]> www.average.org Git - loctrkd.git/blobdiff - gps303/gps303proto.py
fix l3str/l3int breakage provoked by typeckeck
[loctrkd.git] / gps303 / gps303proto.py
index 46f12899e62b2d0f38cc087f774da20d6d6d1530..ab03c6829ccc94b025504ddb79208c5fcac4945b 100755 (executable)
@@ -15,17 +15,28 @@ Forewarnings:
 """
 
 from datetime import datetime, timezone
+from enum import Enum
 from inspect import isclass
-from logging import getLogger
-from struct import pack, unpack
+from struct import error, pack, unpack
+from typing import (
+    Any,
+    Callable,
+    Dict,
+    List,
+    Optional,
+    Tuple,
+    Type,
+    TYPE_CHECKING,
+    Union,
+)
 
 __all__ = (
-    "handle_packet",
+    "class_by_prefix",
     "inline_response",
-    "make_object",
-    "make_response",
     "parse_message",
     "proto_by_name",
+    "DecodeError",
+    "Respond",
     "GPS303Pkt",
     "UNKNOWN",
     "LOGIN",
@@ -39,7 +50,18 @@ __all__ = (
     "WHITELIST_TOTAL",
     "WIFI_OFFLINE_POSITIONING",
     "TIME",
+    "PROHIBIT_LBS",
+    "GPS_LBS_SWITCH_TIMES",
+    "REMOTE_MONITOR_PHONE",
+    "SOS_PHONE",
+    "DAD_PHONE",
     "MOM_PHONE",
+    "STOP_UPLOAD",
+    "GPS_OFF_PERIOD",
+    "DND_PERIOD",
+    "RESTART_SHUTDOWN",
+    "DEVICE",
+    "ALARM_CLOCK",
     "STOP_ALARM",
     "SETUP",
     "SYNCHRONOUS_WHITELIST",
@@ -51,21 +73,149 @@ __all__ = (
     "CHARGER_DISCONNECTED",
     "VIBRATION_RECEIVED",
     "POSITION_UPLOAD_INTERVAL",
+    "SOS_ALARM",
+    "UNKNOWN_B3",
 )
 
-log = getLogger("gps303")
-
 
-class GPS303Pkt:
-    PROTO: int
-    INLINE = True
-
-    def __init__(self, *args, **kwargs):
-        assert len(args) == 0
+class DecodeError(Exception):
+    def __init__(self, e: Exception, **kwargs: Any) -> None:
+        super().__init__(e)
         for k, v in kwargs.items():
             setattr(self, k, v)
 
