"""Pygame Drawing algorithms written in Python. (Work in Progress)

Implement Pygame's Drawing Algorithms in a Python version for testing
and debugging.
"""

from collections import namedtuple
from math import floor, ceil


#   H E L P E R   F U N C T I O N S    #

# fractional part of x


def frac(value):
    """return fractional part of x"""
    return value - floor(value)


def inv_frac(value):
    """return inverse fractional part of x"""
    return 1 - (value - floor(value))  # eg, 1 - frac(x)


BoundingBox = namedtuple("BoundingBox", ["left", "top", "right", "bottom"])
Point = namedtuple("Point", ["x", "y"])


#   L O W   L E V E L   D R A W   F U N C T I O N S   #
# (They are too low-level to be translated into python, right?)


def set_at(surf, in_x, in_y, color):
    """Set the color of a pixel in a surface"""
    surf.set_at((in_x, in_y), color)


def draw_pixel(surf, pos, color, bright, blend=True):
    """draw one blended pixel with given brightness."""
    try:
        other_col = surf.get_at(pos) if blend else (0, 0, 0, 0)
    except IndexError:  # pixel outside the surface
        return
    new_color = tuple(
        (bright * col + (1 - bright) * pix) for col, pix in zip(color, other_col)
    )
    # FIXME what should happen if only one, color or surf_col, has alpha?
    surf.set_at(pos, new_color)


def _drawhorzline(surf, color, x_from, in_y, x_to):
    if x_from == x_to:
        surf.set_at((x_from, in_y), color)
        return

    start, end = (x_from, x_to) if x_from <= x_to else (x_to, x_from)
    for line_x in range(start, end + 1):
        surf.set_at((line_x, in_y), color)


def _drawvertline(surf, color, in_x, y_from, y_to):
    if y_from == y_to:
        surf.set_at((in_x, y_from), color)
        return

    start, end = (y_from, y_to) if y_from <= y_to else (y_to, y_from)
    for line_y in range(start, end + 1):
        surf.set_at((in_x, line_y), color)


#    I N T E R N A L   D R A W   L I N E   F U N C T I O N S    #


def _clip_and_draw_horizline(surf, color, x_from, in_y, x_to):
    """draw clipped horizontal line."""
    # check Y inside surf
    clip = surf.get_clip()
    if in_y < clip.y or in_y >= clip.y + clip.h:
        return

    x_from = max(x_from, clip.x)
    x_to = min(x_to, clip.x + clip.w - 1)

    # check any x inside surf
    if x_to < clip.x or x_from >= clip.x + clip.w:
        return

    _drawhorzline(surf, color, x_from, in_y, x_to)


def _clip_and_draw_vertline(surf, color, in_x, y_from, y_to):
    """draw clipped vertical line."""
    # check X inside surf
    clip = surf.get_clip()

    if in_x < clip.x or in_x >= clip.x + clip.w:
        return

    y_from = max(y_from, clip.y)
    y_to = min(y_to, clip.y + clip.h - 1)

    # check any y inside surf
    if y_to < clip.y or y_from >= clip.y + clip.h:
        return

    _drawvertline(surf, color, in_x, y_from, y_to)


# These constants xxx_EDGE are "outside-the-bounding-box"-flags
LEFT_EDGE = 0x1
RIGHT_EDGE = 0x2
BOTTOM_EDGE = 0x4
TOP_EDGE = 0x8


def encode(pos, b_box):
    """returns a code that defines position with respect to a bounding box"""
    # we use the fact that python interprets booleans (the inequalities)
    # as 0/1, and then multiply them with the xxx_EDGE flags
    return (
        (pos[0] < b_box.left) * LEFT_EDGE
        + (pos[0] > b_box.right) * RIGHT_EDGE
        + (pos[1] < b_box.top) * TOP_EDGE
        + (pos[1] > b_box.bottom) * BOTTOM_EDGE
    )


def clip_line(line, b_box, use_float=False):
    """Algorithm to calculate the clipped line.

