# Source code for canlib.kvadblib.message

    """Wrapper for Kvaser Database API (kvaDbLib)."""

    import ctypes as ct

    from ..canlib import MessageFlag as CanMessageFlag
    from ..frame import Frame
    from . import wrapper
    from .attribute import Attribute
    from .bound_message import BoundMessage
    from .enums import MessageFlag
    from .enums import AttributeOwner, SignalByteOrder, SignalMultiplexMode, SignalType
    from .exceptions import KvdNoAttribute, KvdWrongOwner, KvdNoMessage, KvdNoSignal
    from .node import Node
    from .signal import EnumSignal, Signal, ValueScaling
    from .wrapper import dll

    def _signal_object(db, msg, handle):
        """Instantiate either a `Signal` or an `EnumSignal`

        This function checks whether the signal pointed to by ``handle`` has any
        enumeration values; if it does, an `EnumSignal` is created and
        returned -- otherwise, a `Signal` is created and returned.

        """
        try:
            dll.kvaDbGetFirstEnumValue(handle, ct.c_void_p())
        except KvdNoAttribute:
            return Signal(db, msg, handle)
        else:
            return EnumSignal(db, msg, handle)

    class Message(object):
        """Database message, holds signals."""
        def __init__(self, db, handle,
                     name=None, id=None, flags=None, dlc=None, comment=None):
            """Create a message and optionally set name, id and/or flags."""
            self._handle = handle
            self._can_data = ct.create_string_buffer(64)  # for signal data
            # We need to save a pointer to the database since the API does not have
            # a way to get database handle from a message handle
            self._db = db
            if name is not None:
                self.name = name
            if id is not None:
                self.id = id
            if flags is not None:
                self.flags = flags
            if dlc is not None:
                self.dlc = dlc
            if comment is not None:
                self.comment = comment

        def __eq__(self, other):
            attrs = 'comment dlc id flags name'.split()
            return all(getattr(self, a) == getattr(other, a) for a in attrs)

        def __iter__(self):
            return self.signals()

        def __len__(self):
            """Returns number of signals in message."""
            return sum(1 for _ in self)

        def __ne__(self, other):
            return not self == other

        def __repr__(self):
            return ("Message(name={!r}, id={!r}, flags={!r}, dlc={!r}, comment={!r})".
                    format(self.name, self.id, self.flags,
                           self.dlc, self.comment))

        def asframe(self):
            """Creates a Frame object with empty data matching this message"""
            length = wrapper.dlc_to_bytes(
                self.dlc,
                self._db.protocol.value,
            )
            # convert flags from kvaDbLib format to CANlib format
            can_flags = CanMessageFlag(0)
            if self.flags & MessageFlag.EXT:
                can_flags |= CanMessageFlag.EXT
            return Frame(id_=self.id, data=bytearray(length), flags=can_flags)

        def attributes(self):
            """Return a generator over all message attributes."""
            ah = None
            nah = ct.c_void_p()
            try:
                dll.kvaDbGetFirstMsgAttribute(self._handle, ct.byref(nah))
            except KvdNoAttribute:
                return
            while nah.value is not None:
                ah, nah = nah, ct.c_void_p()
                yield Attribute(self, ah)
                try:
                    dll.kvaDbGetNextAttribute(ah, ct.byref(nah))
                except KvdNoAttribute:
                    return

        def bind(self, frame=None):
            """Bind this message to a frame

            Creates a new BoundMessage object representing this message bound to
            the given Frame object, or a new Frame object if `frame` is `None`.

            """
            return BoundMessage(self, frame or self.asframe())

        def delete_attribute(self, name):
            """Delete attribute from message."""
            ah = ct.c_void_p()
            dll.kvaDbGetMsgAttributeByName(
                self._handle, name.encode('utf-8'), ct.byref(ah))
            dll.kvaDbDeleteMsgAttribute(self._handle, ah)

        def delete_signal(self, signal):
            """Delete signal from message.

            Args:
                signal (:obj:`Signal`): signal to be deleted

            """
            dll.kvaDbDeleteSignal(self._handle, signal._handle)

        def get_attribute_value(self, name):
            """Return attribute value

            If the attribute is not set on the message, we return the attribute
            definition default value.

            """
            ah = ct.c_void_p()

            # Try and find attribute on message
            try:
                dll.kvaDbGetMsgAttributeByName(
                    self._handle, name.encode('utf-8'), ct.byref(ah))
            except KvdNoAttribute:
                # Lookup the attribute definition
                atr_def = self._db.get_attribute_definition_by_name(name)

