#include <X11/X.h>
#include <X11/Xlib.h>
#include <X11/Xutil.h>
#include <X11/keysym.h>
#include <errno.h>
#include <fcntl.h>
#include <pty.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <termios.h>
#include <unistd.h>

#include "config.h"

// There isn't a need for MAX_ROWS or MAX_COLS, but ¯\_(ツ)_/¯
#define MAX_ROWS 1000
#define MAX_COLS 1000
#define CHAR_WIDTH 8
#define CHAR_HEIGHT 16

// General window/terminal stuff
static pid_t child_pid;
static char **terminal_buffer = NULL;
static unsigned long **color_buffer = NULL;
static int **attr_buffer = NULL;
static int term_rows;
static int term_cols;
static unsigned long current_color;
static int current_attr = 0;
static GC gc = NULL;
static GC gc_bold = NULL;
static Display *display = NULL;
static struct timeval last_refresh;
static Pixmap buffer_pixmap = None;
static int master_fd = -1;
static int needs_refresh = 0;
static int window_focused = 0;
static int scroll_top = 0;    // 0 means entire terminal
static int scroll_bottom = 0; // 0 means entire terminal

// Cursor stuff
static int cursor_visible = 1;
static struct timeval last_blink;
static int cursor_x = 0;
static int cursor_y = 0;

// Font stuff
static XFontStruct *regular_font = NULL;
static XFontStruct *bold_font = NULL;
static XFontStruct *italic_font = NULL;
static unsigned long current_bg_color;
static unsigned long **bg_color_buffer = NULL;

// Alternatives to handle the ANSI escape codes
static char **saved_terminal = NULL;
static unsigned long **saved_colors = NULL;
static int **saved_attrs = NULL;
static int saved_cursor_x = 0;
static int saved_cursor_y = 0;
static int using_alternate = 0;

#define ATTR_BOLD (1 << 0)
#define ATTR_ITALIC (1 << 1)
#define ATTR_REVERSE (1 << 2)
// #define ATTR_UNDERLINE (1 << 3) // Underline currently is buggy
#define ATTR_DIM (1 << 4)
#define ATTR_BLINK (1 << 5)

// Pesky static smth smth error, so we "declare" it early
static void draw_terminal(Display *display, Window window);
static void draw_char(Display *display, Drawable d, int x, int y);

// Cursor gameplay <== ==>
static void draw_cursor(Display *display, Window window) {
  if (!gc || !terminal_buffer || !color_buffer || cursor_y >= term_rows ||
      cursor_x >= term_cols)
    return;

  // First restore the character that was under the cursor
  if (cursor_x < term_cols && cursor_y < term_rows) {
    draw_char(display, buffer_pixmap, cursor_x, cursor_y);
  }

  if (cursor_visible) {
    // Save original color
    unsigned long original_color = color_buffer[cursor_y][cursor_x];

    if (!window_focused) {
      XSetForeground(display, gc, original_color);
      XDrawRectangle(display, buffer_pixmap, gc, cursor_x * CHAR_WIDTH,
                     cursor_y * CHAR_HEIGHT, CHAR_WIDTH - 1, CHAR_HEIGHT - 1);
    } else {
      XSetForeground(display, gc, original_color);
      XFillRectangle(display, buffer_pixmap, gc, cursor_x * CHAR_WIDTH,
                     cursor_y * CHAR_HEIGHT, CHAR_WIDTH, CHAR_HEIGHT);

      if (cursor_x < term_cols && cursor_y < term_rows) {
        char str[2] = {terminal_buffer[cursor_y][cursor_x], '\0'};
        XSetForeground(display, gc,
                       XBlackPixel(display, DefaultScreen(display)));

        XFontStruct *font = regular_font;
        if (attr_buffer[cursor_y][cursor_x] & ATTR_BOLD) {
          font = bold_font;
        } else if (attr_buffer[cursor_y][cursor_x] & ATTR_ITALIC) {
          font = italic_font;
        }
        XSetFont(display, gc, font->fid);

        XDrawString(display, buffer_pixmap, gc, cursor_x * CHAR_WIDTH,
                    (cursor_y + 1) * CHAR_HEIGHT - 2, str, 1);
      }
    }
  }

  // Copy the relevant area to the window
  XCopyArea(display, buffer_pixmap, window, gc, cursor_x * CHAR_WIDTH,
            cursor_y * CHAR_HEIGHT, CHAR_WIDTH, CHAR_HEIGHT,
            cursor_x * CHAR_WIDTH, cursor_y * CHAR_HEIGHT);
}

static void update_cursor_state(Display *display, Window window) {
  if (window_focused) {
    cursor_visible = 1;
    return;
  }
}

// resize_buffers visual:
//
// Old buffer (3x3):     New buffer (4x4):
// [a][b][c]            [a][b][c][ ]
// [d][e][f]     ->     [d][e][f][ ]
// [g][h][i]            [g][h][i][ ]
//                      [ ][ ][ ][ ]
//
// 1. Allocates new larger buffer
// 2. Copies existing content
// 3. Fills new space with blanks
// 4. Updates cursor position
// 5. Frees old buffer
static void resize_buffers(int new_rows, int new_cols) {
  if (new_rows > MAX_ROWS)
    new_rows = MAX_ROWS;
  if (new_cols > MAX_COLS)
    new_cols = MAX_COLS;
  if (new_rows < 1)
    new_rows = 1;
  if (new_cols < 1)
    new_cols = 1;

  size_t row_size = ((new_cols * sizeof(char) + 15) & ~15);
  size_t color_row_size = ((new_cols * sizeof(unsigned long) + 15) & ~15);
  size_t attr_row_size = ((new_cols * sizeof(int) + 15) & ~15);
  size_t bg_color_row_size = ((new_cols * sizeof(unsigned long) + 15) & ~15);

  char **new_term_buffer = malloc(new_rows * sizeof(char *));
  unsigned long **new_color_buffer = malloc(new_rows * sizeof(unsigned long *));
  int **new_attr_buffer = malloc(new_rows * sizeof(int *));
  unsigned long **new_bg_color_buffer =
      malloc(new_rows * sizeof(unsigned long *));

  if (!new_term_buffer || !new_color_buffer || !new_attr_buffer ||
      !new_bg_color_buffer) {
    fprintf(stderr, "Failed to allocate memory for buffers\n");
    return;
  }

