#ifndef _LIB_TERM_H
#define _LIB_TERM_H

#include <stddef.h>
#include <stdbool.h>

typedef enum {
  TERM_CODE_RAWMODE_ENABLE,
  TERM_CODE_RAWMODE_DISABLE,
  TERM_CODE_CURSOR_READ,
  TERM_CODE_WINDOW_READ,
  TERM_CODE_KEY_POLL,
  TERM_CODE_KEY_READ,
  TERM_CODE_WRITE,
  TERM_CODE_FLUSH,
} term_code_t;

typedef enum {
  KEY_ENTER = 13,
  KEY_ESC = 27,
  KEY_BACKSPACE = 127,
  KEY_ARROW_LEFT = 1000,
  KEY_ARROW_RIGHT,
  KEY_ARROW_UP,
  KEY_ARROW_DOWN,
  KEY_DEL,
  KEY_HOME,
  KEY_END,
  KEY_PAGE_UP,
  KEY_PAGE_DOWN,
} term_key_t;

typedef struct term term_t;

typedef void (*term_dispatch_fn_t)(term_t *self, term_code_t code, void *data, size_t len);
typedef void *(*term_fetch_fn_t)(term_t *self, term_code_t code, void *data, size_t len, size_t ret_len);

struct term {
  char *buffer;
  size_t len;
  term_dispatch_fn_t dispatch;
  term_fetch_fn_t fetch;
  int fd;
};

term_t term_init(void);
void term_cleanup(term_t *self);
void term_rawmode_enable(term_t *self);
void term_rawmode_disable(term_t *self);
void term_write(term_t *self,  char *str);
void term_writef(term_t *self, const char *format, ...);
void term_flush(term_t *self);
int term_read_cursor(term_t *self, size_t *rows, size_t *cols);
int term_read_window(term_t *self, size_t *rows, size_t *cols);
int term_read_key(term_t *self);
int term_poll_key(term_t *self, int timeout_ms);

#ifdef LIB_TERM_IMPL

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <stdarg.h>

void _term_panic(term_t *self, const char *str) {
  write(self->fd, "\x1b[2J", 4);
  write(self->fd, "\x1b[H", 3);
  write(self->fd, "\x1b[?25h", 6);
  perror(str);
  exit(EXIT_FAILURE);
}

#ifdef LIB_TERM_POSIX

#include <termios.h>
#include <sys/ioctl.h>
#include <poll.h>

static struct termios _posix_termios;

static void posix_rawmode_enable(term_t *self) {
  if (tcgetattr(STDIN_FILENO, &_posix_termios) == -1) {
    _term_panic(self, "tcgetattr");
  }
  struct termios raw = _posix_termios;
  raw.c_iflag &= ~(BRKINT | ICRNL | INPCK | ISTRIP | IXON);
  raw.c_oflag &= ~(OPOST);
  raw.c_cflag |= (CS8);
  raw.c_lflag &= ~(ECHO | ICANON | IEXTEN | ISIG);
  raw.c_cc[VMIN] = 0;
  raw.c_cc[VTIME] = 1;
  if (tcsetattr(STDIN_FILENO, TCSAFLUSH, &raw) == -1) {
    _term_panic(self, "tcsetattr");
  }
}

static void posix_rawmode_disable(term_t *self) {
  if (tcsetattr(STDIN_FILENO, TCSAFLUSH, &_posix_termios) == -1) {
    _term_panic(self, "tcsetattr");
  }
}

static void posix_write(term_t *self, void *data, size_t len) {
  (void) self;
  (void) data;
  (void) len;
}

static void posix_flush(term_t *self, void *data, size_t len) {
  (void) data;
  (void) len;
  if (self->len > 0) {
    write(self->fd, self->buffer, self->len);
    free(self->buffer);
    self->buffer = NULL;
    self->len = 0;
  }
}

static void *posix_read_cursor(term_t *self, void *data, size_t len) {
  (void) data;
  (void) len;
  char buf[32];
  unsigned int i = 0;
  if (write(self->fd, "\x1b[6n", 4) != 4) {
    return NULL;
  }
  while (i < sizeof(buf) - 1) {
    if (read(STDIN_FILENO, &buf[i], 1) != 1) {
      break;
    }
    if (buf[i] == 'R') {
      break;
    }
    i++;
  }
  buf[i] = '\0';
  if (buf[0] != '\x1b' || buf[1] != '[') {
    return NULL;
  }
  size_t *tuple = malloc(2 * sizeof(size_t));
  if (sscanf(&buf[2], "%zu;%zu", &tuple[0], &tuple[1]) != 2) {
    free(tuple);
    return NULL;
  }
  return tuple;
}

