#include <ncurses.h>
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>

#define ROW_SIZE 16
#define CTRL_KEY(k) ((k) & 0x1f)

unsigned char* buffer;
long file_size;
char* filename;
int cursor_pos = 0;
int scroll_offset = 0;

void load_file(const char* fname) {
  FILE* f = fopen(fname, "rb");
  if (!f) {
    perror("Nie można otworzyć pliku");
    exit(1);
  }

  fseek(f, 0, SEEK_END);
  file_size = ftell(f);
  rewind(f);

  buffer = malloc(file_size);
  fread(buffer, 1, file_size, f);
  fclose(f);
}

void save_file() {
  FILE* f = fopen(filename, "wb");
  if (f) {
    fwrite(buffer, 1, file_size, f);
    fclose(f);
  }
}
void draw_interface() {
  clear();
  int max_y, max_x;
  getmaxyx(stdscr, max_y, max_x);

  attron(COLOR_PAIR(1));
  mvprintw(0, 0, "HEXED: %s (ROZMIAR: %ld bajtow)", filename, file_size);
  mvprintw(
      1, 0,
      "^S: Zapisz | ^Q: Wyjscie | Strzalki: Nawigacja | +/-: Zmien wartosc");
  mvhline(2, 0, ACS_HLINE, max_x);
  attroff(COLOR_PAIR(1));

  int rows_to_draw = max_y - 4;

  for (int i = 0; i < rows_to_draw; i++) {
    int offset = scroll_offset + (i * ROW_SIZE);
    if (offset >= file_size) break;

    attron(COLOR_PAIR(1));
    mvprintw(3 + i, 0, "%08X: ", offset);
    attroff(COLOR_PAIR(1));

    for (int j = 0; j < ROW_SIZE; j++) {
      if (offset + j < file_size) {
        unsigned char val = buffer[offset + j];
        int color_pair = (val == 0x00) ? 3 : 2;

        if (offset + j == cursor_pos) {
          attron(COLOR_PAIR(4));
          printw("%02X ", val);
          attroff(COLOR_PAIR(4));
        } else {
          attron(COLOR_PAIR(color_pair));
          printw("%02X ", val);
          attroff(COLOR_PAIR(color_pair));
        }
      } else {
        printw("   ");
      }
    }

    printw("| ");

    for (int j = 0; j < ROW_SIZE; j++) {
      if (offset + j < file_size) {
        unsigned char c = buffer[offset + j];
        char ch = (isprint(c)) ? c : '.';
        int color_pair = (c == 0x00) ? 3 : 2;

        if (offset + j == cursor_pos) {
          attron(COLOR_PAIR(4));
          printw("%c", ch);
          attroff(COLOR_PAIR(4));
        } else {
          attron(COLOR_PAIR(color_pair));
          printw("%c", ch);
          attroff(COLOR_PAIR(color_pair));
        }
      }
    }
  }
  refresh();
}
void update_byte(int ch) {
  int val = -1;
  if (ch >= '0' && ch <= '9') val = ch - '0';
  if (ch >= 'a' && ch <= 'f') val = ch - 'a' + 10;
  if (ch >= 'A' && ch <= 'F') val = ch - 'A' + 10;

  if (val != -1) {
    buffer[cursor_pos] = (buffer[cursor_pos] << 4) | val;
  }
}

int main(int argc, char* argv[]) {
  if (argc < 2) {
    printf("Uzycie: %s <plik>\n", argv[0]);
    return 1;
  }

  filename = argv[1];
  load_file(filename);

  initscr();
  start_color();
  use_default_colors();

  init_pair(1, COLOR_CYAN, -1);
  init_pair(2, COLOR_WHITE, -1);
  init_pair(3, COLOR_BLUE, -1);
  init_pair(4, COLOR_BLACK, COLOR_WHITE);

  raw();
  noecho();
  keypad(stdscr, TRUE);
  curs_set(0);

  int ch;

  int max_y, max_x;
  draw_interface();
  int running = 1;
  while (running) {
    ch = getch();

    getmaxyx(stdscr, max_y, max_x);

    switch (ch) {
      case CTRL_KEY('q'):
        running = 0;
        break;
      case KEY_UP:
        if (cursor_pos >= ROW_SIZE) cursor_pos -= ROW_SIZE;
        break;
      case KEY_DOWN:
        if (cursor_pos + ROW_SIZE < file_size) cursor_pos += ROW_SIZE;
        break;
      case KEY_LEFT:
        if (cursor_pos > 0) cursor_pos--;
        break;
      case KEY_RIGHT:
        if (cursor_pos < file_size - 1) cursor_pos++;
        break;
      case '+':
        buffer[cursor_pos]++;
        break;
      case '-':
        buffer[cursor_pos]--;
        break;
      case CTRL_KEY('s'):
        save_file();
        mvprintw(max_y - 1, 0, "ZAPISANO!");
        break;
      case KEY_NPAGE: {
        int rows = max_y - 4;
        int jump = rows * ROW_SIZE;

        if (cursor_pos + jump < file_size) {
          cursor_pos += jump;
        } else {
          cursor_pos = file_size - 1;
        }
      } break;

      case KEY_PPAGE: {
        int rows = max_y - 4;
        int jump = rows * ROW_SIZE;

        if (cursor_pos - jump >= 0) {
          cursor_pos -= jump;
        } else {
          cursor_pos = 0;
        }
      } break;
      default:
        update_byte(ch);
        break;
    }

    int rows_on_screen = max_y - 4;
    int cursor_row_start = (cursor_pos / ROW_SIZE) * ROW_SIZE;

    if (cursor_pos < scroll_offset) {
      scroll_offset = cursor_row_start;
    }

    else if (cursor_pos >= scroll_offset + (rows_on_screen * ROW_SIZE)) {
      scroll_offset = cursor_row_start - ((rows_on_screen - 1) * ROW_SIZE);

      if (scroll_offset < 0) scroll_offset = 0;
    }

    draw_interface();
  }

  endwin();
  free(buffer);
  return 0;
}