"""
PC-BASIC - modes.py
Emulated video modes

(c) 2013--2018 Rob Hagemans
This file is released under the GNU GPL version 3 or later.
"""

try:
    import numpy
except ImportError:
    numpy = None

import struct

from .. import values
from ..base import error


# mark bytes conversion explicitly
int2byte = chr

# SCREEN 10 EGA pseudocolours, blink state 0 and 1
INTENSITY_EGA_MONO_0 = (0x00, 0x00, 0x00, 0xaa, 0xaa, 0xaa, 0xff, 0xff, 0xff)
INTENSITY_EGA_MONO_1 = (0x00, 0xaa, 0xff, 0x00, 0xaa, 0xff, 0x00, 0xaa, 0xff)
# MDA text intensities: black, dark green, green, bright green
INTENSITY_MDA_MONO = (0x00, 0x40, 0xc0, 0xff)

# default 16-color and ega palettes
CGA16_PALETTE = (0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
EGA_PALETTE = (0, 1, 2, 3, 4, 5, 20, 7, 56, 57, 58, 59, 60, 61, 62, 63)
EGA_MONO_PALETTE = (0, 4, 1, 8)
# adding dark-green (foreground for some exceptional attributes) as #3
MDA_PALETTE = (0, 2, 3, 1)
CGA2_PALETTE = (0, 15)

# http://qbhlp.uebergeord.net/screen-statement-details-colors.html
# underline/intensity/reverse video attributes are slightly different from mda
# attributes 1, 9 should have underlining.
# EGA_MONO_TEXT_PALETTE = (0, 1, 1, 1, 1, 1, 1, 1, 0, 2, 2, 2, 2, 2, 2, 0)
# MDA_PALETTE = (0, 1, 1, 1, 1, 1, 1, 1, 0, 2, 2, 2, 2, 2, 2, 2)

# CGA mono intensities
INTENSITY16 = range(0x00, 0x100, 0x11)
# CGA colours
COLOURS16 = (
    (0x00, 0x00, 0x00), (0x00, 0x00, 0xaa), (0x00, 0xaa, 0x00), (0x00, 0xaa, 0xaa),
    (0xaa, 0x00, 0x00), (0xaa, 0x00, 0xaa), (0xaa, 0x55, 0x00), (0xaa, 0xaa, 0xaa),
    (0x55, 0x55, 0x55), (0x55, 0x55, 0xff), (0x55, 0xff, 0x55), (0x55, 0xff, 0xff),
    (0xff, 0x55, 0x55), (0xff, 0x55, 0xff), (0xff, 0xff, 0x55), (0xff, 0xff, 0xff)
)
# EGA colours
COLOURS64 = (
    (0x00, 0x00, 0x00), (0x00, 0x00, 0xaa), (0x00, 0xaa, 0x00), (0x00, 0xaa, 0xaa),
    (0xaa, 0x00, 0x00), (0xaa, 0x00, 0xaa), (0xaa, 0xaa, 0x00), (0xaa, 0xaa, 0xaa),
    (0x00, 0x00, 0x55), (0x00, 0x00, 0xff), (0x00, 0xaa, 0x55), (0x00, 0xaa, 0xff),
    (0xaa, 0x00, 0x55), (0xaa, 0x00, 0xff), (0xaa, 0xaa, 0x55), (0xaa, 0xaa, 0xff),
    (0x00, 0x55, 0x00), (0x00, 0x55, 0xaa), (0x00, 0xff, 0x00), (0x00, 0xff, 0xaa),
    (0xaa, 0x55, 0x00), (0xaa, 0x55, 0xaa), (0xaa, 0xff, 0x00), (0xaa, 0xff, 0xaa),
    (0x00, 0x55, 0x55), (0x00, 0x55, 0xff), (0x00, 0xff, 0x55), (0x00, 0xff, 0xff),
    (0xaa, 0x55, 0x55), (0xaa, 0x55, 0xff), (0xaa, 0xff, 0x55), (0xaa, 0xff, 0xff),
    (0x55, 0x00, 0x00), (0x55, 0x00, 0xaa), (0x55, 0xaa, 0x00), (0x55, 0xaa, 0xaa),
    (0xff, 0x00, 0x00), (0xff, 0x00, 0xaa), (0xff, 0xaa, 0x00), (0xff, 0xaa, 0xaa),
    (0x55, 0x00, 0x55), (0x55, 0x00, 0xff), (0x55, 0xaa, 0x55), (0x55, 0xaa, 0xff),
    (0xff, 0x00, 0x55), (0xff, 0x00, 0xff), (0xff, 0xaa, 0x55), (0xff, 0xaa, 0xff),
    (0x55, 0x55, 0x00), (0x55, 0x55, 0xaa), (0x55, 0xff, 0x00), (0x55, 0xff, 0xaa),
    (0xff, 0x55, 0x00), (0xff, 0x55, 0xaa), (0xff, 0xff, 0x00), (0xff, 0xff, 0xaa),
    (0x55, 0x55, 0x55), (0x55, 0x55, 0xff), (0x55, 0xff, 0x55), (0x55, 0xff, 0xff),
    (0xff, 0x55, 0x55), (0xff, 0x55, 0xff), (0xff, 0xff, 0x55), (0xff, 0xff, 0xff)
)

