I think >device opens and closes correctly now

Playing with cancellation semantics

Make progress

1 files changed, 44 insertions, 35 deletions

diff --git a/src/midi.clj b/src/midi.clj
index 4c10de0..41a8740 100644
--- a/src/midi.clj
+++ b/src/midi.clj
@@ -30,50 +30,60 @@
   (m/ap (let [device-info (m/?< >midi-device-info)]
           (get-in device-info [device-name :device-info]))))
 
+(defn >device
+  "Returns a device for given device name. Returns nil if device not found."
+  [device-name]
+  (m/stream
+   (m/ap
+    (let [device-info
+          (m/?< (>device-info device-name))
+          ^MidiDevice device (MidiSystem/getMidiDevice ^MidiDevice$Info device-info)]
+       ;; Essential problem: Combining taking element from flow to put in
+       ;; conditional, and cleaning up in catch.
+       ;; NOTE: You need the MidiDevice type hint when you call open and close!
+
+      (m/amb= (do
+                (println "opening device")
+                (m/? (m/via m/blk (.open device)))
+                (println "device opened")
+                (m/amb
+                 device))
+              (try
+                (m/? m/never)
+                (finally
+                  (println "closing device")
+                  (m/compel (m/? (m/via m/blk (.close device))))
+                  (println "device closed"))))))))
+
+;; Key insight: Cancelation shouldn't actually start with the device
+
 (defn >midi-messages
   "A flow of java midi messages"
-  [^MidiDevice device]
+  [device-name]
   (m/stream
    (m/ap
-    (let [^Transmitter transmitter (m/? (m/via m/blk (.getTransmitter device)))
+    (let [^MidiDevice device (m/?< (>device device-name))
+          ^Transmitter transmitter (m/? (m/via m/blk (.getTransmitter device)))
           transmit (atom nil)
-          >transmit (m/eduction (filter some?) (m/watch transmit))
+          >transmit (m/eduction (filter some?) (m/ap (try (m/?< (m/watch transmit)) (catch missionary.Cancelled _ (m/amb)))))
           receiver (reify Receiver
                      (send [_this midi-message _timestamp]
                        (println "HI")
                        (reset! transmit midi-message))
                       ;; TODO: Close
                      (close [this]))]
-      (try
-        (println "Connecting to transmitter")
-        (m/? (m/via m/blk (.setReceiver transmitter receiver)))
-        (println "Connected to transmitter")
-        (m/?< >transmit)
-        (finally
-          (println "Disconnecting from transmitter")
-          (m/? (m/compel (m/via m/blk (.close receiver))))
-          (println "Disconnected from transmitter")))))))
-
-(defn >device
-  "Returns a device for given device name. Returns nil if device not found."
-  [device-name with-device]
-  (m/ap
-   (let [device-info
-         (m/?< (>device-info device-name))
-         ^MidiDevice device (MidiSystem/getMidiDevice ^MidiDevice$Info device-info)]
-      ;; Essential problem: Combining taking element from flow to put in
-      ;; conditional, and cleaning up in catch.
-      ;; NOTE: You need the MidiDevice type hint when you call open and close!
-     (try
-       (println "Opening device")
-       (m/? (m/via m/blk (.open device)))
-       (println "Device opened")
-       (m/?< (with-device device))
-       (finally
-         (println "Closing device")
-         (m/compel (m/? (m/via m/blk (.close device))))
-         (println "Device closed")
-         )))))
+      (m/amb=
+       (do
+         (println "Connecting to transmitter")
+         (m/? (m/via m/blk (.setReceiver transmitter receiver)))
+         (println "Connected to transmitter")
+         (m/?< >transmit))
+       (try (m/?  m/never)
+            (finally
+              (println "Disconnecting from transmitter")
+              (m/? (m/compel (m/via m/blk (.close receiver))))
+              (println "Disconnected from transmitter")
+              (throw (missionary.Cancelled. "Transmitter cancelled.")))))))))
 
 (defn new-device
   "Generate a new midi device.
@@ -111,8 +121,7 @@
 
 (def run
   (m/ap
-    (prn  (m/?< (>device (m/?< >bus-sel)
-                         >midi-messages)))
+    (prn  (m/?< (>device (m/?< >bus-sel))))
     ))
 
 (def close ((m/reduce prn {} run) {} {}))