-    def __repr__(self):
+
+def intx(x: Union[str, int]) -> int:
+    if isinstance(x, str):
+        x = int(x, 0)
+    return x
+
+
+def hhmm(x: str) -> str:
+    """Check for the string that represents hours and minutes"""
+    if not isinstance(x, str) or len(x) != 4:
+        raise ValueError(str(x) + " is not a four-character string")
+    hh = int(x[:2])
+    mm = int(x[2:])
+    if hh < 0 or hh > 23 or mm < 0 or mm > 59:
+        raise ValueError(str(x) + " does not contain valid hours and minutes")
+    return x
+
+
+def l3str(x: Union[str, List[str]]) -> List[str]:
+    if isinstance(x, str):
+        lx = x.split(",")
+    else:
+        lx = x
+    if len(lx) != 3 or not all(isinstance(el, str) for el in x):
+        raise ValueError(str(lx) + " is not a list of three strings")
+    return lx
+
+
+def l3int(x: Union[str, List[int]]) -> List[int]:
+    if isinstance(x, str):
+        lx = [int(el) for el in x.split(",")]
+    else:
+        lx = x
+    if len(lx) != 3 or not all(isinstance(el, int) for el in lx):
+        raise ValueError(str(lx) + " is not a list of three integers")
+    return lx
+
+
+class MetaPkt(type):
+    """
+    For each class corresponding to a message, automatically create
+    two nested classes `In` and `Out` that also inherit from their
+    "nest". Class attribute `IN_KWARGS` defined in the "nest" is
+    copied to the `In` nested class under the name `KWARGS`, and
+    likewise, `OUT_KWARGS` of the nest class is copied as `KWARGS`
+    to the nested class `Out`. In addition, method `encode` is
+    defined in both classes equal to `in_encode()` and `out_encode()`
+    respectively.
+    """
+
+    if TYPE_CHECKING:
+
+        def __getattr__(self, name: str) -> Any:
+            pass
+
+        def __setattr__(self, name: str, value: Any) -> None:
+            pass
+
+    def __new__(
+        cls: Type["MetaPkt"],
+        name: str,
+        bases: Tuple[type, ...],
+        attrs: Dict[str, Any],
+    ) -> "MetaPkt":
+        newcls = super().__new__(cls, name, bases, attrs)
+        newcls.In = super().__new__(
+            cls,
+            name + ".In",
+            (newcls,) + bases,
+            {
+                "KWARGS": newcls.IN_KWARGS,
+                "decode": newcls.in_decode,
+                "encode": newcls.in_encode,
+            },
+        )
+        newcls.Out = super().__new__(
+            cls,
+            name + ".Out",
+            (newcls,) + bases,
+            {
+                "KWARGS": newcls.OUT_KWARGS,
+                "decode": newcls.out_decode,
+                "encode": newcls.out_encode,
+            },
+        )
+        return newcls
+
+
+class Respond(Enum):
+    NON = 0  # Incoming, no response needed
+    INL = 1  # Birirectional, use `inline_response()`
+    EXT = 2  # Birirectional, use external responder
+
+
+class GPS303Pkt(metaclass=MetaPkt):
+    RESPOND = Respond.NON  # Do not send anything back by default
+    PROTO: int
+    IN_KWARGS: Tuple[Tuple[str, Callable[[Any], Any], Any], ...] = ()
+    OUT_KWARGS: Tuple[Tuple[str, Callable[[Any], Any], Any], ...] = ()
+    KWARGS: Tuple[Tuple[str, Callable[[Any], Any], Any], ...] = ()
+    In: Type["GPS303Pkt"]
+    Out: Type["GPS303Pkt"]
+
+    if TYPE_CHECKING:
+
+        def __getattr__(self, name: str) -> Any:
+            pass
+
+        def __setattr__(self, name: str, value: Any) -> None:
+            pass
+
+    def __init__(self, *args: Any, **kwargs: Any):
+        """
+        Construct the object _either_ from (length, payload),
+        _or_ from the values of individual fields
+        """
+        assert not args or (len(args) == 2 and not kwargs)
+        if args:  # guaranteed to be two arguments at this point
+            self.length, self.payload = args
+            try:
+                self.decode(self.length, self.payload)
+            except error as e:
+                raise DecodeError(e, obj=self)
+        else:
+            for kw, typ, dfl in self.KWARGS:
+                setattr(self, kw, typ(kwargs.pop(kw, dfl)))
+            if kwargs:
+                raise ValueError(
+                    self.__class__.__name__ + " stray kwargs " + str(kwargs)
+                )
+
+    def __repr__(self) -> str:
         return "{}({})".format(
             self.__class__.__name__,
             ", ".join(
@@ -80,70 +230,76 @@ class GPS303Pkt:
             ),
         )
 
-    @classmethod
-    def from_packet(cls, length, payload):
-        return cls(payload=payload, length=length)
+    decode: Callable[["GPS303Pkt", int, bytes], None]
+
+    def in_decode(self, length: int, packet: bytes) -> None:
+        # Overridden in subclasses, otherwise do not decode payload
+        return
+
+    def out_decode(self, length: int, packet: bytes) -> None:
+        # Overridden in subclasses, otherwise do not decode payload
+        return
 
-    def to_packet(self):
-        return pack("BB", self.length, self.PROTO) + self.payload
+    encode: Callable[["GPS303Pkt"], bytes]
 