# composite palettes, see http://nerdlypleasures.blogspot.co.uk/2013_11_01_archive.html
COMPOSITE = {
    'cga_old': [
        (0x00, 0x00, 0x00),   (0x00, 0x71, 0x00),   (0x00, 0x3f, 0xff),   (0x00, 0xab, 0xff),
        (0xc3, 0x00, 0x67),   (0x73, 0x73, 0x73),   (0xe6, 0x39, 0xff),   (0x8c, 0xa8, 0xff),
        (0x53, 0x44, 0x00),   (0x00, 0xcd, 0x00),   (0x73, 0x73, 0x73),   (0x00, 0xfc, 0x7e),
        (0xff, 0x39, 0x00),   (0xe2, 0xca, 0x00),   (0xff, 0x7c, 0xf4),   (0xff, 0xff, 0xff)
    ],
    'cga': [
        (0x00, 0x00, 0x00),   (0x00, 0x6a, 0x2c),   (0x00, 0x39, 0xff),   (0x00, 0x94, 0xff),
        (0xca, 0x00, 0x2c),   (0x77, 0x77, 0x77),   (0xff, 0x31, 0xff),   (0xc0, 0x98, 0xff),
        (0x1a, 0x57, 0x00),   (0x00, 0xd6, 0x00),   (0x77, 0x77, 0x77),   (0x00, 0xf4, 0xb8),
        (0xff, 0x57, 0x00),   (0xb0, 0xdd, 0x00),   (0xff, 0x7c, 0xb8),   (0xff, 0xff, 0xff)
    ],
    'tandy': [
        (0x00, 0x00, 0x00),   (0x7c, 0x30, 0x00),   (0x00, 0x75, 0x00),   (0x00, 0xbe, 0x00),
        (0x00, 0x47, 0xee),   (0x77, 0x77, 0x77),   (0x00, 0xbb, 0xc4),   (0x00, 0xfb, 0x3f),
        (0xb2, 0x0f, 0x9d),   (0xff, 0x1e, 0x0f),   (0x77, 0x77, 0x77),   (0xff, 0xb8, 0x00),
        (0xb2, 0x44, 0xff),   (0xff, 0x78, 0xff),   (0x4b, 0xba, 0xff),   (0xff, 0xff, 0xff)
    ],
    'pcjr': [
        (0x00, 0x00, 0x00),
        (0x98, 0x20, 0xcb),   (0x9f, 0x1c, 0x00),   (0xff, 0x11, 0x71),   (0x00, 0x76, 0x00),
        (0x77, 0x77, 0x77),   (0x5b, 0xaa, 0x00),   (0xff, 0xa5, 0x00),   (0x00, 0x4e, 0xcb),
        (0x74, 0x53, 0xff),   (0x77, 0x77, 0x77),   (0xff, 0x79, 0xff),   (0x00, 0xc8, 0x71),
        (0x00, 0xcc, 0xff),   (0x00, 0xfa, 0x00),   (0xff, 0xff, 0xff)
    ]
}

MONO_TINT = {
    'green': [0, 255, 0],
    'amber': [255, 128, 0],
    'grey': [255, 255, 255],
    'mono': [0, 255, 0],
}


###############################################################################
# Low level video (mainly about colours; mode object factory)

class Video(object):
    """Low-level display operations."""

    def __init__(self, capabilities, monitor, low_intensity, aspect, video_mem_size):
        """Initialise colour sets."""
        # public members - used by VideoMode
        # video adapter type - cga, ega, etc
        if capabilities == 'ega' and monitor in MONO_TINT:
            capabilities = 'ega_mono'
        self.capabilities = capabilities
        # monochrome tint in rgb
        self.mono_tint = MONO_TINT.get(monitor, MONO_TINT['green'])
        # emulated monitor type - rgb, composite, mono
        self.monitor = 'mono' if monitor in MONO_TINT else monitor
        # build 16-greyscale and 16-colour sets
        self.colours16_mono = tuple(
            tuple(tint*i//255 for tint in self.mono_tint) for i in INTENSITY16
        )
        # NTSC colorburst settings
        if monitor == 'mono':
            self.colours16 = list(self.colours16_mono)
        else:
            self.colours16 = list(COLOURS16)
        # CGA 4-colour palette / mode 5 settings
        # palette 1: Black, Ugh, Yuck, Bleah, choice of low & high intensity
        # palette 0: Black, Green, Red, Brown/Yellow, low & high intensity
        # tandy/pcjr have high-intensity white, but low-intensity colours
        # mode 5 (SCREEN 1 + colorburst on RGB) has red instead of magenta
        if capabilities in ('pcjr', 'tandy'):
            # pcjr does not have mode 5
            self.cga4_palettes = {0: (0, 2, 4, 6), 1: (0, 3, 5, 15), 5: None}
        elif low_intensity:
            self.cga4_palettes = {0: (0, 2, 4, 6), 1: (0, 3, 5, 7), 5: (0, 3, 4, 7)}
        else:
            self.cga4_palettes = {0: (0, 10, 12, 14), 1: (0, 11, 13, 15), 5: (0, 11, 12, 15)}
        self.cga4_palette = list(self.cga4_palettes[1])
        self.cga4_palette_num = 1
        self.cga_mode_5 = False
        # screen aspect ratio, for CIRCLE
        self.aspect = aspect
        # set up text_data and mode_data
        self.prepare_modes(video_mem_size)

    def get_mode(self, number, width=None):
        """Retrieve graphical mode by screen number."""
        try:
            if number:
                return self._mode_data[number]
            else:
                return self._text_data[width]
        except KeyError:
            # no such mode
            raise error.BASICError(error.IFC)

    def toggle_colour(self, has_colour):
        """Toggle between colour and monochrome (for NTSC colorburst)."""
        # note that colours16 member is only used in certain mode/adapter combinations
        # e.g. in text mode it's only used for 'cga', 'cga_old', 'pcjr', 'tandy'
        if has_colour:
            self.colours16[:] = COLOURS16
        else:
            self.colours16[:] = self.colours16_mono

    def set_cga4_palette(self, num):
        """set the default 4-colour CGA palette."""
        self.cga4_palette_num = num
        # we need to copy into cga4_palette as it's referenced by mode.palette
        if self.cga_mode_5 and self.capabilities in ('cga', 'cga_old'):
            self.cga4_palette[:] = self.cga4_palettes[5]
        else:
            self.cga4_palette[:] = self.cga4_palettes[num]

    def set_colorburst(self, on, is_cga):
        """Set the NTSC colorburst bit."""
        # On a composite monitor with CGA adapter (not EGA, VGA):
        # - on SCREEN 2 this enables artifacting
        # - on SCREEN 1 and 0 this switches between colour and greyscale
        # On an RGB monitor:
        # - on SCREEN 1 this switches between mode 4/5 palettes (RGB)
        # - ignored on other screens
        colorburst_capable = self.capabilities in ('cga', 'cga_old', 'tandy', 'pcjr')
        if is_cga and self.monitor != 'composite':
            # ega ignores colorburst; tandy and pcjr have no mode 5
            self.cga_mode_5 = not on
            self.set_cga4_palette(1)
        else:
            self.toggle_colour(self.monitor != 'mono' and (on or self.monitor != 'composite'))
        return on and colorburst_capable

    def get_allowed_widths(self):
        """Get allowed screen widths."""
        return set(mode.width for mode in self._text_data.values() + self._mode_data.values())