  for (int i = 0; i < new_rows; i++) {
    new_term_buffer[i] = malloc(row_size);
    new_color_buffer[i] = malloc(color_row_size);
    new_attr_buffer[i] = malloc(attr_row_size);
    new_bg_color_buffer[i] = malloc(bg_color_row_size);

    if (!new_term_buffer[i] || !new_color_buffer[i] || !new_attr_buffer[i] ||
        !new_bg_color_buffer[i]) {
      fprintf(stderr, "Failed to allocate memory for buffer row\n");
      // Clean up allocated memory
      for (int j = 0; j < i; j++) {
        free(new_term_buffer[j]);
        free(new_color_buffer[j]);
        free(new_attr_buffer[j]);
        free(new_bg_color_buffer[j]);
      }
      free(new_term_buffer);
      free(new_color_buffer);
      free(new_attr_buffer);
      free(new_bg_color_buffer);
      return;
    }

    if (i < term_rows && i < new_rows && terminal_buffer && color_buffer &&
        attr_buffer && bg_color_buffer) {
      int copy_cols = (new_cols < term_cols) ? new_cols : term_cols;
      memcpy(new_term_buffer[i], terminal_buffer[i], copy_cols * sizeof(char));
      memcpy(new_color_buffer[i], color_buffer[i],
             copy_cols * sizeof(unsigned long));
      memcpy(new_attr_buffer[i], attr_buffer[i], copy_cols * sizeof(int));
      memcpy(new_bg_color_buffer[i], bg_color_buffer[i],
             copy_cols * sizeof(unsigned long));
      if (new_cols > term_cols) {
        memset(new_term_buffer[i] + term_cols, ' ', new_cols - term_cols);
        for (int x = term_cols; x < new_cols; x++) {
          new_color_buffer[i][x] = current_color;
          new_attr_buffer[i][x] = current_attr;
          new_bg_color_buffer[i][x] = current_bg_color;
        }
      }
    } else {
      memset(new_term_buffer[i], ' ', new_cols);
      for (int x = 0; x < new_cols; x++) {
        new_color_buffer[i][x] = current_color;
        new_attr_buffer[i][x] = current_attr;
        new_bg_color_buffer[i][x] = current_bg_color;
      }
    }
  }

  // Free old buffers after successful allocation
  if (terminal_buffer && color_buffer && attr_buffer && bg_color_buffer) {
    for (int i = 0; i < term_rows; i++) {
      free(terminal_buffer[i]);
      free(color_buffer[i]);
      free(attr_buffer[i]);
      free(bg_color_buffer[i]);
    }
    free(terminal_buffer);
    free(color_buffer);
    free(attr_buffer);
    free(bg_color_buffer);
  }

  terminal_buffer = new_term_buffer;
  color_buffer = new_color_buffer;
  attr_buffer = new_attr_buffer;
  bg_color_buffer = new_bg_color_buffer;
  term_rows = new_rows;
  term_cols = new_cols;

  cursor_x = (cursor_x >= term_cols) ? term_cols - 1 : cursor_x;
  cursor_y = (cursor_y >= term_rows) ? term_rows - 1 : cursor_y;

  // Resize buffer pixmap
  if (buffer_pixmap != None) {
    XFreePixmap(display, buffer_pixmap);
  }
  buffer_pixmap = XCreatePixmap(display, DefaultRootWindow(display),
                                term_cols * CHAR_WIDTH, term_rows * CHAR_HEIGHT,
                                DefaultDepth(display, DefaultScreen(display)));
  needs_refresh = 1;
}

static void destroy_cb(Display *display, Window window) {
  if (child_pid > 0) {
    kill(child_pid, SIGTERM);
    waitpid(child_pid, NULL, 0);
  }
  if (gc)
    XFreeGC(display, gc);
  if (gc_bold)
    XFreeGC(display, gc_bold);
  if (buffer_pixmap != None)
    XFreePixmap(display, buffer_pixmap);
  if (display)
    XCloseDisplay(display);
  if (terminal_buffer) {
    for (int i = 0; i < term_rows; i++) {
      free(terminal_buffer[i]);
    }
    free(terminal_buffer);
  }
  if (color_buffer) {
    for (int i = 0; i < term_rows; i++) {
      free(color_buffer[i]);
    }
    free(color_buffer);
  }
  if (attr_buffer) {
    for (int i = 0; i < term_rows; i++) {
      free(attr_buffer[i]);
    }
    free(attr_buffer);
  }
  if (bg_color_buffer) {
    for (int i = 0; i < term_rows; i++) {
      free(bg_color_buffer[i]);
    }
    free(bg_color_buffer);
  }
  if (master_fd >= 0)
    close(master_fd);
  exit(0);
}

static void draw_char(Display *display, Drawable d, int x, int y) {
  if (!gc || !terminal_buffer || !color_buffer || !attr_buffer ||
      !bg_color_buffer)
    return;
  if (x < 0 || x >= term_cols || y < 0 || y >= term_rows)
    return;

  unsigned long fg_color = color_buffer[y][x];
  unsigned long bg_color = bg_color_buffer[y][x];
  int attrs = attr_buffer[y][x];
  static unsigned long last_bg_color = 0;
  static int last_x = -1;
  static int last_y = -1;

  if (attrs & ATTR_REVERSE) {
    unsigned long temp = fg_color;
    fg_color = bg_color;
    bg_color = temp;
  }

  if (last_x != x || last_y != y || last_bg_color != bg_color) {
    XSetForeground(display, gc, bg_color);
    XFillRectangle(display, d, gc, x * CHAR_WIDTH, y * CHAR_HEIGHT, CHAR_WIDTH,
                   CHAR_HEIGHT);
    last_x = x;
    last_y = y;
    last_bg_color = bg_color;
  }

  XSetForeground(display, gc, fg_color);

  char str[2] = {terminal_buffer[y][x], '\0'};

  // Select appropriate font based on attributes
  XFontStruct *font = regular_font;
  if (attrs & ATTR_BOLD) {
    font = bold_font;
  } else if (attrs & ATTR_ITALIC) {
    font = italic_font;
  }
  XSetFont(display, gc, font->fid);

