const std = @import("std");
const sdl = @cImport({
    @cInclude("SDL.h");
});

// From: https://github.com/Nelarius/weekend-raytracer-zig/blob/master/src/main.zig
// See https://github.com/zig-lang/zig/issues/565
// SDL_video.h:#define SDL_WINDOWPOS_UNDEFINED         SDL_WINDOWPOS_UNDEFINED_DISPLAY(0)
// SDL_video.h:#define SDL_WINDOWPOS_UNDEFINED_DISPLAY(X)  (SDL_WINDOWPOS_UNDEFINED_MASK|(X))
// SDL_video.h:#define SDL_WINDOWPOS_UNDEFINED_MASK    0x1FFF0000u
const SDL_WINDOWPOS_UNDEFINED = @bitCast(c_int, sdl.SDL_WINDOWPOS_UNDEFINED_MASK);

const win_width = 640;
const win_height = 320;
const fps = 60;

pub fn main() anyerror!void {
    if (sdl.SDL_Init(sdl.SDL_INIT_VIDEO) != 0) {
        std.log.err("Unable to initialize SDL: {}", .{sdl.SDL_GetError()});
        return error.SDLInitializationFailed;
    }
    defer sdl.SDL_Quit();

    const window = sdl.SDL_CreateWindow("Raytracing in One Weekend", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, win_width, win_height, sdl.SDL_WINDOW_OPENGL) orelse {
        std.log.err("Unable to create window: {}", .{sdl.SDL_GetError()});
        return error.SDLInitializationFailed;
    };

    const surface = sdl.SDL_GetWindowSurface(window) orelse {
        std.log.err("Unable to get window surface: {}", .{sdl.SDL_GetError()});
        return error.SDLInitializationFailed;
    };

    {
        _ = sdl.SDL_LockSurface(surface);

        var h: usize = 0;
        while (h < win_height) {
            var w: usize = 0;
            while (w < win_width) {
                // std.log.info("w = {}, h = {}", .{ w, h });
                const index = w * 4 + h * @intCast(usize, surface.*.pitch);
                const target_pixel = @ptrToInt(surface.*.pixels) + index;
                @intToPtr(*u32, target_pixel).* = 0xffffffff;
                w += 1;
            }
            h += 1;
        }
        defer sdl.SDL_UnlockSurface(surface);
    }

    if (sdl.SDL_UpdateWindowSurface(window) != 0) {
        std.log.err("Error updating window surface: {}", .{sdl.SDL_GetError()});
        return error.SDLUpdateWindowFailed;
    }

    var running = true;
    while (running) {
        var event: sdl.SDL_Event = undefined;
        while (sdl.SDL_PollEvent(&event) != 0) {
            switch (event.@"type") {
                sdl.SDL_QUIT => {
                    running = false;
                },
                else => {},
            }
        }
        sdl.SDL_Delay(1000 / fps);
    }
}