    ###########################################################################
    # video modes

    def prepare_modes(self, video_mem_size):
        """Build lists of allowed graphics modes."""
        video_mem_size = int(video_mem_size)
        # initialise tinted monochrome palettes
        colours_ega_mono_0 = tuple(
            tuple(tint*i//255 for tint in self.mono_tint) for i in INTENSITY_EGA_MONO_0
        )
        colours_ega_mono_1 = tuple(
            tuple(tint*i//255 for tint in self.mono_tint) for i in INTENSITY_EGA_MONO_1
        )
        colours_mda_mono = tuple(
            tuple(tint*i//255 for tint in self.mono_tint) for i in INTENSITY_MDA_MONO
        )
        # Tandy/PCjr pixel aspect ratio is different from normal
        # suggesting screen aspect ratio is not 4/3.
        # Tandy pixel aspect ratios, experimentally found with CIRCLE:
        # screen 2, 6:     48/100   normal if aspect = 3072, 2000
        # screen 1, 4, 5:  96/100   normal if aspect = 3072, 2000
        # screen 3:      1968/1000
        # screen 3 is strange, slighly off the 192/100 you'd expect
        graphics_mode = {
            # 04h 320x200x4  16384B 2bpp 0xb8000    screen 1
            # tandy:2 pages if 32k memory; ega: 1 page only
            '320x200x4': CGAMode(
                '320x200x4', 320, 200, 25, 40, 3,
                self.cga4_palette, self.colours16, bitsperpixel=2,
                interleave_times=2, bank_size=0x2000,
                aspect=self.aspect,
                num_pages=(
                    video_mem_size // (2*0x2000)
                    if self.capabilities in ('pcjr', 'tandy')
                    else 1
                )
            ),
            # 06h 640x200x2  16384B 1bpp 0xb8000    screen 2
            '640x200x2': CGAMode(
                '640x200x2', 640, 200, 25, 80, 1,
                CGA2_PALETTE, self.colours16, bitsperpixel=1,
                interleave_times=2, bank_size=0x2000, num_pages=1,
                aspect=self.aspect,
                supports_artifacts=True
            ),
            # 08h 160x200x16 16384B 4bpp 0xb8000    PCjr/Tandy screen 3
            '160x200x16': CGAMode(
                '160x200x16', 160, 200, 25, 20, 15,
                CGA16_PALETTE, self.colours16, bitsperpixel=4,
                interleave_times=2, bank_size=0x2000,
                num_pages=video_mem_size//(2*0x2000),
                pixel_aspect=(1968, 1000), cursor_index=3
            ),
            #     320x200x4  16384B 2bpp 0xb8000   Tandy/PCjr screen 4
            '320x200x4pcjr': CGAMode(
                '320x200x4pcjr', 320, 200, 25, 40, 3,
                self.cga4_palette, self.colours16, bitsperpixel=2,
                interleave_times=2, bank_size=0x2000,
                num_pages=video_mem_size//(2*0x2000),
                aspect=self.aspect,
                cursor_index=3
            ),
            # 09h 320x200x16 32768B 4bpp 0xb8000    Tandy/PCjr screen 5
            '320x200x16pcjr': CGAMode(
                '320x200x16pcjr', 320, 200, 25, 40, 15,
                CGA16_PALETTE, self.colours16, bitsperpixel=4,
                interleave_times=4, bank_size=0x2000,
                num_pages=video_mem_size//(4*0x2000),
                aspect=self.aspect,
                cursor_index=3
            ),
            # 0Ah 640x200x4  32768B 2bpp 0xb8000   Tandy/PCjr screen 6
            '640x200x4': Tandy6Mode(
                '640x200x4', 640, 200, 25, 80, 3,
                self.cga4_palette, self.colours16, bitsperpixel=2,
                interleave_times=4, bank_size=0x2000,
                num_pages=video_mem_size//(4*0x2000),
                aspect=self.aspect,
                cursor_index=3
            ),
            # 0Dh 320x200x16 32768B 4bpp 0xa0000    EGA screen 7
            '320x200x16': EGAMode(
                '320x200x16', 320, 200, 25, 40, 15,
                CGA16_PALETTE, self.colours16, bitsperpixel=4,
                num_pages=video_mem_size//(4*0x2000),
                aspect=self.aspect,
                interleave_times=1, bank_size=0x2000
            ),
            # 0Eh 640x200x16    EGA screen 8
            '640x200x16': EGAMode(
                '640x200x16', 640, 200, 25, 80, 15,
                CGA16_PALETTE, self.colours16, bitsperpixel=4,
                num_pages=video_mem_size//(4*0x4000),
                aspect=self.aspect,
                interleave_times=1, bank_size=0x4000
            ),
            # 10h 640x350x16    EGA screen 9
            '640x350x16': EGAMode(
                '640x350x16', 640, 350, 25, 80, 15,
                EGA_PALETTE, COLOURS64, bitsperpixel=4,
                num_pages=video_mem_size//(4*0x8000),
                aspect=self.aspect,
                interleave_times=1, bank_size=0x8000
            ),
            # 0Fh 640x350x4     EGA monochrome screen 10
            '640x350x4': EGAMode(
                '640x350x16', 640, 350, 25, 80, 1,
                EGA_MONO_PALETTE, colours_ega_mono_0, bitsperpixel=2,
                interleave_times=1, bank_size=0x8000,
                num_pages=video_mem_size//(2*0x8000),
                aspect=self.aspect,
                colours1=colours_ega_mono_1, has_blink=True,
                planes_used=(1, 3)
            ),
            # 40h 640x400x2   1bpp  olivetti screen 3
            '640x400x2': CGAMode(
                '640x400x2', 640, 400, 25, 80, 1,
                CGA2_PALETTE, self.colours16, bitsperpixel=1,
                interleave_times=4, bank_size=0x2000,
                num_pages=1,
                aspect=self.aspect,
                has_blink=True
            ),
            # hercules screen 3
