305 lines
13 KiB
Org Mode
305 lines
13 KiB
Org Mode
#+TITLE: Communication Protocol (communication.lisp)
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#+AUTHOR: Agent
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#+FILETAGS: :harness:protocol:
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#+STARTUP: content
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#+PROPERTY: header-args:lisp :tangle ../lisp/core-communication.lisp
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* Overview: Architectural Intent
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The Communication Protocol defines how Passepartout speaks to the outside world. It sits between the metabolic loop and the network, providing framed, length-prefixed message transport over TCP.
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Every message is an S-expression (plist) prefixed with a 6-character hex length:
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00002C(:TYPE :EVENT :PAYLOAD (:ACTION :handshake :VERSION "0.2.0"))
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This is a deliberate rejection of JSON, Protocol Buffers, or any other serialization format. The message format is Lisp-native because:
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1. The agent generates and consumes these messages inside the cognitive loop — no serialization layer needed
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2. The format is human-readable and trivially debuggable with a text editor
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3. The length prefix prevents framing attacks (no "read until newline" ambiguity)
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** Why Length-Prefixed Framing?
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A naive TCP protocol that reads until newline fails when:
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- A message contains a newline character (which Lisp plists can)
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- A message is split across TCP packets (read returns partial data)
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- A malicious client sends an infinite stream without newlines
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The length prefix solves all three problems. The reader reads exactly 6 characters (the hex length), then reads exactly that many additional characters. No ambiguous termination, no partial message handling, no newline worries.
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The 6-character hex length supports messages up to ~16MB (0xFFFFFF bytes). This is sufficient for any single message the agent would produce. Larger payloads should be split across multiple messages.
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** Contract
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1. (frame-message msg): serializes a plist message to a length-prefixed
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string. The first 6 characters are the hex-encoded payload length.
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2. (read-framed-message stream): reads a framed message from a stream,
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returning the deserialized plist. Consumes exactly the length-prefixed
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bytes.
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3. Round-trip invariant: ~(read-framed-message (make-string-input-stream
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(frame-message msg)))~ equals ~msg~.
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* Implementation
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** Package Context
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#+begin_src lisp
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(in-package :passepartout)
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#+end_src
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** Protocol Accessor (proto-get)
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Case-insensitive property list accessor used throughout the pipeline.
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Returns the value associated with KEY in PLIST by interning a keyword.
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;; REPL-VERIFIED: 2026-05-03T13:00:00
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#+begin_src lisp
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(defun proto-get (plist key)
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"Look up KEY in PLIST with case-insensitive keyword normalization."
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(let ((key-upcase (string-upcase (string key))))
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(loop for (k v) on plist by #'cddr
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when (and (keywordp k)
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(string-equal (string k) key-upcase))
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do (return v))))
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#+end_src
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** Actuator Registry
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The global registry mapping target keywords (~:cli~, ~:telegram~, ~:signal~, etc.) to their physical actuator functions. Extensible at runtime — skills can register new actuators via ~register-actuator~.
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#+begin_src lisp
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(defvar *actuator-registry* (make-hash-table :test 'equalp)
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"Global registry mapping target keywords to their physical actuator functions.")
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(defun register-actuator (name fn)
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"Registers an actuator function. Actuators receive: (ACTION CONTEXT)."
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(let ((key (if (keywordp name) name (intern (string-upcase (string name)) :keyword))))
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(setf (gethash key *actuator-registry*) fn)))
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#+end_src
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** Message Framing
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Three functions handle the full message lifecycle: sanitize (strip non-serializable state), frame (serialize + prefix), and read (parse from stream).
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*** Sanitize Protocol Message
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Strips transient runtime state (~:reply-stream~, ~:socket~, ~:stream~) from a message plist before sending it over the network. These are Lisp stream objects that cannot be serialized and have no meaning to the remote end.
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#+begin_src lisp
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(defun protocol-message-sanitize (msg)
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"Recursively strips non-serializable objects from a protocol plist."
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(if (and msg (listp msg))
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(let ((clean nil))
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(loop for (k v) on msg by #'cddr
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do (unless (member k '(:reply-stream :socket :stream))
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(push k clean)
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(push (if (listp v) (protocol-message-sanitize v) v) clean)))
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(nreverse clean))
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msg))
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#+end_src
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*** Frame Message
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Serializes a plist to a length-prefixed string: 6-character hex length followed by the ~prin1~ representation.
