_slang)
 
 macro render_file(filename)
   String.build do |__io__|
     Kilt.embed({{filename}}, "__io__")
   end
-end
+end

src/kilt.cr

@@ -2,14 +2,20 @@ require "ecr/macros"
 require "./kilt/*"
 
 module Kilt
+  # macro only constant
+  TEMPLATES = {} of String => Int32
+
+  macro register_template(ext, embed_macro)
+    {% ::Kilt::TEMPLATES[ext] = embed_macro %}
+  end
 
   macro embed(filename, io_name = "__kilt_io__")
-    {% if filename.ends_with?(".ecr") %}
-      embed_ecr({{filename}}, {{io_name}})
-    {% elsif filename.ends_with?(".slang") %}
-      embed_slang({{filename}}, {{io_name}})
+    {% ext = filename.split(".").last %}
+
+    {% if ::Kilt::TEMPLATES[ext] %}
+      {{::Kilt::TEMPLATES[ext]}}({{filename}}, {{io_name}})
     {% else %}
-      raise Kilt::Exception.new("Unsupported template type \"" + {{filename.split(".").last}} + "\"")
+      raise Kilt::Exception.new("Unsupported template type \"" + {{ext}} + "\"")
     {% end %}
   end
 
@@ -18,5 +24,6 @@ module Kilt
       Kilt.embed({{filename}}, {{io_name}})
     end
   end
-
 end
+
+::Kilt.register_template("ecr", embed_ecr)