            '720x348x2': CGAMode(
                # this actually produces 350, not 348
                '720x348x2', 720, 350, 25, 80, 1,
                CGA2_PALETTE, self.colours16_mono, bitsperpixel=1,
                interleave_times=4, bank_size=0x2000,
                num_pages=2,
                aspect=self.aspect,
                has_blink=True
            ),
        }
        if self.capabilities == 'vga':
            # technically, VGA text does have underline
            # but it's set to an invisible scanline
            # so not, so long as we're not allowing to set the scanline
            self._text_data = {
                40: TextMode('vgatext40', 25, 40, 16, 9, 7, EGA_PALETTE, COLOURS64, num_pages=8),
                80: TextMode('vgatext80', 25, 80, 16, 9, 7, EGA_PALETTE, COLOURS64, num_pages=4)
            }
            self._mode_data = {
                1: graphics_mode['320x200x4'],
                2: graphics_mode['640x200x2'],
                7: graphics_mode['320x200x16'],
                8: graphics_mode['640x200x16'],
                9: graphics_mode['640x350x16']
            }
        elif self.capabilities == 'ega':
            self._text_data = {
                40: TextMode('egatext40', 25, 40, 14, 8, 7, EGA_PALETTE, COLOURS64, num_pages=8),
                80: TextMode('egatext80', 25, 80, 14, 8, 7, EGA_PALETTE, COLOURS64, num_pages=4)
            }
            self._mode_data = {
                1: graphics_mode['320x200x4'],
                2: graphics_mode['640x200x2'],
                7: graphics_mode['320x200x16'],
                8: graphics_mode['640x200x16'],
                9: graphics_mode['640x350x16']
            }
        elif self.capabilities == 'ega_mono':
            self._text_data = {
                40: MonoTextMode(
                    'ega_monotext40', 25, 40, 14, 8, 7,
                    MDA_PALETTE, colours_mda_mono, is_mono=True, num_pages=8
                ),
                80: MonoTextMode(
                    'ega_monotext80', 25, 80, 14, 8, 7,
                    MDA_PALETTE, colours_mda_mono, is_mono=True, num_pages=4
                )
            }
            self._mode_data = {
                10: graphics_mode['640x350x4']
            }
        elif self.capabilities == 'mda':
            self._text_data = {
                40: MonoTextMode(
                    'mdatext40', 25, 40, 14, 9, 7,
                    MDA_PALETTE, colours_mda_mono, is_mono=True, num_pages=1
                ),
                80: MonoTextMode(
                    'mdatext80', 25, 80, 14, 9, 7,
                    MDA_PALETTE, colours_mda_mono, is_mono=True, num_pages=1
                )
            }
            self._mode_data = {}
        elif self.capabilities in ('cga', 'cga_old', 'pcjr', 'tandy'):
            if self.capabilities == 'tandy':
                self._text_data = {
                    40: TextMode(
                        'tandytext40', 25, 40, 9, 8, 7, CGA16_PALETTE, self.colours16, num_pages=8
                    ),
                    80: TextMode(
                        'tandytext80', 25, 80, 9, 8, 7, CGA16_PALETTE, self.colours16, num_pages=4
                    )
                }
            else:
                self._text_data = {
                    40: TextMode(
                        'cgatext40', 25, 40, 8, 8, 7,
                        CGA16_PALETTE, self.colours16, num_pages=8
                    ),
                    80: TextMode(
                        'cgatext80', 25, 80, 8, 8, 7,
                        CGA16_PALETTE, self.colours16, num_pages=4
                    )
                }
            if self.capabilities in ('cga', 'cga_old'):
                self._mode_data = {
                    1: graphics_mode['320x200x4'],
                    2: graphics_mode['640x200x2']
                }
            else:
                self._mode_data = {
                    1: graphics_mode['320x200x4'],
                    2: graphics_mode['640x200x2'],
                    3: graphics_mode['160x200x16'],
                    4: graphics_mode['320x200x4pcjr'],
                    5: graphics_mode['320x200x16pcjr'],
                    6: graphics_mode['640x200x4']
                }
        elif self.capabilities == 'hercules':
            # herc attributes shld distinguish black, dim, normal, bright
            # see http://www.seasip.info/VintagePC/hercplus.html
            self._text_data = {
                40: MonoTextMode(
                    'herculestext40', 25, 40, 14, 9, 7,
                    MDA_PALETTE, colours_mda_mono, is_mono=True, num_pages=2
                ),
                80: MonoTextMode(
                    'herculestext80', 25, 80, 14, 9, 7,
                    MDA_PALETTE, colours_mda_mono, is_mono=True, num_pages=2
                )
            }
            self._mode_data = {
                3: graphics_mode['720x348x2']
            }
        elif self.capabilities == 'olivetti':
            self._text_data = {
                40: TextMode(
                    'olivettitext40', 25, 40, 16, 8, 7, CGA16_PALETTE, self.colours16, num_pages=8
                ),
                80: TextMode(
                    'olivettitext80', 25, 80, 16, 8, 7, CGA16_PALETTE, self.colours16, num_pages=4
                )
            }
            self._mode_data = {
                1: graphics_mode['320x200x4'],
                2: graphics_mode['640x200x2'],
                3: graphics_mode['640x400x2']
            }
            # on Olivetti M24, all numbers 3-255 give the same altissima risoluzione
            for mode in range(4, 256):
                self._mode_data[mode] = graphics_mode['640x400x2']


