#include <stdio.h>
#include <SDL.h>
#include <unistd.h>
#include <time.h>

#include "platform.h"
#include "system.h"

#include "gfx_window_manager_api.h"
#include "gfx_screen_config.h"

static SDL_Window* wnd;
static SDL_GLContext ctx;
static SDL_Renderer* renderer;
static int sdl_to_lus_table[512];
static bool vsync_enabled = true;
// OTRTODO: These are redundant. Info can be queried from SDL.
static int window_width = DESIRED_SCREEN_WIDTH;
static int window_height = DESIRED_SCREEN_HEIGHT;
static uint32_t fullscreen_flag = SDL_WINDOW_FULLSCREEN_DESKTOP;
static bool fullscreen_state;
static bool maximized_state;
static bool is_running = true;
static void (*on_fullscreen_changed_callback)(bool is_now_fullscreen);

static int target_fps = 120; // above 60 since vsync is enabled by default
static uint64_t previous_time;
static uint64_t qpc_freq;

#define FRAME_INTERVAL_US_NUMERATOR 1000000
#define FRAME_INTERVAL_US_DENOMINATOR (target_fps)

static void set_fullscreen(bool on, bool call_callback) {
    if (fullscreen_state == on) {
        return;
    }
    fullscreen_state = on;
    SDL_SetWindowFullscreen(wnd, on ? fullscreen_flag : 0);
    if (call_callback && on_fullscreen_changed_callback) {
        on_fullscreen_changed_callback(on);
    }
}

static void set_maximize_window(bool on) {
	if (maximized_state == on) {
		return;
	}
	maximized_state = on;
	if (on) {
		SDL_MaximizeWindow(wnd);
	} else {
		SDL_RestoreWindow (wnd);
	}
}

static void gfx_sdl_get_active_window_refresh_rate(uint32_t* refresh_rate) {
    int display_in_use = SDL_GetWindowDisplayIndex(wnd);

    SDL_DisplayMode mode;
    SDL_GetCurrentDisplayMode(display_in_use, &mode);
    *refresh_rate = mode.refresh_rate;
}

static void gfx_sdl_init(const struct GfxWindowInitSettings *set) {
    window_width = set->width;
    window_height = set->height;

#ifdef SDL_HINT_VIDEO_HIGHDPI_DISABLED
    if (!set->allow_hidpi) {
        // HiDPI control, if available
        SDL_SetHint(SDL_HINT_VIDEO_HIGHDPI_DISABLED, "1");
#if defined(PLATFORM_WIN32) && defined(SDL_HINT_WINDOWS_DPI_AWARENESS)
        // if HiDPI is disabled, declare ourselves DPI aware to get 1:1 window size on Windows
        SDL_SetHint(SDL_HINT_WINDOWS_DPI_AWARENESS, "permonitor");
#endif
    }
#endif

    if (SDL_Init(SDL_INIT_VIDEO) != 0) {
        sysFatalError("Could not init SDL:\n%s", SDL_GetError());
    }

    SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24);
    SDL_GL_SetAttribute(SDL_GL_STENCIL_SIZE, 8);
    SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_COMPATIBILITY);
    if (sysArgCheck("--debug-gl")) {
        SDL_GL_SetAttribute(SDL_GL_CONTEXT_FLAGS, SDL_GL_CONTEXT_DEBUG_FLAG);
    }

    int posX = set->x;
    int posY = set->y;
    int display_in_use = SDL_GetWindowDisplayIndex(wnd);
    if (display_in_use < 0) { // Fallback to default if out of bounds
        posX = 100;
        posY = 100;
    }

    if (set->fullscreen_is_exclusive) {
        fullscreen_flag = SDL_WINDOW_FULLSCREEN;
    }

    Uint32 flags = SDL_WINDOW_SHOWN | SDL_WINDOW_RESIZABLE | SDL_WINDOW_OPENGL;

    // if fullscreen was requested, start the window in fullscreen right away
    if (set->fullscreen) {
        flags |= fullscreen_flag;
        fullscreen_state = true;
    }

    if (set->maximized) {
        flags |= SDL_WINDOW_MAXIMIZED;
        maximized_state = true;
    }

