State Machines
COP-3223H

switch(game_state) {
  case xturn:
    // ...
    break;
  case oturn:
    // ...
    break;
  case xwin:
    // ...
    break;
  case owin:
    // ...
    break;
}

// https://sourceware.org/glibc/manual/latest/html_mono/libc.html#Noncanon-Example

#include <stdio.h>
#include <stdbool.h>

#include "term.c"

int main(int argc, char **argv) {
  set_input_mode ();
  printf("\033[?25l"); // hide cursor

  int width = 40;
  int height = 20;

  // player data
  enum { vulnerable, invincible, dead };
  int player_state = vulnerable;
  int player_x = width / 2;
  int player_y = height / 2;

  // enemy data
  int enemy_x = 1;
  int enemy_y = 1;
  enum { chasing, running, defeated };
  int enemy_state = chasing;

  // potion data
  int potion_x = 29;
  int potion_y = 11;
  int random = 1;

  enum { available, using, done };
  int potion_state = available;
  int potion_counter = 0;

  while (1) {
    printf("\x1b[2J");
    printf("\x1b[H");

    switch (potion_state) {
    case available:
      printf("\033[%d;%dH", potion_y, potion_x);
      printf("/\\");
      printf("\033[%d;%dH", potion_y + 1, potion_x);
      printf("\\/");
      break;
    }

    printf("\033[%d;%dH", enemy_y, enemy_x);
    switch (enemy_state) {
    case chasing:
      putchar('@');
      break;
    case running:
      putchar('@');
      break;
    case defeated:
      putchar('X');
    }

    // draw characters
    printf("\033[%d;%dH", player_y, player_x);
    switch (player_state) {
    case vulnerable:
      putchar('h');
      break;
    case invincible:
      putchar('H');
      break;
    case dead:
      printf(":(");
    }

    /* // debugging output */
    /* printf("\033[%d;%dH", height + 1, 0); */
    /* printf("player_y: %d\n", player_y); */
    /* printf("player_x: %d\n", player_x); */
    /* printf("enemy_y: %d\n", enemy_y); */
    /* printf("enemy_x: %d\n", enemy_x); */
    /* printf("potion_y: %d\n", potion_y); */
    /* printf("potion_x: %d\n", potion_x); */

    // read input

    int direction_x = 0;
    int direction_y = 0;
    bool valid = true;
    do {
      char c = '\0';
      scanf("%c", &c);
      switch (c) {
      case 'i':
        direction_y = -2;
        break;
      case 'k':
        direction_y = 2;
        break;
      case 'j':
        direction_x = -2;
        break;
      case 'l':
        direction_x = 2;
        break;
      default:
        valid = false;
        break;
      }
    } while (! valid);

    switch(player_state) {
    case vulnerable:
      player_x += direction_x;
      player_y += direction_y;
      break;
    case invincible:
      player_x += direction_x;
      player_y += direction_y;
      if (enemy_x - 1 <= player_x && player_x <= enemy_x + 1 &&
          enemy_y - 1 <= player_y && player_y <= enemy_y + 1) {
        player_state = vulnerable;
        enemy_state = defeated;
        potion_state = done;
      }
      break;
    }

    switch (enemy_state) {
    case chasing: // chasing
      if (player_x > enemy_x) {
        enemy_x += 1;
      }
      if (player_x < enemy_x) {
        enemy_x -= 1;
      }
      if (player_y > enemy_y) {
        enemy_y += 1;
      }
      if (player_y < enemy_y) {
        enemy_y -= 1;
      }

      if ((player_x == enemy_x || player_x == enemy_x + 1) &&
          (player_y == enemy_y || player_y == enemy_y + 1)) {
        player_state = dead;
      }
      break;
    case running:
      if (player_x > enemy_x) {
        enemy_x -= 1;
      }
      if (player_x < enemy_x) {
        enemy_x += 1;
      }
      if (player_y > enemy_y) {
        enemy_y -= 1;
      }
      if (player_y < enemy_y) {
        enemy_y += 1;
      }
      if (enemy_x < 0) {
        enemy_x = 0;
      }
      if (enemy_x > width) {
        enemy_x = width;
      }
      if (enemy_y < 0) {
        enemy_y = 0;
      }
      if (enemy_y > height) {
        enemy_y = height;
      }
      break;
    }

    switch (potion_state) {
    case available:
      if ((player_x == potion_x || player_x == potion_x + 1) &&
          (player_y == potion_y || player_y == potion_y + 1)) {
        player_state = invincible;
        enemy_state = running;
        potion_state = using;
        potion_counter = 10;
      }
      break;
    case using:
      potion_counter -= 1;
      if (potion_counter == 1) {
        player_state = vulnerable;
        enemy_state = chasing;
        potion_state = available;
        random = (random * 97) % 65533;
        potion_x = random % width;
        random = (random * 97) % 65533;
        potion_y = random % height;
      }
      break;
    }      
  }
}

enum { vulnerable, invincible, dead };

enum { chasing, running, defeated };

enum { available, using, done };