+(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)))
+ (make-agenda-intern queue prompt port-mapping))
+
+(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)))
+
+(define %current-agenda (make-parameter #f))