emacs-jupyter/jupyter-monads.el
2023-02-13 20:22:49 -06:00

425 lines
15 KiB
EmacsLisp

;;; jupyter-monads.el --- Monadic Jupyter I/O -*- lexical-binding: t -*-
;; Copyright (C) 2020 Nathaniel Nicandro
;; Author: Nathaniel Nicandro <nathanielnicandro@gmail.com>
;; Created: 11 May 2020
;; This program is free software; you can redistribute it and/or
;; modify it under the terms of the GNU General Public License as
;; published by the Free Software Foundation; either version 3, or (at
;; your option) any later version.
;; This program is distributed in the hope that it will be useful, but
;; WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
;; General Public License for more details.
;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs; see the file COPYING. If not, write to the
;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
;; Boston, MA 02111-1307, USA.
;;; Commentary:
;;
;;; Code:
(defgroup jupyter-monads nil
"Monadic Jupyter I/O"
:group 'jupyter)
(defun jupyter-return (value)
(declare (indent 0))
(lambda (_io) value))
;; Adapted from `thunk-delay'
(defmacro jupyter-return-delayed (&rest body)
(declare (indent 0))
;; Return a delayed value, the value being evaluated in the next IO
;; context.
`(let (forced val)
(lambda (_io)
(unless forced
(setf val (progn ,@body))
(setf forced t))
val)))
(defconst jupyter-io-nil (jupyter-return nil))
(defvar jupyter-current-io
(lambda (&rest args)
(error "Unhandled IO: %s" args)))
(defun jupyter-bind-delayed (io-value io-fn)
"Bind IO-VALUE to IO-FN.
Binding causes the evaluation of a delayed value, IO-VALUE, in
the current I/O context. The unwrapped value is then passed to
IO-FN which returns another delayed value. Thus binding involves
unwrapping a value by evaluating a closure, IO-VALUE, passing the
current I/O context as argument, and passing the result to IO-FN
which returns another delayed value to be bound at some future
time. Before, between, and after the two calls to IO-VALUE and
IO-FN, the context of the I/O monad is maintained."
(declare (indent 1))
(pcase (funcall io-value jupyter-current-io)
((and req (cl-struct jupyter-request client)
(let jupyter-current-client client))
(funcall io-fn req))
(`(timeout ,(and req (cl-struct jupyter-request)))
(error "Timed out: %s" (cl-prin1-to-string req)))
(`,value (funcall io-fn value))))
;; mlet* is like do, but for varlist. The IO values in varlist are
;; bound, just like do, and then body is evaluated in the functional
;; context.
(defmacro jupyter-mlet* (varlist &rest body)
"Bind the delayed values in VARLIST, evaluate BODY."
(declare (indent 1))
(letrec ((val (make-symbol "val"))
(binder
(lambda (vars)
(if (zerop (length vars))
`(let ((res (progn ,@body)))
(if res (jupyter-return res)
jupyter-io-nil))
`(jupyter-bind-delayed
(cadar vars)
(lambda (,val)
,@(unless (eq (caar vars) '_)
`((setq ,(caar vars) ,val)))
,(funcall binder (cdr vars))))))))
`(let (,@(mapcar #'car varlist))
,(funcall binder varlist))))
(defmacro jupyter-with-io (io &rest body)
(declare (indent 1))
`(let ((jupyter-current-io ,io))
,@body))
(defmacro jupyter-do (&rest io-fns)
(declare (indent 0))
;; Thread IO through the monad, return the resulting IO-VALUE.
(if (zerop (length io-fns))
'jupyter-io-nil
`(cl-reduce #'jupyter-bind-delayed
(list ,@io-fns)
:initial-value jupyter-io-nil)))
(defun jupyter-after (io-value io-fn)
"Return an I/O action that binds IO-VALUE to IO-FN.
That is, IO-FN is evaluated after binding IO-VALUE within the I/O
context."
(declare (indent 1))
(lambda (_)
(jupyter-bind-delayed io-value io-fn)))
;;; Kernel
;;
;; I/O actions that manage a kernel's lifetime.
;; TODO: Swap definitions with `jupyter-launch', same for the others.
;; (jupyter-launch :kernel "python")
;; (jupyter-launch :spec "python")
(defun jupyter-kernel-launch (&rest args)
(lambda (_)
(let ((kernel (apply #'jupyter-kernel args)))
(jupyter-launch kernel)
kernel)))
(defun jupyter-kernel-interrupt (io-kernel)
(lambda (_)
(jupyter-interrupt kernel)
nil))
;; TODO: Have this notify the I/O context by returning something like
;;
;; ('shutdown kernel).