-    @classmethod
-    def make_packet(cls, payload):
-        assert isinstance(payload, bytes)
+    def in_encode(self) -> bytes:
+        # Necessary to emulate terminal, which is not implemented
+        raise NotImplementedError(
+            self.__class__.__name__ + ".encode() not implemented"
+        )
+
+    def out_encode(self) -> bytes:
+        # Overridden in subclasses, otherwise make empty payload
+        return b""
+
+    @property
+    def packed(self) -> bytes:
+        payload = self.encode()
         length = len(payload) + 1
-        if length > 6:
-            length -= 6
-        return pack("BB", length, cls.PROTO) + payload
-
-    @classmethod
-    def inline_response(cls, packet):
-        if cls.INLINE:
-            return cls.make_packet(b"")
-        else:
-            return None
+        return pack("BB", length, self.PROTO) + payload
 
 
 class UNKNOWN(GPS303Pkt):
     PROTO = 256  # > 255 is impossible in real packets
-    INLINE = False
 
 
 class LOGIN(GPS303Pkt):
     PROTO = 0x01
+    RESPOND = Respond.INL
+    # Default response for ACK, can also respond with STOP_UPLOAD
 
-    @classmethod
-    def from_packet(cls, length, payload):
-        self = super().from_packet(length, payload)
+    def in_decode(self, length: int, payload: bytes) -> None:
         self.imei = payload[:-1].hex()
         self.ver = unpack("B", payload[-1:])[0]
-        return self
 
 
-class SUPERVISION(GPS303Pkt):  # Server sends supervision number status
+class SUPERVISION(GPS303Pkt):
     PROTO = 0x05
-    INLINE = False
+    OUT_KWARGS = (("status", int, 1),)
 
-    def response(self, supnum=0):
+    def out_encode(self) -> bytes:
         # 1: The device automatically answers Pickup effect
         # 2: Automatically Answering Two-way Calls
         # 3: Ring manually answer the two-way call
-        return self.make_packet(pack("B", supnum))
+        return pack("B", self.status)
 
 
 class HEARTBEAT(GPS303Pkt):
     PROTO = 0x08
+    RESPOND = Respond.INL
 
 
 class _GPS_POSITIONING(GPS303Pkt):
-    @classmethod
-    def from_packet(cls, length, payload):
-        self = super().from_packet(length, payload)
+    RESPOND = Respond.INL
+
+    def in_decode(self, length: int, payload: bytes) -> None:
         self.dtime = payload[:6]
         if self.dtime == b"\0\0\0\0\0\0":
             self.devtime = None
         else:
+            yr, mo, da, hr, mi, se = unpack("BBBBBB", self.dtime)
             self.devtime = datetime(
-                *unpack("BBBBBB", self.dtime), tzinfo=timezone.utc
+                2000 + yr, mo, da, hr, mi, se, tzinfo=timezone.utc
             )
         self.gps_data_length = payload[6] >> 4
         self.gps_nb_sat = payload[6] & 0x0F
@@ -153,14 +309,14 @@ class _GPS_POSITIONING(GPS303Pkt):
         flip_lat = not bool(flags & 0b0000010000000000)  # bit 5
         self.heading = flags & 0b0000001111111111  # bits 6 - last
         self.latitude = lat / (30000 * 60) * (-1 if flip_lat else 1)
-        self.longitude = lon / (30000 * 60) * (-2 if flip_lon else 1)
+        self.longitude = lon / (30000 * 60) * (-1 if flip_lon else 1)
         self.speed = speed
         self.flags = flags
-        return self
 
-    @classmethod
-    def inline_response(cls, packet):
-        return cls.make_packet(packet[2:8])
+    def out_encode(self) -> bytes:
+        tup = datetime.utcnow().timetuple()
+        ttup = (tup[0] % 100,) + tup[1:6]
+        return pack("BBBBBB", *ttup)
 
 
 class GPS_POSITIONING(_GPS_POSITIONING):
@@ -173,54 +329,42 @@ class GPS_OFFLINE_POSITIONING(_GPS_POSITIONING):
 
 class STATUS(GPS303Pkt):
     PROTO = 0x13
-    INLINE = False
-
-    @classmethod
-    def from_packet(cls, length, payload):
-        self = super().from_packet(length, payload)
-        if len(payload) == 5:
-            (
-                self.batt,
-                self.ver,
-                self.timezone,
-                self.intvl,
-                self.signal,
-            ) = unpack("BBBBB", payload)
-        elif len(payload) == 4:
-            self.batt, self.ver, self.timezone, self.intvl = unpack(
-                "BBBB", payload
-            )
+    RESPOND = Respond.EXT
+    OUT_KWARGS = (("upload_interval", int, 25),)
+
+    def in_decode(self, length: int, payload: bytes) -> None:
+        self.batt, self.ver, self.timezone, self.intvl = unpack(
+            "BBBB", payload[:4]
+        )
+        if len(payload) > 4:
+            self.signal: Optional[int] = payload[4]
+        else:
             self.signal = None
-        return self
 