static void *posix_read_window(term_t *self, void *data, size_t len) {
  struct winsize ws;
  if (ioctl(self->fd, TIOCGWINSZ, &ws) == -1 || ws.ws_col == 0) {
    if (write(self->fd, "\x1b[999C\x1b[999B", 12) == 12) {
      return posix_read_cursor(self, data, len);
    }
  }
  else {
    size_t *tuple = malloc(2 * sizeof(size_t));
    tuple[0] = ws.ws_row;
    tuple[1] = ws.ws_col;
    return tuple;
  }
  return NULL;
}

static void *posix_read_key(term_t *self) {
  int len;
  char c;
  int key;
  while ((len = read(STDIN_FILENO, &c, 1)) != 1) {
    if (len == -1 && errno != EAGAIN) {
      _term_panic(self, "read");
    }
  }
  if (c == '\x1b') {
    char seq[3];
    if (read(STDIN_FILENO, &seq[0], 1) != 1) {
      key = '\x1b';
    }
    if (read(STDIN_FILENO, &seq[1], 1) != 1) {
      key = '\x1b';
    }
    if (seq[0] == '[') {
      if (seq[1] >= '0' && seq[1] <= '9') {
        if (read(STDIN_FILENO, &seq[2], 1) != 1) {
          key = '\x1b';
        }
        if (seq[2] == '~') {
          switch (seq[1]) {
            case '1':
              key = KEY_HOME;
              break;
            case '3':
              key = KEY_DEL;
              break;
            case '4':
              key = KEY_END;
              break;
            case '5':
              key = KEY_PAGE_UP;
              break;
            case '6':
              key = KEY_PAGE_DOWN;
              break;
            case '7':
              key = KEY_HOME;
              break;
            case '8':
              key = KEY_END;
              break;
            default:
              break;
          }
        }
      }
      else {
        switch (seq[1]) {
          case 'A':
            key = KEY_ARROW_UP;
            break;
          case 'B':
            key = KEY_ARROW_DOWN;
            break;
          case 'C':
            key = KEY_ARROW_RIGHT;
            break;
          case 'D':
            key = KEY_ARROW_LEFT;
            break;
          case 'H':
            key = KEY_HOME;
            break;
          case 'F':
            key = KEY_END;
            break;
          default:
            key = '\x1b';
            break;
        }
      }
    }
    else if (seq[0] == 'O') {
      switch (seq[1]) {
        case 'H':
          key = KEY_HOME;
          break;
        case 'F':
          key = KEY_END;
          break;
        default:
          break;
      }
    }
  }
  else {
    key = c;
  }
  int *ret = malloc(sizeof(int));
  *ret = key;
  return ret;
}

static void *posix_poll_key(term_t *self, void *data, size_t len) {
  (void) len;
  struct pollfd fds[1];
  fds[0].fd = STDIN_FILENO;
  fds[0].events = POLLIN | POLLPRI;
  int timeout_ms = *(int *) data;
  if (poll(fds, 1, timeout_ms)) {
    return posix_read_key(self);
  }
  int *ret = malloc(sizeof(int));
  *ret = 0;
  return ret;
}

static void posix_dispatch(term_t *self, term_code_t code, void *data, size_t len) {
  switch (code) {
    case TERM_CODE_RAWMODE_ENABLE:
      posix_rawmode_enable(self);
      break;
    case TERM_CODE_RAWMODE_DISABLE:
      posix_rawmode_disable(self);
      break;
    case TERM_CODE_WRITE:
      posix_write(self, data, len);
      break;
    case TERM_CODE_FLUSH:
      posix_flush(self, data, len);
      break;
    default:
      break;
  }
}

static void *posix_fetch(term_t *self, term_code_t code, void *data, size_t len, size_t ret_len) {
  (void) ret_len;
  switch (code) {
    case TERM_CODE_CURSOR_READ:
      return posix_read_cursor(self, data, len);
    case TERM_CODE_WINDOW_READ:
      return posix_read_window(self, data, len);
    case TERM_CODE_KEY_READ:
      return posix_read_key(self);
    case TERM_CODE_KEY_POLL:
      return posix_poll_key(self, data, len);
    default:
      return NULL;
  }
}