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#+begin_src lisp
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(defun frame-message (msg)
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"Serializes a message plist and prefixes it with a 6-character hex length."
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(let* ((sanitized (protocol-message-sanitize msg))
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(payload (let ((*print-pretty* nil) (*read-eval* nil)) (format nil "~s" sanitized)))
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(len (length payload)))
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(format nil "~6,'0x~a" len payload)))
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#+end_src
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*** Read Framed Message
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Reads a complete framed message from a TCP stream. Handles leading whitespace between messages, partial reads, and malformed length headers gracefully. Returns the parsed S-expression, or ~:eof~ if the stream is closed, or ~:error~ if the message is malformed.
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#+begin_src lisp
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(defun read-framed-message (stream)
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"Reads a hex-length prefixed S-expression from the stream securely."
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(let ((length-buffer (make-string 6)))
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(handler-case
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(progn
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(loop for char = (peek-char nil stream nil :eof)
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while (and (not (eq char :eof)) (member char '(#\Space #\Newline #\Tab #\Return)))
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do (read-char stream))
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(let ((count (read-sequence length-buffer stream)))
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(if (< count 6)
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:eof
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(let ((len (ignore-errors (parse-integer length-buffer :radix 16))))
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(if (not len)
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:error
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(let ((msg-buffer (make-string len)))
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(read-sequence msg-buffer stream)
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(let ((*read-eval* nil))
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(handler-case (read-from-string msg-buffer)
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(error () :error)))))))))
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(error () :error))))
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#+end_src
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** Server Listener (daemon-start)
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The TCP server that accepts connections from CLI and TUI clients. Each connection gets a dedicated thread (~client-handle-connection~).
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The daemon sends a handshake message on connection, then enters a read loop, injecting each received message into the metabolic loop via ~stimulus-inject~. The ~:health-check~ message type is handled inline (not sent to the cognitive loop) so that health checks work even when the agent is busy.
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#+begin_src lisp
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(defvar *daemon-socket* nil)
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(defun client-handle-connection (socket)
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"Handles a single TUI/CLI client connection in a dedicated thread."
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(let ((stream (usocket:socket-stream socket)))
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(handler-case
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(progn
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(format stream "~a" (frame-message (make-hello-message "0.2.0")))
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(finish-output stream)
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(loop
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(let ((msg (read-framed-message stream)))
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(cond
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((eq msg :eof) (return))
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((eq msg :error) (return))
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((eq (getf msg :type) :health-check)
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(let ((health-msg (list :type :health-response
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:status (or (and (boundp 'passepartout::*system-health*)
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(symbol-value 'passepartout::*system-health*))
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:unknown)
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:checked-p (or (and (boundp 'passepartout::*health-check-ran*)
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(symbol-value 'passepartout::*health-check-ran*))
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nil))))
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(format stream "~a" (frame-message health-msg))
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(finish-output stream)))
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(t (stimulus-inject msg :stream stream))))))
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(error (c) (log-message "CLIENT ERROR: ~a" c)))
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(ignore-errors (usocket:socket-close socket))))
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(defun start-daemon (&key (port 9105))
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"Starts the network listener for TUI/CLI clients."
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(setf *daemon-socket* (usocket:socket-listen "127.0.0.1" port :reuse-address t))
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(log-message "DAEMON: Listening on localhost:~a" port)
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(bt:make-thread
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(lambda ()
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(loop
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(let ((client-socket (usocket:socket-accept *daemon-socket*)))
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(when client-socket
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(bt:make-thread (lambda () (client-handle-connection client-socket))
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:name "passepartout-client-handler")))))
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:name "passepartout-server-listener"))
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#+end_src
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** Handshake Logic
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The first message sent to every new connection. The client can use this to verify the protocol version and the daemon's capabilities.
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#+begin_src lisp
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(defun make-hello-message (version)
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"Constructs the standard HELLO handshake message."
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(list :TYPE :EVENT
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:PAYLOAD (list :ACTION :handshake
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:VERSION version
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:CAPABILITIES '(:AUTH :ORG-AST))))
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#+end_src
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** Structural Validation
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Validates that an incoming message has the minimum required structure: a plist with a valid ~:type~ field. Used by the protocol validator skill to reject malformed messages before they enter the cognitive loop.
