Only / Exclude Paths in Middleware (#245)

Add only / exclude paths in Middlewares

src/kemal.cr

@@ -1,6 +1,7 @@
 require "http"
 require "multipart"
 require "./kemal/*"
+require "./kemal/ext/*"
 require "./kemal/helpers/*"
 require "./kemal/middleware/*"
 

src/kemal/ext/handler.cr

@@ -0,0 +1,64 @@
+class Kemal::Handler < HTTP::Handler
+  @@only_routes_tree = Radix::Tree(String).new
+  @@exclude_routes_tree = Radix::Tree(String).new
+
+  macro only(paths, method = "GET")
+    class_name = {{@type.name}}
+    {{paths}}.each do |path|
+      @@only_routes_tree.add "#{class_name}/#{{{method}}.downcase}#{path}", "/#{{{method}}.downcase}#{path}"
+    end
+  end
+
+  macro exclude(paths, method = "GET")
+    class_name = {{@type.name}}
+    {{paths}}.each do |path|
+      @@exclude_routes_tree.add "#{class_name}/#{{{method}}.downcase}#{path}", "/#{{{method}}.downcase}#{path}"
+    end
+  end
+
+  def call(env)
+    call_next(env)
+  end
+
+  # Processes the path based on `only` paths which is a `Array(String)`.
+  # If the path is not found on `only` conditions the handler will continue processing.
+  # If the path is found in `only` conditions it'll stop processing and will pass the request
+  # to next handler.
+  #
+  # However this is not done automatically. All handlers must inherit from `Kemal::Handler`.
+  #
+  #     OnlyHandler < Kemal::Handler
+  #       only ["/"]
+  #
+  #       def call(env)
+  #         return call_next(env) unless only_match?(env)
+  #         puts "If the path is / i will be doing some processing here."
+  #       end
+  #     end
+  def only_match?(env)
+    @@only_routes_tree.find(radix_path(env.request.method, env.request.path)).found?
+  end
+
+  # Processes the path based on `exclude` paths which is a `Array(String)`.
+  # If the path is not found on `exclude` conditions the handler will continue processing.
+  # If the path is found in `exclude` conditions it'll stop processing and will pass the request
+  # to next handler.
+  #
+  # However this is not done automatically. All handlers must inherit from `Kemal::Handler`.
+  #
+  #     ExcludeHandler < Kemal::Handler
+  #       exclude ["/"]
+  #
+  #       def call(env)
+  #         return call_next(env) if exclude_match?(env)
+  #         puts "If the path is not / i will be doing some processing here."
+  #       end
+  #     end
+  def exclude_match?(env)
+    @@exclude_routes_tree.find(radix_path(env.request.method, env.request.path)).found?
+  end
+
+  private def radix_path(method : String, path)
+    "#{self.class}/#{method.downcase}#{path}"
+  end
+end