  XDrawString(display, d, gc, x * CHAR_WIDTH, (y + 1) * CHAR_HEIGHT - 2, str,
              1);

  // if (attrs & ATTR_UNDERLINE) {
  // XDrawLine(display, d, gc, x * CHAR_WIDTH, (y + 1) * CHAR_HEIGHT - 1,
  // (x + 1) * CHAR_WIDTH, (y + 1) * CHAR_HEIGHT - 1);
  // }
}

static void draw_terminal(Display *display, Window window) {
  if (!gc) {
    gc = XCreateGC(display, window, 0, NULL);

    regular_font = XLoadQueryFont(display, REGULAR_FONT);
    bold_font = XLoadQueryFont(display, BOLD_FONT);
    italic_font = XLoadQueryFont(display, ITALICS_FONT);

    if (!regular_font)
      regular_font = XLoadQueryFont(display, "fixed");
    if (!bold_font)
      bold_font = regular_font;
    if (!italic_font)
      italic_font = regular_font;

    XSetFont(display, gc, regular_font->fid);
  }

  if (!terminal_buffer || !color_buffer || !attr_buffer)
    return;

  if (buffer_pixmap == None) {
    buffer_pixmap = XCreatePixmap(
        display, DefaultRootWindow(display), term_cols * CHAR_WIDTH,
        term_rows * CHAR_HEIGHT, DefaultDepth(display, DefaultScreen(display)));
  }

  // Only draw the changed parts of the terminal to the buffer
  if (needs_refresh) {
    for (int y = 0; y < term_rows; y++) {
      for (int x = 0; x < term_cols; x++) {
        draw_char(display, buffer_pixmap, x, y);
      }
    }
  }

  // Copy buffer to window
  XCopyArea(display, buffer_pixmap, window, gc, 0, 0, term_cols * CHAR_WIDTH,
            term_rows * CHAR_HEIGHT, 0, 0);

  draw_cursor(display, window);
  XFlush(display);
  needs_refresh = 0;
}

static void check_refresh(Display *display, Window window) {
  if (!needs_refresh)
    return;

  struct timeval now;
  gettimeofday(&now, NULL);

  long elapsed = (now.tv_sec - last_refresh.tv_sec) * 1000000 +
                 (now.tv_usec - last_refresh.tv_usec);

  if (elapsed >= REFRESH_INTERVAL) {
    draw_terminal(display, window);
    last_refresh = now;
  }
}

// Scroll the terminal up one line
static void scroll_up(void) {
  // Move all lines up one position
  for (int y = 0; y < term_rows - 1; y++) {
    memcpy(terminal_buffer[y], terminal_buffer[y + 1], term_cols);
    memcpy(color_buffer[y], color_buffer[y + 1],
           term_cols * sizeof(unsigned long));
    memcpy(attr_buffer[y], attr_buffer[y + 1], term_cols * sizeof(int));
    memcpy(bg_color_buffer[y], bg_color_buffer[y + 1],
           term_cols * sizeof(unsigned long));
  }

  // Clear the bottom line
  memset(terminal_buffer[term_rows - 1], ' ', term_cols);
  for (int x = 0; x < term_cols; x++) {
    color_buffer[term_rows - 1][x] = current_color;
    attr_buffer[term_rows - 1][x] = current_attr;
    bg_color_buffer[term_rows - 1][x] = current_bg_color;
  }
  needs_refresh = 1;
}

static void scroll_region_up(int amount) {
  char **temp_buffer = NULL;
  unsigned long **temp_color_buffer = NULL;
  int **temp_attr_buffer = NULL;
  unsigned long **temp_bg_color_buffer = NULL;

  temp_buffer = malloc(term_rows * sizeof(char *));
  temp_color_buffer = malloc(term_rows * sizeof(unsigned long *));
  temp_attr_buffer = malloc(term_rows * sizeof(int *));
  temp_bg_color_buffer = malloc(term_rows * sizeof(unsigned long *));

  if (!temp_buffer || !temp_color_buffer || !temp_attr_buffer ||
      !temp_bg_color_buffer) {
    fprintf(stderr, "Failed to allocate memory for temp buffers\n");
    return;
  }

  for (int i = 0; i < term_rows; i++) {
    temp_buffer[i] = malloc(term_cols * sizeof(char));
    temp_color_buffer[i] = malloc(term_cols * sizeof(unsigned long));
    temp_attr_buffer[i] = malloc(term_cols * sizeof(int));
    temp_bg_color_buffer[i] = malloc(term_cols * sizeof(unsigned long));
    if (!temp_buffer[i] || !temp_color_buffer[i] || !temp_attr_buffer[i] ||
        !temp_bg_color_buffer[i]) {
      fprintf(stderr, "Failed to allocate memory for temp buffer row\n");
      free(temp_buffer);
      free(temp_color_buffer);
      free(temp_attr_buffer);
      free(temp_bg_color_buffer);
      return;
    }
  }

  if (scroll_top == 0 && scroll_bottom == 0) {
    for (int i = 0; i < term_rows; i++) {
      memcpy(temp_buffer[i], terminal_buffer[i], term_cols * sizeof(char));
      memcpy(temp_color_buffer[i], color_buffer[i],
             term_cols * sizeof(unsigned long));
      memcpy(temp_attr_buffer[i], attr_buffer[i], term_cols * sizeof(int));
      memcpy(temp_bg_color_buffer[i], bg_color_buffer[i],
             term_cols * sizeof(unsigned long));
    }
    for (int j = 0; j < amount; j++) {
      // Move all lines up one position
      for (int y = 0; y < term_rows - 1; y++) {
        memcpy(terminal_buffer[y], temp_buffer[y + 1], term_cols);
        memcpy(color_buffer[y], temp_color_buffer[y + 1],
               term_cols * sizeof(unsigned long));
        memcpy(attr_buffer[y], temp_attr_buffer[y + 1],
               term_cols * sizeof(int));
        memcpy(bg_color_buffer[y], temp_bg_color_buffer[y + 1],
               term_cols * sizeof(unsigned long));
      }

