Add Pico UART client and tests

pico-dashboard/comms/uart_client.py

@@ -0,0 +1,40 @@
+import json
+
+
+class UartClient:
+    def __init__(self, uart):
+        self.uart = uart
+        self.buffer = ""
+
+    def send_message(self, message):
+        payload = json.dumps(message, separators=(",", ":")) + "\n"
+        self.uart.write(payload.encode("utf-8"))
+
+    def read_available_messages(self):
+        messages = []
+
+        while self.uart.any():
+            chunk = self.uart.read()
+
+            if not chunk:
+                break
+
+            self.buffer += chunk.decode("utf-8")
+
+            while "\n" in self.buffer:
+                line, self.buffer = self.buffer.split("\n", 1)
+                line = line.strip()
+
+                if not line:
+                    continue
+
+                try:
+                    messages.append(json.loads(line))
+                except ValueError:
+                    messages.append({
+                        "type": "error",
+                        "message": "invalid_json",
+                        "raw": line,
+                    })
+
+        return messages

tests/test_pico_core.py

@@ -78,3 +78,75 @@ def test_screen_manager():
 
     screens.previous_screen()
     assert screens.current_screen == "battery"
+
+
+class FakeUart:
+    def __init__(self):
+        self.writes = []
+        self.read_chunks = []
+
+    def write(self, data):
+        self.writes.append(data)
+
+    def any(self):
+        return len(self.read_chunks) > 0
+
+    def read(self):
+        if self.read_chunks:
+            return self.read_chunks.pop(0)
+        return b""
+
+
+def test_uart_client_send_message():
+    from comms.uart_client import UartClient
+
+    fake = FakeUart()
+    client = UartClient(fake)
+
+    client.send_message({"type": "status_request"})
+
+    assert fake.writes == [b'{"type":"status_request"}\n']
+
+
+def test_uart_client_reads_newline_delimited_json():
+    from comms.uart_client import UartClient
+
+    fake = FakeUart()
+    fake.read_chunks = [
+        b'{"type":"status_response","timestamp":1}\n',
+        b'{"type":"relay_response","relay":"fridge","enabled":true}\n',
+    ]
+
+    client = UartClient(fake)
+    messages = client.read_available_messages()
+
+    assert messages == [
+        {"type": "status_response", "timestamp": 1},
+        {"type": "relay_response", "relay": "fridge", "enabled": True},
+    ]
+
+
+def test_uart_client_handles_partial_messages():
+    from comms.uart_client import UartClient
+
+    fake = FakeUart()
+    client = UartClient(fake)
+
+    fake.read_chunks = [b'{"type":"status_', b'response"}\n']
+
+    messages = client.read_available_messages()
+
+    assert messages == [{"type": "status_response"}]
+
+
+def test_uart_client_handles_invalid_json():
+    from comms.uart_client import UartClient
+
+    fake = FakeUart()
+    fake.read_chunks = [b'not json\n']
+
+    client = UartClient(fake)
+    messages = client.read_available_messages()
+
+    assert messages[0]["type"] == "error"
+    assert messages[0]["message"] == "invalid_json"