# fx-92 Scientifique Collège+ language interpreter: On-screen drawing

from sdl2 import *

class Window:
    """
    An SDL window with pixel scaling.
    """

    BLACK = (0, 0, 0, 255)
    WHITE = (255, 255, 255, 255)

    def __init__(self, width, height, scale, quiet=False):
        self.width = width
        self.height = height
        self.scale = scale
        self.quiet = quiet

    def __enter__(self):
        """
        Enter window context: allocate and create a window.
        """

        if SDL_WasInit(SDL_INIT_VIDEO):
            raise Exception("Cannot create two windows")

        if SDL_Init(SDL_INIT_VIDEO) < 0:
            raise Exception("Failed to initialize SDL")

        # Create the window
        mode = SDL_WINDOW_HIDDEN if self.quiet else SDL_WINDOW_SHOWN
        self.w = SDL_CreateWindow("fx-92 Scientifique Collège+".encode(),
            SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED,
            self.width*self.scale, self.height*self.scale, mode)
        if self.w is None:
            raise Exception("Failed to create window")

        # Create the renderer
        self.r = SDL_CreateRenderer(self.w, -1, SDL_RENDERER_ACCELERATED)
        if self.r is None:
            SDL_DestroyWindow(self.w)
            raise Exception("Failed to create renderer")

        # Create the base texture where things will be rendered at scale 1
        self.t = SDL_CreateTexture(self.r, SDL_PIXELFORMAT_ARGB8888,
            SDL_TEXTUREACCESS_TARGET, self.width, self.height)
        if self.t is None:
            SDL_DestroyRenderer(r)
            SDL_DestroyWindow(w)
            raise Exception("Failed to create texture")

        SDL_SetHint(SDL_HINT_RENDER_SCALE_QUALITY, b'0')
        SDL_SetRenderTarget(self.r, self.t)

        self.clear(self.WHITE)
        self.update()

        return self

    def __exit__(self, *args):
        """
        Exit context: close and destroy window.
        """

        if self.t is not None:
            SDL_SetRenderTarget(self.r, None)
            SDL_DestroyTexture(self.t)
        if self.r is not None:
            SDL_DestroyRenderer(self.r)
        if self.w is not None:
            SDL_DestroyWindow(self.w)

        SDL_Quit()

    def clear(self, color):
        """Clear screen in a uniform color."""

        SDL_SetRenderDrawColor(self.r, *color)
        SDL_RenderClear(self.r)

    def line(self, x1, y1, x2, y2, color):
        """Draw a straight line."""

        SDL_SetRenderDrawColor(self.r, *color)

        # Bresenham line drawing algorithm
        sgn = lambda x: -1 if x < 0 else (1 if x > 0 else 0)

        x, y = x1, y1
        dx, dy = x2 - x1, y2 - y1
        sx, sy = sgn(dx), sgn(dy)
        dx, dy = abs(dx), abs(dy)
        cumul = 0

        SDL_RenderDrawPoint(self.r, x, y)

        if dx >= dy:
            cumul = dx // 2
            for i in range(dx):
                x += sx
                cumul += dy
                if cumul > dx:
                    cumul -= dx
                    y += sy
                SDL_RenderDrawPoint(self.r, x, y)
        else:
            cumul = dy // 2
            for i in range(dy):
                y += sy
                cumul += dx
                if cumul > dy:
                    cumul -= dy
                    x += sx
                SDL_RenderDrawPoint(self.r, x, y)

    def wait(self, allow_any=False):
        """Wait for the window to be closed."""

        if self.quiet:
            return

        event = SDL_Event()
        while 1:
            SDL_WaitEvent(event)

            if event.type == SDL_QUIT:
                break
            if event.type == SDL_KEYDOWN and allow_any:
                break

    def pause(self):
        """Display a pause message."""

        # TODO: Display "paused"
        self.wait(allow_any=True)

    def save(self, out):
        """Save the output into a BMP file."""
        SDL_SetRenderTarget(self.r, self.t)

        surface = SDL_CreateRGBSurface(0, self.width, self.height, 32,0,0,0,0)
        fmt    = surface.contents.format.contents.format
        pixels = surface.contents.pixels
        pitch  = surface.contents.pitch

        SDL_RenderReadPixels(self.r, None, fmt, pixels, pitch);
        SDL_SaveBMP(surface, out.encode())
        SDL_FreeSurface(surface)

    def update(self):
        """Push window contents on-screen."""

        # Target the window with scaling
        SDL_SetRenderTarget(self.r, None)
        SDL_RenderSetScale(self.r, self.scale, self.scale)

        # Push that to the screen
        SDL_RenderCopy(self.r, self.t, None, None)
        SDL_RenderPresent(self.r)

        # Go back to the texture
        SDL_SetRenderTarget(self.r, self.t)
        SDL_RenderSetScale(self.r, 1, 1)