<?php
  $title = "Lab 6 - Self-referring Forms w/ Data Validation";
  $file = "lab6.php";
  $description = "This lab page will have an HTML form that refers back to itself, and will use PHP to handle data validation.";
  $date = "Date: March 23, 2018";
  $banner = "Lab 6: Self-referring Forms w/ Data Validation";
  include 'header.php'; //moved this to here
  define('MAX_ITERATIONS','100');

  $start = "";
  $stop = "";
  $incr = "";
  $error = "";
  $output = ""; //changed this from $result

  if ($_SERVER["REQUEST_METHOD"] == "post")
  {
    $start = trim($_POST["startTemp"]);
    $stop = trim($_POST["stopTemp"]);
    $incr = trim($_POST["incrRate"]);

    if(!isset($start) || $start == "")
    {
      $error .= "You need to enter a starting value.";
    }
    else if(!is_numeric($start))
    {
      $error .= "You need to enter a number in the initial value box.";
      $start = "";
    }

    if(!isset($stop) || $stop == "")
    {
      $error .= "You need to enter an ending value.";
    }
    else if(!is_numeric($stop))
    {
      $error .= "You need to enter a number in the final value box.";
      $stop = "";
    }

    if(!isset($incr) || $incr == "")
    {
      $error .= "You need to enter an increment rate.";
    }
    else if(!is_numeric($incr))
    {
      $error .= "You need to enter a number in the increment rate box.";
      $incr = "";
    }

    if((($stop - $start)/$incr) > MAX_ITERATIONS)
    {
      $error .= "The maximum number of iterations has been exceded. Please enter a lower increment rate";
    }
    else
    {
      if($error == "" && $_SERVER["REQUEST_METHOD"] == "post")
      {
        $output = "<table border='2px'>";
        $output .= "<tr>";
        $output .= "<th>Celcius</th>";
        $output .= "<th>Fahrenheit</tr>";
        $output .= "</tr>";
        for($celc = $start; $celc <= $stop; $celc += $incr)
        {
          $fahr = (9.0 / 5.0) * $celc + 32;
          $output .= "<tr><td align='center'>$celc&deg;</td><td align='center'>$fahr&deg;</td></tr>";
        }
        $output .= "</table>"; //missed ;
      }
      else
      {
        $error .= "<br/>Please try again.";
      }
    }
  }
?>

<form action="<?php echo $_SERVER['PHP_SELF']; ?>" method="post">
  Enter your initial value: <input type="text" name="startTemp" value="<?php echo $start; ?>" size = "5" /><br/>
  Enter your final value: <input type = "text" name = "stopTemp" value = "<?php echo $stop; ?>" size = "5" /><br/>
  Enter your initial value: <input type = "text" name = "incrRate" value = "<?php echo $incr; ?>" size = "5" /><br/>
  <input type = "submit" value = "Create Temperature Conversion Table" />
</form>

<h2><?php echo $output; ?></h2>
<h3><?php echo $error; ?></h3>
<?php include 'footer.php'; ?>