#include "SDL_error.h"
#include "SDL_stdinc.h"
#include "SDL_surface.h"
#include "mgba/core/config.h"
#include <stdint.h>
#define SDL_MAIN_USE_CALLBACKS 1
#include "SDL3/SDL_init.h"
#include "SDL3/SDL_log.h"
#include "SDL3/SDL_main.h"
#include "SDL3/SDL_pixels.h"
#include "SDL3/SDL_render.h"
#include "SDL3/SDL_timer.h"
#include "SDL3/SDL_video.h"

#include "mgba/core/core.h"
#include "mgba/core/interface.h"
#include "mgba/feature/commandline.h"
#include "mgba-util/image.h"

static SDL_Window* window = NULL;
static SDL_Renderer* renderer = NULL;
static SDL_Camera* camera = NULL;
static SDL_CameraSpec spec;
static SDL_Texture* texture = NULL;
static SDL_bool texture_updated = SDL_FALSE;
static SDL_Surface* frame_current = NULL;
static SDL_CameraDeviceID front_camera = 0;
static SDL_CameraDeviceID back_camera = 0;
static SDL_Surface* scaled = NULL;
static SDL_Surface* screen = NULL;

static struct mCore* core = NULL;

enum mColorFormat pixfmt_sdl_to_mgba(uint32_t sdl_fmt) {
    switch (sdl_fmt) {
        case SDL_PIXELFORMAT_ABGR1555: return mCOLOR_BGR5;
        case SDL_PIXELFORMAT_ABGR8888: return mCOLOR_ABGR8;
        case SDL_PIXELFORMAT_ARGB1555: return mCOLOR_RGB5;
        case SDL_PIXELFORMAT_ARGB8888: return mCOLOR_ARGB8;
        case SDL_PIXELFORMAT_BGR565: return mCOLOR_BGR565;
        case SDL_PIXELFORMAT_BGRA8888: return mCOLOR_BGRA8;
        case SDL_PIXELFORMAT_BGRX8888: return mCOLOR_BGRX8;
        case SDL_PIXELFORMAT_RGB565: return mCOLOR_RGB565;
        case SDL_PIXELFORMAT_RGBA8888: return mCOLOR_RGBA8;
        case SDL_PIXELFORMAT_RGBX8888: return mCOLOR_RGBX8;
        case SDL_PIXELFORMAT_XBGR1555: return mCOLOR_BGR5;
        case SDL_PIXELFORMAT_XBGR8888: return mCOLOR_XBGR8;
        case SDL_PIXELFORMAT_XRGB1555: return mCOLOR_RGB5;
        case SDL_PIXELFORMAT_XRGB8888: return mCOLOR_XRGB8;
        // does this even make sense?
        case SDL_PIXELFORMAT_INDEX8: return mCOLOR_PAL8;
        // others don't quite match between mgba and SDL
        default: return mCOLOR_ANY;
    }
}

void myStartRequestImage(struct mImageSource* self, unsigned w, unsigned h, int colorFormats) {
    SDL_DestroySurface(scaled);
    scaled = SDL_CreateSurface(w, h, SDL_PIXELFORMAT_XBGR1555);

    SDL_Log("scaled: %d x %d", w, h);
    
//    SDL_DestroyTexture(texture);
//    texture = SDL_CreateTextureFromSurface(renderer, scaled);
}

void myStopRequestImage(struct mImageSource* self) {
    SDL_DestroySurface(scaled);
    scaled = NULL;
}

void myRequestImage(struct mImageSource* self, const void** buf, size_t* stride, enum mColorFormat* fmt) {
    if (scaled != NULL && frame_current != NULL) {
        struct SDL_Rect srcrect = frame_current->clip_rect;
        int w = srcrect.h * scaled->clip_rect.w / scaled->clip_rect.h;
        if (w >= srcrect.w) {
            srcrect.x = (srcrect.w - w) / 2;
            srcrect.w = w;
        } else {
            int h = srcrect.w * scaled->clip_rect.h / scaled->clip_rect.w;
            srcrect.y = (srcrect.h - h) / 2;
            srcrect.h = h;
        }
        int res = SDL_BlitSurfaceScaled(frame_current, &srcrect, scaled, &scaled->clip_rect, SDL_SCALEMODE_NEAREST);
        if (res != 0) {
            SDL_Log("failed to scale: %s", SDL_GetError());
        }
        *fmt = pixfmt_sdl_to_mgba(scaled->format->format);
        *stride = scaled->pitch / (BYTES_PER_PIXEL / scaled->format->bytes_per_pixel);
        *buf = scaled->pixels;
    }
}

const struct mImageSource gb_img_src = {
    .requestImage = myRequestImage,
    .startRequestImage = myStartRequestImage,
    .stopRequestImage = myStopRequestImage,
};

int SDL_AppInit(int argc, char *argv[]) {
    int devcount = 0;
    int i;

    struct mArguments args = {};
    bool parsed = mArgumentsParse(&args, argc, argv, NULL, 0);