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#+begin_src lisp :tangle ../lisp/core-communication.lisp
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(in-package :passepartout)
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(defun protocol-schema-validate (msg)
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"Strict structural validation for incoming protocol messages."
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(unless (listp msg) (error "Message must be a plist"))
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(let ((type (proto-get msg :type)))
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(unless (member type '(:REQUEST :EVENT :RESPONSE :LOG :STATUS))
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(error "Invalid message type '~a'" type))
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t))
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#+end_src
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** Backward-Compatibility Alias
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;; REPL-VERIFIED: 2026-05-03T14:00:00
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#+begin_src lisp
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(defun validate-communication-protocol-schema (msg)
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"Backward-compatibility alias for protocol-schema-validate."
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(protocol-schema-validate msg))
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#+end_src
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** Protocol Smoke Test (manual for REPL evaluation)
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Use this function to manually verify that the daemon is alive and the framing protocol works end-to-end. It connects to a running daemon, reads the HELLO handshake, sends a "hi" message, and reads the response.
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#+begin_src lisp :tangle no
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(defun test-daemon-protocol ()
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(handler-case
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(let* ((socket (usocket:socket-connect "127.0.0.1" 9105))
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(stream (usocket:socket-stream socket)))
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(format t "Connected.~%")
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(let* ((len-buf (make-string 6))
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(count (read-sequence len-buf stream)))
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(when (= count 6)
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(let* ((len (parse-integer len-buf :radix 16))
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(msg-buf (make-string len)))
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(read-sequence msg-buf stream)
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(format t "HELLO: ~a~%" msg-buf))))
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(let* ((msg '(:TYPE :EVENT :META (:SOURCE :tui) :PAYLOAD (:SENSOR :user-input :TEXT "hi")))
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(framed (frame-message msg)))
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(format stream "~a" framed)
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(finish-output stream)
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(let* ((len-buf (make-string 6))
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(count (read-sequence len-buf stream)))
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(when (= count 6)
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(let* ((len (parse-integer len-buf :radix 16))
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(msg-buf (make-string len)))
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(read-sequence msg-buf stream)
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(format t "Response: ~a~%" msg-buf)))))
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(usocket:socket-close socket))
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(error (c) (format t "Error: ~a~%" c))))
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#+end_src
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* Test Suite
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Verifies that the framing protocol correctly serializes and deserializes messages.
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#+begin_src lisp :tangle ../lisp/core-communication.lisp
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(eval-when (:compile-toplevel :load-toplevel :execute)
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(ql:quickload :fiveam :silent t))
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(defpackage :passepartout-communication-tests
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(:use :cl :fiveam :passepartout)
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(:export #:communication-protocol-suite))
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(in-package :passepartout-communication-tests)
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(def-suite communication-protocol-suite :description "Communication Protocol Suite")
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(in-suite communication-protocol-suite)
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(test test-framing
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"Contract 1: frame-message produces correct hex length prefix."
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(let* ((msg '(:type :EVENT :payload (:action :handshake)))
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(framed (frame-message msg)))
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(is (string= "00002C" (string-upcase (subseq framed 0 6))))))
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(test test-framing-round-trip
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"Contract 3: frame → read-frame preserves message identity."
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(let* ((msg '(:type :EVENT :payload (:action :handshake :version "1.0") :meta (:source :tui)))
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(framed (frame-message msg))
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(unframed (read-framed-message (make-string-input-stream framed))))
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(is (equal msg unframed))))
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(test test-framing-empty-message
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"Contract 1: simple messages frame with valid hex length."
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(let* ((msg '(:type :ping))
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(framed (frame-message msg)))
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(is (> (length framed) 5))
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(is (every (lambda (c) (digit-char-p c 16)) (subseq framed 0 6)))))
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(test test-read-framed-message
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"Contract 2: read-framed-message decodes a framed message correctly."
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(let* ((original '(:type :EVENT :payload (:text "decoded" :id 42)))
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(framed (frame-message original))
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(decoded (read-framed-message (make-string-input-stream framed))))
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(is (equal original decoded))))
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(test test-read-framed-message-eof
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"Contract 2: read-framed-message returns :eof on incomplete stream."
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(let ((decoded (read-framed-message (make-string-input-stream "000"))))
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(is (eq :eof decoded))))
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#+end_src
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