/* -------------------------------------------------------------
 * waveform_tcp.c
 *
 *  * 600×400 ARGB8888 frame is streamed over a single‑client TCP socket.
 *  * The received frame is transformed so that the resulting bitmap
 *    can be displayed on a video waveform monitor and will look like
 *    the original picture.
 *
 *  Build (Linux/macOS):
 *      gcc -Wall -Wextra -pedantic -std=c11 waveform_tcp.c \
 *          -lSDL2 -lpthread -o waveform_tcp
 *
 *  Run:
 *      ./waveform_tcp            # opens a window and listens on 0.0.0.0:12345
 *
 *  Test client (Unix‑like, sends one frame of solid gray):
 *      dd if=/dev/zero bs=1 count=$((600*400*4)) | tr \\0 \\377 > gray.bin
 *      cat gray.bin | nc 127.0.0.1 12345
 *
 * ------------------------------------------------------------- */
#include <SDL2/SDL.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>               // memcpy, memset
#include <unistd.h>               // close, read, write
#include <fcntl.h>                // fcntl
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <errno.h>

/* -------------------------------------------------------------
 * Configuration
 * ------------------------------------------------------------- */
#define WIDTH          800
#define HEIGHT         600
#define LISTEN_PORT    12345          // change if you like
#define BACKLOG        1              // only one pending connection

/* -------------------------------------------------------------
 * Simple pixel helpers (ARGB8888 – 0xAARRGGBB in memory)
 * ------------------------------------------------------------- */
typedef Uint32 pixel_t;

static inline pixel_t make_pixel(Uint8 r, Uint8 g, Uint8 b, Uint8 a)
{
    return (pixel_t)((a << 24) | (r << 16) | (g << 8) | b);
}
#define MAKE_OPAQUE_PIXEL(r,g,b)  make_pixel((r),(g),(b),0xFF)

/* -------------------------------------------------------------
 * Global buffers
 * ------------------------------------------------------------- */
/* 1. The raw frame received from the network */
static pixel_t net_frame[HEIGHT][WIDTH];

/* 2. The image that we actually draw (after the waveform conversion) */
static pixel_t draw_buf[HEIGHT][WIDTH];

/* -------------------------------------------------------------
 * Demo pattern – what we see until the first network frame arrives
 * ------------------------------------------------------------- */
static void init_demo_pattern(void)
{
    for (int y = 0; y < HEIGHT; ++y) {
        for (int x = 0; x < WIDTH; ++x) {
            Uint8 r = (HEIGHT-y)*255/HEIGHT;//(Uint8)((x * 255) / (WIDTH  - 1));
            Uint8 g = (HEIGHT-y)*255/HEIGHT;//(Uint8)((y * 255) / (HEIGHT - 1));
            Uint8 b = (HEIGHT-y)*255/HEIGHT;//0x80;
            draw_buf[y][x] = MAKE_OPAQUE_PIXEL(r, g, b);
        }
    }
}

/* -------------------------------------------------------------
 * Luminance conversion – ITU‑BT.601 (Y = 0.299R + 0.587G + 0.114B)
 * ------------------------------------------------------------- */
static inline Uint8 rgb_to_luma(Uint8 r, Uint8 g, Uint8 b)
{
    /* weighted sum, integer arithmetic, rounded */
    return (Uint8)((299 * r + 587 * g + 114 * b) / 1000);
}

/* -------------------------------------------------------------
 * Transform the raw ARGB frame into a waveform‑ready image.
 *
 *   * dest is the global draw_buf
 *   * every source pixel (sx, sy) becomes a white dot at
 *         dx = sx
 *         dy = round( luma * (HEIGHT‑1) / 255 )
 *
 * The whole destination buffer is cleared to black first.
 * ------------------------------------------------------------- */
static void convert_to_waveform(void)
{
    const pixel_t WHITE = 0xFFFFFFFFU;   /* ARGB = opaque white */
    const pixel_t BLACK = 0xFF000000U;   /* opaque black (background) */

