(define-module (loopy agenda) #:use-module (srfi srfi-9) #:use-module (srfi srfi-9 gnu) #:use-module (ice-9 q) #:use-module (ice-9 match) #:use-module (ice-9 receive) #:export (make-agenda agenda? agenda-queue agenda-prompt-tag agenda-port-pmapping agenda-schedule make-async-prompt-tag make-time-segment time-segment? time-segment-time time-segment-queue time-< time-= time-<= make-schedule schedule-add! schedule-empty? schedule-segments schedule-segments-split schedule-extract-until! add-segments-contents-to-queue! make-port-mapping port-mapping-set! port-mapping-remove! port-mapping-empty? port-mapping-non-empty? %current-agenda start-agenda agenda-run-once)) ;; @@: Using immutable agendas here, so wouldn't it make sense to ;; replace this queue stuff with using pfds based immutable queues? ;;; Agenda definition ;;; ================= ;;; The agenda consists of: ;;; - a queue of immediate items to handle ;;; - sheduled future events to be added to a future queue ;;; - a tag by which running processes can escape for some asynchronous ;;; operation (from which they can be returned later) ;;; - a mapping of ports to various handler procedures ;;; ;;; The goal, eventually, is for this all to be immutable and functional. ;;; However, we aren't there yet. Some tricky things: ;;; - The schedule needs to be immutable, yet reasonably efficient. ;;; - Need to use immutable queues (ijp's pfds library?) ;;; - Modeling reading from ports as something repeatable, ;;; and with reasonable separation from functional components? (define-immutable-record-type (make-agenda-intern queue prompt-tag port-mapping schedule) agenda? (queue agenda-queue) (prompt-tag agenda-prompt-tag) (port-mapping agenda-port-mapping) (schedule agenda-schedule)) (define (make-async-prompt-tag) (make-prompt-tag "prompt")) (define* (make-agenda #:key (queue (make-q)) (prompt (make-prompt-tag)) (port-mapping (make-port-mapping)) (schedule (make-schedule))) (make-agenda-intern queue prompt port-mapping schedule)) ;;; Schedule ;;; ======== ;;; This is where we handle timed events for the future ;; This section totally borrows from SICP ;; <3 <3 <3 ;; NOTE: time is a cons of (seconds . microseconds) (define-record-type (make-time-segment-intern time queue) time-segment? (time time-segment-time) (queue time-segment-queue)) (define (time-segment-right-format time) (match time ;; time is already a cons of second and microsecnd (((? integer? s) . (? integer? u)) time) ;; time was just an integer (just the second) ((? integer? _) (cons time 0)) (_ (throw 'invalid-time "Invalid time" time)))) (define* (make-time-segment time #:optional (queue (make-q))) (make-time-segment-intern time queue)) (define (time-< time1 time2) (cond ((< (car time1) (car time2)) #t) ((and (= (car time1) (car time2)) (< (cdr time1) (cdr time2))) #t) (else #f))) (define (time-= time1 time2) (and (= (car time1) (car time2)) (= (cdr time1) (cdr time2)))) (define (time-<= time1 time2) (or (time-< time1 time2) (time-= time1 time2))) (define-record-type (make-schedule-intern segments) schedule? (segments schedule-segments set-schedule-segments!)) (define* (make-schedule #:optional segments) (make-schedule-intern (or segments '()))) ;; TODO: This code is reasonably easy to read but it ;; mutates AND is worst case of O(n) in both space and time :( ;; but at least it'll be reasonably easy to refactor to ;; a more functional setup? (define (schedule-add! time proc schedule) (let ((time (time-segment-right-format time))) (define (new-time-segment) (let ((new-segment (make-time-segment time))) (enq! (time-segment-queue new-segment) proc) new-segment)) (define (loop segments) (define (segment-equals-time? segment) (time-= time (time-segment-time segment))) (define (segment-more-than-time? segment) (time-< time (time-segment-time segment))) ;; We could switch this out to be more mutate'y ;; and avoid the O(n) of space... is that over-optimizing? (match segments ;; If we're at the end of the list, time to make a new ;; segment... ('() (cons (new-time-segment) '())) ;; If the segment's time is exactly our time, good news ;; everyone! Let's append our stuff to its queue (((? segment-equals-time? first) rest ...) (enq! (time-segment-queue