/*
 * Step 1: Check current index's color
 * Step 2: Rotate ant either CW or CCW based on index's color
 * Step 3: Change current index's color to next color in list
 * Step 4: Move ant forward based on rotation state. (If facing north, move up an index (curIndex + array width), east (curIndex++))
 */

void main(){
  var colors = ['!', '@', '#', '%', '&'];
  var colorDir = [-1, 1, -1, 1, -1]; // 1 = RIGHT, -1 = LEFT

  var width = 75;
  var height = 75;

  var grid = new List<String>(width * height);
  grid.fillRange(0, grid.length, colors[0]);
  var antStart = (grid.length / 2).ceil(); // ~~CENTER OF LIST

  var currentPos = antStart;
  var currentDir = 0; // 0 = NORTH, 1 = EAST, 2 = SOUTH, -1 = WEST, < -1, SET 2   > 3, SET -1
  var currentColor = colors.indexOf('!'); // CURRENTCOLOR DEFAULT = 0 [!], CANNOT EXCEED COLORS.LENGTH

  var ticks = 30000;

  for(int i = 0; i < ticks; i++){

    // STEP 1

    currentColor = colors.indexOf(grid[currentPos]);

    // STEP 2

    currentDir = currentDir + colorDir[currentColor];

    if(currentDir < -1){
      currentDir = 2;
    }

    if(currentDir > 2){
      currentDir = -1;
    }

    // STEP 3

    currentColor++;

    if(currentColor > colors.length - 1){
      currentColor = 0;
    }

    grid[currentPos] = colors[currentColor];

    // STEP 4

    switch(currentDir){
      case 0: // NORTH
        currentPos -= width;
        break;
      case 1: // EAST
        currentPos++;
        break;
      case 2: // SOUTH
        currentPos += width;
        break;
      case -1: // WEST
        currentPos--;
        break;
    }

  }
  toString(grid, width);
}

void toString(List<String> grid, int width){
  String formattedGrid = '';

  for(int i = 0; i < grid.length; i++){
    formattedGrid += grid[i] + ' ';
    if((i % width) == (width - 1)){
      formattedGrid += '\n';
    }
  }
  print(formattedGrid);
}