Support mount-specific swagger_root and add swagger_filter setting

lib/swagger_rails/middleware/swagger_json.rb

@@ -0,0 +1,35 @@
+require 'json'
+
+module SwaggerRails
+  class SwaggerJson
+
+    def initialize(app, config)
+      @app = app
+      @config = config
+    end
+
+    def call(env)
+      path = env['PATH_INFO']
+      filename = "#{@config.resolve_swagger_root(env)}/#{path}"
+
+      if env['REQUEST_METHOD'] == 'GET' && File.file?(filename)
+        swagger = load_json(filename)
+        @config.swagger_filter.call(swagger, env) unless @config.swagger_filter.nil?
+
+        return [
+          '200',
+          { 'Content-Type' => 'application/json' },
+          [ JSON.dump(swagger) ]
+        ]
+      end
+        
+      return @app.call(env)
+    end
+
+    private
+
+    def load_json(filename)
+      JSON.parse(File.read(filename))
+    end
+  end
+end