      // Clear the bottom line
      memset(terminal_buffer[term_rows - 1], ' ', term_cols);
      for (int x = 0; x < term_cols; x++) {
        color_buffer[term_rows - 1][x] = current_color;
        attr_buffer[term_rows - 1][x] = current_attr;
        bg_color_buffer[term_rows - 1][x] = current_bg_color;
      }
    }
  } else {
    for (int i = 0; i < term_rows; i++) {
      memcpy(temp_buffer[i], terminal_buffer[i], term_cols * sizeof(char));
      memcpy(temp_color_buffer[i], color_buffer[i],
             term_cols * sizeof(unsigned long));
      memcpy(temp_attr_buffer[i], attr_buffer[i], term_cols * sizeof(int));
      memcpy(temp_bg_color_buffer[i], bg_color_buffer[i],
             term_cols * sizeof(unsigned long));
    }
    for (int j = 0; j < amount; j++) {
      int start = (scroll_top - 1);
      int end = (scroll_bottom - 1);
      if (start < 0)
        start = 0;
      if (end < 0)
        end = 0;
      if (end >= term_rows)
        end = term_rows - 1;
      // Move all lines up one position
      for (int y = start; y < end; y++) {
        memcpy(terminal_buffer[y], temp_buffer[y + 1], term_cols);
        memcpy(color_buffer[y], temp_color_buffer[y + 1],
               term_cols * sizeof(unsigned long));
        memcpy(attr_buffer[y], temp_attr_buffer[y + 1],
               term_cols * sizeof(int));
        memcpy(bg_color_buffer[y], temp_bg_color_buffer[y + 1],
               term_cols * sizeof(unsigned long));
      }

      // Clear the bottom line
      memset(terminal_buffer[end], ' ', term_cols);
      for (int x = 0; x < term_cols; x++) {
        color_buffer[end][x] = current_color;
        attr_buffer[end][x] = current_attr;
        bg_color_buffer[end][x] = current_bg_color;
      }
    }
  }

  for (int i = 0; i < term_rows; i++) {
    free(temp_buffer[i]);
    free(temp_color_buffer[i]);
    free(temp_attr_buffer[i]);
    free(temp_bg_color_buffer[i]);
  }
  free(temp_buffer);
  free(temp_color_buffer);
  free(temp_attr_buffer);
  free(temp_bg_color_buffer);
  needs_refresh = 1;
}

static void scroll_region_down(int amount) {
  char **temp_buffer = NULL;
  unsigned long **temp_color_buffer = NULL;
  int **temp_attr_buffer = NULL;
  unsigned long **temp_bg_color_buffer = NULL;

  temp_buffer = malloc(term_rows * sizeof(char *));
  temp_color_buffer = malloc(term_rows * sizeof(unsigned long *));
  temp_attr_buffer = malloc(term_rows * sizeof(int *));
  temp_bg_color_buffer = malloc(term_rows * sizeof(unsigned long *));

  if (!temp_buffer || !temp_color_buffer || !temp_attr_buffer ||
      !temp_bg_color_buffer) {
    fprintf(stderr, "Failed to allocate memory for temp buffers\n");
    return;
  }
  for (int i = 0; i < term_rows; i++) {
    temp_buffer[i] = malloc(term_cols * sizeof(char));
    temp_color_buffer[i] = malloc(term_cols * sizeof(unsigned long));
    temp_attr_buffer[i] = malloc(term_cols * sizeof(int));
    temp_bg_color_buffer[i] = malloc(term_cols * sizeof(unsigned long));

    if (!temp_buffer[i] || !temp_color_buffer[i] || !temp_attr_buffer[i] ||
        !temp_bg_color_buffer[i]) {
      fprintf(stderr, "Failed to allocate memory for temp buffer row\n");
      free(temp_buffer);
      free(temp_color_buffer);
      free(temp_attr_buffer);
      free(temp_bg_color_buffer);
      return;
    }
  }

  if (scroll_top == 0 && scroll_bottom == 0) {
    for (int i = 0; i < term_rows; i++) {
      memcpy(temp_buffer[i], terminal_buffer[i], term_cols * sizeof(char));
      memcpy(temp_color_buffer[i], color_buffer[i],
             term_cols * sizeof(unsigned long));
      memcpy(temp_attr_buffer[i], attr_buffer[i], term_cols * sizeof(int));
      memcpy(temp_bg_color_buffer[i], bg_color_buffer[i],
             term_cols * sizeof(unsigned long));
    }
    for (int j = 0; j < amount; j++) {
      // Move all lines down one position
      for (int y = term_rows - 1; y > 0; y--) {
        memcpy(terminal_buffer[y], temp_buffer[y - 1], term_cols);
        memcpy(color_buffer[y], temp_color_buffer[y - 1],
               term_cols * sizeof(unsigned long));
        memcpy(attr_buffer[y], temp_attr_buffer[y - 1],
               term_cols * sizeof(int));
        memcpy(bg_color_buffer[y], temp_bg_color_buffer[y - 1],
               term_cols * sizeof(unsigned long));
      }
      // Clear the top line
      memset(terminal_buffer[0], ' ', term_cols);
      for (int x = 0; x < term_cols; x++) {
        color_buffer[0][x] = current_color;
        attr_buffer[0][x] = current_attr;
        bg_color_buffer[0][x] = current_bg_color;
      }
    }
  } else {
    for (int i = 0; i < term_rows; i++) {
      memcpy(temp_buffer[i], terminal_buffer[i], term_cols * sizeof(char));
      memcpy(temp_color_buffer[i], color_buffer[i],
             term_cols * sizeof(unsigned long));
      memcpy(temp_attr_buffer[i], attr_buffer[i], term_cols * sizeof(int));
      memcpy(temp_bg_color_buffer[i], bg_color_buffer[i],
             term_cols * sizeof(unsigned long));
    }
    for (int j = 0; j < amount; j++) {
      int start = (scroll_top - 1);
      int end = (scroll_bottom - 1);
      if (start < 0)
        start = 0;
      if (end < 0)
        end = 0;
      if (end >= term_rows)
        end = term_rows - 1;

      // Move all lines down one position
      for (int y = end; y > start; y--) {
        memcpy(terminal_buffer[y], temp_buffer[y - 1], term_cols);
        memcpy(color_buffer[y], temp_color_buffer[y - 1],
               term_cols * sizeof(unsigned long));
        memcpy(attr_buffer[y], temp_attr_buffer[y - 1],
               term_cols * sizeof(int));
        memcpy(bg_color_buffer[y], temp_bg_color_buffer[y - 1],
               term_cols * sizeof(unsigned long));
      }