#endif // LIB_TERM_POSIX

#ifdef LIB_TERM_WINDOWS

#include <windows.h>
#include <conio.h>

static DWORD _windows_console_mode;

static void windows_rawmode_enable(term_t *self) {
  HANDLE handle = GetStdHandle(STD_INPUT_HANDLE);
  DWORD mode;
  if (!GetConsoleMode(handle, &mode)) {
    _term_panic(self, "GetConsoleMode");
  }
  _windows_console_mode = mode;
  mode &= ~(ENABLE_ECHO_INPUT | ENABLE_LINE_INPUT | ENABLE_PROCESSED_INPUT);
  if (!SetConsoleMode(handle, mode)) {
    _term_panic(self, "SetConsoleMode");
  }
}

static void windows_rawmode_disable(term_t *self) {
  HANDLE handle = GetStdHandle(STD_INPUT_HANDLE);
  if (!SetConsoleMode(handle, _windows_console_mode)) {
    _term_panic(self, "SetConsoleMode");
  }
}

static void windows_write(term_t *self, void *data, size_t len) {
  DWORD written;
  WriteConsole(GetStdHandle(self->fd), data, (DWORD) len, &written, NULL);
}

static void windows_flush(term_t *self, void *data, size_t len) {
  (void) data;
  (void) len;
  if (self->len > 0) {
    DWORD written;
    WriteConsole(GetStdHandle(self->fd), self->buffer, (DWORD) self->len, &written, NULL);
    free(self->buffer);
    self->buffer = NULL;
    self->len = 0;
  }
}

static void *windows_read_cursor(term_t *self, void *data, size_t len) {
  (void) data;
  (void) len;
  CONSOLE_SCREEN_BUFFER_INFO console_info;
  if (!GetConsoleScreenBufferInfo(GetStdHandle(self->fd), &console_info)) {
    return NULL;
  }
  size_t *tuple = malloc(2 * sizeof(size_t));
  tuple[0] = console_info.dwCursorPosition.Y + 1;
  tuple[1] = console_info.dwCursorPosition.X + 1;
  return tuple;
}

static void *windows_read_window(term_t *self, void *data, size_t len) {
  (void) data;
  (void) len;
  CONSOLE_SCREEN_BUFFER_INFO console_info;
  if (!GetConsoleScreenBufferInfo(GetStdHandle(self->fd), &console_info)) {
    return NULL;
  }
  size_t *tuple = malloc(2 * sizeof(size_t));
  tuple[0] = console_info.srWindow.Bottom - console_info.srWindow.Top + 1;
  tuple[1] = console_info.srWindow.Right - console_info.srWindow.Left + 1;
  return tuple;
}

static void *windows_read_key(term_t *self) {
  (void) self;
  int c = _getch();
  if (c == 0 || c == 224) {
    int ext = _getch();
    switch (ext) {
      case 72:
        c = KEY_ARROW_UP;
        break;
      case 80:
        c = KEY_ARROW_DOWN;
        break;
      case 75:
        c = KEY_ARROW_LEFT;
        break;
      case 77:
        c = KEY_ARROW_RIGHT;
        break;
      case 71:
        c = KEY_HOME;
        break;
      case 79:
        c = KEY_END;
        break;
      case 73:
        c = KEY_PAGE_UP;
        break;
      case 81:
        c = KEY_PAGE_DOWN;
        break;
      case 83:
        c = KEY_DEL;
        break;
      default:
      c = 0;
      break;
    }
  }
  int *ret = malloc(sizeof(int));
  *ret = c;
  return ret;
}

static void *windows_poll_key(term_t *self, void *data, size_t len) {
  (void) len;
  int timeout_ms = *(int *) data;
  DWORD start = GetTickCount();
  while (GetTickCount() - start < (DWORD) timeout_ms) {
    if (_kbhit()) {
      return windows_read_key(self);
    }
    Sleep(1);
  }
  int *ret = malloc(sizeof(int));
  *ret = 0;
  return ret;
}