#ifdef SDL_WINDOW_ALLOW_HIGHDPI
    if (set->allow_hidpi) {
        flags |= SDL_WINDOW_ALLOW_HIGHDPI;
    }
#endif

    wnd = SDL_CreateWindow(set->title, posX, posY, window_width, window_height, flags);
    if (!wnd) {
        sysFatalError("Could not open SDL window:\n%s", SDL_GetError());
    }

    // ideally we need 3.0 compat
    // if that doesn't work, try 3.2 core in case we're on mac, 2.1 compat as a last resort
    static u32 glver[][3] = {
        { 0, 0, 0                                    }, // for command line override
        { 3, 0, SDL_GL_CONTEXT_PROFILE_COMPATIBILITY },
        { 3, 2, SDL_GL_CONTEXT_PROFILE_CORE },
        { 4, 1, SDL_GL_CONTEXT_PROFILE_CORE },
        { 2, 1, SDL_GL_CONTEXT_PROFILE_COMPATIBILITY }, // will still require GLSL130
    };

    u32 glcore = false;
    u32 verstart = 1;
    const u32 verend = sizeof(glver) / sizeof(*glver);
    const char *verstr = sysArgGetString("--gl-version");
    if (verstr && *verstr) {
        // user override
        glver[0][2] = strstr(verstr, "core") ? SDL_GL_CONTEXT_PROFILE_CORE :
            SDL_GL_CONTEXT_PROFILE_COMPATIBILITY;
        sscanf(verstr, "%d.%d", &glver[0][0], &glver[0][1]);
        if (glver[0][0] >= 1 && glver[0][0] <= 4 && glver[0][1] < 9) {
            verstart = 0;
        }
    }

    ctx = NULL;
    u32 vmin = 0, vmaj = 0;
    for (u32 i = verstart; i < verend; ++i) {
        vmaj = glver[i][0];
        vmin = glver[i][1];
        SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, vmaj);
        SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, vmin);
        SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, glver[i][2]);
        ctx = SDL_GL_CreateContext(wnd);
        if (!ctx) {
            sysLogPrintf(LOG_WARNING, "GL: could not create GL%d.%d context: %s", vmaj, vmin, SDL_GetError());
        } else {
            glcore = (glver[i][2] == SDL_GL_CONTEXT_PROFILE_CORE);
            break;
        }
    }

    if (!ctx) {
        sysFatalError("Could not create an OpenGL context of any supported version.\nSDL error: %s", SDL_GetError());
    } else {
        sysLogPrintf(LOG_NOTE, "GL: created GL%d.%d%s context", vmaj, vmin, glcore ? "core" : "");
    }

    SDL_GL_MakeCurrent(wnd, ctx);
    SDL_GL_SetSwapInterval(1);

    qpc_freq = SDL_GetPerformanceFrequency();
}

static void gfx_sdl_close(void) {
    is_running = false;
}

static void gfx_sdl_set_fullscreen_changed_callback(void (*on_fullscreen_changed)(bool is_now_fullscreen)) {
    on_fullscreen_changed_callback = on_fullscreen_changed;
}

static void gfx_sdl_set_fullscreen(bool enable) {
    set_fullscreen(enable, true);
}

static void gfx_sdl_set_fullscreen_exclusive(bool enable) {
    const uint32_t newflag = enable ? SDL_WINDOW_FULLSCREEN : SDL_WINDOW_FULLSCREEN_DESKTOP;
    if (fullscreen_flag != newflag) {
        fullscreen_flag = newflag;
        // reset fullscreen to take new value into account if it already is in fullscreen
        if (fullscreen_state) {
            fullscreen_state = false;
            set_fullscreen(enable, true);
        }
    }
}

static void gfx_sdl_set_maximize_window(bool enable) {
    set_maximize_window(enable);
}

static void gfx_sdl_set_cursor_visibility(bool visible) {
    if (visible) {
        SDL_ShowCursor(SDL_ENABLE);
    } else {
        SDL_ShowCursor(SDL_DISABLE);
    }
}

static void gfx_sdl_get_dimensions(uint32_t* width, uint32_t* height, int32_t* posX, int32_t* posY) {
    SDL_GL_GetDrawableSize(wnd, static_cast<int*>((void*)width), static_cast<int*>((void*)height));
    SDL_GetWindowPosition(wnd, static_cast<int*>(posX), static_cast<int*>(posY));
}