      // Clear the top line
      memset(terminal_buffer[start], ' ', term_cols);
      for (int x = 0; x < term_cols; x++) {
        color_buffer[start][x] = current_color;
        attr_buffer[start][x] = current_attr;
        bg_color_buffer[start][x] = current_bg_color;
      }
    }
  }
  for (int i = 0; i < term_rows; i++) {
    free(temp_buffer[i]);
    free(temp_color_buffer[i]);
    free(temp_attr_buffer[i]);
    free(temp_bg_color_buffer[i]);
  }
  free(temp_buffer);
  free(temp_color_buffer);
  free(temp_attr_buffer);
  free(temp_bg_color_buffer);
  needs_refresh = 1;
}

// Alternative buffer visual:
//
// Normal buffer:             Alternate buffer:
// [C][o][w]                  [ ][ ][ ]
// [T][e][r]                  [ ][ ][ ]
// [m][!][ ]       <->        [ ][ ][ ]
//
// When applications like vim switch to alternate buffer it SHOULD:
// 1. Save the current buffer state (saved_terminal etc.)
// 2. creates a new empty alternate buffer
// 3. The application draws to the alternate buffer
// 4. When done, alternate buffer is freed
// 5. And the original buffer state is restored
//
// References:
// saved_terminal = backup of normal buffer
// saved_colors/attrs = backup of attributes
// using_alternate = tracks which buffer is active
static void handle_alternate_buffer(const char *buf, int *idx, int max_len,
                                    Window window) {
  char num_buf[32] = {0};
  size_t num_idx = 0;

  (*idx)++;
  while (*idx < max_len && buf[*idx] != 'h' && buf[*idx] != 'l') {
    if (num_idx >= sizeof(num_buf) - 1)
      break;
    if (buf[*idx] >= '0' && buf[*idx] <= '9') {
      num_buf[num_idx++] = buf[*idx];
    }
    (*idx)++;
  }
  if (num_buf[0] != '\0') {
    int code = atoi(num_buf);
    if (buf[*idx] == 'h' || buf[*idx] == 'l') {
      switch (code) {
      case 1047: // Alternate screen buffer
        if (buf[*idx] == 'h') {
          if (!saved_terminal) {
            saved_terminal = terminal_buffer;
            saved_colors = color_buffer;
            saved_attrs = attr_buffer;
            saved_colors = bg_color_buffer;
            terminal_buffer = malloc(term_rows * sizeof(char *));
            color_buffer = malloc(term_rows * sizeof(unsigned long *));
            attr_buffer = malloc(term_rows * sizeof(int *));
            bg_color_buffer = malloc(term_rows * sizeof(unsigned long *));
            for (int i = 0; i < term_rows; i++) {
              terminal_buffer[i] = calloc(term_cols, sizeof(char));
              color_buffer[i] = calloc(term_cols, sizeof(unsigned long));
              attr_buffer[i] = calloc(term_cols, sizeof(int));
              bg_color_buffer[i] = calloc(term_cols, sizeof(unsigned long));
            }
            using_alternate = 1;
            needs_refresh = 1;
            draw_terminal(display, window);
          }
        } else if (using_alternate) {
          for (int i = 0; i < term_rows; i++) {
            free(terminal_buffer[i]);
            free(color_buffer[i]);
            free(attr_buffer[i]);
            free(bg_color_buffer[i]);
          }
          free(terminal_buffer);
          free(color_buffer);
          free(attr_buffer);
          free(bg_color_buffer);
          terminal_buffer = saved_terminal;
          color_buffer = saved_colors;
          attr_buffer = saved_attrs;
          bg_color_buffer = saved_colors;
          saved_terminal = NULL;
          using_alternate = 0;
          needs_refresh = 1;
          draw_terminal(display, window);
        }
        break;
      case 1048: // Save/restore cursor
        if (buf[*idx] == 'h') {
          saved_cursor_x = cursor_x;
          saved_cursor_y = cursor_y;
        } else {
          cursor_x = saved_cursor_x;
          cursor_y = saved_cursor_y;
        }
        break;
      case 1049: // Combined alternate buffer + cursor
        if (buf[*idx] == 'h') {
          saved_cursor_x = cursor_x;
          saved_cursor_y = cursor_y;
          if (!saved_terminal) {
            saved_terminal = terminal_buffer;
            saved_colors = color_buffer;
            saved_attrs = attr_buffer;
            saved_colors = bg_color_buffer;
            terminal_buffer = malloc(term_rows * sizeof(char *));
            color_buffer = malloc(term_rows * sizeof(unsigned long *));
            attr_buffer = malloc(term_rows * sizeof(int *));
            bg_color_buffer = malloc(term_rows * sizeof(unsigned long *));
            for (int i = 0; i < term_rows; i++) {
              terminal_buffer[i] = calloc(term_cols, sizeof(char));
              color_buffer[i] = calloc(term_cols, sizeof(unsigned long));
              attr_buffer[i] = calloc(term_cols, sizeof(int));
              bg_color_buffer[i] = calloc(term_cols, sizeof(unsigned long));
            }
            using_alternate = 1;
            needs_refresh = 1;
            draw_terminal(display, window);
          }
        } else if (using_alternate) {
          for (int i = 0; i < term_rows; i++) {
            free(terminal_buffer[i]);
            free(color_buffer[i]);
            free(attr_buffer[i]);
            free(bg_color_buffer[i]);
          }
          free(terminal_buffer);
          free(color_buffer);
          free(attr_buffer);
          free(bg_color_buffer);
          terminal_buffer = saved_terminal;
          color_buffer = saved_colors;
          attr_buffer = saved_attrs;
          bg_color_buffer = saved_colors;
          saved_terminal = NULL;
          cursor_x = saved_cursor_x;
          cursor_y = saved_cursor_y;
          using_alternate = 0;
          needs_refresh = 1;
          draw_terminal(display, window);
        }
        break;
      }
    }
  }
}

static unsigned long get_ansi_color(int index) {
  static const unsigned long colors[] = {0x000000, RED,     GREEN, YELLOW,
                                         BLUE,     MAGENTA, CYAN,  0xFFFFFF};
  return colors[index & 7];
}

static unsigned long get_bright_ansi_color(int index) {
  static const unsigned long colors[] = {
      DARK_GRAY,  LIGHT_RED,     LIGHT_GREEN, LIGHT_YELLOW,
      LIGHT_BLUE, LIGHT_MAGENTA, LIGHT_CYAN,  0xFFFFFF};
  return colors[index & 7];
}

