#define SDL_MAIN_USE_CALLBACKS 1
#include "SDL3/SDL_blendmode.h"
#include "SDL3/SDL_error.h"
#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_stdinc.h"
#include "SDL3/SDL_surface.h"
#include "SDL3/SDL_timer.h"
#include "SDL3/SDL_video.h"

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

#define NUM_CHANNELS 3
#define FRAMESKIP_LIMIT 20

#if BYTES_PER_PIXEL == 4
    #define SCREEN_FMT SDL_PIXELFORMAT_XBGR8888
#elif BYTES_PER_PIXEL == 2
    #define SCREEN_FMT SDL_PIXELFORMAT_XBGR1555
#else
    #error "unknown pixel format"
#endif

static SDL_Window* window = NULL;
static SDL_Renderer* renderer = NULL;
static SDL_Camera* camera = NULL;
static SDL_CameraSpec spec;
static SDL_Texture* textures[NUM_CHANNELS] = { NULL, NULL, NULL };
static SDL_bool texture_updated = SDL_FALSE;
static SDL_CameraDeviceID front_camera = 0;
static SDL_CameraDeviceID back_camera = 0;
static SDL_Surface* scaled = NULL;
static SDL_Surface* filtered[NUM_CHANNELS] = { NULL, NULL, NULL };
static SDL_Surface* screens[NUM_CHANNELS] = { NULL, NULL, NULL };

static struct mCore* cores[NUM_CHANNELS] = { NULL, NULL, 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 myStartRequestImageRed(struct mImageSource* self, unsigned w, unsigned h, int colorFormats) {
    SDL_DestroySurface(scaled);
    SDL_DestroySurface(filtered[0]);
    scaled = SDL_CreateSurface(w, h, SDL_PIXELFORMAT_XBGR1555);
    filtered[0] = SDL_CreateSurface(w, h, SDL_PIXELFORMAT_XBGR1555);
    SDL_Log("red: %d x %d", w, h);
}

void myStartRequestImageGreen(struct mImageSource* self, unsigned w, unsigned h, int colorFormats) {
    SDL_DestroySurface(filtered[1]);
    filtered[1] = SDL_CreateSurface(w, h, SDL_PIXELFORMAT_XBGR1555);
    SDL_Log("green: %d x %d", w, h);
}

void myStartRequestImageBlue(struct mImageSource* self, unsigned w, unsigned h, int colorFormats) {
    SDL_DestroySurface(filtered[2]);
    filtered[2] = SDL_CreateSurface(w, h, SDL_PIXELFORMAT_XBGR1555);
    SDL_Log("blue: %d x %d", w, h);
}

void myStopRequestImageRed(struct mImageSource* self) {
    SDL_DestroySurface(scaled);
    SDL_DestroySurface(filtered[0]);
    scaled = NULL;
    filtered[0] = NULL;
}

void myStopRequestImageGreen(struct mImageSource* self) {
    SDL_DestroySurface(filtered[1]);
    filtered[1] = NULL;
}

void myStopRequestImageBlue(struct mImageSource* self) {
    SDL_DestroySurface(filtered[2]);
    filtered[2] = NULL;
}

void myRequestImageRed(struct mImageSource* self, const void** buf, size_t* stride, enum mColorFormat* fmt) {
    SDL_Surface* source = filtered[0];
    if (source != NULL) {
        *fmt = pixfmt_sdl_to_mgba(source->format->format);
        *stride = source->pitch / (BYTES_PER_PIXEL / source->format->bytes_per_pixel);
        *buf = source->pixels;
    }
}

void myRequestImageGreen(struct mImageSource* self, const void** buf, size_t* stride, enum mColorFormat* fmt) {
    SDL_Surface* source = filtered[1];
    if (source != NULL) {
        *fmt = pixfmt_sdl_to_mgba(source->format->format);
        *stride = source->pitch / (BYTES_PER_PIXEL / source->format->bytes_per_pixel);
        *buf = source->pixels;
    }
}

void myRequestImageBlue(struct mImageSource* self, const void** buf, size_t* stride, enum mColorFormat* fmt) {
    SDL_Surface* source = filtered[2];
    if (source != NULL) {
        *fmt = pixfmt_sdl_to_mgba(source->format->format);
        *stride = source->pitch / (BYTES_PER_PIXEL / source->format->bytes_per_pixel);
        *buf = source->pixels;
    }
}

struct mImageSource gb_img_src[3];

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

    SDL_CameraDeviceID *devices;
    SDL_CameraDeviceID devid;

