Add send_file to helpers

spec/helpers_spec.cr

@@ -84,4 +84,30 @@ describe "Macros" do
       response.headers["Content-Type"].should eq("text/plain")
     end
   end
+
+  describe "#send_file" do
+    it "sends file with given path and default mime-type" do
+      get "/" do |env|
+        send_file env, "./spec/asset/hello.ecr"
+      end
+
+      request = HTTP::Request.new("GET", "/")
+      response = call_request_on_app(request)
+      response.status_code.should eq(200)
+      response.headers["Content-Type"].should eq("application/octet-stream")
+      response.headers["Content-Length"].should eq("20")
+    end
+
+    it "sends file with given path and given mime-type" do
+      get "/" do |env|
+        send_file env, "./spec/asset/hello.ecr", "image/jpeg"
+      end
+
+      request = HTTP::Request.new("GET", "/")
+      response = call_request_on_app(request)
+      response.status_code.should eq(200)
+      response.headers["Content-Type"].should eq("image/jpeg")
+      response.headers["Content-Length"].should eq("20")
+    end
+  end
 end

src/kemal/helpers/helpers.cr

@@ -40,3 +40,20 @@ end
 def headers(env, additional_headers)
   env.response.headers.merge!(additional_headers)
 end
+
+# Send a file with given path and default `application/octet-stream` mime_type.
+#
+#   send_file env, "./path/to/file"
+#
+# Optionally you can override the mime_type
+#
+#   send_file env, "./path/to/file", "image/jpeg"
+def send_file(env, path : String, mime_type : String? = nil)
+  file_path = File.expand_path(path, Dir.current)
+  mime_type = "application/octet-stream" unless mime_type
+  env.response.headers.add "Content-Type", mime_type
+  env.response.content_length = File.size(file_path)
+  File.open(file_path) do |file|
+    IO.copy(file, env.response)
+  end
+end