    /* Enable standard application logging */
    SDL_LogSetPriority(SDL_LOG_CATEGORY_APPLICATION, SDL_LOG_PRIORITY_INFO);

    if (!parsed) {
        SDL_Log("Couldn't parse arguments");
        return -1;
    }

    core = mCoreFind(args.fname);
    if (!core || !core->init(core)) {
        SDL_Log("Couldn't initialize mgba core!");
        return -1;
    }

    if (!mCoreLoadFile(core, args.fname)) {
        SDL_Log("Failed to load ROM");
        return -1;
    }

    mCoreConfigInit(&core->config, NULL);
    //mCoreConfigLoad(&core->config);

    mArgumentsApply(&args, NULL, 0, &core->config);
    mCoreConfigSetDefaultValue(&core->config, "idleOptimization", "detect");
    mCoreConfigSetDefaultValue(&core->config, "sgb.borders", "0");

    mCoreLoadConfig(core);

    unsigned w, h;
    core->currentVideoSize(core, &w, &h);

    if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_CAMERA) != 0) {
        SDL_Log("Couldn't initialize SDL3: %s", SDL_GetError());
        return -1;
    }

    window = SDL_CreateWindow("cgbwebcam", w, h, 0);
    if (!window) {
        SDL_Log("Couldn't create window: %s", SDL_GetError());
        return -1;
    }

    renderer = SDL_CreateRenderer(window, NULL, 0);
    if (!renderer) {
        SDL_Log("Couldn't create renderer: %s", SDL_GetError());
        return -1;
    }

    SDL_LogSetAllPriority(SDL_LOG_PRIORITY_VERBOSE);

    SDL_CameraDeviceID *devices = SDL_GetCameraDevices(&devcount);
    if (!devices) {
        SDL_Log("SDL_GetCameraDevices failed: %s", SDL_GetError());
        return -1;
    }

    SDL_Log("Saw %d camera devices.", devcount);
    for (i = 0; i < devcount; i++) {
        const SDL_CameraDeviceID device = devices[i];
        char *name = SDL_GetCameraDeviceName(device);
        const SDL_CameraPosition position = SDL_GetCameraDevicePosition(device);
        const char *posstr = "";
        if (position == SDL_CAMERA_POSITION_FRONT_FACING) {
            front_camera = device;
            posstr = "[front-facing] ";
        } else if (position == SDL_CAMERA_POSITION_BACK_FACING) {
            back_camera = device;
            posstr = "[back-facing] ";
        }
        SDL_Log("  - Camera #%d: %s %s", i, posstr, name);
        SDL_free(name);
    }

    const SDL_CameraDeviceID devid = front_camera ? front_camera : devices[0];  /* no front-facing? just take the first one. */
    SDL_free(devices);

    if (!devid) {
        SDL_Log("No cameras available?");
        return -1;
    }

    SDL_CameraSpec spec = {
        .format = SDL_PIXELFORMAT_XBGR1555,
        .width = 320,
        .height = 240,
        .interval_numerator = 1,
        .interval_denominator = 30,
    };
    camera = SDL_OpenCameraDevice(devid, &spec);
    if (!camera) {
        SDL_Log("Failed to open camera device: %s", SDL_GetError());
        return -1;
    }

#if BYTES_PER_PIXEL == 4
    screen = SDL_CreateSurface(w, h, SDL_PIXELFORMAT_XBGR8888);
#elif BYTES_PER_PIXEL == 2
    screen = SDL_CreateSurface(w, h, SDL_PIXELFORMAT_XBGR1555);
#else
    #error "unknown pixel format"
#endif
    core->setVideoBuffer(core, screen->pixels, screen->pitch / BYTES_PER_PIXEL);