    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;
    }

    gb_img_src[0].requestImage = myRequestImageRed;
    gb_img_src[0].startRequestImage = myStartRequestImageRed;
    gb_img_src[0].stopRequestImage = myStopRequestImageRed;
    gb_img_src[1].requestImage = myRequestImageGreen;
    gb_img_src[1].startRequestImage = myStartRequestImageGreen;
    gb_img_src[1].stopRequestImage = myStopRequestImageGreen;
    gb_img_src[2].requestImage = myRequestImageBlue;
    gb_img_src[2].startRequestImage = myStartRequestImageBlue;
    gb_img_src[2].stopRequestImage = myStopRequestImageBlue;

    for (i = 0; i < NUM_CHANNELS; i++) {
        struct mCore* 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);

        cores[i] = core;
    }

    /* without loss of generality */
    cores[0]->currentVideoSize(cores[0], &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, SDL_RENDERER_PRESENTVSYNC);
    if (!renderer) {
        SDL_Log("Couldn't create renderer: %s", SDL_GetError());
        return -1;
    }

    SDL_LogSetAllPriority(SDL_LOG_PRIORITY_VERBOSE);

    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);
    }

    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;
    }

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

    for (i = 0; i < NUM_CHANNELS; i++) {
        int j;
        struct mCore* core = cores[i];
        SDL_Texture* texture;
        SDL_Surface* screen = SDL_CreateSurface(w, h, SCREEN_FMT);

        core->setVideoBuffer(core, screen->pixels, screen->pitch / BYTES_PER_PIXEL);
        screens[i] = screen;

        /* Create texture with appropriate format */
        texture = SDL_CreateTextureFromSurface(renderer, screens[0]);
        if (!texture) {
            SDL_Log("Couldn't create texture: %s", SDL_GetError());
            return -1;
        }
        SDL_SetTextureBlendMode(texture, SDL_BLENDMODE_ADD);
        textures[i] = texture;

        core->setPeripheral(core, mPERIPH_IMAGE_SOURCE, &gb_img_src[i]);

        core->reset(core);

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

        SDL_Log("prepared core %d", i);
    }

    SDL_SetTextureColorMod(textures[0], 255, 0, 0);
    SDL_SetTextureColorMod(textures[1], 0, 255, 0);
    SDL_SetTextureColorMod(textures[2], 0, 0, 255);

    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!");

            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) {
    int i;
    static int since_last_present = 0;

    if (scaled != NULL) {
        Uint64 timestampNS = 0;
        SDL_Surface *frame = camera ? SDL_AcquireCameraFrame(camera, &timestampNS) : NULL;

        if (frame) {
            struct SDL_Rect srcrect = frame->clip_rect;
            int w = srcrect.h * scaled->clip_rect.w / scaled->clip_rect.h;

            /*SDL_Log("new frame %d x %d %s", frame->w, frame->h, SDL_GetPixelFormatName(frame->format->format));*/
            texture_updated = SDL_FALSE;

            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;
            }
            if (SDL_BlitSurfaceScaled(frame, &srcrect, scaled, &scaled->clip_rect, SDL_SCALEMODE_NEAREST) < 0) {
                SDL_Log("failed to scale: %s", SDL_GetError());
            }

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

            SDL_SetSurfaceColorMod(scaled, 255, 0, 0);
            SDL_BlitSurface(scaled, NULL, filtered[0], NULL);
            SDL_SetSurfaceColorMod(scaled, 0, 255, 0);
            SDL_BlitSurface(scaled, NULL, filtered[1], NULL);
            SDL_SetSurfaceColorMod(scaled, 0, 0, 255);
            SDL_BlitSurface(scaled, NULL, filtered[2], NULL);
        }
    }

    if (since_last_present < FRAMESKIP_LIMIT) {
        for (i = 0; i < NUM_CHANNELS; i++) {
            struct mCore* core = cores[i];
            core->runFrame(core);
        }
    }

    if (!texture_updated) {
        SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255);
        SDL_RenderClear(renderer);

        /* Update SDL_Texture with last video frame (only once per new frame) */
        for (i = 0; i < NUM_CHANNELS; i++) {
            SDL_Surface* screen = screens[i];
            SDL_Texture* texture = textures[i];
            SDL_UpdateTexture(texture, NULL, screen->pixels, screen->pitch);
            texture_updated = SDL_TRUE;
            SDL_RenderTexture(renderer, texture, NULL, NULL);
        }

        SDL_RenderPresent(renderer);
        since_last_present = 0;
    } else {
        since_last_present++;
        if (since_last_present >= FRAMESKIP_LIMIT) {
          SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255);
          SDL_RenderClear(renderer);
          for (i = 0; i < NUM_CHANNELS; i++) {
            SDL_Texture *texture = textures[i];
            SDL_RenderTexture(renderer, texture, NULL, NULL);
          }
          SDL_RenderPresent(renderer);
        }
    }

    return 0;  /* keep iterating. */
}

void SDL_AppQuit(void) {
    int i;
    for (i = 0; i < NUM_CHANNELS; i++) {
        mCoreConfigDeinit(&cores[i]->config);
        cores[i]->deinit(cores[i]);
        SDL_DestroyTexture(textures[i]);
    }

    SDL_CloseCamera(camera);
    SDL_DestroyRenderer(renderer);
    SDL_DestroyWindow(window);
}