                # only attributes with message as owner are valid, name is also
                # unique accross all attributes so it is enough to check this one
                # for owner
                if atr_def.owner != AttributeOwner.MESSAGE:
                    raise KvdWrongOwner()
                value = atr_def.definition.default
            else:
                attribute = Attribute(self._db, ah)
                value = attribute.value
            return value

        def get_signal(self, name):
            """Find signal in message by name."""
            return self.get_signal_by_name(name)

        def get_signal_by_name(self, name):
            """Find signal in message by name."""
            sh = ct.c_void_p(None)
            dll.kvaDbGetSignalByName(
                self._handle, name.encode('utf-8'), ct.byref(sh))
            signal = _signal_object(self._db, self, sh)
            return signal

        def new_signal(self, name, type=SignalType.UNSIGNED,
                       byte_order=SignalByteOrder.INTEL,
                       mode=SignalMultiplexMode.SIGNAL,
                       representation=None, size=None,
                       scaling=ValueScaling(factor=1, offset=0),
                       limits=None, unit=None, comment=None, enums={}):
            """Create and add a new signal to the message."""
            sh = ct.c_void_p(None)
            dll.kvaDbAddSignal(self._handle, ct.byref(sh))
            if type > SignalType._ENUM_SEPARATOR:
                type -= SignalType._ENUM_SEPARATOR
                signal = EnumSignal(self._db, self, sh, name, type,
                                    byte_order, mode, size, scaling, limits, unit,
                                    comment, dict(enums))
            else:
                signal = Signal(self._db, self, sh,
                                name=name, type=type, byte_order=byte_order, mode=mode,
                                representation=representation, size=size,
                                scaling=scaling, limits=limits, unit=unit,
                                comment=comment)
            return signal

        def set_attribute_value(self, name, value):
            """Set value of attribute 'name' on message.

            If no attribute called 'name' is set on message, attach a message
            attribute from the database attribute definition first.

            """
            ah = ct.c_void_p()

            # Try and find attribute on message
            try:
                dll.kvaDbGetMsgAttributeByName(
                    self._handle, name.encode('utf-8'), ct.byref(ah))
            except KvdNoAttribute:
                # If no attribute was found, lookup the attribute definition and
                # add a new attribute to the message
                attrib_def = self._db.get_attribute_definition_by_name(name)
                dll.kvaDbAddMsgAttribute(
                    self._handle, attrib_def._handle, ct.byref(ah))
            # Set the value in the message attribute
            attribute = Attribute(self._db, ah)
            attribute.value = value

        def signals(self):
            """Return a generator of all signals in message."""
            sh = ct.c_void_p(None)
            try:
                dll.kvaDbGetFirstSignal(self._handle, ct.byref(sh))
            except (KvdNoSignal, KvdNoMessage):
                # KvdNoMessage is reported with older (5.22?) dlls
                return
            while sh.value is not None:
                yield _signal_object(self._db, self, sh)
                sh = ct.c_void_p()
                try:
                    dll.kvaDbGetNextSignal(self._handle, ct.byref(sh))
                except (KvdNoSignal, KvdNoMessage):
                    # KvdNoMessage is reported with older (5.22?) dlls
                    return

        @property
        def comment(self):
            """`str`: Comment message"""
            buf = ct.create_string_buffer(255)
            dll.kvaDbGetMsgComment(self._handle, buf, ct.sizeof(buf))
            return buf.value.decode('utf-8')

        @comment.setter
        def comment(self, value):
            dll.kvaDbSetMsgComment(self._handle, value.encode('utf-8'))

        @property
        def dlc(self):
            """`int`: The message dlc"""
            c_dlc = ct.c_int(0)
            dll.kvaDbGetMsgDlc(self._handle, ct.byref(c_dlc))
            return c_dlc.value

        @dlc.setter
        def dlc(self, dlc):
            dll.kvaDbSetMsgDlc(self._handle, dlc)

        @property
        def id(self):
            """`int`: The message identifier"""
            c_id = ct.c_uint(0)
            dll.kvaDbGetMsgIdEx(self._handle, ct.byref(c_id))
            return c_id.value

        @id.setter
        def id(self, value):
            dll.kvaDbSetMsgIdEx(self._handle, value)

        @property
        def flags(self):
            """`MessageFlag`: The message flags"""
            c_flags = ct.c_uint(0)
            dll.kvaDbGetMsgFlags(self._handle, ct.byref(c_flags))
            try:
                # There is no guarantee the flags from the dbc file will be valid
                # MessageFlags
                return MessageFlag(c_flags.value)
            except ValueError:
                return c_flags.value

        @flags.setter
        def flags(self, value):
            """Set the message flags."""
            dll.kvaDbSetMsgFlags(self._handle, value)

        @property
        def name(self):
            """`str`: The message name"""
            buf = ct.create_string_buffer(255)
            dll.kvaDbGetMsgName(self._handle, buf, ct.sizeof(buf))
            return buf.value.decode('utf-8')

        @name.setter
        def name(self, value):
            dll.kvaDbSetMsgName(self._handle, value.encode('utf-8'))

        @property
        def qualified_name(self):
            """`str`: The qualified message name

            Returns database and message names separated by a dot.
            """
            buf = ct.create_string_buffer(255)
            dll.kvaDbGetMsgQualifiedName(
                self._handle, buf, ct.sizeof(buf))
            return buf.value.decode('utf-8')

        @property
        def send_node(self):
            """`Node`: The send node for this message."""
            nh = ct.c_void_p()
            dll.kvaDbGetMsgSendNode(self._handle, ct.byref(nh))
            node = Node(self._db, nh)
            return node

        @send_node.setter
        def send_node(self, value):
            dll.kvaDbSetMsgSendNode(self._handle, value._handle)