static void windows_dispatch(term_t *self, term_code_t code, void *data, size_t len) {
  switch (code) {
    case TERM_CODE_RAWMODE_ENABLE:
      windows_rawmode_enable(self);
      break;
    case TERM_CODE_RAWMODE_DISABLE:
      windows_rawmode_disable(self);
      break;
    case TERM_CODE_WRITE:
      windows_write(self, data, len);
      break;
    case TERM_CODE_FLUSH:
      windows_flush(self, data, len);
      break;
    default:
      break;
  }
}

static void *windows_fetch(term_t *self, term_code_t code, void *data, size_t len, size_t ret_len) {
  (void) ret_len;
  switch (code) {
    case TERM_CODE_CURSOR_READ:
      return windows_read_cursor(self, data, len);
    case TERM_CODE_WINDOW_READ:
      return windows_read_window(self, data, len);
    case TERM_CODE_KEY_READ:
      return windows_read_key(self);
    case TERM_CODE_KEY_POLL:
      return windows_poll_key(self, data, len);
    default:
      return NULL;
  }
}

#endif // LIB_TERM_WINDOWS

term_t term_init(void) {
  term_t self = {
    .buffer = NULL,
    .len = 0,
    .dispatch = NULL,
    .fetch = NULL,
    .fd = 0,
  };
  #ifdef LIB_TERM_POSIX
  self.dispatch = posix_dispatch;
  self.fetch = posix_fetch;
  self.fd = STDOUT_FILENO;
  #endif /* LIB_TERM_POSIX */
  #ifdef LIB_TERM_WINDOWS
  self.dispatch = windows_dispatch;
  self.fetch = windows_fetch;
  self.fd = STD_OUTPUT_HANDLE;
  #endif /* LIB_TERM_WINDOWS */
  return self;
}

void term_cleanup(term_t *self) {
  if (self) {
    if (self->buffer) {
      free(self->buffer);
      self->buffer = NULL;
      self->len = 0;
    }
  }
}

void term_rawmode_enable(term_t *self) {
  self->dispatch(self, TERM_CODE_RAWMODE_ENABLE, NULL, 0);
}

void term_rawmode_disable(term_t *self) {
  self->dispatch(self, TERM_CODE_RAWMODE_DISABLE, NULL, 0);
}

void term_write(term_t *self,  char *str) {
  self->dispatch(self, TERM_CODE_WRITE, NULL, 0);
  size_t str_len = strlen(str);
  char *new_buffer = (char *) realloc(self->buffer, sizeof(char) * (self->len + str_len + 1));
  if (new_buffer == NULL) {
    fprintf(stderr, "Cannot realloc memory!\n");
    return;
  }
  self->buffer = new_buffer;
  memcpy(self->buffer + self->len, str, str_len);
  self->len += str_len;
  self->buffer[self->len] = '\0';
}

void term_writef(term_t *self, const char *format, ...) {
  va_list args;
  va_start(args, format);
  char str[1000];
  vsnprintf(str, sizeof(str), format, args);
  term_write(self, str);
  va_end(args);
}

void term_flush(term_t *self) {
  self->dispatch(self, TERM_CODE_FLUSH, NULL, 0);
}

int term_read_cursor(term_t *self, size_t *rows, size_t *cols) {
  void *data = self->fetch(self, TERM_CODE_CURSOR_READ, NULL, 0, 2 * sizeof(size_t));
  if (data) {
    size_t *tuple = (size_t *) data;
    *rows = tuple[0];
    *cols = tuple[1];
    free(data);
    return 0;
  }
  return -1;
}

int term_read_window(term_t *self, size_t *rows, size_t *cols) {
  void *data = self->fetch(self, TERM_CODE_WINDOW_READ, NULL, 0, 2 * sizeof(size_t));
  if (data) {
    size_t *tuple = (size_t *) data;
    *rows = tuple[0];
    *cols = tuple[1];
    free(data);
    return 0;
  }
  return -1;
}

int term_read_key(term_t *self) {
  void *data = self->fetch(self, TERM_CODE_KEY_READ, NULL, 0, sizeof(int));
  if (data) {
    int *single = (int *) data;
    int key = *single;
    free(data);
    return key;
  }
  return -1;
}

int term_poll_key(term_t *self, int timeout_ms) {
  void *data = self->fetch(self, TERM_CODE_KEY_POLL, &timeout_ms, sizeof(timeout_ms), sizeof(int));
  if (data) {
    int *single = (int *) data;
    int key = *single;
    free(data);
    return key;
  }
  return -1;
}

#endif // LIB_TERM_IMPL
#endif // _LIB_TERM_H