dailyprogrammer challenge on reddit: spiral

draw_spiral.php

<?php
// https://www.reddit.com/r/dailyprogrammer/comments/6i60lr/20170619_challenge_320_easy_spiral_ascension/

/**
 * @param array $arguments
 * @return int
 */
function check_args_and_get_number(array $arguments)
{
  $parameter_name = 'n';
  $filename = $arguments[0];
  
  if(!array_key_exists(1, $arguments))
  {
    die('Please enter a number as parameter like "php ' . $filename . ' ' . $parameter_name . '=5"');
  }
  
  list($given_parameter_name, $number) = explode('=', $arguments[1]);
  
  $number = intval($number);
  
  if($given_parameter_name != $parameter_name)
  {
    die('Please enter a number as parameter like "php ' . $filename . ' ' . $parameter_name . '=5"');
  }
  
  if(!is_integer($number) || $number < 1)
  {
    die('Your input ' . $number . ' wasn\'t a positive number.');
  }
  
  return $number;
}

/**
 * @param int $number
 * @return array
 */
function get_empty_canvas(int $number)
{
  $canvas = [];
  
  for($i = 0; $i < $number; $i++)
  {
    for($j = 0; $j < $number; $j++)
    {
      $canvas[$i][$j] = 0;
    }
  }
  
  return $canvas;
}

/**
 * @param array $canvas
 * @param int   $number
 */
function draw_spiral_on_canvas(array &$canvas, int $number)
{
  $column = $row = 0;
  $direction = 'right';
  
  for($i = 1; $i <= $number ** 2; $i++)
  {
    $canvas[$row][$column] = $i;
    
    make_a_step($row, $column, $direction);
    
    // make a turn if the cursor is out of bound or would replace a value different from zero
    if(!isset($canvas[$row][$column]) || $canvas[$row][$column] != 0)
    {
      make_a_turn($direction, $row, $column);
    }
  }
}

/**
 * @param int    $row
 * @param int    $column
 * @param string $direction
 */
function make_a_step(int &$row, int &$column, string $direction)
{
  switch($direction)
  {
    case 'right':
      $column++;
      break;
    case 'down':
      $row++;
      break;
    case 'left':
      $column--;
      break;
    case 'up':
      $row--;
      break;
  }
}

/**
 * @param string $direction
 * @param int    $row
 * @param int    $column
 */
function make_a_turn(string &$direction, int &$row, int &$column)
{
  switch($direction)
  {
    case 'right':
      $direction = 'down';
      $row++;
      $column--;
      break;
    case 'down':
      $direction = 'left';
      $row--;
      $column--;
      break;
    case 'left':
      $direction = 'up';
      $row--;
      $column++;
      break;
    case 'up':
      $direction = 'right';
      $row++;
      $column++;
      break;
  }
}

/**
 * @param array $canvas
 * @param int   $number
 */
function print_canvas(array $canvas, int $number)
{
  $out = '';
  $padding_left = strlen($number ** 2) + 1;
  
  foreach($canvas as $lines)
  {
    foreach($lines as $field)
    {
      $out .= str_pad($field, $padding_left, " ", STR_PAD_LEFT);
    }
    
    $out .= PHP_EOL;
  }
  
  echo $out;
}

$number = check_args_and_get_number($argv);
$canvas = get_empty_canvas($number);
draw_spiral_on_canvas($canvas, $number);
print_canvas($canvas, $number);