    /* 1. clear destination */
    for (int y = 0; y < HEIGHT; ++y)
        memset(draw_buf[y], 0, WIDTH * sizeof(pixel_t));
    for (int y = 0; y < HEIGHT; ++y)
        for (int x = 0; x < WIDTH; ++x)
            draw_buf[y][x] = BLACK;

    /* 2. plot points */
    for (int sy = 0; sy < HEIGHT; ++sy) {
        for (int sx = 0; sx < WIDTH; ++sx) {
            pixel_t p = net_frame[sy][sx];
            Uint8 r = (Uint8)((p >> 16) & 0xFF);
            Uint8 g = (Uint8)((p >>  8) & 0xFF);
            Uint8 b = (Uint8)( p        & 0xFF);

            Uint8 luma = rgb_to_luma(r, g, b);          /* 0‑255 */
	    if(luma >= 150)
		    draw_buf[sy][sx] = 0xff<<24 | (255-sy/2) << 16 | (255-sy/2) << 8 | (255-sy/2);                  /* overwrite – white dot */
	    else
		    draw_buf[sy][sx] = 0xff<<24;
		    //draw_buf[sy][sx] = (255-sy/2)<<24 | 0xFFFFFFU;
        }
    }
}

/* -------------------------------------------------------------
 * ----------  TCP SERVER  ------------------------------------
 * ------------------------------------------------------------- */

/* Returns a non‑blocking listening socket, or -1 on error. */
static int create_listen_socket(void)
{
    int lst = socket(AF_INET, SOCK_STREAM, 0);
    if (lst < 0) {
        perror("socket");
        return -1;
    }

    int opt = 1;
    setsockopt(lst, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));

    struct sockaddr_in addr = {
        .sin_family = AF_INET,
        .sin_port   = htons(LISTEN_PORT),
        .sin_addr   = { .s_addr = INADDR_ANY }
    };

    if (bind(lst, (struct sockaddr *)&addr, sizeof(addr)) < 0) {
        perror("bind");
        close(lst);
        return -1;
    }

    if (listen(lst, BACKLOG) < 0) {
        perror("listen");
        close(lst);
        return -1;
    }

    /* make non‑blocking */
    int flags = fcntl(lst, F_GETFL, 0);
    fcntl(lst, F_SETFL, flags | O_NONBLOCK);

    printf("[net] Listening on 0.0.0.0:%d (single client allowed)\n", LISTEN_PORT);
    return lst;
}

/* Helper – set a socket to non‑blocking mode */
static void set_nonblocking(int fd)
{
    int flags = fcntl(fd, F_GETFL, 0);
    if (flags != -1) fcntl(fd, F_SETFL, flags | O_NONBLOCK);
}

/* -------------------------------------------------------------
 * MAIN
 * ------------------------------------------------------------- */
int main(void)
{
    /* ---------- SDL initialisation -------------------------------- */
    if (SDL_Init(SDL_INIT_VIDEO) != 0) {
        fprintf(stderr, "SDL_Init error: %s\n", SDL_GetError());
        return EXIT_FAILURE;
    }

    SDL_Window   *window   = SDL_CreateWindow("Waveform‑ready demo (TCP input)",
                                             SDL_WINDOWPOS_CENTERED,
                                             SDL_WINDOWPOS_CENTERED,
                                             WIDTH, HEIGHT,
                                             SDL_WINDOW_SHOWN);
    if (!window) {
        fprintf(stderr, "SDL_CreateWindow error: %s\n", SDL_GetError());
        SDL_Quit();
        return EXIT_FAILURE;
    }

    SDL_Renderer *renderer = SDL_CreateRenderer(window, -1,
                               SDL_RENDERER_ACCELERATED |
                               SDL_RENDERER_PRESENTVSYNC);
    if (!renderer) {
        fprintf(stderr, "SDL_CreateRenderer error: %s\n", SDL_GetError());
        SDL_DestroyWindow(window);
        SDL_Quit();
        return EXIT_FAILURE;
    }

