import fonts.sans24
import micropython

@micropython.viper
def _bitblit(bitbuf, pixels, bgfg: int, count: int):
    mv = ptr8(bitbuf)
    px = ptr8(pixels)

    bghi = (bgfg >> 24) & 0xff
    bglo = (bgfg >> 16) & 0xff
    fghi = (bgfg >>  8) & 0xff
    fglo = (bgfg      ) & 0xff

    bitselect = 0x80
    pxp = 0
    mvp = 0

    for bit in range(count):
        # Draw the pixel
        active = px[pxp] & bitselect
        mv[mvp] = fghi if active else bghi
        mvp += 1
        mv[mvp] = fglo if active else bglo
        mvp += 1

        # Advance to the next bit
        bitselect >>= 1
        if not bitselect:
            bitselect = 0x80
            pxp += 1

def _bounding_box(s, font):
    w = 0
    for ch in s:
        (_, h, wc) = font.get_ch(ch)
        w += wc + 1

    return (w, h)

def _draw_glyph(display, glyph, x, y, bgfg):
    (px, h, w) = glyph

    buf = memoryview(display.linebuffer)[0:2*(w+1)]
    bytes_per_row = (w + 7) // 8

    for row in range(h):
        _bitblit(buf, px[row*bytes_per_row:], bgfg, w)
        buf[2*w] = 0
        buf[2*w + 1] = 0
        display.rawblit(buf, x, y+row, w+1, 1)

class Draw565(object):
    """Drawing library for RGB565 displays.

    A full framebufer is not required although the library will
    'borrow' a line buffer from the underlying display driver.
    """

    def __init__(self, display):
        """Initialise the library.

        Defaults to white-on-black for monochrome drawing operations
        and 24 pt Sans Serif text.
        """
        self._display = display
        self.set_color(0xffff)
        self.set_font(fonts.sans24)

    def set_color(self, color, bg=0):
        """Set the foreground (color) and background (bg) color.

        The supplied color will be used for all monochrome drawing operations.
        If no background color is provided then the background will be set
        to black.
        """
        self._bgfg = (bg << 16) + color

    def set_font(self, font):
        """Set the font used for rendering text."""
        self._font = font

    def string(self, s, x, y, width=None):
        """Draw a string at the supplied position.

        If no width is provided then the text will be left justified,
        otherwise the text will be centered within the provided width and,
        importantly, the remaining width will be filled with the background
        color (to ensure that if we update one string with a narrower one
        there is no need to "undraw" it)
        """
        display = self._display
        bgfg = self._bgfg
        font = self._font

        if width:
            (w, h) = _bounding_box(s, font)
            leftpad = (width - w) // 2
            rightpad = width - w - leftpad
            display.fill(0, x, y, leftpad, h)
            x += leftpad

        for ch in s:
            glyph = font.get_ch(ch)
            _draw_glyph(display, glyph, x, y, bgfg)
            x += glyph[2] + 1

        if width:
            display.fill(0, x, y, rightpad, h)