core: extend synapse: may return Symbol, handle in forward()

scopes/core/core.py

@@ -14,9 +14,9 @@ from scopes import util
 from scopes.util import keywords as k, Symbol, Symbols
 
 # keywords (domains, actions, classes, stages, data keys):
-k('csys ctl env',
-  'connect create created data default query set value',
-  'c00 e00 s00 rcvr op',
+k('csys env _meta',
+  'connect create created data default query remove set value',
+  'c00 e00 s00 op rcvr',
   'initial active retired',
   'address pred succ')
 
@@ -25,7 +25,7 @@ type Categ = tuple[Symbol, Symbol]
 type Proc = Callable[[Message, Scope], Awaitable[Scope | None]]
 type Program = Callable[[Scope], Proc]
 type ProgramSpec = dict[tuple[Symbol, Symbol], Proc]
-type Syn = Callable[[Message], Awaitable[None]]
+type Syn = Callable[[Message], Awaitable[Symbol | None]]
 type SynOp = Callable[[Message], Message | None]
 
 type Handler = Callable[[Message, Scope], 
@@ -41,12 +41,11 @@ def neuron(scope: Scope) -> Mailbox:
     return actor.create(process)
 
 def synapse(rcvr: Mailbox, op: SynOp = lambda x: x) -> Syn:
-    async def syn(msg: Message) -> None:
-        # op = update_op(msg) (=> return?)
-        # rv = check_return(msg) => return rv
+    async def syn(msg: Message) -> Symbol | None:
         msg_new = op(msg)
         if msg_new is not None:
-            await rcvr.put(msg_new)
+            await rcvr.put(msg_new) # return actor.send(rcvr, msg_new)
+        return None
     return syn
 
 env_dummy: Mailbox = asyncio.Queue()
@@ -89,7 +88,7 @@ class Scope:
     stage: Symbol = k.initial
     proc: Proc = field(init=False)
     program: Program = gen_program({})
-    syns: list[Syn] = field(default_factory=list)
+    syns: list[Syn | None] = field(default_factory=list)
     environ: Mailbox = env_dummy
 
     def __post_init__(self):
@@ -117,10 +116,23 @@ async def create_zero(env: Mailbox) -> Mailbox:
 
 # predefined action handlers and Action sets
 
-def forward() -> Handler:
+def noop(no_forward: bool = False) -> Handler:
+    async def handle(msg: Message, scope: Scope) -> Message | None:
+        return None if no_forward else msg
+    return handle
+
+def forward(no_syns_notify: bool = False) -> Handler:
+    do_notify = notify() if no_syns_notify else None
     async def handle(msg: Message, scope: Scope) -> None:
-        for syn in scope.syns:
-            await syn(msg)
+        count = 0
+        for idx, syn in enumerate(scope.syns):
+            res = await syn(msg) if syn is not None else None
+            if res == k.remove:
+                scope.syns[idx] = None
+            else:
+                count += 1
+        if count == 0 and do_notify:
+            do_notify(msg, scope)
     return handle
 
 def value_add() -> Handler:
@@ -161,5 +173,5 @@ def std_proc(actions: Actions | None = None, finalize: Handler = forward(),
 
 async def notify_created(msg: Message, new: Mailbox, scope: Scope) -> None:
     msg = Message(msg.domain, k.created, data=msg.data | {k.new: new})
-    await scope.environ.put(msg)
+    await notify()(msg, scope)