first) proc) segments) ;; If the first segment is more than our time, ;; ours belongs before this one, so add it and ;; start consing our way back (((? segment-more-than-time? first) rest ...) (cons (new-time-segment) segments)) ;; Otherwise, build up recursive result ((first rest ... ) (cons first (loop rest))))) (set-schedule-segments! schedule (loop (schedule-segments schedule))))) (define (schedule-empty? schedule) (eq? (schedule-segments schedule) '())) (define (schedule-segments-split schedule time) "Does a multiple value return of time segments before/at and after TIME" (let ((time (time-segment-right-format time))) (define (segment-is-now? segment) (time-= (time-segment-time segment) time)) (define (segment-is-before-now? segment) (time-< (time-segment-time segment) time)) (let loop ((segments-before '()) (segments-left (schedule-segments schedule))) (match segments-left ;; end of the line, return ('() (values (reverse segments-before) '())) ;; It's right now, so time to stop, but include this one in before ;; but otherwise return (((? segment-is-now? first) rest ...) (values (reverse (cons first segments-before)) rest)) ;; This is prior or at now, so add it and keep going (((? segment-is-before-now? first) rest ...) (loop (cons first segments-before) rest)) ;; Otherwise it's past now, just return what we have (segments-after (values segments-before segments-after)))))) (define (schedule-extract-until! schedule time) "Extract all segments until TIME from SCHEDULE, and pop old segments off" (receive (segments-before segments-after) (schedule-segments-split schedule time) (set-schedule-segments! schedule segments-after) segments-before)) (define (add-segments-contents-to-queue! segments queue) (for-each (lambda (segment) (let ((seg-queue (time-segment-queue segment))) (while (not (q-empty? seg-queue)) (enq! queue (deq! seg-queue))))) segments)) ;;; Port handling ;;; ============= (define (make-port-mapping) (make-hash-table)) (define* (port-mapping-set! port-mapping port #:optional read write except) "Sets port-mapping for reader / writer / exception handlers" (if (not (or read write except)) (throw 'no-handlers-given "No handlers given for port" port)) (hashq-set! port-mapping port `#(,read ,write ,except))) (define (port-mapping-remove! port-mapping port) (hashq-remove! port-mapping port)) ;; TODO: This is O(n), I'm pretty sure :\ ;; ... it might be worthwhile for us to have a ;; port-mapping record that keeps a count of how many ;; handlers (maybe via a promise?) (define (port-mapping-empty? port-mapping) "Is this port mapping empty?" (eq? (hash-count (const #t) port-mapping) 0)) (define (port-mapping-non-empty? port-mapping) "Whether this port-mapping contains any elements" (not (port-mapping-empty? port-mapping))) ;;; Execution of agenda, and current agenda ;;; ======================================= (define %current-agenda (make-parameter #f)) (define* (start-agenda agenda #:optional stop-condition) (let loop ((agenda agenda)) (let ((new-agenda ;; @@: Hm, maybe here would be a great place to handle ;; select'ing on ports. ;; We could compose over agenda-run-once and agenda-read-ports (parameterize ((%current-agenda agenda)) (agenda-run-once agenda)))) (if (and stop-condition (stop-condition agenda)) 'done (loop new-agenda))))) (define (agenda-run-once agenda) "Run once through the agenda, and produce a new agenda based on the results" (define (call-proc proc) (call-with-prompt (agenda-prompt-tag agenda) (lambda () (proc)) ;; TODO (lambda (k) k))) (let ((queue (agenda-queue agenda)) (next-queue (make-q))) (while (not (q-empty? queue)) (let* ((proc (q-pop! queue)) (proc-result (call-proc proc)) (enqueue (lambda (new-proc) (enq! next-queue new-proc)))) ;; @@: We might support delay-wrapped procedures here (match proc-result ;; TODO: replace procedure with something that indicates ;; intent to run. Use a (run foo) procedure ((? procedure? new-proc) (enqueue new-proc)) (((? procedure? new-procs) ...) (for-each (lambda (new-proc) (enqueue new-proc)) new-procs)) ;; do nothing (_ #f)))) ;; TODO: Selecting on ports would happen here? ;; Return new agenda, with next queue set (set-field agenda (agenda-queue) next-queue)))