-    def response(self, upload_interval=25):  # Set interval in minutes
-        return self.make_packet(pack("B", upload_interval))
+    def out_encode(self) -> bytes:  # Set interval in minutes
+        return pack("B", self.upload_interval)
 
 
-class HIBERNATION(GPS303Pkt):
+class HIBERNATION(GPS303Pkt):  # Server can send to send devicee to sleep
     PROTO = 0x14
 
 
-class RESET(GPS303Pkt):  # Device sends when it got reset SMS
+class RESET(GPS303Pkt):
+    # Device sends when it got reset SMS
+    # Server can send to initiate factory reset
     PROTO = 0x15
-    INLINE = False
-
-    def response(self):  # Server can send to initiate factory reset
-        return self.make_packet(b"")
 
 
 class WHITELIST_TOTAL(GPS303Pkt):  # Server sends to initiage sync (0x58)
     PROTO = 0x16
-    INLINE = False
+    OUT_KWARGS = (("number", int, 3),)
 
-    def response(self, number=3):  # Number of whitelist entries
-        return self.make_packet(pack("B", number))
+    def out_encode(self) -> bytes:  # Number of whitelist entries
+        return pack("B", self.number)
 
 
 class _WIFI_POSITIONING(GPS303Pkt):
-    @classmethod
-    def from_packet(cls, length, payload):
-        self = super().from_packet(length, payload)
+    def in_decode(self, length: int, payload: bytes) -> None:
         self.dtime = payload[:6]
         if self.dtime == b"\0\0\0\0\0\0":
             self.devtime = None
@@ -243,108 +387,188 @@ class _WIFI_POSITIONING(GPS303Pkt):
                 "!HHB", gsm_slice[4 + i * 5 : 9 + i * 5]
             )
             self.gsm_cells.append((locac, cellid, -sigstr))
-        return self
 
 
 class WIFI_OFFLINE_POSITIONING(_WIFI_POSITIONING):
     PROTO = 0x17
+    RESPOND = Respond.INL
 
-    @classmethod
-    def inline_response(cls, packet):
-        return cls.make_packet(packet[2:8])
+    def out_encode(self) -> bytes:
+        return bytes.fromhex(datetime.utcnow().strftime("%y%m%d%H%M%S"))
 
 
 class TIME(GPS303Pkt):
     PROTO = 0x30
+    RESPOND = Respond.INL
 
-    @classmethod
-    def inline_response(cls, packet):
-        return pack(
-            "!BBHBBBBB", 7, cls.PROTO, *datetime.utcnow().timetuple()[:6]
-        )
+    def out_encode(self) -> bytes:
+        return pack("!HBBBBB", *datetime.utcnow().timetuple()[:6])
 
 
 class PROHIBIT_LBS(GPS303Pkt):
     PROTO = 0x33
-    INLINE = False
+    OUT_KWARGS = (("status", int, 1),)
 
-    def response(self, status=1):  # Server sent, 0-off, 1-on
-        return self.make_packet(pack("B", status))
+    def out_encode(self) -> bytes:  # Server sent, 0-off, 1-on
+        return pack("B", self.status)
 
 
-class LBS_SWITCH_TIMES(GPS303Pkt):
+class GPS_LBS_SWITCH_TIMES(GPS303Pkt):
     PROTO = 0x34
-    INLINE = False
 