    We calculate the coordinates of the part of the line segment within the
    bounding box (defined by left, top, right, bottom). The we write
    the coordinates of the line segment into "line", much like the C-algorithm.
    With `use_float` True, clip_line is usable for float-clipping.

    Returns: true if the line segment cuts the bounding box (false otherwise)
    """

    def inside(code):
        return not code

    def accept(code_a, code_b):
        return not (code_a or code_b)

    def reject(code_a, code_b):
        return code_a and code_b

    assert isinstance(line, list)
    x_1, y_1, x_2, y_2 = line
    dtype = float if use_float else int

    while True:
        # the coordinates are progressively modified with the codes,
        # until they are either rejected or correspond to the final result.
        code1 = encode((x_1, y_1), b_box)
        code2 = encode((x_2, y_2), b_box)

        if accept(code1, code2):
            # write coordinates into "line" !
            line[:] = x_1, y_1, x_2, y_2
            return True
        if reject(code1, code2):
            return False

        # We operate on the (x_1, y_1) point,
        # and swap if it is inside the bbox:
        if inside(code1):
            x_1, x_2 = x_2, x_1
            y_1, y_2 = y_2, y_1
            code1, code2 = code2, code1
        slope = (y_2 - y_1) / float(x_2 - x_1) if (x_2 != x_1) else 1.0
        # Each case, if true, means that we are outside the border:
        # calculate x_1 and y_1 to be the "first point" inside the bbox...
        if code1 & LEFT_EDGE:
            y_1 += dtype((b_box.left - x_1) * slope)
            x_1 = b_box.left
        elif code1 & RIGHT_EDGE:
            y_1 += dtype((b_box.right - x_1) * slope)
            x_1 = b_box.right
        elif code1 & BOTTOM_EDGE:
            if x_2 != x_1:
                x_1 += dtype((b_box.bottom - y_1) / slope)
            y_1 = b_box.bottom
        elif code1 & TOP_EDGE:
            if x_2 != x_1:
                x_1 += dtype((b_box.top - y_1) / slope)
            y_1 = b_box.top


def _draw_line(surf, color, start, end):
    """draw a non-horizontal line (without anti-aliasing)."""
    # Variant of https://en.wikipedia.org/wiki/Bresenham's_line_algorithm
    #
    # This strongly differs from craw.c implementation, because we use a
    # "slope" variable (instead of delta_x and delta_y) and a "error" variable.
    # And we can not do pointer-arithmetic with "BytesPerPixel", like in
    # the C-algorithm.
    if start.x == end.x:
        # This case should not happen...
        raise ValueError

    slope = abs((end.y - start.y) / (end.x - start.x))
    error = 0.0

    if slope < 1:
        # Here, it's a rather horizontal line

        # 1. check in which octants we are & set init values
        if end.x < start.x:
            start.x, end.x = end.x, start.x
            start.y, end.y = end.y, start.y
        line_y = start.y
        dy_sign = 1 if (start.y < end.y) else -1

        # 2. step along x coordinate
        for line_x in range(start.x, end.x + 1):
            set_at(surf, line_x, line_y, color)
            error += slope
            if error >= 0.5:
                line_y += dy_sign
                error -= 1
    else:
        # Case of a rather vertical line

        # 1. check in which octants we are & set init values
        if start.y > end.y:
            start.x, end.x = end.x, start.x
            start.y, end.y = end.y, start.y
        line_x = start.x
        slope = 1 / slope
        dx_sign = 1 if (start.x < end.x) else -1

        # 2. step along y coordinate
        for line_y in range(start.y, end.y + 1):
            set_at(surf, line_x, line_y, color)
            error += slope
            if error >= 0.5:
                line_x += dx_sign
                error -= 1


def _draw_aaline(surf, color, start, end, blend):
    """draw an anti-aliased line.

    The algorithm yields identical results with _draw_line for horizontal,
    vertical or diagonal lines, and results changes smoothly when changing
    any of the endpoint coordinates.

