Encode `arg` as `typ`.

    `arg` will be encoded in a best effort manner, were necessary the function
    will try to correctly define the underlying binary representation (ie.
    decoding a hex-encoded address/hash).

    Args:
        typ (Tuple[(str, int, list)]): A 3-tuple defining the `arg` type.

            The first element defines the type name.
            The second element defines the type length in bits.
            The third element defines if it's an array type.

            Together the first and second defines the elementary type, the third
            element must be present but is ignored.

            Valid type names are:
                - uint
                - int
                - bool
                - ufixed
                - fixed
                - string
                - bytes
                - hash
                - address

        arg (object): The object to be encoded, it must be a python object
            compatible with the `typ`.

    Raises:
        ValueError: when an invalid `typ` is supplied.
        ValueOutOfBounds: when `arg` cannot be encoded as `typ` because of the
            binary contraints.

    Note:
        This function don't work with array types, for that use the `enc`
        function.

def encode_single(typ, arg):  # pylint: disable=too-many-return-statements,too-many-branches,too-many-statements,too-many-locals
    """ Encode `arg` as `typ`.

    `arg` will be encoded in a best effort manner, were necessary the function
    will try to correctly define the underlying binary representation (ie.
    decoding a hex-encoded address/hash).

    Args:
        typ (Tuple[(str, int, list)]): A 3-tuple defining the `arg` type.

            The first element defines the type name.
            The second element defines the type length in bits.
            The third element defines if it's an array type.

            Together the first and second defines the elementary type, the third
            element must be present but is ignored.

            Valid type names are:
                - uint
                - int
                - bool
                - ufixed
                - fixed
                - string
                - bytes
                - hash
                - address

        arg (object): The object to be encoded, it must be a python object
            compatible with the `typ`.

    Raises:
        ValueError: when an invalid `typ` is supplied.
        ValueOutOfBounds: when `arg` cannot be encoded as `typ` because of the
            binary contraints.

    Note:
        This function don't work with array types, for that use the `enc`
        function.
    """
    base, sub, _ = typ

    if base == 'uint':
        sub = int(sub)

        if not (0 < sub <= 256 and sub % 8 == 0):
            raise ValueError(
                'invalid unsigned integer bit length {}'.format(sub))

        try:
            i = decint(arg, signed=False)
        except EncodingError:
            # arg is larger than 2**256
            raise ValueOutOfBounds(repr(arg))

        if not 0 <= i < 2 ** sub:
            raise ValueOutOfBounds(repr(arg))

        value_encoded = int_to_big_endian(i)
        return zpad(value_encoded, 32)

    if base == 'int':
        sub = int(sub)
        bits = sub - 1

        if not (0 < sub <= 256 and sub % 8 == 0):
            raise ValueError('invalid integer bit length {}'.format(sub))

        try:
            i = decint(arg, signed=True)
        except EncodingError:
            # arg is larger than 2**255
            raise ValueOutOfBounds(repr(arg))

        if not -2 ** bits <= i < 2 ** bits:
            raise ValueOutOfBounds(repr(arg))

        value = i % 2 ** 256  # convert negative to "equivalent" positive
        value_encoded = int_to_big_endian(value)
        return zpad(value_encoded, 32)

    if base == 'bool':
        if arg is True:
            value_encoded = int_to_big_endian(1)
        elif arg is False:
            value_encoded = int_to_big_endian(0)
        else:
            raise ValueError('%r is not bool' % arg)

        return zpad(value_encoded, 32)

    if base == 'ufixed':
        sub = str(sub)  # pylint: disable=redefined-variable-type

        high_str, low_str = sub.split('x')
        high = int(high_str)
        low = int(low_str)

        if not (0 < high + low <= 256 and high % 8 == 0 and low % 8 == 0):
            raise ValueError('invalid unsigned fixed length {}'.format(sub))

        if not 0 <= arg < 2 ** high:
            raise ValueOutOfBounds(repr(arg))

        float_point = arg * 2 ** low
        fixed_point = int(float_point)
        return zpad(int_to_big_endian(fixed_point), 32)

    if base == 'fixed':
        sub = str(sub)  # pylint: disable=redefined-variable-type

        high_str, low_str = sub.split('x')
        high = int(high_str)
        low = int(low_str)
        bits = high - 1

        if not (0 < high + low <= 256 and high % 8 == 0 and low % 8 == 0):
            raise ValueError('invalid unsigned fixed length {}'.format(sub))

        if not -2 ** bits <= arg < 2 ** bits:
            raise ValueOutOfBounds(repr(arg))

        float_point = arg * 2 ** low
        fixed_point = int(float_point)
        value = fixed_point % 2 ** 256
        return zpad(int_to_big_endian(value), 32)

    # Decimals
    if base == 'decimal':
        val_to_encode = int(arg * 10**int(sub))
        return zpad(encode_int(val_to_encode % 2**256), 32)

    if base == 'string':
        if isinstance(arg, utils.unicode):
            arg = arg.encode('utf8')
        else:
            try:
                arg.decode('utf8')
            except UnicodeDecodeError:
                raise ValueError('string must be utf8 encoded')

        if len(sub):  # fixed length
            if not 0 <= len(arg) <= int(sub):
                raise ValueError('invalid string length {}'.format(sub))

            if not 0 <= int(sub) <= 32:
                raise ValueError('invalid string length {}'.format(sub))

            return rzpad(arg, 32)

        if not 0 <= len(arg) < TT256:
            raise Exception('Integer invalid or out of range: %r' % arg)

        length_encoded = zpad(int_to_big_endian(len(arg)), 32)
        value_encoded = rzpad(arg, utils.ceil32(len(arg)))

        return length_encoded + value_encoded

    if base == 'bytes':
        if not is_string(arg):
            if isinstance(arg, str):
                arg = bytes(arg, 'utf8')
            else:
                raise EncodingError('Expecting string: %r' % arg)

        arg = utils.to_string(arg)  # py2: force unicode into str

        if len(sub):  # fixed length
            if not 0 <= len(arg) <= int(sub):
                raise ValueError('string must be utf8 encoded')

            if not 0 <= int(sub) <= 32:
                raise ValueError('string must be utf8 encoded')

            return rzpad(arg, 32)

        if not 0 <= len(arg) < TT256:
            raise Exception('Integer invalid or out of range: %r' % arg)

        length_encoded = zpad(int_to_big_endian(len(arg)), 32)
        value_encoded = rzpad(arg, utils.ceil32(len(arg)))

        return length_encoded + value_encoded

    if base == 'hash':
        if not (int(sub) and int(sub) <= 32):
            raise EncodingError('too long: %r' % arg)

        if is_numeric(arg):
            return zpad(encode_int(arg), 32)

        if len(arg) == int(sub):
            return zpad(arg, 32)

        if len(arg) == int(sub) * 2:
            return zpad(decode_hex(arg), 32)

        raise EncodingError('Could not parse hash: %r' % arg)

    if base == 'address':
        assert sub == ''

        if is_numeric(arg):
            return zpad(encode_int(arg), 32)

        if len(arg) == 20:
            return zpad(arg, 32)

        if len(arg) == 40:
            return zpad(decode_hex(arg), 32)

        if len(arg) == 42 and arg[:2] == '0x':
            return zpad(decode_hex(arg[2:]), 32)

        raise EncodingError('Could not parse address: %r' % arg)
    raise EncodingError('Unhandled type: %r %r' % (base, sub))