class VideoMode(object):
    """Base class for video modes."""
    def __init__(
                self, name, height, width,
                font_height, font_width,
                attr, palette, colours,
                num_pages, has_blink,
                video_segment, page_size
            ):
        """Initialise video mode settings."""
        self.is_text_mode = False
        self.name = name
        self.height = int(height)
        self.width = int(width)
        self.font_height = int(font_height)
        self.font_width = int(font_width)
        self.pixel_height = self.height*self.font_height
        self.pixel_width = self.width*self.font_width
        self.attr = int(attr)
        # palette is a reference (changes with cga_mode_5 and cga4_palette_num)
        self.palette = palette
        self.num_attr = len(palette)
        # colours is a reference (changes with colorburst on composite)
        self.colours = colours
        # colours1 is only used by EGA mono mode
        self.colours1 = None
        # this is used by interface plugins (which use this object as mode_info)
        self.has_blink = has_blink
        self.video_segment = int(video_segment)
        self.page_size = int(page_size)
        self.num_pages = int(num_pages) # or video_mem_size // self.page_size)

    def split_attr(self, attr):
        """Split attribute byte into constituent parts."""
        # 7  6 5 4  3 2 1 0
        # Bl b b b  f f f f
        back = (attr >> 4) & 7
        blink = (attr >> 7) == 1
        fore = attr & 0xf
        underline = False
        return fore, back, blink, underline

    def pixel_to_text_pos(self, x, y):
        """Convert pixel position to text position."""
        return 1 + y // self.font_height, 1 + x // self.font_width

    def pixel_to_text_area(self, x0, y0, x1, y1):
        """Convert from pixel area to text area."""
        col0 = min(self.width, max(1, 1 + x0 // self.font_width))
        row0 = min(self.height, max(1, 1 + y0 // self.font_height))
        col1 = min(self.width, max(1, 1 + x1 // self.font_width))
        row1 = min(self.height, max(1, 1 + y1 // self.font_height))
        return row0, col0, row1, col1

    def text_to_pixel_area(self, row0, col0, row1, col1):
        """Convert area text area to pixel area."""
        # area bounds are all inclusive
        return (
            (col0-1) * self.font_width, (row0-1) * self.font_height,
            (col1-col0+1) * self.font_width-1, (row1-row0+1) * self.font_height-1
        )

    def get_all_memory(self, screen):
        """Obtain a copy of all video memory."""
        return self.get_memory(screen, self.video_segment*0x10, self.page_size*self.num_pages)

    def set_all_memory(self, screen, mem_copy):
        """Restore a copy of all video memory."""
        return self.set_memory(screen, self.video_segment*0x10, mem_copy)

    def get_memory(self, screen, addr, num_bytes):
        """Retrieve bytes from video memory, stub."""

    def set_memory(self, screen, addr, bytes):
        """Set bytes in video memory, stub."""


class TextMode(VideoMode):
    """Default settings for a text mode."""

    def __init__(
                self, name, height, width,
                font_height, font_width, attr, palette, colours,
                num_pages, is_mono=False, has_blink=True
            ):
        """Initialise video mode settings."""
        video_segment = 0xb000 if is_mono else 0xb800
        page_size = 0x1000 if width == 80 else 0x800
        VideoMode.__init__(
            self, name, height, width,
            font_height, font_width, attr, palette, colours,
            num_pages, has_blink, video_segment, page_size
        )
        self.is_text_mode = True
        self.num_attr = 32

    def get_memory(self, screen, addr, num_bytes):
        """Retrieve bytes from textmode video memory."""
        addr -= self.video_segment*0x10
        mem_bytes = bytearray(num_bytes)
        for i in xrange(num_bytes):
            page = (addr+i) // self.page_size
            offset = (addr+i) % self.page_size
            ccol = 1 + (offset % (self.width*2)) // 2
            crow = 1 + offset // (self.width*2)
            try:
                if (addr+i) % 2:
                    mem_bytes[i] = screen.text_screen.text.get_attr(page, crow, ccol)
                else:
                    mem_bytes[i] = screen.text_screen.text.get_char(page, crow, ccol)
            except IndexError:
                pass
        return mem_bytes

    def set_memory(self, screen, addr, mem_bytes):
        """Set bytes in textmode video memory."""
        addr -= self.video_segment*0x10
        last_row = 0
        for i in xrange(len(mem_bytes)):
            page = (addr+i) // self.page_size
            offset = (addr+i) % self.page_size
            ccol = 1 + (offset % (self.width*2)) // 2
            crow = 1 + offset // (self.width*2)
            try:
                if (addr+i) % 2:
                    c = screen.text_screen.text.get_char(page, crow, ccol)
                    a = mem_bytes[i]
                else:
                    c = mem_bytes[i]
                    a = screen.text_screen.text.get_attr(page, crow, ccol)
                screen.text_screen.text.put_char_attr(page, crow, ccol, int2byte(c), a)
                if last_row > 0 and last_row != crow:
                    screen.text_screen.refresh_range(page, last_row, 1, self.width)
            except IndexError:
                pass
            last_row = crow
        if last_row >= 1 and last_row <= self.height and page >= 0 and page < self.num_pages:
            screen.text_screen.refresh_range(page, last_row, 1, self.width)


class MonoTextMode(TextMode):
    """MDA-style text mode with underlining."""
    def split_attr(self, attr):
        """Split attribute byte into constituent parts."""
        # MDA text attributes: http://www.seasip.info/VintagePC/mda.html
        # see also http://support.microsoft.com/KB/35148
        # don't try to change this with PALETTE, it won't work correctly
        underline = (attr % 8) == 1
        blink = (attr & 0x80) != 0
        # background is almost always black
        back = 0
        # intensity set by bit 3
        fore = 1 if not (attr & 0x8) else 2
        # exceptions
        if attr in (0x00, 0x08, 0x80, 0x88):
            fore, back = 0, 0
        elif attr in (0x70, 0xf0):
            fore, back = 0, 1
        elif attr in (0x78, 0xf8):
            fore, back = 3, 1
        return fore, back, blink, underline