-    def response(self):
-        return self.make_packet(b"")
+    # Data is in packed decimal
+    # 00/01 - GPS on/off
+    # 00/01 - Don't set / Set upload period
+    # HHMMHHMM - Upload period
+    # 00/01 - LBS on/off
+    # 00/01 - Don't set / Set time of boot
+    # HHMM  - Time of boot
+    # 00/01 - Don't set / Set time of shutdown
+    # HHMM  - Time of shutdown
+    def out_encode(self) -> bytes:
+        return b""  # TODO
+
+
+class _SET_PHONE(GPS303Pkt):
+    OUT_KWARGS = (("phone", str, ""),)
+
+    def out_encode(self) -> bytes:
+        self.phone: str
+        return self.phone.encode("")
 
 
-class REMOTE_MONITOR_PHONE(GPS303Pkt):
+class REMOTE_MONITOR_PHONE(_SET_PHONE):
     PROTO = 0x40
-    INLINE = False
 
 
-class SOS_PHONE(GPS303Pkt):
+class SOS_PHONE(_SET_PHONE):
     PROTO = 0x41
-    INLINE = False
 
 
-class DAD_PHONE(GPS303Pkt):
+class DAD_PHONE(_SET_PHONE):
     PROTO = 0x42
-    INLINE = False
 
 
-class MOM_PHONE(GPS303Pkt):
+class MOM_PHONE(_SET_PHONE):
     PROTO = 0x43
-    INLINE = False
 
 
 class STOP_UPLOAD(GPS303Pkt):  # Server response to LOGIN to thwart the device
     PROTO = 0x44
 
 
+class GPS_OFF_PERIOD(GPS303Pkt):
+    PROTO = 0x46
+    OUT_KWARGS = (
+        ("onoff", int, 0),
+        ("fm", hhmm, "0000"),
+        ("to", hhmm, "2359"),
+    )
+
+    def out_encode(self) -> bytes:
+        return (
+            pack("B", self.onoff)
+            + bytes.fromhex(self.fm)
+            + bytes.fromhex(self.to)
+        )
+
+
+class DND_PERIOD(GPS303Pkt):
+    PROTO = 0x47
+    OUT_KWARGS = (
+        ("onoff", int, 0),
+        ("week", int, 3),
+        ("fm1", hhmm, "0000"),
+        ("to1", hhmm, "2359"),
+        ("fm2", hhmm, "0000"),
+        ("to2", hhmm, "2359"),
+    )
+
+    def out_encode(self) -> bytes:
+        return (
+            pack("B", self.onoff)
+            + pack("B", self.week)
+            + bytes.fromhex(self.fm1)
+            + bytes.fromhex(self.to1)
+            + bytes.fromhex(self.fm2)
+            + bytes.fromhex(self.to2)
+        )
+
+
+class RESTART_SHUTDOWN(GPS303Pkt):
+    PROTO = 0x48
+    OUT_KWARGS = (("flag", int, 0),)
+
+    def out_encode(self) -> bytes:
+        # 1 - restart
+        # 2 - shutdown
+        return pack("B", self.flag)
+
+
+class DEVICE(GPS303Pkt):
+    PROTO = 0x49
+    OUT_KWARGS = (("flag", int, 0),)
+
+    # 0 - Stop looking for equipment
+    # 1 - Start looking for equipment
+    def out_encode(self) -> bytes:
+        return pack("B", self.flag)
+
+
+class ALARM_CLOCK(GPS303Pkt):
+    PROTO = 0x50
+
+    def out_encode(self) -> bytes:
+        # TODO implement parsing kwargs
+        alarms = ((0, "0000"), (0, "0000"), (0, "0000"))
+        return b"".join(
+            pack("B", day) + bytes.fromhex(tm) for day, tm in alarms
+        )
+
+
 class STOP_ALARM(GPS303Pkt):
     PROTO = 0x56
 