    Note that this yields strange results for very short lines, eg
    a line from (0, 0) to (0, 1) will draw 2 pixels, and a line from
    (0, 0) to (0, 1.1) will blend 10 % on the pixel (0, 2).
    """
    # The different requirements that we have on an antialiasing algorithm
    # implies to make some compromises:
    # 1. We want smooth evolution wrt to the 4 endpoint coordinates
    #    (this means also that we want a smooth evolution when the angle
    #     passes +/- 45°
    # 2. We want the same behavior when swapping the endpoints
    # 3. We want understandable results for the endpoint values
    #    (eg we want to avoid half-integer values to draw a simple plain
    #     horizontal or vertical line between two integer l endpoints)
    #
    # This implies to somehow make the line artificially 1 pixel longer
    # and to draw a full pixel when we have the  endpoints are identical.
    d_x = end.x - start.x
    d_y = end.y - start.y

    if d_x == 0 and d_y == 0:
        # For smoothness reasons, we could also do some blending here,
        # but it seems overshoot...
        set_at(surf, int(start.x), int(start.y), color)
        return

    if start.x > end.x or start.y > end.y:
        start.x, end.x = end.x, start.x
        start.y, end.y = end.y, start.y
        d_x = -d_x
        d_y = -d_y

    if abs(d_x) >= abs(d_y):
        slope = d_y / d_x

        def draw_two_pixel(in_x, float_y, factor):
            flr_y = floor(float_y)
            draw_pixel(surf, (in_x, flr_y), color, factor * inv_frac(float_y), blend)
            draw_pixel(surf, (in_x, flr_y + 1), color, factor * frac(float_y), blend)

        _draw_aaline_dx(d_x, slope, end, start, draw_two_pixel)
    else:
        slope = d_x / d_y

        def draw_two_pixel(float_x, in_y, factor):
            fl_x = floor(float_x)
            draw_pixel(surf, (fl_x, in_y), color, factor * inv_frac(float_x), blend)
            draw_pixel(surf, (fl_x + 1, in_y), color, factor * frac(float_x), blend)

        _draw_aaline_dy(d_y, slope, end, start, draw_two_pixel)


def _draw_aaline_dy(d_y, slope, end, start, draw_two_pixel):
    g_y = ceil(start.y)
    g_x = start.x + (g_y - start.y) * slope
    # 1. Draw start of the segment
    if start.y < g_y:
        draw_two_pixel(g_x - slope, floor(start.y), inv_frac(start.y))
    # 2. Draw end of the segment
    rest = frac(end.y)
    s_y = ceil(end.y)
    if rest > 0:
        s_x = start.x + slope * (d_y + 1 - rest)
        draw_two_pixel(s_x, s_y, rest)
    else:
        s_y += 1
    # 3. loop for other points
    for line_y in range(g_y, s_y):
        line_x = g_x + slope * (line_y - g_y)
        draw_two_pixel(line_x, line_y, 1)


def _draw_aaline_dx(d_x, slope, end, start, draw_two_pixel):
    # A and G are respectively left and right to the "from" point, but
    # with integer-x-coordinate, (and only if from_x is not integer).
    # Hence they appear in following order on the line in general case:
    #  A   from-pt    G    .  .  .        to-pt    S
    #  |------*-------|--- .  .  . ---|-----*------|-
    g_x = ceil(start.x)
    g_y = start.y + (g_x - start.x) * slope
    # 1. Draw start of the segment if we have a non-integer-part
    if start.x < g_x:
        # this corresponds to the point "A"
        draw_two_pixel(floor(start.x), g_y - slope, inv_frac(start.x))
    # 2. Draw end of the segment: we add one pixel for homogeneity reasons
    rest = frac(end.x)
    s_x = ceil(end.x)
    if rest > 0:
        # Again we draw only if we have a non-integer-part
        s_y = start.y + slope * (d_x + 1 - rest)
        draw_two_pixel(s_x, s_y, rest)
    else:
        s_x += 1
    # 3. loop for other points
    for line_x in range(g_x, s_x):
        line_y = g_y + slope * (line_x - g_x)
        draw_two_pixel(line_x, line_y, 1)


#   C L I P   A N D   D R A W   L I N E   F U N C T I O N S    #


def _clip_and_draw_line(surf, rect, color, pts):
    """clip the line into the rectangle and draw if needed.

