Make Payload case-insensitive (Fixes #108)

spec/cable/connection_spec.cr

@@ -65,6 +65,18 @@ describe Cable::Connection do
       end
     end
 
+    it "accepts a case-insensitive command and keys (issue #108)" do
+      connect do |connection, socket|
+        connection.receive({"Command" => "Subscribe", "Identifier" => {channel: "ChatChannel", room: "1"}.to_json}.to_json)
+        sleep 100.milliseconds
+
+        socket.messages.should contain({"type" => "confirm_subscription", "identifier" => {channel: "ChatChannel", room: "1"}.to_json}.to_json)
+
+        connection.close
+        socket.close
+      end
+    end
+
     it "accepts without params hash key" do
       connect do |connection, socket|
         connection.receive({"command" => "subscribe", "identifier" => {channel: "AppearanceChannel"}.to_json}.to_json)

spec/cable/payload_spec.cr

@@ -36,6 +36,20 @@ describe Cable::Payload do
     payload.action.should eq("invite")
   end
 
+  it "parses case-insensitive top-level keys (issue #108)" do
+    payload_json = {
+      "Command"    => "message",
+      "Identifier" => {channel: "ChatChannel"}.to_json,
+      "DATA"       => {invite_id: 3, action: "invite"}.to_json,
+    }.to_json
+
+    payload = Cable::Payload.from_json(payload_json)
+    payload.command.should eq("message")
+    payload.channel.should eq("ChatChannel")
+    payload.data.should eq({"invite_id" => 3})
+    payload.action.should eq("invite")
+  end
+
   it "raises a SerializableError when the identifier is not a string" do
     payload_json = {
       command:    "subscribe",

src/cable/connection.cr

@@ -123,9 +123,13 @@ module Cable
       return unless message.presence
       payload = Cable::Payload.from_json(message)
 
-      return subscribe(payload) if payload.command == "subscribe"
-      return unsubscribe(payload) if payload.command == "unsubscribe"
-      return message(payload) if payload.command == "message"
+      # Compare case-insensitively so a command like "Subscribe" still
+      # dispatches correctly (see issue #108).
+      case payload.command.downcase
+      when "subscribe"   then subscribe(payload)
+      when "unsubscribe" then unsubscribe(payload)
+      when "message"     then message(payload)
+      end
     end
 
     def subscribe(payload : Cable::Payload)

src/cable/payload.cr

@@ -39,6 +39,31 @@ module Cable
     @[JSON::Field(ignore: true)]
     getter action : String = ""
 
+    # Crystal's JSON parsing is case-sensitive, but cable clients in the wild
+    # aren't always consistent about the casing of the top-level protocol keys.
+    # Normalize them to lowercase before deserializing so a payload such as
+    # `{"Command": "subscribe", ...}` is accepted instead of raising
+    # "Missing JSON attribute: command".
+    #
+    # Only the top-level keys (command/identifier/data) are touched; the nested
+    # values — channel names and the identifier/data blobs — are left exactly as
+    # sent, since those remain case-sensitive. See issue #108.
+    def self.from_json(string : String) : self
+      if object = JSON.parse(string).as_h?
+        string = String.build do |io|
+          JSON.build(io) do |json|
+            json.object do
+              object.each do |key, value|
+                json.field(key.downcase) { value.to_json(json) }
+              end
+            end
+          end
+        end
+      end
+
+      new(JSON::PullParser.new(string))
+    end
+
     # After the Payload is deserialized, parse the data.
     # This will ensure we know if it's an action.
     def after_initialize