+    def in_decode(self, length: int, payload: bytes) -> None:
+        self.flag = payload[0]
+
 
 class SETUP(GPS303Pkt):
     PROTO = 0x57
-    INLINE = False
-
-    def response(
-        self,
-        uploadintervalseconds=0x0300,
-        binaryswitch=0b00110001,
-        alarms=[0, 0, 0],
-        dndtimeswitch=0,
-        dndtimes=[0, 0, 0],
-        gpstimeswitch=0,
-        gpstimestart=0,
-        gpstimestop=0,
-        phonenumbers=["", "", ""],
-    ):
-        def pack3b(x):
+    RESPOND = Respond.EXT
+    OUT_KWARGS = (
+        ("uploadintervalseconds", intx, 0x0300),
+        ("binaryswitch", intx, 0b00110001),
+        ("alarms", l3int, [0, 0, 0]),
+        ("dndtimeswitch", int, 0),
+        ("dndtimes", l3int, [0, 0, 0]),
+        ("gpstimeswitch", int, 0),
+        ("gpstimestart", int, 0),
+        ("gpstimestop", int, 0),
+        ("phonenumbers", l3str, ["", "", ""]),
+    )
+
+    def out_encode(self) -> bytes:
+        def pack3b(x: int) -> bytes:
             return pack("!I", x)[1:]
 
-        payload = b"".join(
+        return b"".join(
             [
-                pack("!H", uploadintervalseconds),
-                pack("B", binaryswitch),
+                pack("!H", self.uploadintervalseconds),
+                pack("B", self.binaryswitch),
             ]
-            + [pack3b(el) for el in alarms]
+            + [pack3b(el) for el in self.alarms]
             + [
-                pack("B", dndtimeswitch),
+                pack("B", self.dndtimeswitch),
             ]
-            + [pack3b(el) for el in dndtimes]
+            + [pack3b(el) for el in self.dndtimes]
             + [
-                pack("B", gpstimeswitch),
-                pack("!H", gpstimestart),
-                pack("!H", gpstimestop),
+                pack("B", self.gpstimeswitch),
+                pack("!H", self.gpstimestart),
+                pack("!H", self.gpstimestop),
             ]
-            + [b";".join([el.encode() for el in phonenumbers])]
+            + [b";".join([el.encode() for el in self.phonenumbers])]
         )
-        return self.make_packet(payload)
 
 
 class SYNCHRONOUS_WHITELIST(GPS303Pkt):
@@ -357,21 +581,36 @@ class RESTORE_PASSWORD(GPS303Pkt):
 
 class WIFI_POSITIONING(_WIFI_POSITIONING):
     PROTO = 0x69
-    INLINE = False
+    RESPOND = Respond.EXT
+    OUT_KWARGS = (("latitude", float, None), ("longitude", float, None))
 
-    def response(self, lat=None, lon=None):
-        if lat is None or lon is None:
-            payload = b""
-        else:
-            payload = "{:+#010.8g},{:+#010.8g}".format(lat, lon).encode(
-                "ascii"
-            )
-        return self.make_packet(payload)
+    def out_encode(self) -> bytes:
+        if self.latitude is None or self.longitude is None:
+            return b""
+        return "{:+#010.8g},{:+#010.8g}".format(
+            self.latitude, self.longitude
+        ).encode()
+
+    def out_decode(self, length: int, payload: bytes) -> None:
+        lat, lon = payload.decode().split(",")
+        self.latitude = float(lat)
+        self.longitude = float(lon)
 
 
 class MANUAL_POSITIONING(GPS303Pkt):
     PROTO = 0x80
-    INLINE = False
+
+    def in_decode(self, length: int, payload: bytes) -> None:
+        self.flag = payload[0] if len(payload) > 0 else -1
+        self.reason = {
+            1: "Incorrect time",
+            2: "LBS less",
+            3: "WiFi less",
+            4: "LBS search > 3 times",
+            5: "Same LBS and WiFi data",
+            6: "LBS prohibited, WiFi absent",
+            7: "GPS spacing < 50 m",
+        }.get(self.flag, "Unknown")
 
 
 class BATTERY_CHARGE(GPS303Pkt):
@@ -392,22 +631,28 @@ class VIBRATION_RECEIVED(GPS303Pkt):
 
 class POSITION_UPLOAD_INTERVAL(GPS303Pkt):
     PROTO = 0x98
-    INLINE = False
+    RESPOND = Respond.EXT
+    OUT_KWARGS = (("interval", int, 10),)
 
-    @classmethod
-    def from_packet(cls, length, payload):
-        self = super().from_packet(length, payload)
+    def in_decode(self, length: int, payload: bytes) -> None:
         self.interval = unpack("!H", payload[:2])
-        return self
 
