/**
 * \file main.c
 * \author Arthur Barraux
 * \brief Base file of Beluga text editor. Contain fonctions for terminal
 * interactions. \version 0.1 \date 21 septembre 2024
 */

#include "main.h"
#include <asm-generic/ioctls.h>
#include <ctype.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/ioctl.h>
#include <termios.h>
#include <unistd.h>

/* defines */
#define CTRL_KEY(k) ((k) & 0x1f)
#define CURSOR_TOP_LEFT "\x1b[H"

/* data */
/**
 * \struct editorConfig
 * \brief Containing our editor state.
 */
struct editorConfig {
  int screenrows;
  int screencols;
  struct termios orig_termios;
};

struct editorConfig E;

/* terminal */

/**
 * \fn void die(const char *s)
 * \brief Exit program and return s error message.
 * \param *s Error string
 * */
void die(const char *s) {
  wipeScreen();
  perror(s);
  exit(1);
}

void disableRawMode() {
  if (tcsetattr(STDIN_FILENO, TCSAFLUSH, &E.orig_termios) == -1) {
    die("tcsetattr");
  }
}

void enableRawMode() {
  if (tcgetattr(STDIN_FILENO, &E.orig_termios) == -1) {
    die("tcgetattr");
  }
  atexit(disableRawMode);

  struct termios raw = E.orig_termios;
  raw.c_iflag &= ~(BRKINT | ICRNL | INPCK | ISTRIP | IXON);
  raw.c_oflag &= ~(OPOST);
  raw.c_cflag |= (CS8);
  raw.c_lflag &= ~(ECHO | ICANON | ISIG | IEXTEN);
  raw.c_cc[VMIN] = 0;
  raw.c_cc[VTIME] = 1;

  if (tcsetattr(STDIN_FILENO, TCSAFLUSH, &raw) == -1) {
    die("tcgetattr");
  }
}

char editorReadKey() {
  int nread;
  char c;
  while ((nread = read(STDIN_FILENO, &c, 1)) != 1) {
    if (nread == -1 && errno != EAGAIN) {
      die("read");
    }
  }
  return c;
}

int getCursorPosition(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 getWindowSize(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 getCursorPosition(rows, cols);
  } else {
    *cols = ws.ws_col;
    *rows = ws.ws_row;
    return 0;
  }
}

/* output */

/** \fn void wipeScreen()
 * \brief Wipe the terminal screen and put the cursor on the top left corner.
 * */
void wipeScreen() {
  /* Clear the screen */
  write(STDOUT_FILENO, "\x1b[2J", 4);
  /* Put the cursor at the top left corner */
  write(STDOUT_FILENO, CURSOR_TOP_LEFT, 3);
}

/**
 * \fn void editorDrawRows()
 * \brief Draws left rows of the editor.
 */
void editorDrawRows() {
  int y;
  for (y = 0; y < E.screenrows; ++y) {
    write(STDOUT_FILENO, "~\r\n", 3);
  }
}

void editorRefreshScreen() {
  wipeScreen();
  editorDrawRows();

  write(STDOUT_FILENO, CURSOR_TOP_LEFT, 3);
}

/* input */

/**
 * \fn void editorProcessKeypress()
 * \brief Get the last key input and do the proper action.
 */
void editorProcessKeypress() {
  char c = editorReadKey();

  switch (c) {
  case CTRL_KEY('q'):
    wipeScreen();
    exit(0);
    break;
  }
}

/* init */

/**
 * \fn void initEditor()
 * \brief Job's function is to initialize all the fields of editorConfig.
 * */
void initEditor() {
  if (getWindowSize(&E.screenrows, &E.screencols) == -1) {
    die("getWindowSize");
  }
}

int main() {

  enableRawMode();
  initEditor();

  while (1) {
    editorRefreshScreen();
    editorProcessKeypress();
  }
  return 0;
}