// Handles those pesky ANSI color escape codes that terminals use.
// When \033[<number>m is sent to the terminal, it changes text color:
//   30 = Black    31 = Red      32 = Green   33 = Yellow
//   34 = Blue     35 = Magenta  36 = Cyan    37 = White
// 0 sets everything back to plain white
// P.S. yes I had to google this up
static void parse_ansi_code(const char *buf, int *idx, int max_len,
                            Window window) {
  char num_buf[32] = {0};
  int params[32] = {0};
  size_t num_idx = 0;
  size_t param_idx = 0;
  (*idx)++; // Skip [

  // Handle '?' prefix for private sequences
  if (buf[*idx] == '?') {
    handle_alternate_buffer(buf, idx, max_len, window);
    return;
  }

  while (*idx < max_len && buf[*idx] != 'm' && buf[*idx] != 'H' &&
         buf[*idx] != 'A' && buf[*idx] != 'B' && buf[*idx] != 'C' &&
         buf[*idx] != 'D' && buf[*idx] != 'K' && buf[*idx] != 'J' &&
         buf[*idx] != 'f' && buf[*idx] != 'r' && buf[*idx] != 's' &&
         buf[*idx] != 'u' && buf[*idx] != 'h' && buf[*idx] != 'l') {
    if (num_idx >= sizeof(num_buf) - 1 ||
        param_idx >= sizeof(params) / sizeof(params[0]) - 1) {
      break;
    }
    if (buf[*idx] >= '0' && buf[*idx] <= '9') {
      num_buf[num_idx++] = buf[*idx];
    } else if (buf[*idx] == ';') {
      if (num_buf[0] != '\0') {
        params[param_idx++] = atoi(num_buf);
        memset(num_buf, 0, sizeof(num_buf));
        num_idx = 0;
      }
    }
    (*idx)++;
  }

  if (num_buf[0] != '\0' && param_idx < sizeof(params) / sizeof(params[0])) {
    params[param_idx++] = atoi(num_buf);
  }

  switch (buf[*idx]) {
  case 'H': // Set cursor position
  case 'f': // Alternative set cursor position
    if (param_idx >= 2) {
      cursor_y =
          (params[0] - 1 < 0)
              ? 0
              : ((params[0] - 1) >= term_rows ? term_rows - 1 : params[0] - 1);
      cursor_x =
          (params[1] - 1 < 0)
              ? 0
              : ((params[1] - 1) >= term_cols ? term_cols - 1 : params[1] - 1);
    } else {
      cursor_x = cursor_y = 0;
    }
    break;
  case 'A': // Cursor up
    cursor_y -= params[0] ? params[0] : 1;
    if (cursor_y < 0)
      cursor_y = 0;
    break;
  case 'B': // Cursor down
    cursor_y += params[0] ? params[0] : 1;
    if (cursor_y >= term_rows)
      cursor_y = term_rows - 1;
    break;
  case 'C': // Cursor forward
    cursor_x += params[0] ? params[0] : 1;
    if (cursor_x >= term_cols)
      cursor_x = term_cols - 1;
    break;
  case 'D': // Cursor back
    cursor_x -= params[0] ? params[0] : 1;
    if (cursor_x < 0)
      cursor_x = 0;
    break;
  case 'K': // Clear line
    for (int i = cursor_x; i < term_cols; i++) {
      terminal_buffer[cursor_y][i] = ' ';
      color_buffer[cursor_y][i] = current_color;
      attr_buffer[cursor_y][i] = current_attr;
      bg_color_buffer[cursor_y][i] = current_bg_color;
    }
    break;
  case 'J': // Clear screen
    if (params[0] == 2) {
      for (int y = 0; y < term_rows; y++) {
        memset(terminal_buffer[y], ' ', term_cols);
        for (int x = 0; x < term_cols; x++) {
          color_buffer[y][x] = current_color;
          attr_buffer[y][x] = current_attr;
          bg_color_buffer[y][x] = current_bg_color;
        }
      }
      needs_refresh = 1;
    }
    break;
  case 'r': // Set scrolling region
    if (param_idx == 0) {
      scroll_top = 0; // Entire terminal
      scroll_bottom = 0;
    } else if (param_idx == 1) {
      scroll_top = (params[0] <= 0)
                       ? 1
                       : (params[0] > term_rows ? term_rows : params[0]);
      scroll_bottom = 0;
    } else if (param_idx >= 2) {
      scroll_top = (params[0] <= 0)
                       ? 1
                       : (params[0] > term_rows ? term_rows : params[0]);
      scroll_bottom = (params[1] <= 0)
                          ? term_rows
                          : (params[1] > term_rows ? term_rows : params[1]);

