Add Chattle protocol

chattle.py

@@ -0,0 +1,42 @@
+import json
+import struct
+
+
+class Message:
+    """
+    Data carrier for messages. Before a Message may be sent over the network, it must be encoded using the
+    `encode_message` function
+    """
+    def __init__(self, buffer: bytes) -> None:
+        # The byte layout of the structure is a buffer of JSON data preceded by a 2-byte header that specifies how long
+        # it is.
+        message_length_size = 2
+        message_length = struct.unpack(">H", buffer[0:message_length_size])[0]
+        message = json.loads(buffer[message_length_size:(message_length_size + message_length)])
+        self.author = message["author"]
+        self.body = message["body"]
+
+    def as_command(self) -> str:
+        """
+        Attempts to extract a command from the message.
+
+        :return: Contents of the command without the command character or an empty string if `self` is not a command.
+        """
+        return (self.body[1:] if self.body.startswith("/") else "")
+
+
+def encode_message(author: str, body: str) -> bytes:
+    """
+    Encodes a message in the Chattle protocol format for transporting over a network connection.
+
+    :param author: Screen name of the user that the message originated from
+    :param body: Content of the message. Note that any trailing whitespace characters are stripped.
+    :return: An encoded byte buffer of the message that can be decoded by creating a `Message` instance from it.
+    """
+
+    message = json.dumps({
+        "author": author,
+        "body": body.strip(),
+    }).encode("utf-8")
+
+    return (struct.pack(">H", len(message)) + message)