/* ----------------------------------------------------------------------- *
 * Life: A game program that emulates the growth of cells in a petri dish
 *
 * Author: Suzi Anvin
 *
 * Rules: Cells die if lonely or overcrowded.  They only live if the 8
 *        surrounding squares have 2 or 3 other cells.  Cells can be created 
 *        in any empty square that is adjacent to 3 other cells.
 *
 * Operation: (Versions 0.X) Non-operational development stages.  Version 0.1 
 *            inputs one line of text, converts it inot a bit array, prints 
 *            bits and then prints the line of cells.  An error message is 
 *            returned if the computer does not recognize the input and asks
 *            for the string again.  After displaying correct line, program
 *            asks if the user want's to try again and quits if they answer 
 *            'n' Oterwise it restarts.
 *
 * Goal:      (Versions 1.X) User enters a string of text on several lines, 
 *            representing cells as '@' and empty spaces as '.'  This is 
 *            converted into an array of bits.  "Life" then runs step by step 
 *            through the lifecycle of the cells, re-drawing the display each 
 *            time the user presses enter.  The display quits when the user 
 *            types 'Q' and then asks the user if they want to play again.
 *            If the user's answer begins with 'Y' the program restarts.
 *            Otherwise, it quits.
 * ----------------------------------------------------------------------- */
#include <stdint.h>
#include <stdio.h>

inline void set_bit (uint8_t array[], unsigned int bit)
{
  array[bit/8] |= 1<<(bit%8);
}

inline void clr_bit (uint8_t array[], unsigned int bit)
{
  array[bit/8] &= ~(1<<(bit%8));
}

/* test_bit returns 1 if the bit is 1 and 0 if the bit is 0. */
inline int test_bit (const uint8_t array[], unsigned int bit)
{
  return (array[bit/8]>>(bit%8)) & 1;
}

/* set_bmp_line takes a text line of @'s and .'s.  It assigns them to 
 * one line of a bitmap array with @ = 1 and . = 0
 *  
 * When passing the array to set_bmp_line, be sure to specify the line
 * number [in brackets]. 
 *
 * set_bmp_line returns 0 if all bits are correctly assigned and 1 if
 * it does not recognize a character from the text line. */
int set_bmp_line (uint8_t array[], char line[])
{
  int i;			/* counter */
  
  clr_bit (array, 0);
  for (i=1; i <= 38; i++) {
    switch (line[i-1]) {
    case '@':
      set_bit (array, i);
      break;
    case '.':
      clr_bit (array, i);
      break;
    default:
      return (1);
    }
  }
  clr_bit (array, 39);
  return (0);
}

/* draw_bmp_line is a preliminary function to draw one line of the bitmap
 * seperately.  Each line of the array is passed individually, and bits 1-38 
 * are drawn on the screen, with 1 = '@' and 0 = '.'. the comand call needs to 
 * specify the current line # [in brackets] to use the function.
 *  
 * I'm told I'm "already using pointers" to pass in the 1 
 * dimensional array.  That's fine, I'll wait til I have a better clue before 
 * passing in both dimensions.  In version 1.1 or so this function should 
 * be updated to draw the whole bitmap. */
void draw_bmp_line (uint8_t array[])
{
  int i;			/* counter(s) */

  putchar(' ');
  for (i=1; i<= 38; i++) {
    if (test_bit(array, i))
      putchar('@');
    else
      putchar('.');
  }
  putchar('\n');
}

/* debug_bits prints out the bits as the appear in the array.  This tests that 
 * they have been encoded correctly. */ 
void debug_bits (uint8_t array[])
{
  int i;
  
  for (i=0; i < 40; i++) {
    printf("%d", test_bit(array, i));
  }
  putchar('\n');
}
      
/* set up bitmap array as [line #] [byte # in that line] */

/* temporary main function to test the set_bmp_line and draw_bmp_line 
   * functions */

int main()
{
  char line[50];
  uint8_t bitmap[5];		/* one dimensional bitmap array */

  while (1) {			/* loop for debugging */
    printf("Welcome to the game of Life, development version 0.1.\n"
	   "Please enter your cells one line at a time,\n"
	   "with no more than 38 characters per line\n"
	   "as indicated by the line of ---'s.\n");
    while(1){
      printf("Use @ to indicate a cell and a period to "
	     "indicate an empty space.\n"
	     " --------------------------------------\n ");
      fgets(line, sizeof(line), stdin);
      line[38] = '\0';
      if (set_bmp_line(bitmap, line) == 1) {
	printf("Error: Unrecognized character in string.\n"
	       "Please enter your cells again.\n");
	continue;
      }
      else
	break;
    }
  debug_bits(bitmap);
  draw_bmp_line(bitmap);
  printf("try again? (y/n)");
  fgets(line, sizeof(line), stdin);
  if (line[0] == 'n')
    break;
  }
  return (0);
}