"""
Image data section structure.

:py:class:`ImageData` corresponds to the last section of the PSD/PSB file
where a composited image is stored. When the file does not contain layers,
this is the only place pixels are saved.
"""
from __future__ import absolute_import, unicode_literals
import attr
import logging
import io

from psd_tools.compression import compress, decompress
from psd_tools.constants import Compression
from psd_tools.psd.base import BaseElement
from psd_tools.validators import in_
from psd_tools.utils import read_fmt, write_fmt, write_bytes, pack

logger = logging.getLogger(__name__)


@attr.s(repr=False, slots=True)
class ImageData(BaseElement):
    """
    Merged channel image data.

    .. py:attribute:: compression

        See :py:class:`~psd_tools.constants.Compression`.

    .. py:attribute:: data

        `bytes` as compressed in the `compression` flag.
    """
    compression = attr.ib(
        default=Compression.RAW,
        converter=Compression,
        validator=in_(Compression)
    )
    data = attr.ib(default=b'', type=bytes)

    @classmethod
    def read(cls, fp):
        start_pos = fp.tell()
        compression = Compression(read_fmt('H', fp)[0])
        data = fp.read()  # TODO: Parse data here. Need header.
        logger.debug('  read image data, len=%d' % (fp.tell() - start_pos))
        return cls(compression, data)

    def write(self, fp):
        start_pos = fp.tell()
        written = write_fmt(fp, 'H', self.compression.value)
        written += write_bytes(fp, self.data)
        logger.debug('  wrote image data, len=%d' % (fp.tell() - start_pos))
        return written

    def get_data(self, header, split=True):
        """
        Get decompressed data.

        :param header: See :py:class:`~psd_tools.psd.header.FileHeader`.
        :return: `list` of bytes corresponding each channel.
        """
        data = decompress(
            self.data, self.compression, header.width,
            header.height * header.channels, header.depth, header.version
        )
        if split:
            plane_size = len(data) // header.channels
            with io.BytesIO(data) as f:
                return [f.read(plane_size) for _ in range(header.channels)]
        return data

    def set_data(self, data, header):
        """
        Set raw data and compress.

        :param data: list of raw data bytes corresponding channels.
        :param compression: compression type,
            see :py:class:`~psd_tools.constants.Compression`.
        :param header: See :py:class:`~psd_tools.psd.header.FileHeader`.
        :return: length of compressed data.
        """
        self.data = compress(
            b''.join(data), self.compression, header.width,
            header.height * header.channels, header.depth, header.version
        )
        return len(self.data)

    @classmethod
    def new(cls, header, color=0, compression=Compression.RAW):
        """
        Create a new image data object.

        :param header: FileHeader.
        :param compression: compression type.
        :param color: default color. int or iterable for channel length.
        """
        plane_size = header.width * header.height
        if isinstance(color, (bool, int, float)):
            color = (color, ) * header.channels
        if len(color) != header.channels:
            raise ValueError(
                'Invalid color %s for channel size %d' %
                (color, header.channels)
            )
        # Bitmap is not supported here.
        fmt = {8: 'B', 16: 'H', 32: 'I'}.get(header.depth)
        data = []
        for i in range(header.channels):
            data.append(pack(fmt, color[i]) * plane_size)
        self = cls(compression=compression)
        self.set_data(data, header)
        return self