      // if top is bigger than bottom, swap values
      if (scroll_top > scroll_bottom) {
        int tmp = scroll_top;
        scroll_top = scroll_bottom;
        scroll_bottom = tmp;
        break;
      case 'S': // Scroll up
        scroll_region_up(params[0] == 0 ? 1 : params[0]);
        needs_refresh = 1;
        break;
      case 'T': // Scroll down
        scroll_region_down(params[0] == 0 ? 1 : params[0]);
        needs_refresh = 1;
        break;
      case 'E': // Cursor next line
        cursor_x = 0;
        cursor_y += params[0] ? params[0] : 1;
        if (cursor_y >= term_rows) {
          cursor_y = term_rows - 1;
        }
        break;
      case 'F': // Cursor line before
        cursor_x = 0;
        cursor_y -= params[0] ? params[0] : 1;
        if (cursor_y < 0) {
          cursor_y = 0;
        }
        break;
      }
    }
    break;
  case 'm': // Handling of text
    for (int i = 0; i < param_idx; i++) {
      if (params[i] == 0) { // Reset Everything
        current_color = XWhitePixel(display, DefaultScreen(display));
        current_bg_color = XBlackPixel(display, DefaultScreen(display));
        current_attr = 0;
      } else if (params[i] == 1) { // Apply ATTRS
        current_attr |= ATTR_BOLD;
      } else if (params[i] == 2) {
        current_attr |= ATTR_DIM;
      } else if (params[i] == 3) {
        current_attr |= ATTR_ITALIC;
        // } else if (params[i] == 4) {
        // current_attr |= ATTR_UNDERLINE;
      } else if (params[i] == 5) { // Slow blink
        current_attr |= ATTR_BLINK;
      } else if (params[i] == 7) {
        current_attr |= ATTR_REVERSE;
      } else if (params[i] == 22) { // Reset ATTRS
        current_attr &= ~ATTR_BOLD;
      } else if (params[i] == 23) {
        current_attr &= ~ATTR_ITALIC;
        // } else if (params[i] == 24) {
        // current_attr &= ~ATTR_UNDERLINE;
      } else if (params[i] == 25) {
        current_attr &= ~ATTR_BLINK;
      } else if (params[i] == 27) {
        current_attr &= ~ATTR_REVERSE;
      } else if (params[i] >= 30 && params[i] <= 37) { // Foreground colors
        current_color = get_ansi_color(params[i] - 30);
      } else if (params[i] >= 40 && params[i] <= 47) { // Background colors
        current_bg_color = get_ansi_color(params[i] - 40);
      } else if (params[i] >= 90 &&
                 params[i] <= 97) { // Bright foreground colors
        current_color = get_bright_ansi_color(params[i] - 90);
      } else if (params[i] >= 100 &&
                 params[i] <= 107) { // Bright background colors
        current_bg_color = get_bright_ansi_color(params[i] - 100);
      }
    }
    break;
  }
}

static int master_cb(int fd, void *data, Window window) {
  if (!terminal_buffer || !color_buffer || !attr_buffer || !bg_color_buffer)
    return 0;
  char buf[4096];
  ssize_t bytes_read;
  struct {
    Display *display;
    Window window;
  } *ctx = data;

  bytes_read = read(fd, buf, sizeof(buf));
  if (bytes_read <= 0 && errno != EAGAIN && errno != EINTR) {
    destroy_cb(ctx->display, ctx->window);
    return 0;
  }
  if (bytes_read > 0) {
    for (int i = 0; i < bytes_read; i++) {
      if (buf[i] == '\033' && i + 1 < bytes_read && buf[i + 1] == '[') {
        parse_ansi_code(buf, &i, bytes_read, window);
        continue;
      }
      if (buf[i] == '\n') {
        cursor_x = 0;
        cursor_y++;
        if (cursor_y >= term_rows) {
          scroll_up();
          cursor_y = term_rows - 1;
        }
        needs_refresh = 1;
      } else if (buf[i] == '\r') {
        cursor_x = 0;
      } else if (buf[i] == '\b') {
        if (cursor_x > 0) {
          cursor_x--;
          needs_refresh = 1;
        } else if (cursor_y > 0) {
          cursor_y--;
          cursor_x = term_cols - 1;
          while (cursor_x > 0 &&
                 terminal_buffer[cursor_y][cursor_x - 1] == ' ') {
            cursor_x--;
          }
          needs_refresh = 1;
        }
      } else {
        if (cursor_y < term_rows && cursor_x < term_cols) {
          terminal_buffer[cursor_y][cursor_x] = buf[i];
          color_buffer[cursor_y][cursor_x] = current_color;
          attr_buffer[cursor_y][cursor_x] = current_attr;
          bg_color_buffer[cursor_y][cursor_x] = current_bg_color;
          needs_refresh = 1;
          cursor_x++;
          if (cursor_x >= term_cols) {
            cursor_x = 0;
            cursor_y++;
            if (cursor_y >= term_rows) {
              scroll_up();
              cursor_y = term_rows - 1;
            }
          }
        }
      }
    }
    cursor_visible = 1;
    if (needs_refresh) {
      check_refresh(ctx->display, ctx->window);
    } else {
      draw_cursor(ctx->display, ctx->window);
      XFlush(ctx->display);
    }
  }
  return 1;
}

static void key_press_cb(XKeyEvent *event, void *data) {
  int *master = (int *)data;
  char buf[32];
  KeySym keysym;
  int len;

  len = XLookupString(event, buf, sizeof(buf), &keysym, NULL);

  if (event->state & ControlMask) {
    if ((keysym & 0x1f) == ('L' & 0x1f)) {
      write(*master, "\f", 1);
      return;
    }
    if ((keysym & 0x1f) == ('C' & 0x1f)) {
      write(*master, "\x03", 1);
      return;
    }
    if ((keysym & 0x1f) == ('U' & 0x1f)) {
      write(*master, "\025", 1);
      return;
    }
    char ctrl_char = '@' + (keysym & 0x1f);
    write(*master, &ctrl_char, 1);
    return;
  }

  if (keysym == XK_Return || keysym == XK_KP_Enter) {
    write(*master, "\r", 1); // Shell handles return
  } else if (keysym == XK_BackSpace) {
    if (cursor_x > 0) {
      write(*master, "\b \b", 3); // Shell handles backspace
    } else if (cursor_y > 0) {
      char seq[8];
      snprintf(seq, sizeof(seq), "\033[A\033[%dC", term_cols);
      write(*master, seq, strlen(seq));
    }
  } else if (keysym == XK_Left) {
    if (cursor_x > 0) {
      write(*master, "\033[D", 3);
    } else if (cursor_y > 0) {
      char seq[8];
      snprintf(seq, sizeof(seq), "\033[A\033[%dC", term_cols);
      write(*master, seq, strlen(seq));
    }
    needs_refresh = 1;
  } else if (keysym == XK_Right) {
    if (cursor_x < term_cols - 1) {
      write(*master, "\033[C", 3);
    } else if (cursor_y < term_rows - 1) {
      write(*master, "\033[B\033[G", 6);
    }
    needs_refresh = 1;
  } else if (keysym == XK_Up) { // Go up through history
    write(*master, "\033[A", 3);
  } else if (keysym == XK_Down) { // Go down through history
    write(*master, "\033[B", 3);
  } else if (keysym == XK_Tab) {
    write(*master, "\t", 1); // Shell handles autocomplete
  } else if (len > 0) {
    write(*master, buf, len);
    if (cursor_x >= term_cols - 1) {
      write(*master, "\r\n", 2);
    }
  }
}