    SDL_Texture *texture = SDL_CreateTexture(renderer,
                               SDL_PIXELFORMAT_ARGB8888,
                               SDL_TEXTUREACCESS_STREAMING,
                               WIDTH, HEIGHT);
    if (!texture) {
        fprintf(stderr, "SDL_CreateTexture error: %s\n", SDL_GetError());
        SDL_DestroyRenderer(renderer);
        SDL_DestroyWindow(window);
        SDL_Quit();
        return EXIT_FAILURE;
    }

    /* ---------- Demo pattern (until first network frame) ---------- */
    init_demo_pattern();

    /* ---------- Networking --------------------------------------- */
    int listen_sock = create_listen_socket();   /* may be -1 on failure */
    int client_sock = -1;                       /* -1 → no client yet */

    const size_t FRAME_BYTES = WIDTH * HEIGHT * sizeof(pixel_t);
    size_t recv_offset = 0;                     /* bytes already received */

    bool quit = false;
    SDL_Event ev;

    /* ---------- Main loop --------------------------------------- */
    while (!quit) {
        /* 1) SDL events */
        while (SDL_PollEvent(&ev)) {
            if (ev.type == SDL_QUIT) quit = true;
            else if (ev.type == SDL_KEYDOWN && ev.key.keysym.sym == SDLK_ESCAPE)
                quit = true;
        }

        /* 2) Accept a new client if none is present */
        if (listen_sock >= 0 && client_sock < 0) {
            struct sockaddr_in remote;
            socklen_t remote_len = sizeof(remote);
            int tmp = accept(listen_sock,
                             (struct sockaddr *)&remote,
                             &remote_len);
            if (tmp >= 0) {
                client_sock = tmp;
                set_nonblocking(client_sock);
                recv_offset = 0;
                char ip[INET_ADDRSTRLEN];
                inet_ntop(AF_INET, &remote.sin_addr, ip, sizeof(ip));
                printf("[net] Client connected from %s:%d\n", ip,
                       ntohs(remote.sin_port));
            } else if (errno != EAGAIN && errno != EWOULDBLOCK) {
                perror("[net] accept");
            }
        }

        /* 3) Read raw pixel data from the client */
        if (client_sock >= 0) {
            size_t still_needed = FRAME_BYTES - recv_offset;
            ssize_t n = recv(client_sock,
                             ((Uint8 *)net_frame) + recv_offset,
                             still_needed,
                             0);
            if (n > 0) {
                recv_offset += (size_t)n;
                if (recv_offset == FRAME_BYTES) {
                    /* Full frame received – convert to waveform image */
                    convert_to_waveform();
                    recv_offset = 0;          /* ready for the next frame */
                }
            } else if (n == 0) {
                printf("[net] Client disconnected.\n");
                close(client_sock);
                client_sock = -1;
            } else if (n < 0 && errno != EAGAIN && errno != EWOULDBLOCK) {
                perror("[net] recv");
                close(client_sock);
                client_sock = -1;
            }
        }

        /* 4) Copy the (possibly transformed) draw buffer into the texture */
        void *tex_pixels;
        int   tex_pitch;
        if (SDL_LockTexture(texture, NULL, &tex_pixels, &tex_pitch) != 0) {
            fprintf(stderr, "SDL_LockTexture error: %s\n", SDL_GetError());
            break;
        }

        for (int y = 0; y < HEIGHT; ++y) {
            memcpy((Uint8 *)tex_pixels + y * tex_pitch,
                   draw_buf[y],
                   WIDTH * sizeof(pixel_t));
        }
        SDL_UnlockTexture(texture);

        /* 5) Render */
        SDL_RenderClear(renderer);
        SDL_RenderCopy(renderer, texture, NULL, NULL);
        SDL_RenderPresent(renderer);
        /* VSYNC caps the loop to the monitor refresh rate. */
    }

    /* -------------------------------------------------------------
     * Cleanup
     * ------------------------------------------------------------- */
    if (client_sock >= 0) close(client_sock);
    if (listen_sock >= 0) close(listen_sock);

    SDL_DestroyTexture(texture);
    SDL_DestroyRenderer(renderer);
    SDL_DestroyWindow(window);
    SDL_Quit();

    return EXIT_SUCCESS;
}