# SPDX-FileCopyrightText: 2016 Ole Martin Bjorndalen <ombdalen@gmail.com>
#
# SPDX-License-Identifier: MIT

import re

from .checks import check_data, check_msgdict, check_value
from .decode import decode_message
from .encode import encode_message
from .specs import REALTIME_TYPES, SPEC_BY_TYPE, make_msgdict
from .strings import msg2str, str2msg


class BaseMessage:
    """Abstract base class for messages."""
    is_meta = False

    def copy(self):
        raise NotImplementedError

    def bytes(self):
        raise NotImplementedError

    def bin(self):
        """Encode message and return as a bytearray.

        This can be used to write the message to a file.
        """
        return bytearray(self.bytes())

    def hex(self, sep=' '):
        """Encode message and return as a string of hex numbers,

        Each number is separated by the string sep.
        """
        return sep.join(f'{byte:02X}' for byte in self.bytes())

    def dict(self):
        """Returns a dictionary containing the attributes of the message.

        Example: {'type': 'sysex', 'data': [1, 2], 'time': 0}

        Sysex data will be returned as a list.
        """
        data = vars(self).copy()
        if data['type'] == 'sysex':
            # Make sure we return a list instead of a SysexData object.
            data['data'] = list(data['data'])

        return data

    @classmethod
    def from_dict(cls, data):
        """Create a message from a dictionary.

        Only "type" is required. The other will be set to default
        values.
        """
        return cls(**data)

    def _get_value_names(self):
        # This is overridden by MetaMessage.
        return list(SPEC_BY_TYPE[self.type]['value_names']) + ['time']

    def __repr__(self):
        items = [repr(self.type)]
        for name in self._get_value_names():
            items.append(f'{name}={getattr(self, name)!r}')
        return '{}({})'.format(type(self).__name__, ', '.join(items))

    @property
    def is_realtime(self):
        """True if the message is a system realtime message."""
        return self.type in REALTIME_TYPES

    def is_cc(self, control=None):
        """Return True if the message is of type 'control_change'.

        The optional control argument can be used to test for a specific
        control number, for example:

        if msg.is_cc(7):
            # Message is control change 7 (channel volume).
        """
        if self.type != 'control_change':
            return False
        elif control is None:
            return True
        else:
            return self.control == control

    def __delattr__(self, name):
        raise AttributeError('attribute cannot be deleted')

    def __setattr__(self, name, value):
        raise AttributeError('message is immutable')

    def __eq__(self, other):
        if not isinstance(other, BaseMessage):
            raise TypeError(f'can\'t compare message to {type(other)}')

        # This includes time in comparison.
        return vars(self) == vars(other)


class SysexData(tuple):
    """Special kind of tuple accepts and converts any sequence in +=."""
    def __iadd__(self, other):
        check_data(other)
        return self + SysexData(other)


class Message(BaseMessage):
    def __init__(self, type, skip_checks=False, **args):
        msgdict = make_msgdict(type, args)
        if type == 'sysex':
            msgdict['data'] = SysexData(msgdict['data'])

        if not skip_checks:
            check_msgdict(msgdict)

        vars(self).update(msgdict)

    def copy(self, skip_checks=False, **overrides):
        """Return a copy of the message.

        Attributes will be overridden by the passed keyword arguments.
        Only message specific attributes can be overridden. The message
        type can not be changed.

        The skip_checks arg can be used to bypass validation of message
        attributes and should be used cautiously.
        """
        if not overrides:
            # Bypass all checks.
            msg = self.__class__.__new__(self.__class__)
            vars(msg).update(vars(self))
            return msg

        if 'type' in overrides and overrides['type'] != self.type:
            raise ValueError('copy must be same message type')

        if 'data' in overrides:
            overrides['data'] = bytearray(overrides['data'])

        msgdict = vars(self).copy()
        msgdict.update(overrides)

        if not skip_checks:
            check_msgdict(msgdict)

        return self.__class__(skip_checks=skip_checks, **msgdict)

    @classmethod
    def from_bytes(cl, data, time=0):
        """Parse a byte encoded message.

        Accepts a byte string or any iterable of integers.

        This is the reverse of msg.bytes() or msg.bin().
        """
        msg = cl.__new__(cl)
        msgdict = decode_message(data, time=time)
        if 'data' in msgdict:
            msgdict['data'] = SysexData(msgdict['data'])
        vars(msg).update(msgdict)
        return msg

    @classmethod
    def from_hex(cl, text, time=0, sep=None):
        """Parse a hex encoded message.

        This is the reverse of msg.hex().
        """
        # bytearray.fromhex() is a bit picky about its input
        # so we need to replace all whitespace characters with spaces.
        text = re.sub(r'\s', ' ', text)

        if sep is not None:
            # We also replace the separator with spaces making sure
            # the string length remains the same so char positions will
            # be correct in bytearray.fromhex() error messages.
            text = text.replace(sep, ' ' * len(sep))

        return cl.from_bytes(bytearray.fromhex(text), time=time)

    @classmethod
    def from_str(cl, text):
        """Parse a string encoded message.

        This is the reverse of str(msg).
        """
        return cl(**str2msg(text))

    def __len__(self):
        if self.type == 'sysex':
            return 2 + len(self.data)
        else:
            return SPEC_BY_TYPE[self.type]['length']

    def __str__(self):
        return msg2str(vars(self))

    def _setattr(self, name, value):
        if name == 'type':
            raise AttributeError('type attribute is read only')
        elif name not in vars(self):
            raise AttributeError('{} message has no '
                                 'attribute {}'.format(self.type,
                                                       name))
        else:
            check_value(name, value)
            if name == 'data':
                vars(self)['data'] = SysexData(value)
            else:
                vars(self)[name] = value

    __setattr__ = _setattr

    def bytes(self):
        """Encode message and return as a list of integers."""
        return encode_message(vars(self))


def parse_string(text):
    """Parse a string of text and return a message.

    The string can span multiple lines, but must contain
    one full message.

    Raises ValueError if the string could not be parsed.
    """
    return Message.from_str(text)


def parse_string_stream(stream):
    """Parse a stream of messages and yield (message, error_message)

    stream can be any iterable that generates text strings, where each
    string is a string encoded message.

    If a string can be parsed, (message, None) is returned. If it
    can't be parsed, (None, error_message) is returned. The error
    message contains the line number where the error occurred.
    """
    line_number = 1
    for line in stream:
        try:
            line = line.split('#')[0].strip()
            if line:
                yield parse_string(line), None
        except ValueError as exception:
            error_message = 'line {line_number}: {msg}'.format(
                line_number=line_number,
                msg=exception.args[0])
            yield None, error_message
        line_number += 1


def format_as_string(msg, include_time=True):
    """Format a message and return as a string.

    This is equivalent to str(message).

    To leave out the time attribute, pass include_time=False.
    """
    return msg2str(vars(msg), include_time=include_time)