int main(void) {
  int master, slave;
  pid_t pid;

  term_rows = 24;
  term_cols = 80;

  gettimeofday(&last_blink, NULL);
  gettimeofday(&last_refresh, NULL);

  struct winsize ws = {.ws_row = term_rows,
                       .ws_col = term_cols,
                       .ws_xpixel = term_cols * CHAR_WIDTH,
                       .ws_ypixel = term_rows * CHAR_HEIGHT};

  terminal_buffer = malloc(term_rows * sizeof(char *));
  color_buffer = malloc(term_rows * sizeof(unsigned long *));
  attr_buffer = malloc(term_rows * sizeof(int *));
  bg_color_buffer = malloc(term_rows * sizeof(unsigned long *));

  if (!terminal_buffer || !color_buffer || !attr_buffer || !bg_color_buffer) {
    fprintf(stderr, "Failed to allocate memory for buffers\n");
    return 1;
  }

  for (int i = 0; i < term_rows; i++) {
    terminal_buffer[i] = malloc(term_cols * sizeof(char));
    color_buffer[i] = malloc(term_cols * sizeof(unsigned long));
    attr_buffer[i] = malloc(term_cols * sizeof(int));
    bg_color_buffer[i] = malloc(term_cols * sizeof(unsigned long));

    if (!terminal_buffer[i] || !color_buffer[i] || !attr_buffer[i] ||
        !bg_color_buffer[i]) {
      fprintf(stderr, "Failed to allocate memory for buffer row\n");
      return 1;
    }
    memset(terminal_buffer[i], ' ', term_cols);
    memset(attr_buffer[i], 0, term_cols * sizeof(int));
  }

  display = XOpenDisplay(NULL);
  if (!display) {
    fprintf(stderr, "Cannot open display\n");
    return 1;
  }
  XInitThreads();

  current_color = XWhitePixel(display, DefaultScreen(display));
  current_bg_color = XBlackPixel(display, DefaultScreen(display));
  current_attr = 0;

  for (int y = 0; y < term_rows; y++) {
    for (int x = 0; x < term_cols; x++) {
      bg_color_buffer[y][x] = current_bg_color;
    }
  }

  for (int y = 0; y < term_rows; y++) {
    for (int x = 0; x < term_cols; x++) {
      color_buffer[y][x] = current_color;
      attr_buffer[y][x] = current_attr;
    }
  }

  XSizeHints hints;
  hints.flags = PResizeInc | PMinSize;
  hints.width_inc = CHAR_WIDTH;
  hints.height_inc = CHAR_HEIGHT;
  hints.min_width = CHAR_WIDTH * 4;
  hints.min_height = CHAR_HEIGHT * 1;

  Window window = XCreateSimpleWindow(
      display, DefaultRootWindow(display), 0, 0, term_cols * CHAR_WIDTH,
      term_rows * CHAR_HEIGHT, 0, XBlackPixel(display, DefaultScreen(display)),
      XBlackPixel(display, DefaultScreen(display)));

  buffer_pixmap = XCreatePixmap(display, DefaultRootWindow(display),
                                term_cols * CHAR_WIDTH, term_rows * CHAR_HEIGHT,
                                DefaultDepth(display, DefaultScreen(display)));

  XSetWMNormalHints(display, window, &hints);
  XStoreName(display, window, window_name);
  XSelectInput(display, window,
               KeyPressMask | ExposureMask | StructureNotifyMask |
                   FocusChangeMask);
  XMapWindow(display, window);

  if (openpty(&master, &slave, NULL, NULL, &ws) == -1) {
    perror("openpty");
    return 1;
  }

  master_fd = master;

  pid = fork();
  if (pid < 0) {
    perror("fork");
    return 1;
  }

  if (pid == 0) {
    close(master);
    close(STDIN_FILENO);
    close(STDOUT_FILENO);
    close(STDERR_FILENO);

    setsid();
    dup2(slave, 0);
    dup2(slave, 1);
    dup2(slave, 2);

    if (slave > 2)
      close(slave);

    char *shell = getenv("SHELL");
    if (!shell)
      shell = "/bin/sh";

    setenv("TERM", "xterm-256color", 1);
    execlp(shell, shell, NULL);
    perror("execlp");
    exit(1);
  }

  child_pid = pid;
  close(slave);

  struct {
    Display *display;
    Window window;
  } ctx = {display, window};

  XEvent event;
  while (1) {
    int status;
    pid_t wpid = waitpid(child_pid, &status, WNOHANG);
    if (wpid == child_pid) {
      destroy_cb(display, window);
      return 0;
    }

    while (XPending(display)) {
      XNextEvent(display, &event);
      switch (event.type) {
      case ConfigureNotify: {
        XConfigureEvent *ce = (XConfigureEvent *)&event;
        int new_rows = ce->height / CHAR_HEIGHT;
        int new_cols = ce->width / CHAR_WIDTH;
        if (new_rows != term_rows || new_cols != term_cols) {
          resize_buffers(new_rows, new_cols);
          ws.ws_row = term_rows;
          ws.ws_col = term_cols;
          ws.ws_xpixel = term_cols * CHAR_WIDTH;
          ws.ws_ypixel = term_rows * CHAR_HEIGHT;
          ioctl(master, TIOCSWINSZ, &ws);
        }
        break;
      }
      case FocusIn:
        window_focused = 1;
        needs_refresh = 1;
        break;
      case FocusOut:
        window_focused = 0;
        needs_refresh = 1;
        break;
      case KeyPress:
        key_press_cb((XKeyEvent *)&event, &master);
        break;
      case Expose:
        needs_refresh = 1;
        check_refresh(display, window);
        break;
      }
    }

    fd_set fds;
    struct timeval tv = {0, 1000}; // 1ms timeout for faster refresh
    FD_ZERO(&fds);
    FD_SET(master, &fds);
    if (select(master + 1, &fds, NULL, NULL, &tv) > 0) {
      master_cb(master, &ctx, window);
    }

    check_refresh(display, window);
    update_cursor_state(display, window);
  }

  return 0;
}