# helper functions: convert between attribute lists and byte arrays

if numpy:
    def bytes_to_interval(byte_array, pixels_per_byte, mask=1):
        """Convert masked attributes packed into bytes to a scanline interval."""
        bpp = 8 // pixels_per_byte
        attrmask = (1<<bpp) - 1
        bitval = numpy.array([128, 64, 32, 16, 8, 4, 2, 1], dtype=numpy.uint8)
        bitmask = bitval[0::bpp]
        for i in xrange(1, bpp):
            bitmask |= bitval[i::bpp]
        pre_mask = numpy.tile(bitmask, len(byte_array))
        post_shift = numpy.tile(
            numpy.array([7, 6, 5, 4, 3, 2, 1, 0])[(bpp-1)::bpp], len(byte_array)
        )
        attrs = numpy.right_shift(
            numpy.repeat(numpy.array(byte_array).astype(int), pixels_per_byte) & pre_mask,
            post_shift
        ) & attrmask
        return numpy.array(attrs) * mask

    def interval_to_bytes(colours, pixels_per_byte, plane=0):
        """Convert a scanline interval into masked attributes packed into bytes."""
        num_pixels = len(colours)
        num_bytes, odd_out = divmod(num_pixels, pixels_per_byte)
        if odd_out:
            num_bytes += 1
        bpp = 8 // pixels_per_byte
        attrmask = (1<<bpp) - 1
        colours = numpy.array(colours).astype(int)
        if odd_out:
            colours.resize(len(colours)+pixels_per_byte-odd_out)
        shift = numpy.tile(numpy.array([7, 6, 5, 4, 3, 2, 1, 0])[(bpp-1)::bpp], num_bytes)
        attrs = numpy.right_shift(colours, plane)
        attrs = numpy.left_shift(attrs & attrmask, shift)
        # below is much faster than:
        #   return list([ sum(attrs[i:i+pixels_per_byte])
        #                 for i in xrange(0, len(attrs), pixels_per_byte) ])
        # and anything involving numpy.array_split or numpy.dot is even slower.
        # numpy.roll is ok but this is the fastest I've found:
        nattrs = attrs[0::pixels_per_byte]
        for i in xrange(1, pixels_per_byte):
            nattrs |= attrs[i::pixels_per_byte]
        return bytearray(list(nattrs))

else:
    def bytes_to_interval(byte_array, pixels_per_byte, mask=1):
        """Convert masked attributes packed into bytes to a scanline interval."""
        bpp = 8 // pixels_per_byte
        attrmask = (1<<bpp) - 1
        return [
            ((byte >> (8-bpp-shift)) & attrmask) * mask
            for byte in byte_array for shift in xrange(0, 8, bpp)
        ]

    def interval_to_bytes(colours, pixels_per_byte, plane=0):
        """Convert a scanline interval into masked attributes packed into bytes."""
        num_pixels = len(colours)
        num_bytes, odd_out = divmod(num_pixels, pixels_per_byte)
        if odd_out:
            num_bytes += 1
        bpp = 8//pixels_per_byte
        attrmask = (1<<bpp) - 1
        colours = list(colours)
        byte_list = bytearray(num_bytes)
        shift, byte = -1, -1
        for x in xrange(num_pixels):
            if shift < 0:
                shift = 8 - bpp
                byte += 1
            byte_list[byte] |= ((colours[x] >> plane) & attrmask) << shift
            shift -= bpp
        return byte_list

def walk_memory(self, addr, num_bytes, factor=1):
    """Yield parts of graphics memory corresponding to pixels."""
    # factor supports tandy-6 mode, which has 8 pixels per 2 bytes
    # with alternating planes in even and odd bytes (i.e. ppb==8)
    ppb = factor * self.ppb
    page_size = self.page_size//factor
    bank_size = self.bank_size//factor
    row_size = self.bytes_per_row//factor
    # first row
    page, x, y = self.get_coords(addr)
    offset = min(row_size - x//ppb, num_bytes)
    if self.coord_ok(page, x, y):
        yield page, x, y, 0, offset
    # full rows
    bank_offset, page_offset, start_y = 0, 0, y
    while page_offset + bank_offset + offset < num_bytes:
        y += self.interleave_times
        # not an integer number of rows in a bank
        if offset >= bank_size:
            bank_offset += bank_size
            start_y += 1
            offset, y = 0, start_y
            if bank_offset >= page_size:
                page_offset += page_size
                page += 1
                bank_offset, offset = 0, 0
                y, start_y = 0, 0
        if self.coord_ok(page, 0, y):
            ofs = page_offset + bank_offset + offset
            if ofs + row_size > num_bytes:
                yield page, 0, y, ofs, num_bytes - ofs
            else:
                yield page, 0, y, ofs, row_size
        offset += row_size

def sprite_size_to_record_ega(self, dx, dy):
    """Write 4-byte record of sprite size in EGA modes."""
    return struct.pack('<HH', dx, dy)

def record_to_sprite_size_ega(self, byte_array):
    """Read 4-byte record of sprite size in EGA modes."""
    return struct.unpack('<HH', byte_array[0:4])

def sprite_to_array_ega(self, attrs, dx, dy, byte_array, offs):
    """Build the sprite byte array in EGA modes."""
    # for EGA modes, sprites have 8 pixels per byte
    # with colour planes in consecutive rows
    # each new row is aligned on a new byte
    #
    # this is much faster for wide selections
    # but for narrow selections storing in an array and indexing take longer
    # than just getting each pixel separately
    row_bytes = (dx+7) // 8
    length = dy * self.bitsperpixel * row_bytes
    if offs+length > len(byte_array):
        raise ValueError('Sprite exceeds array byte size')
    byte_array[offs:offs+length] = b'\0'*length
    for row in attrs:
        for plane in range(self.bitsperpixel):
            byte_array[offs:offs+row_bytes] = interval_to_bytes(row, 8, plane)
            offs += row_bytes