    Returns true if anything has been drawn, else false."""
    # "pts" is a list with the four coordinates of the two endpoints
    # of the line to be drawn : pts = x1, y1, x2, y2.
    # The data format is like that to stay closer to the C-algorithm.
    if not clip_line(
        pts, BoundingBox(rect.x, rect.y, rect.x + rect.w - 1, rect.y + rect.h - 1)
    ):
        # The line segment defined by "pts" is not crossing the rectangle
        return 0
    if pts[1] == pts[3]:  # eg y1 == y2
        _drawhorzline(surf, color, pts[0], pts[1], pts[2])
    elif pts[0] == pts[2]:  # eg x1 == x2
        _drawvertline(surf, color, pts[0], pts[1], pts[3])
    else:
        _draw_line(surf, color, Point(pts[0], pts[1]), Point(pts[2], pts[3]))
    return 1


def _clip_and_draw_line_width(surf, rect, color, line, width):
    yinc = xinc = 0
    if abs(line[0] - line[2]) > abs(line[1] - line[3]):
        yinc = 1
    else:
        xinc = 1
    newpts = line[:]
    if _clip_and_draw_line(surf, rect, color, newpts):
        anydrawn = 1
        frame = newpts[:]
    else:
        anydrawn = 0
        frame = [10000, 10000, -10000, -10000]

    for loop in range(1, width // 2 + 1):
        newpts[0] = line[0] + xinc * loop
        newpts[1] = line[1] + yinc * loop
        newpts[2] = line[2] + xinc * loop
        newpts[3] = line[3] + yinc * loop
        if _clip_and_draw_line(surf, rect, color, newpts):
            anydrawn = 1
            frame[0] = min(newpts[0], frame[0])
            frame[1] = min(newpts[1], frame[1])
            frame[2] = max(newpts[2], frame[2])
            frame[3] = max(newpts[3], frame[3])

        if loop * 2 < width:
            newpts[0] = line[0] - xinc * loop
            newpts[1] = line[1] - yinc * loop
            newpts[2] = line[2] - xinc * loop
            newpts[3] = line[3] - yinc * loop
            if _clip_and_draw_line(surf, rect, color, newpts):
                anydrawn = 1
                frame[0] = min(newpts[0], frame[0])
                frame[1] = min(newpts[1], frame[1])
                frame[2] = max(newpts[2], frame[2])
                frame[3] = max(newpts[3], frame[3])

    return anydrawn


def _clip_and_draw_aaline(surf, rect, color, line, blend):
    """draw anti-aliased line between two endpoints."""
    if not clip_line(
        line,
        BoundingBox(rect.x - 1, rect.y - 1, rect.x + rect.w, rect.y + rect.h),
        use_float=True,
    ):
        return  # TODO Rect(rect.x, rect.y, 0, 0)
    _draw_aaline(surf, color, Point(line[0], line[1]), Point(line[2], line[3]), blend)
    return  # TODO Rect(-- affected area --)


#    D R A W   L I N E   F U N C T I O N S    #


def draw_aaline(surf, color, from_point, to_point, blend=True):
    """draw anti-aliased line between two endpoints."""
    line = [from_point[0], from_point[1], to_point[0], to_point[1]]
    return _clip_and_draw_aaline(surf, surf.get_clip(), color, line, blend)


def draw_line(surf, color, from_point, to_point, width=1):
    """draw anti-aliased line between two endpoints."""
    line = [from_point[0], from_point[1], to_point[0], to_point[1]]
    return _clip_and_draw_line_width(surf, surf.get_clip(), color, line, width)