static void gfx_sdl_handle_events(void) {
    SDL_Event event;
    while (SDL_PollEvent(&event)) {
        switch (event.type) {
            case SDL_KEYDOWN:
                if (event.key.keysym.sym == SDLK_RETURN && (event.key.keysym.mod & KMOD_ALT)) {
                    // alt-enter received, switch fullscreen state
                    set_fullscreen(!fullscreen_state, true);
                }
                break;
            case SDL_WINDOWEVENT:
                if (event.window.event == SDL_WINDOWEVENT_SIZE_CHANGED) {
                    SDL_GL_GetDrawableSize(wnd, &window_width, &window_height);
                } else if (event.window.event == SDL_WINDOWEVENT_CLOSE &&
                           event.window.windowID == SDL_GetWindowID(wnd)) {
                    // We listen specifically for main window close because closing main window
                    // on macOS does not trigger SDL_Quit.
                    exit(0);
                }
                break;
            case SDL_QUIT:
                exit(0);
                break;
        }
    }
}

static bool gfx_sdl_start_frame(void) {
    return true;
}

static uint64_t qpc_to_100ns(uint64_t qpc) {
    return qpc / qpc_freq * 10000000 + qpc % qpc_freq * 10000000 / qpc_freq;
}

static inline void sync_framerate_with_timer(void) {
    uint64_t t;
    t = qpc_to_100ns(SDL_GetPerformanceCounter());

    const int64_t next = previous_time + 10 * FRAME_INTERVAL_US_NUMERATOR / FRAME_INTERVAL_US_DENOMINATOR;
    int64_t left = next - t;
    // We want to exit a bit early, so we can busy-wait the rest to never miss the deadline
    left -= 15000UL;
    if (left > 0) {
        sysSleep(left);
    }

    do {
        sysCpuRelax();
        t = qpc_to_100ns(SDL_GetPerformanceCounter());
    } while ((int64_t)t < next);

    t = qpc_to_100ns(SDL_GetPerformanceCounter());
    if (left > 0 && t - next < 10000) {
        // In case it takes some time for the application to wake up after sleep,
        // or inaccurate timer,
        // don't let that slow down the framerate.
        t = next;
    }
    previous_time = t;
}

static void gfx_sdl_swap_buffers_begin(void) {
    if (target_fps) {
        sync_framerate_with_timer();
    }
    SDL_GL_SwapWindow(wnd);
}

static void gfx_sdl_swap_buffers_end(void) {

}

static double gfx_sdl_get_time(void) {
    return SDL_GetPerformanceCounter() / (double)qpc_freq;
}

static void gfx_sdl_set_target_fps(int fps) {
    target_fps = fps;
}

static bool gfx_sdl_can_disable_vsync(void) {
    return true;
}

static void *gfx_sdl_get_window_handle(void) {
    return (void *)wnd;
}

static void gfx_sdl_set_window_title(const char *title) {
    SDL_SetWindowTitle(wnd, title);
}

static bool gfx_sdl_set_swap_interval(int interval) {
    const bool success = SDL_GL_SetSwapInterval(interval) >= 0;
    vsync_enabled = success && (interval != 0);
    if (!success) {
        sysLogPrintf(LOG_WARNING, "SDL: failed to set vsync %d: %s", interval, SDL_GetError());
    }
    return success;
}

struct GfxWindowManagerAPI gfx_sdl = { 
    gfx_sdl_init,
    gfx_sdl_close,
    gfx_sdl_set_fullscreen_changed_callback,
    gfx_sdl_set_fullscreen,
    gfx_sdl_set_fullscreen_exclusive,
    gfx_sdl_set_maximize_window,
    gfx_sdl_get_active_window_refresh_rate,
    gfx_sdl_set_cursor_visibility,
    gfx_sdl_get_dimensions,
    gfx_sdl_handle_events,
    gfx_sdl_start_frame,
    gfx_sdl_swap_buffers_begin,
    gfx_sdl_swap_buffers_end,
    gfx_sdl_get_time,
    gfx_sdl_set_target_fps,
    gfx_sdl_can_disable_vsync,
    gfx_sdl_get_window_handle,
    gfx_sdl_set_window_title,
    gfx_sdl_set_swap_interval,
};