(defun jupyter-kernel-shutdown (kernel)
(lambda (_)
(jupyter-shutdown kernel)
nil))
;;; Publisher/subscriber
;; TODO: What is the structure of these functions when combined with
;; the current IO? This is like a bind, but in what Monad? The
;; current IO is the unwrapped value and the function being returned,
;; when called, takes you into the event monad. The lambda being
;; returned represents the lifting of an IO value into the event
;; monad.
(defun jupyter-publish-to-subscribers (subs args)
(delq nil
(mapcar
(lambda (sub)
(let ((keep nil))
(with-demoted-errors "Jupyter: Error in subscriber: %S"
(cl-block nil
(apply sub args)
(setq keep t))
(when keep fn))))
subs)))
(defun jupyter-bind-subscribers (subs fn content)
;; Th monadic values are lists with 'message or 'subscribe as the
;; first element. In the case of 'message, the rest of the list is
;; the unwrapped value passed to FN.
(pcase content
(`('message . ,msg)
;; The expansion of the monadic context is represented by the
;; unwrapping of the msg, application of FN, and then re-wrapping
;; into a 'message for the next publisher context.
(if-let* ((mapped-msg (funcall fn msg)))
(jupyter-publish-to-subscribers
subs (cons 'message mapped-msg))
subs))
(`('subscribe ,sub)
(cons sub subs))
(_ (error "Unhandled I/O: %s" args))))
(defun jupyter-publisher (&optional fn)
"Return a publisher that maps messages using FN.
FN defaults to `identity'.
If FN returns nil, the chain of subscriber calls is suppressed
for the returned publisher."
(let ((subs '())
(fn (or fn #'identity)))
(lambda (&rest content)
(setq subs
(jupyter-bind-subscribers subs fn content)))))
(defun jupyter-source (value)
"Return a publisher that maps published values to VALUE."
(jupyter-publisher
(lambda (_) (list value))))
(defun jupyter--sink (fn content)
(pcase content
(`('message . ,msg) (funcall fn msg))
(`('subscribe ,sub) (error "Cannot subscribe to a subscriber"))
(_ (error "Unhandled I/O: %s" content))))
(defun jupyter-sink (fn)
"Return a publisher that errors on subscription."
(declare (indent 0))
(lambda (&rest content)
(jupyter--sink fn content)))
(defun jupyter-publish (&rest msg)
(lambda (io)
(apply io 'message msg)
io))
(defun jupyter-filter-content (pub fn)
"Filter the content published by PUB through FN. Return a new
publisher of the filtered content. If FN returns nil for a
message, prevent the new publisher's subscribers from being
evaluated."
(declare (indent 1))
(let ((filter (jupyter-publisher fn)))
(jupyter-with-io pub
(jupyter-do
(jupyter-subscribe filter)))
filter))
(defun jupyter-subscribe (subscriber)
"Return an I/O action that adds SUBSCRIBER as a handler of the current I/O's event stream.
The action returns the current I/O in the context of the I/O
action."
(declare (indent 0))
(lambda (io)
(funcall io 'subscribe (lambda (&rest args)
(apply subscriber args)))
subscriber))
;;; IO Event
(defun jupyter-default-io ()
(jupyter-return
(lambda (&rest args)
(pcase (car args)
((or 'message 'subscribe)
(error "Not implemented"))
(_ (error "Unhandled IO: %s" args))))))
;; A monadic function that, given session endpoints, returns a monadic
;; value that, when evaluated, returns an I/O stream sink that can
;; subscribe to some other source of messages.
;;
;; (funcall channel-io 'message 'start)
;;
;; The current I/O context when the value is evaluated should be one
;; in which the socket endpoints of SESSION can be controlled by
;; 'start-channel, 'stop-channel, and 'alive-p messages.