# elementwise OR, in-place if possible
if numpy:
    or_i = numpy.ndarray.__ior__
else:
    def or_i(list0, list1):
        return [ x | y for x, y in zip(list0, list1) ]

def array_to_sprite_ega(self, byte_array, offset, dx, dy):
    """Build sprite from byte_array in EGA modes."""
    row_bytes = (dx+7) // 8
    attrs = []
    for y in range(dy):
        row = bytes_to_interval(byte_array[offset:offset+row_bytes], 8, 1)
        offset += row_bytes
        for plane in range(1, self.bitsperpixel):
            row = or_i(row, bytes_to_interval(byte_array[offset:offset+row_bytes], 8, 1 << plane))
            offset += row_bytes
        attrs.append(row[:dx])
    return attrs

def build_tile_cga(self, pattern):
    """Build a flood-fill tile for CGA screens."""
    tile = []
    bpp = self.bitsperpixel
    strlen = len(pattern)
    # in modes 1, (2), 3, 4, 5, 6 colours are encoded in consecutive bits
    # each byte represents one scan line
    mask = 8 - bpp
    for y in range(strlen):
        line = []
        for x in range(8): # width is 8//bpp
            c = 0
            for b in range(bpp-1, -1, -1):
                c = (c<<1) + ((pattern[y] >> (mask+b)) & 1)
            mask -= bpp
            if mask < 0:
                mask = 8 - bpp
            line.append(c)
        tile.append(line)
    return tile


class GraphicsMode(VideoMode):
    """Default settings for a graphics mode."""

    def __init__(
                self, name, pixel_width, pixel_height,
                text_height, text_width,
                attr, palette, colours, bitsperpixel,
                interleave_times, bank_size,
                num_pages=None,
                has_blink=False,
                supports_artifacts=False,
                cursor_index=None,
                pixel_aspect=None, aspect=None,
                video_segment=0xb800,
            ):
        """Initialise video mode settings."""
        font_width = int(pixel_width // text_width)
        font_height = int(pixel_height // text_height)
        self.interleave_times = int(interleave_times)
        # cga bank_size = 0x2000 interleave_times=2
        self.bank_size = int(bank_size)
        page_size = self.interleave_times * self.bank_size
        VideoMode.__init__(
            self, name, text_height, text_width,
            font_height, font_width, attr, palette, colours,
            num_pages, has_blink, video_segment, page_size
        )
        self.is_text_mode = False
        self.bitsperpixel = int(bitsperpixel)
        # number of pixels referenced in each byte of a plane
        self.ppb = 8 // self.bitsperpixel
        self.num_attr = 2**self.bitsperpixel
        self.bytes_per_row = int(pixel_width) * self.bitsperpixel // 8
        self.supports_artifacts = supports_artifacts
        self.cursor_index = cursor_index
        if pixel_aspect:
            self.pixel_aspect = pixel_aspect
        else:
            self.pixel_aspect = (self.pixel_height * aspect[0], self.pixel_width * aspect[1])

    def coord_ok(self, page, x, y):
        """Check if a page and coordinates are within limits."""
        return (
            page >= 0 and page < self.num_pages and
            x >= 0 and x < self.pixel_width and
            y >= 0 and y < self.pixel_height
        )

    def cutoff_coord(self, x, y):
        """Ensure coordinates are within screen + 1 pixel."""
        return min(self.pixel_width, max(-1, x)), min(self.pixel_height, max(-1, y))

    def set_plane(self, plane):
        """Set the current colour plane (EGA only)."""
        pass

    def set_plane_mask(self, mask):
        """Set the current colour plane mask (EGA only)."""
        pass


class CGAMode(GraphicsMode):
    """Default settings for a CGA graphics mode."""

    def get_coords(self, addr):
        """Get video page and coordinates for address."""
        addr = int(addr) - self.video_segment * 0x10
        # modes 1-5: interleaved scan lines, pixels sequentially packed into bytes
        page, addr = addr//self.page_size, addr%self.page_size
        # 2 x interleaved scan lines of 80bytes
        bank, offset = addr//self.bank_size, addr%self.bank_size
        row, col = offset//self.bytes_per_row, offset%self.bytes_per_row
        x = col * 8 // self.bitsperpixel
        y = bank + self.interleave_times * row
        return page, x, y

    def set_memory(self, screen, addr, byte_array):
        """Set bytes in CGA memory."""
        for page, x, y, ofs, length in walk_memory(self, addr, len(byte_array)):
            screen.drawing.put_interval(
                page, x, y, bytes_to_interval(byte_array[ofs:ofs+length], self.ppb)
            )

    def get_memory(self, screen, addr, num_bytes):
        """Retrieve bytes from CGA memory."""
        byte_array = bytearray(num_bytes)
        for page, x, y, ofs, length in walk_memory(self, addr, num_bytes):
            byte_array[ofs:ofs+length] = interval_to_bytes(
                screen.pixels.pages[page].get_interval(x, y, length*self.ppb), self.ppb
            )
        return byte_array

    def sprite_size_to_record(self, dx, dy):
        """Write 4-byte record of sprite size."""
        return struct.pack('<HH', dx*self.bitsperpixel, dy)

    def record_to_sprite_size(self, byte_array):
        """Read 4-byte record of sprite size."""
        return struct.unpack('<HH', byte_array[0:4])

    def sprite_to_array(self, attrs, dx, dy, byte_array, offs):
        """Build the sprite byte array."""
        row_bytes = (dx * self.bitsperpixel + 7) // 8
        length = row_bytes*dy
        if offs+length > len(byte_array):
            # NOTE: if we use memoryviews instead of bytearrays, we won't need
            # this check as the assignment will fail with ValueError anyway
            raise ValueError('Sprite exceeds array byte size')
        byte_array[offs:offs+length] = b'\0'*length
        for row in attrs:
            byte_array[offs:offs+row_bytes] = interval_to_bytes(row, 8//self.bitsperpixel, 0)
            offs += row_bytes

    def array_to_sprite(self, byte_array, offset, dx, dy):
        """Build sprite from byte_array."""
        row_bytes = (dx * self.bitsperpixel + 7) // 8
        # illegal fn call if outside screen boundary
        attrs = []
        for y in range(dy):
            row = bytes_to_interval(byte_array[offset:offset+row_bytes], 8//self.bitsperpixel, 1)
            offset += row_bytes
            attrs.append(row[:dx])
        return attrs

    build_tile = build_tile_cga


class EGAMode(GraphicsMode):
    """Default settings for a EGA graphics mode."""