#   M U L T I L I N E   F U N C T I O N S   #


def _multi_lines(
    surf,
    color,
    closed,  # pylint: disable=too-many-arguments
    points,
    width=1,
    blend=False,
    aaline=False,
):
    """draw several lines, either anti-aliased or not."""
    # The code for anti-aliased or not is almost identical, so it's factorized
    if len(points) <= 2:
        raise TypeError
    line = [0] * 4  # store x1, y1 & x2, y2 of the lines to be drawn

    xlist = [pt[0] for pt in points]
    ylist = [pt[1] for pt in points]
    line[0] = xlist[0]
    line[1] = ylist[0]
    b_box = BoundingBox(left=xlist[0], right=xlist[0], top=ylist[0], bottom=ylist[0])

    for line_x, line_y in points[1:]:
        b_box.left = min(b_box.left, line_x)
        b_box.right = max(b_box.right, line_x)
        b_box.top = min(b_box.top, line_y)
        b_box.bottom = max(b_box.bottom, line_y)

    rect = surf.get_clip()
    for loop in range(1, len(points)):
        line[0] = xlist[loop - 1]
        line[1] = ylist[loop - 1]
        line[2] = xlist[loop]
        line[3] = ylist[loop]
        if aaline:
            _clip_and_draw_aaline(surf, rect, color, line, blend)
        else:
            _clip_and_draw_line_width(surf, rect, color, line, width)

    if closed:
        line[0] = xlist[len(points) - 1]
        line[1] = ylist[len(points) - 1]
        line[2] = xlist[0]
        line[3] = ylist[0]
        if aaline:
            _clip_and_draw_aaline(surf, rect, color, line, blend)
        else:
            _clip_and_draw_line_width(surf, rect, color, line, width)

    # TODO Rect(...)


def draw_lines(surf, color, closed, points, width=1):
    """draw several lines connected through the points."""
    return _multi_lines(surf, color, closed, points, width, aaline=False)


def draw_aalines(surf, color, closed, points, blend=True):
    """draw several anti-aliased lines connected through the points."""
    return _multi_lines(surf, color, closed, points, blend=blend, aaline=True)


def draw_polygon(surface, color, points, width):
    """Draw a polygon"""
    if width:
        draw_lines(surface, color, 1, points, width)
        return  # TODO Rect(...)
    num_points = len(points)
    point_x = [x for x, y in points]
    point_y = [y for x, y in points]

    miny = min(point_y)
    maxy = max(point_y)

    if miny == maxy:
        minx = min(point_x)
        maxx = max(point_x)
        _clip_and_draw_horizline(surface, color, minx, miny, maxx)
        return  # TODO Rect(...)

    for y_coord in range(miny, maxy + 1):
        x_intersect = []
        for i in range(num_points):
            _draw_polygon_inner_loop(i, point_x, point_y, y_coord, x_intersect)

        x_intersect.sort()
        for i in range(0, len(x_intersect), 2):
            _clip_and_draw_horizline(
                surface, color, x_intersect[i], y_coord, x_intersect[i + 1]
            )

    # special case : horizontal border lines
    for i in range(num_points):
        i_prev = i - 1 if i else num_points - 1
        if miny < point_y[i] == point_y[i_prev] < maxy:
            _clip_and_draw_horizline(
                surface, color, point_x[i], point_y[i], point_x[i_prev]
            )

    return  # TODO Rect(...)


def _draw_polygon_inner_loop(index, point_x, point_y, y_coord, x_intersect):
    i_prev = index - 1 if index else len(point_x) - 1

    y_1 = point_y[i_prev]
    y_2 = point_y[index]

    if y_1 < y_2:
        x_1 = point_x[i_prev]
        x_2 = point_x[index]
    elif y_1 > y_2:
        y_2 = point_y[i_prev]
        y_1 = point_y[index]
        x_2 = point_x[i_prev]
        x_1 = point_x[index]
    else:  # special case handled below
        return

    if (y_2 > y_coord >= y_1) or ((y_coord == max(point_y)) and (y_coord <= y_2)):
        x_intersect.append((y_coord - y_1) * (x_2 - x_1) // (y_2 - y_1) + x_1)