#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <termios.h>
#include <sys/ioctl.h>
#include <errno.h>
#include <stdarg.h>
#include <poll.h>

#include "libterm.h"

struct termios termios;
term_t term = { NULL, 0 };

void term_panic(const char *str) {
  write(STDOUT_FILENO, "\x1b[2J", 4);
  write(STDOUT_FILENO, "\x1b[H", 3);
  write(STDOUT_FILENO, "\x1b[?25h", 6);
  perror(str);
  exit(EXIT_FAILURE);
}

void term_disable_raw_mode() {
  if (tcsetattr(STDIN_FILENO, TCSAFLUSH, &termios) == -1) {
    term_panic("tcsetattr");
  }
}

void term_enable_raw_mode() {
  if (tcgetattr(STDIN_FILENO, &termios) == -1) {
    term_panic("tcgetattr");
  }
  atexit(term_disable_raw_mode);
  struct termios raw = 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("tcsetattr");
  }
}

int term_read_cursor_pos(int *rows, int *cols) {
  char buf[32];
  unsigned int i = 0;
  if (write(STDOUT_FILENO, "\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], "%d;%d", rows, cols) != 2) {
    return -1;
  }
  return -0;
}

int term_read_window_size(int *rows, int *cols) {
  struct winsize ws;
  if (ioctl(STDOUT_FILENO, TIOCGWINSZ, &ws) == -1 || ws.ws_col == 0) {
    if (write(STDOUT_FILENO, "\x1b[999C\x1b[999B", 12) != 12) {
      return -1;
    }
    return term_read_cursor_pos(rows, cols);
  }
  else {
    *cols = ws.ws_col;
    *rows = ws.ws_row;
    return 0;
  }
}

int term_poll_key(int timeout) {
  struct pollfd fds[1];
  fds[0].fd = STDIN_FILENO;
  fds[0].events = POLLIN | POLLPRI;
  if (poll(fds, 1, timeout)) {
    return term_read_key();
  }
  return 0;
}

int term_read_key(void) {
  int len;
  char c;
  while ((len = read(STDIN_FILENO, &c, 1)) != 1) {
    if (len == -1 && errno != EAGAIN) {
      term_panic("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;
}

void term_write(char *str) {
  int str_len = strlen(str);
  char *new_buffer = realloc(term.buffer, sizeof(char) * (term.len + str_len + 1));
  if (new_buffer == NULL) {
    fprintf(stderr, "Cannot realloc memory!\n");
    return;
  }
  term.buffer = new_buffer;
  memcpy(term.buffer + term.len, str, str_len);
  term.len += str_len;
  term.buffer[term.len] = '\0';
}

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

void term_flush(void) {
  if (term.len > 0) {
    write(STDOUT_FILENO, term.buffer, term.len);
    free(term.buffer);
    term.buffer = NULL;
    term.len = 0;
  }
}