(defun jupyter-channel-io (session)
(let* ((channels '(:shell :iopub :stdin))
(ch-group
(cl-loop
with endpoints = (jupyter-session-endpoints session)
for ch in channels
collect ch
collect (list 'endpoint (plist-get endpoints ch)
'alive-p nil))))
(cl-macrolet ((continue-after
(cond on-timeout)
`(jupyter-with-timeout
(nil jupyter-default-timeout ,on-timeout)
,cond)))
(cl-labels ((ch-put
(ch prop value)
(plist-put (plist-get ch-group ch) prop value))
(ch-get
(ch prop)
(plist-get (plist-get ch-group ch) prop))
(ch-alive-p
(ch)
(and (funcall io 'alive-p)
(ch-get ch 'alive-p)))
(ch-start
(ch)
(unless (ch-alive-p ch)
(funcall io 'message 'start-channel ch
(ch-get ch 'endpoint))
(continue-after
(ch-alive-p ch)
(error "Channel not started: %s" ch))))
(ch-stop
(ch)
(when (ch-alive-p ch)
(funcall io 'message 'stop-channel ch)
(continue-after
(not (ch-alive-p ch))
(error "Channel not stopped: %s" ch)))))
(jupyter-io-lambda (_)
('start
(cl-loop
for ch in channels
do (ch-start ch)))
('stop
(cl-loop
for ch in channels
do (ch-stop ch))
(and hb (jupyter-hb-pause hb))
(setq hb nil))
('alive-p
(and (or (null hb) (jupyter-alive-p hb))
(cl-loop
for ch in channels
do (ch-alive-p ch))))
('hb
(unless hb
(setq hb
(make-instance
'jupyter-hb-channel
:session session
:endpoint (plist-get endpoints :hb))))
hb))))))
;; Kernel -> IO Function
(defun jupyter-kernel-websocket-io (kernel)
(jupyter-launch kernel)
(pcase-let* (((cl-struct jupyter-server-kernel server id) kernel)
(websocket (jupyter-api-kernel-websocket server id)))
(jupyter-websocket-io websocket)))
;;; Websocket IO
;; A monadic function in the I/O stream monad.
;;
;; There is a gap in evaluation time between sending and receiving.
;; We do not know when a message will be received. A stream fires of
;; message events
(defun jupyter-websocket-io (websocket &optional custom-header-alist)
(let ((handlers '())
(events '()))
(cl-labels
((on-message
(_ws frame)
;; This represents a source of new IO messages.
(cl-case (websocket-frame-opcode frame)
((text binary)
(let* ((msg (jupyter-read-plist-from-string
(websocket-frame-payload frame)))
;; TODO: Get rid of some of these explicit/implicit `intern' calls
(channel (intern (concat ":" (plist-get msg :channel))))
(msg-type (jupyter-message-type-as-keyword
(jupyter-message-type msg)))
(parent-header (plist-get msg :parent_header)))
(plist-put msg :msg_type msg-type)
(plist-put parent-header :msg_type msg-type)
;; NOTE: The nil is the identity field expected by a
;; `jupyter-channel-ioloop', it is mimicked here.
(jupyter-run-handlers handlers
(cl-list* 'message channel nil msg))))
(t
(error "Unhandled websocket frame opcode (%s)"
(websocket-frame-opcode frame))))))
;; The pattern is (with-io pub (subscribe subscriber) pub)
;; passing along the publisher to attach subscribers.
(jupyter-io-lambda (&rest args)
('message
(cl-destructuring-bind (channel msg-type msg &optional msg-id) args
(websocket-send-text
ws (jupyter-encode-raw-message
(plist-get (websocket-client-data ws) :session) msg-type
:channel (substring (symbol-name channel) 1)
:msg-id msg-id
:content msg))))
('subscribe )
('start (websocket-ensure-connected websocket))
('stop (websocket-close websocket))
('alive-p (websocket-openp websocket))))))
;;; Request
(defun jupyter-idle (io-req)
;; After an IO-REQ is made, wait until the request is idle and
;; return it. If `jupyter-default-timeout' seconds elapses before
;; the request is idle, signal an error. Waiting for idleness is
;; delayed until the returned I/O action is bound.
(jupyter-after io-req
(lambda (req)
(jupyter-return-delayed
(if (jupyter-wait-until-idle req) req
(list 'timeout req))))))
;; MsgType -> MsgList -> (IO -> Req)
;; (IO -> Req) represents an IO monadic value. IO Req
(defun jupyter-request (type &rest content)
"Return an IO action that sends a `jupyter-request'.
TYPE is the message type of the message that CONTENT, a property
list, represents.
See `jupyter-io' for more information on IO actions."
(declare (indent 1))
(setq type (intern (format ":%s-request"
(replace-regexp-in-string "_" "-" type))))
(lambda (io)
(let* ((req (make-jupyter-request
:client jupyter-current-client
:type type
:content content))
(ch (if (memq type '(:input-reply :input-request))
:stdin
:shell))
(id (jupyter-request-id req)))
(letrec ((handler
(lambda (event)
(pcase (car event)
((and 'message (let `(,channel . ,msg) (cdr event))
(guard (string= id (jupyter-message-parent-id msg))))
(cl-callf nconc (jupyter-request-messages req)
(list msg))
(when (jupyter--message-completes-request-p msg)
(setf (jupyter-request-idle-p req) t)
(jupyter-send io 'remove-handler handler)))))))
(jupyter-send io 'message ch type content id)
(jupyter-send io 'add-handler handler)
req))))
(provide 'jupyter-monads)
;;; jupyter-monads.el ends here