#include <SDL2/SDL.h>
#include <SDL2/SDL2_gfxPrimitives.h>
#include <stdio.h>
#include <stdint.h>
#include <unistd.h>
#include <time.h>
#include <limits.h>

#define ENERGY_PATH "/sys/class/powercap/intel-rapl:0/energy_uj"

static uint64_t read_energy_uj(const char *path) {
    FILE *f = fopen(path, "r");
    if (!f) return UINT64_MAX;
    unsigned long long val = 0ULL;
    if (fscanf(f, "%llu", &val) != 1) {
        fclose(f);
        return UINT64_MAX;
    }
    fclose(f);
    return (uint64_t)val;
}

static double cur_time() {
    struct timespec ts; clock_gettime(CLOCK_MONOTONIC, &ts);
    return (double)ts.tv_sec + (double)ts.tv_nsec / 1e9;
}

int running = 1;
double current_watts = 0.0;
SDL_mutex *watt_lock;

int watt_reader(void *arg) {
    const char *path = (const char *)arg;
    uint64_t prev_uj = read_energy_uj(path);
    double prev_t = cur_time();
    while (running) {
        usleep(100000);
        uint64_t curr_uj = read_energy_uj(path);
        if (curr_uj == UINT64_MAX) continue;
        double curr_t = cur_time();
        double dJ = (double)((curr_uj >= prev_uj) ? (curr_uj - prev_uj) : 0ULL) / 1e6;
        double dt = curr_t - prev_t;
        double watts = (dt > 0) ? dJ / dt : 0.0;
        prev_uj = curr_uj;
        prev_t = curr_t;
        SDL_LockMutex(watt_lock);
        current_watts = watts;
        SDL_UnlockMutex(watt_lock);
    }
    return 0;
}

int main(int argc, char **argv) {
    const char *energy_path = (argc > 1) ? argv[1] : ENERGY_PATH;
    int refresh_ms = (argc > 2) ? atoi(argv[2]) : 1000;
    float window_opacity = 1.0f;

    SDL_SetHint(SDL_HINT_X11_WINDOW_TYPE, "_NET_WM_WINDOW_TYPE_DOCK");
    SDL_SetHint(SDL_HINT_VIDEO_X11_NET_WM_BYPASS_COMPOSITOR, "0");
    
    if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_TIMER | SDL_INIT_EVENTS) != 0) return 1;

    SDL_Window *win = SDL_CreateWindow("overlay",
        SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED,
        160, 36,
        SDL_WINDOW_BORDERLESS | SDL_WINDOW_ALWAYS_ON_TOP | SDL_WINDOW_ALLOW_HIGHDPI);

    SDL_SetWindowAlwaysOnTop(win, SDL_TRUE);
    
    SDL_Renderer *ren = SDL_CreateRenderer(win, -1, SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC);
    if (!ren) ren = SDL_CreateRenderer(win, -1, SDL_RENDERER_SOFTWARE);
    
    SDL_SetRenderDrawBlendMode(ren, SDL_BLENDMODE_BLEND);
    SDL_SetWindowOpacity(win, window_opacity);

    int fontScale = 2;
    const int pad = 8;

    watt_lock = SDL_CreateMutex();
    SDL_Thread *reader = SDL_CreateThread(watt_reader, "reader", (void *)energy_path);
    
    int dragging = 0, drag_off_x = 0, drag_off_y = 0;
    char text[64] = "--.-- W";
    uint32_t next_tick = SDL_GetTicks();
    
    while (running) {
        SDL_Event e;
        while (SDL_PollEvent(&e)) {
            switch (e.type) {
                case SDL_QUIT: running = 0; break;
                case SDL_KEYDOWN:
                    switch (e.key.keysym.sym) {
                        case SDLK_ESCAPE: case SDLK_q: running = 0; break;
                        case SDLK_UP: window_opacity += 0.05f; if (window_opacity > 1.0f) window_opacity = 1.0f; SDL_SetWindowOpacity(win, window_opacity); break;
                        case SDLK_DOWN: window_opacity -= 0.05f; if (window_opacity < 0.2f) window_opacity = 0.2f; SDL_SetWindowOpacity(win, window_opacity); break;
                        case SDLK_RIGHT: refresh_ms += 100; if (refresh_ms > 5000) refresh_ms = 5000; break;
                        case SDLK_LEFT: refresh_ms -= 100; if (refresh_ms < 100) refresh_ms = 100; break;
                        case SDLK_EQUALS: case SDLK_PLUS: fontScale++; if (fontScale>6) fontScale=6; break;
                        case SDLK_MINUS: if (fontScale>1) fontScale--; break;
                    }
                    break;
                case SDL_MOUSEBUTTONDOWN:
                    if (e.button.button == SDL_BUTTON_LEFT) {
                        dragging = 1;
                        int wx, wy; SDL_GetWindowPosition(win, &wx, &wy);
                        int mx, my; SDL_GetGlobalMouseState(&mx, &my);
                        drag_off_x = mx - wx; drag_off_y = my - wy;
                    }
                    break;
                case SDL_MOUSEBUTTONUP:
                    if (e.button.button == SDL_BUTTON_LEFT) dragging = 0;
                    break;
                case SDL_MOUSEMOTION:
                    if (dragging) {
                        int mx, my; SDL_GetGlobalMouseState(&mx, &my);
                        SDL_SetWindowPosition(win, mx - drag_off_x, my - drag_off_y);
                    }
                    break;
            }
        }
        uint32_t now = SDL_GetTicks();
        if ((int)(now - next_tick) >= 0) {
            SDL_LockMutex(watt_lock);
            double watts = current_watts;
            SDL_UnlockMutex(watt_lock);
            snprintf(text, sizeof(text), "%.2f W", watts);
            int baseW = (int)strlen(text) * 8;
            int baseH = 8;
            int w = baseW * fontScale + pad*2;
            int h = baseH * fontScale + pad*2;
            SDL_SetWindowSize(win, w, h);
            SDL_SetRenderDrawColor(ren, 0, 0, 0, 0);
            SDL_RenderClear(ren);
            SDL_Texture *tmp = SDL_CreateTexture(ren, SDL_PIXELFORMAT_RGBA8888, SDL_TEXTUREACCESS_TARGET, baseW, baseH);
            SDL_SetTextureBlendMode(tmp, SDL_BLENDMODE_BLEND);
            SDL_SetRenderTarget(ren, tmp);
            SDL_SetRenderDrawColor(ren, 0,0,0,0); SDL_RenderClear(ren);
            stringRGBA(ren, 0, 0, text, 255, 255, 255, 255);
            SDL_SetRenderTarget(ren, NULL);
            SDL_Rect dst = { pad, pad, baseW*fontScale, baseH*fontScale };
            SDL_RenderCopy(ren, tmp, NULL, &dst);
            SDL_DestroyTexture(tmp);
            SDL_RenderPresent(ren);
            next_tick = now + (uint32_t)refresh_ms;
        }
        SDL_Delay(10);
    }
    running = 0;
    SDL_WaitThread(reader, NULL);
    SDL_DestroyMutex(watt_lock);
    SDL_DestroyRenderer(ren);
    SDL_DestroyWindow(win);
    SDL_Quit();
    return 0;
}