-    def response(self, interval=10):
-        return self.make_packet(pack("!H", interval))
+    def out_encode(self) -> bytes:
+        return pack("!H", self.interval)
 
 
 class SOS_ALARM(GPS303Pkt):
     PROTO = 0x99
 
 
+class UNKNOWN_B3(GPS303Pkt):
+    PROTO = 0xB3
+    IN_KWARGS = (("asciidata", str, ""),)
+
+    def in_decode(self, length: int, payload: bytes) -> None:
+        self.asciidata = payload.decode()
+
+
 # Build dicts protocol number -> class and class name -> protocol number
 CLASSES = {}
 PROTOS = {}
@@ -424,56 +669,57 @@ if True:  # just to indent the code, sorry!
             PROTOS[cls.__name__] = cls.PROTO
 
 
-def proto_by_name(name):
-    return PROTOS.get(name, -1)
+def class_by_prefix(
+    prefix: str,
+) -> Union[Type[GPS303Pkt], List[Tuple[str, int]]]:
+    lst = [
+        (name, proto)
+        for name, proto in PROTOS.items()
+        if name.upper().startswith(prefix.upper())
+    ]
+    if len(lst) != 1:
+        return lst
+    _, proto = lst[0]
+    return CLASSES[proto]
 
 
-def proto_of_message(packet):
-    return unpack("B", packet[1:2])[0]
+def proto_by_name(name: str) -> int:
+    return PROTOS.get(name, -1)
 
 
-def inline_response(packet):
-    proto = proto_of_message(packet)
-    if proto in CLASSES:
-        return CLASSES[proto].inline_response(packet)
-    else:
-        return None
+def proto_of_message(packet: bytes) -> int:
+    return packet[1]
 
 
-def make_object(length, proto, payload):
+def inline_response(packet: bytes) -> Optional[bytes]:
+    proto = proto_of_message(packet)
     if proto in CLASSES:
-        return CLASSES[proto].from_packet(length, payload)
-    else:
-        retobj = UNKNOWN.from_packet(length, payload)
-        retobj.PROTO = proto  # Override class attr with object attr
-        return retobj
+        cls = CLASSES[proto]
+        if cls.RESPOND is Respond.INL:
+            return cls.Out().packed
+    return None
 
 
-def parse_message(packet):
+def parse_message(packet: bytes, is_incoming: bool = True) -> GPS303Pkt:
+    """From a packet (without framing bytes) derive the XXX.In object"""
     length, proto = unpack("BB", packet[:2])
     payload = packet[2:]
-    adjust = 2 if proto == STATUS.PROTO else 4  # Weird special case
-    if (
-        proto not in (WIFI_POSITIONING.PROTO, WIFI_OFFLINE_POSITIONING.PROTO)
-        and length > 1
-        and len(payload) + adjust != length
-    ):
-        log.warning(
-            "With proto %d length is %d but payload length is %d+%d",
-            proto,
-            length,
-            len(payload),
-            adjust,
+    if proto not in CLASSES:
+        cause: Union[DecodeError, ValueError] = ValueError(
+            f"Proto {proto} is unknown"
         )
-    return make_object(length, proto, payload)
-
-
-def handle_packet(packet):  # DEPRECATED
-    if len(packet) < 6 or packet[:2] != b"xx" or packet[-2:] != b"\r\n":
-        return UNKNOWN.from_packet(len(packet), packet)
-    return parse_message(packet[2:-2])
-
-
-def make_response(msg, **kwargs):  # DEPRECATED
-    inframe = msg.response(**kwargs)
-    return None if inframe is None else b"xx" + inframe + b"\r\n"
+    else:
+        try:
+            if is_incoming:
+                return CLASSES[proto].In(length, payload)
+            else:
+                return CLASSES[proto].Out(length, payload)
+        except DecodeError as e:
+            cause = e
+    if is_incoming:
+        retobj = UNKNOWN.In(length, payload)
+    else:
+        retobj = UNKNOWN.Out(length, payload)
+    retobj.PROTO = proto  # Override class attr with object attr
+    retobj.cause = cause
+    return retobj