    /* Create texture with appropriate format */
    texture = SDL_CreateTextureFromSurface(renderer, screen);
    if (!texture) {
        SDL_Log("Couldn't create texture: %s", SDL_GetError());
        return -1;
    }

    core->setPeripheral(core, mPERIPH_IMAGE_SOURCE, (void*)&gb_img_src);

    core->reset(core);

    core->setKeys(core, 0);
    for (i = 0; i < 600; i++) {
        core->runFrame(core);
    }
    core->setKeys(core, 1); // title screen
    core->runFrame(core);
    core->setKeys(core, 0);
    for (i = 0; i < 25; i++) {
        core->runFrame(core);
    }
    core->setKeys(core, 1); // select 'shoot'
    core->runFrame(core);
    core->setKeys(core, 0);
    for (i = 0; i < 75; i++) {
        core->runFrame(core);
    }
    core->setKeys(core, 1); // select 'shoot' again
    core->runFrame(core);
    core->setKeys(core, 0);
    for (i = 0; i < 100; i++) {
        core->runFrame(core);
    }

    return 0;  /* start the main app loop. */
}

static int FlipCamera(void) {
    static Uint64 last_flip = 0;
    if ((SDL_GetTicks() - last_flip) < 3000) {  /* must wait at least 3 seconds between flips. */
        return 0;
    }

    if (camera) {
        const SDL_CameraDeviceID current = SDL_GetCameraInstanceID(camera);
        SDL_CameraDeviceID nextcam = 0;
        if (current == front_camera) {
            nextcam = back_camera;
        } else if (current == back_camera) {
            nextcam = front_camera;
        }

        if (nextcam) {
            SDL_Log("Flip camera!");

            if (frame_current) {
                SDL_ReleaseCameraFrame(camera, frame_current);
                frame_current = NULL;
            }

            SDL_CloseCamera(camera);

            camera = SDL_OpenCameraDevice(nextcam, NULL);
            if (!camera) {
                SDL_Log("Failed to open camera device: %s", SDL_GetError());
                return -1;
            }

            last_flip = SDL_GetTicks();
        }
    }

    return 0;
}

int SDL_AppEvent(const SDL_Event *event) {
    switch (event->type) {
        case SDL_EVENT_KEY_DOWN: {
            const SDL_Keycode sym = event->key.keysym.sym;
            if (sym == SDLK_ESCAPE || sym == SDLK_AC_BACK) {
                SDL_Log("Key : Escape!");
                return 1;
            } else if (sym == SDLK_SPACE) {
                FlipCamera();
                return 0;
            }
            break;
        }

        case SDL_EVENT_MOUSE_BUTTON_DOWN:
            /* !!! FIXME: only flip if clicked in the area of a "flip" icon. */
            return FlipCamera();

        case SDL_EVENT_QUIT:
            SDL_Log("Quit!");
            return 1;

        case SDL_EVENT_CAMERA_DEVICE_APPROVED:
            SDL_Log("Camera approved!");
            if (SDL_GetCameraFormat(camera, &spec) < 0) {
                SDL_Log("Couldn't get camera spec: %s", SDL_GetError());
                return -1;
            }
            break;

        case SDL_EVENT_CAMERA_DEVICE_DENIED:
            SDL_Log("Camera denied!");
            return -1;
    }

    return 0;
}

int SDL_AppIterate(void) {
    SDL_SetRenderDrawColor(renderer, 0x99, 0x99, 0x99, 255);
    SDL_RenderClear(renderer);

    Uint64 timestampNS = 0;
    SDL_Surface *frame_next = camera ? SDL_AcquireCameraFrame(camera, &timestampNS) : NULL;

    if (frame_next) {
        if (frame_current) {
            if (SDL_ReleaseCameraFrame(camera, frame_current) < 0) {
                SDL_Log("err SDL_ReleaseCameraFrame: %s", SDL_GetError());
            }
        }

        SDL_Log("new frame %d x %d %s", frame_next->w, frame_next->h, SDL_GetPixelFormatName(frame_next->format->format));
        
        /* It's not needed to keep the frame once updated the texture is updated.
         * But in case of 0-copy, it's needed to have the frame while using the texture.
         */
         frame_current = frame_next;
         texture_updated = SDL_FALSE;
    }

    core->runFrame(core);
    /* Update SDL_Texture with last video frame (only once per new frame) */
    if (frame_current && !texture_updated) {
//        if (scaled) SDL_UpdateTexture(texture, NULL, scaled->pixels, scaled->pitch);
        SDL_UpdateTexture(texture, NULL, screen->pixels, screen->pitch);
        texture_updated = SDL_TRUE;
    }

    SDL_RenderTexture(renderer, texture, NULL, NULL);
    SDL_RenderPresent(renderer);

    return 0;  /* keep iterating. */
}

void SDL_AppQuit(void) {
    mCoreConfigDeinit(&core->config);
    core->deinit(core);

    SDL_ReleaseCameraFrame(camera, frame_current);
    SDL_CloseCamera(camera);
    SDL_DestroyTexture(texture);
    SDL_DestroyRenderer(renderer);
    SDL_DestroyWindow(window);
}