#ifndef _LIB_TERM_H
#define _LIB_TERM_H

#include <stddef.h>
#include <stdbool.h>
#include <termios.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_keycode_t;

typedef void (*term_dispatch_fn_t)(int fd, term_code_t code, void *data, size_t len);
typedef void *(*term_fetch_fn_t)(int fd, term_code_t code, void *data, size_t len, size_t ret_len);

typedef struct {
  struct termios termios;
  char *buffer;
  size_t len;
  bool teleterm_mode;
  term_dispatch_fn_t dispatch;
  term_fetch_fn_t fetch;
  int fd;
} term_t;

term_t term_init(void);
void term_cleanup(term_t *self);
void term_fd_set(term_t *self, int fd);
void term_teleterm_enable(term_t *self, term_dispatch_fn_t dispatch, term_fetch_fn_t fetch);
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 <sys/ioctl.h>
#include <errno.h>
#include <stdarg.h>
#include <poll.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);
}

term_t term_init(void) {
  return (term_t) {
    .buffer = NULL,
    .len = 0,
    .teleterm_mode = false,
    .dispatch = NULL,
    .fetch = NULL,
    .fd = STDOUT_FILENO,
  };
}

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

void term_fd_set(term_t *self, int fd) {
  self->fd = fd;
}

void term_teleterm_enable(term_t *self, term_dispatch_fn_t dispatch, term_fetch_fn_t fetch) {
  self->teleterm_mode = true;
  self->dispatch = dispatch;
  self->fetch = fetch;
}

void term_rawmode_enable(term_t *self) {
  if (self->teleterm_mode) {
    self->dispatch(self->fd, TERM_CODE_RAWMODE_ENABLE, NULL, 0);
    return;
  }
  if (tcgetattr(STDIN_FILENO, &self->termios) == -1) {
    _term_panic(self, "tcgetattr");
  }
  struct termios raw = self->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");
  }
}

void term_rawmode_disable(term_t *self) {
  if (self->teleterm_mode) {
    self->dispatch(self->fd, TERM_CODE_RAWMODE_DISABLE, NULL, 0);
    return;
  }
  if (tcsetattr(STDIN_FILENO, TCSAFLUSH, &self->termios) == -1) {
    _term_panic(self, "tcsetattr");
  }
}

void term_write(term_t *self,  char *str) {
  if (self->teleterm_mode) {
    self->dispatch(self->fd, 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) {
  if (self->len > 0) {
    if (self->teleterm_mode) {
      self->dispatch(self->fd, TERM_CODE_FLUSH, self->buffer, self->len);
    }
    else {
      write(self->fd, self->buffer, self->len);
    }
    free(self->buffer);
    self->buffer = NULL;
    self->len = 0;
  }
}

int term_read_cursor(term_t *self, size_t *rows, size_t *cols) {
  if (self->teleterm_mode) {
    void *data = self->fetch(self->fd, 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;
  }
  char buf[32];
  unsigned int i = 0;
  if (write(self->fd, "\x1b[6n", 4) != 4) {
    return -1;
  }
  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 -1;
  }
  if (sscanf(&buf[2], "%zu;%zu", rows, cols) != 2) {
    return -1;
  }
  return 0;
}

int term_read_window(term_t *self, size_t *rows, size_t *cols) {
  if (self->teleterm_mode) {
    void *data = self->fetch(self->fd, 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;
  }
  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 -1;
    }
    return term_read_cursor(self, rows, cols);
  }
  else {
    *cols = ws.ws_col;
    *rows = ws.ws_row;
    return 0;
  }
}

int term_read_key(term_t *self) {
  if (self->teleterm_mode) {
    void *data = self->fetch(self->fd, TERM_CODE_KEY_READ, NULL, 0, sizeof(int));
    if (data) {
      int *single = (int *) data;
      int key = *single;
      free(data);
      return key;
    }
    return -1;
  }
  int len;
  char c;
  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) {
      return '\x1b';
    }
    if (read(STDIN_FILENO, &seq[1], 1) != 1) {
      return '\x1b';
    }
    if (seq[0] == '[') {
      if (seq[1] >= '0' && seq[1] <= '9') {
        if (read(STDIN_FILENO, &seq[2], 1) != 1) {
          return '\x1b';
        }
        if (seq[2] == '~') {
          switch (seq[1]) {
            case '1':
              return KEY_HOME;
            case '3':
              return KEY_DEL;
            case '4':
              return KEY_END;
            case '5':
              return KEY_PAGE_UP;
            case '6':
              return KEY_PAGE_DOWN;
            case '7':
              return KEY_HOME;
            case '8':
              return KEY_END;
          }
        }
      }
      else {
        switch (seq[1]) {
          case 'A':
            return KEY_ARROW_UP;
          case 'B':
            return KEY_ARROW_DOWN;
          case 'C':
            return KEY_ARROW_RIGHT;
          case 'D':
            return KEY_ARROW_LEFT;
          case 'H':
            return KEY_HOME;
          case 'F':
            return KEY_END;
        }
        return '\x1b';
      }
    }
    else if (seq[0] == 'O') {
      switch (seq[1]) {
        case 'H':
          return KEY_HOME;
        case 'F':
          return KEY_END;
      }
    }
  }
  return c;
}

int term_poll_key(term_t *self, int timeout_ms) {
  if (self->teleterm_mode) {
    void *data = self->fetch(self->fd, 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;
  }
  struct pollfd fds[1];
  fds[0].fd = STDIN_FILENO;
  fds[0].events = POLLIN | POLLPRI;
  if (poll(fds, 1, timeout_ms)) {
    return term_read_key(self);
  }
  return 0;
}

#endif // LIB_TERM_IMPL
#endif // _LIB_TERM_H