From fdf94da4955040dc568a08ce8e32a2be4398355c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sergiusz=20=27q3k=27=20Baza=C5=84ski?= <q3k@q3k.org>
Date: Fri, 20 Sep 2013 11:23:48 +0200
Subject: [PATCH] Basic watch communication working.

---
 main.py               |  8 ++++
 metawatch/protocol.py | 94 +++++++++++++++++++++++++++++++++++++++++--
 metawatch/watch.py    | 28 +++++++++++++
 tests/test_packets.py |  9 ++++-
 4 files changed, 135 insertions(+), 4 deletions(-)
 create mode 100644 main.py
 create mode 100644 metawatch/watch.py

diff --git a/main.py b/main.py
new file mode 100644
index 0000000..ed5faff
--- /dev/null
+++ b/main.py
@@ -0,0 +1,8 @@
+import serial
+
+from metawatch.watch import Watch
+
+w = Watch(serial.Serial('/dev/rfcomm0'))
+print(w.get_device_type())
+print(w.get_rtc())
+
diff --git a/metawatch/protocol.py b/metawatch/protocol.py
index 6da3003..c0b50bd 100644
--- a/metawatch/protocol.py
+++ b/metawatch/protocol.py
@@ -1,4 +1,5 @@
 import struct
+import datetime
 from functools import reduce
 
 # Adapted & Pythonized from pymetawatch by Travis Goodspeed
@@ -53,10 +54,97 @@ class OutboundPacket:
         stream.write(self._data)
         stream.flush()
 
+
 class GetDeviceType(OutboundPacket):
     def __init__(self):
-        self._generate(1, 0)
+        self._generate(0x01, 0)
 
-class GetInformationString(OutboundPacket):
+class GetRTC(OutboundPacket):
     def __init__(self):
-        self._generate(3, 0)
+        self._generate(0x27, 0)
+
+class PacketDecodeError(Exception):
+    pass
+
+
+class TypedInboundPacket:
+    def __init__(self, inbound):
+        self._payload = inbound._payload
+        self._type = inbound._type
+        self._options = inbound._options
+
+    def _assert_payload_length(self, l):
+        """Asserts that the received payload is at least `l` bytes long."""
+        if len(self._payload) < l:
+            raise PacketDecodeError("Incorrect payload length! Is {} bytes long, should be at least {}.".format(len(self._payload), l))
+
+    def _assert_type(self, _type):
+        if self._type != _type:
+            raise PacketDecodeError("Incorrect message type! Expected {0:x}, got {1:x}.".format(_type, self._type))
+
+
+class GetDeviceTypeResponse(TypedInboundPacket):
+    def parse(self):
+        self._assert_type(0x02)
+        self._assert_payload_length(1)
+        self.device_type = self._payload[0]
+
+
+class GetRTCResponse(TypedInboundPacket):
+    def parse(self):
+        self._assert_type(0x28)
+        self._assert_payload_length(8)
+        year = (self._payload[1] << 8) | self._payload[0]
+        month = self._payload[2]
+        day = self._payload[3]
+        h, m, s = self._payload[4:7]
+        dt = datetime.datetime(year=year, month=month, day=day, hour=h, minute=m, second=s)
+        self.datetime = dt
+
+class InboundPacket:
+    PACKET_TYPES = {
+        0x02: GetDeviceTypeResponse,
+        0x28: GetRTCResponse,
+    }
+    def __init__(self, stream):
+        self._s = stream
+   
+    def _start_crc(self):
+        self._crc_check = []
+
+    def _read(self, count):
+        """Gets bytes and saves them to an list for later CRC-Checking."""
+        b = self._s.read(count)
+        self._crc_check += b
+        return b
+
+    def _end_crc(self):
+        mspcrc = MSPCRC()
+        return mspcrc.checksum_bytes(bytes(self._crc_check))
+   
+    def read(self):
+        self._start_crc()
+        start, = self._read(1)
+        if start != 1:
+            raise PacketDecodeError("Bad start byte (received 0x{0:x}).".format(start))
+        length, = self._read(1)
+        if length > 32 or length < 6:
+            raise PacketDecodeError("Length not in spec (got {}).".format(length))
+
+        payload_length = length - 6
+        self._type, = self._read(1)
+        self._options, = self._read(1)
+        self._payload = self._read(payload_length)
+        
+        received_crc, = struct.unpack('<H', self._s.read(2))
+        correct_crc = self._end_crc()
+        if received_crc != correct_crc:
+            raise PacketDecodeError("Wrong CRC! Got 0x{0:x}, expected 0x{1:x}.".format(received_crc, correct_crc))
+        if self._type not in self.PACKET_TYPES:
+            raise PacketDecodeError("Unknown packet type {0:x}.".format(self._type))
+
+        p = self.PACKET_TYPES[self._type](self)
+        p.parse()
+        return p
+
+
diff --git a/metawatch/watch.py b/metawatch/watch.py
new file mode 100644
index 0000000..101c644
--- /dev/null
+++ b/metawatch/watch.py
@@ -0,0 +1,28 @@
+import queue
+
+from metawatch import protocol
+
+class Watch:
+    def __init__(self, fd):
+        self._fd = fd
+        self._extra_packets = queue.Queue()
+
+    def _read_packet(self, expected):
+        while True:
+            ib = protocol.InboundPacket(self._fd)
+            p = ib.read()
+            if isinstance(p, expected):
+                return p
+            self._extra_packets.put(p)
+    
+    def get_device_type(self):
+        o = protocol.GetDeviceType()
+        o.emit(self._fd)
+        i = self._read_packet(protocol.GetDeviceTypeResponse)
+        return i.device_type
+
+    def get_rtc(self):
+        o = protocol.GetRTC()
+        o.emit(self._fd)
+        i = self._read_packet(protocol.GetRTCResponse)
+        return i.datetime
diff --git a/tests/test_packets.py b/tests/test_packets.py
index e44dc8f..5d4e18d 100644
--- a/tests/test_packets.py
+++ b/tests/test_packets.py
@@ -30,5 +30,12 @@ class TestPackets(unittest.TestCase):
     def test_4_get_device_type(self):
         self._test_packet(b'\x01\x06\x01\x00\x0B\xD9', protocol.GetDeviceType)
 
-    def test_5_get_information_string(self):
+    def test_4_get_information_string(self):
         self._test_packet(b'\x01\x06\x03\x00\xc7\xd4', protocol.GetInformationString)
+
+    def test_5_decode_packet(self):
+        i = io.BytesIO(b'\x01\x07\x02\x00\x01\x13\x3b')
+        ib = protocol.InboundPacket(i)
+        p = ib.read()
+        self.assertIsInstance(p, protocol.GetDeviceTypeResponse)
+        self.assertEqual(p.device_type, 1)