    def __init__(
                self, name, pixel_width, pixel_height,
                text_height, text_width,
                attr, palette, colours, bitsperpixel,
                interleave_times, bank_size, num_pages,
                colours1=None, has_blink=False, planes_used=range(4),
                aspect=None
            ):
        """Initialise video mode settings."""
        GraphicsMode.__init__(
            self, name, pixel_width, pixel_height,
            text_height, text_width,
            attr, palette, colours, bitsperpixel,
            interleave_times, bank_size,
            num_pages, has_blink, aspect=aspect
        )
        # EGA uses colour planes, 1 bpp for each plane
        self.ppb = 8
        self.bytes_per_row = pixel_width // 8
        self.video_segment = 0xa000
        self.planes_used = planes_used
        # additional colour plane mask
        self.master_plane_mask = sum([ 2**x for x in planes_used ])
        # this is a reference
        self.colours1 = colours1
        # current ega memory colour plane to read
        self.plane = 0
        # current ega memory colour planes to write to
        self.plane_mask = 0xff

    def set_plane(self, plane):
        """Set the current colour plane."""
        self.plane = plane

    def set_plane_mask(self, mask):
        """Set the current colour plane mask."""
        self.plane_mask = mask

    def get_coords(self, addr):
        """Get video page and coordinates for address."""
        addr = int(addr) - self.video_segment * 0x10
        # modes 7-9: 1 bit per pixel per colour plane
        page, addr = addr//self.page_size, addr%self.page_size
        x, y = (addr%self.bytes_per_row)*8, addr//self.bytes_per_row
        return page, x, y

    def get_memory(self, screen, addr, num_bytes):
        """Retrieve bytes from EGA memory."""
        plane = self.plane % (max(self.planes_used)+1)
        byte_array = bytearray(num_bytes)
        if plane not in self.planes_used:
            return byte_array
        for page, x, y, ofs, length in walk_memory(self, addr, num_bytes):
            byte_array[ofs:ofs+length] = interval_to_bytes(
                screen.pixels.pages[page].get_interval(x, y, length*self.ppb),
                self.ppb, plane
            )
        return byte_array

    def set_memory(self, screen, addr, byte_array):
        """Set bytes in EGA video memory."""
        # EGA memory is planar with memory-mapped colour planes.
        # Within a plane, 8 pixels are encoded into each byte.
        # The colour plane is set through a port OUT and
        # determines which bit of each pixel's attribute is affected.
        mask = self.plane_mask & self.master_plane_mask
        # return immediately for unused colour planes
        if mask == 0:
            return
        for page, x, y, ofs, length in walk_memory(self, addr, len(byte_array)):
            screen.drawing.put_interval(page, x, y,
                bytes_to_interval(byte_array[ofs:ofs+length], self.ppb, mask), mask
            )

    sprite_to_array = sprite_to_array_ega
    array_to_sprite = array_to_sprite_ega

    sprite_size_to_record = sprite_size_to_record_ega
    record_to_sprite_size = record_to_sprite_size_ega

    def build_tile(self, pattern):
        """Build a flood-fill tile."""
        tile = []
        bpp = self.bitsperpixel
        while len(pattern) % bpp != 0:
            # finish off the pattern with zeros
            pattern.append(0)
        strlen = len(pattern)
        # in modes (2), 7, 8, 9 each byte represents 8 bits
        # colour planes encoded in consecutive bytes
        mask = 7
        for y in range(strlen//bpp):
            line = []
            for x in range(8):
                c = 0
                for b in range(bpp-1, -1, -1):
                    c = (c<<1) + ((pattern[(y*bpp+b)%strlen] >> mask) & 1)
                mask -= 1
                if mask < 0:
                    mask = 7
                line.append(c)
            tile.append(line)
        return tile


class Tandy6Mode(GraphicsMode):
    """Default settings for Tandy graphics mode 6."""

    def __init__(self, *args, **kwargs):
        """Initialise video mode settings."""
        GraphicsMode.__init__(self, *args, **kwargs)
        # mode 6: 4x interleaved scan lines, 8 pixels per two bytes,
        # low attribute bits stored in even bytes, high bits in odd bytes.
        self.bytes_per_row = self.pixel_width * 2 // 8
        self.video_segment = 0xb800

    def get_coords(self, addr):
        """Get video page and coordinates for address."""
        addr =  int(addr) - self.video_segment * 0x10
        page, addr = addr//self.page_size, addr%self.page_size
        # 4 x interleaved scan lines of 160bytes
        bank, offset = addr//self.bank_size, addr%self.bank_size
        row, col = offset//self.bytes_per_row, offset%self.bytes_per_row
        x = (col // 2) * 8
        y = bank + 4 * row
        return page, x, y

    def get_memory(self, screen, addr, num_bytes):
        """Retrieve bytes from Tandy 640x200x4 """
        # 8 pixels per 2 bytes
        # low attribute bits stored in even bytes, high bits in odd bytes.
        half_len = (num_bytes+1) // 2
        hbytes = bytearray(half_len), bytearray(half_len)
        for parity in (0, 1):
            for page, x, y, ofs, length in walk_memory(self, addr, num_bytes, 2):
                hbytes[parity][ofs:ofs+length] = interval_to_bytes(
                    screen.pixels.pages[page].get_interval(x, y, length*self.ppb*2),
                    self.ppb*2, parity ^ (addr%2)
                )
        # resulting array may be too long by one byte, so cut to size
        return [item for pair in zip(*hbytes) for item in pair] [:num_bytes]

    def set_memory(self, screen, addr, byte_array):
        """Set bytes in Tandy 640x200x4 memory."""
        hbytes = byte_array[0::2], byte_array[1::2]
        # Tandy-6 encodes 8 pixels per byte, alternating colour planes.
        # I.e. even addresses are 'colour plane 0', odd ones are 'plane 1'
        for parity in (0, 1):
            mask = 2 ** (parity^(addr%2))
            for page, x, y, ofs, length in walk_memory(self, addr, len(byte_array), 2):
                screen.drawing.put_interval(
                    page, x, y,
                    bytes_to_interval(hbytes[parity][ofs:ofs+length], 2*self.ppb, mask),
                    mask
                )

    sprite_to_array = sprite_to_array_ega
    array_to_sprite = array_to_sprite_ega

    sprite_size_to_record = sprite_size_to_record_ega
    record_to_sprite_size = record_to_sprite_size_ega

    build_tile = build_tile_cga
