add dora-joy node publishing gamepad axes and buttons

dora_joy/main.py

@@ -0,0 +1,69 @@
+"""The dora event loop: one reading published per tick.
+
+Every tick, changed or not. That is deliberate — the stream is also a heartbeat,
+and it is what lets a consumer tell "the pad is being held still" from "this node
+died". A consumer driving anything that moves needs both answers, and only one of
+them can be inferred from silence.
+
+Nothing here decides what a reading means. The pad is read in
+:mod:`dora_joy.gamepad` and packed in :mod:`dora_joy.message`, and that is the
+whole node.
+"""
+
+import argparse
+
+from dora import Node
+
+from dora_joy import message
+from dora_joy.config import Config
+from dora_joy.gamepad import Gamepad
+from dora_joy.log import log
+
+
+def main() -> None:
+    """Start reading the pad and publish it until the tick closes."""
+    args = _parse_args()
+    config = Config.from_env()
+
+    # Passing the name lets the node also run standalone as a dynamic node; when
+    # dora spawns it, the id from the dataflow wins.
+    node = Node(args.name)
+    gamepad = Gamepad(config.joystick_index)
+    gamepad.start()
+    log(f"publishing joystick {config.joystick_index} on every tick")
+
+    present = None
+
+    try:
+        for event in node:
+            if event["type"] == "ERROR":
+                raise RuntimeError(event["error"])
+            if event["type"] == "INPUT_CLOSED" and event.get("id") == "tick":
+                break
+            if event["type"] != "INPUT" or event["id"] != "tick":
+                continue
+
+            sample = gamepad.read()
+            # A pad arriving or going away is worth one line each; the readings
+            # themselves are on the wire for anyone who wants them.
+            if sample.present != present:
+                present = sample.present
+                log("gamepad connected" if present else "no gamepad")
+            node.send_output("joy", message.pack(sample))
+    finally:
+        gamepad.shutdown()
+
+
+def _parse_args() -> argparse.Namespace:
+    """Read the node name, for when dora did not spawn us."""
+    parser = argparse.ArgumentParser(description="Publish a gamepad's axes and buttons into a dataflow.")
+    parser.add_argument(
+        "--name",
+        default="joy",
+        help="The name of the node in the dataflow, used when running as a dynamic node.",
+    )
+    return parser.parse_args()
+
+
+if __name__ == "__main__":
+    main()