<?php
	$errors = []; //To store errors
	$result = array(); //Pass back the data to `form.php`


	//Overall outline of the question
	// peopleOnBus = people on the bus
	// numberOfPeopleGettingOn = people who want to get on the bus
	// busMaxCapacity =  Total capacity

	$peopleOnBus = 0;
	// extract the data from the form
	$busMaxCapacity = $_POST['busMaxCapacity'];
	$numberOfPeopleGettingOn = $_POST['numberOfPeopleGettingOn'];
	$numberOfPeopleGettingOff = $_POST['numberOfPeopleGettingOff'];

	//Process
	$peopleCurrentlyOnBus = $peopleOnBus + $numberOfPeopleGettingOn - $numberOfPeopleGettingOff;

	if($numberOfPeopleGettingOff > $busMaxCapacity)
	{
		$errors['invalid'] = 'The values inserted are not valid. Go back to the previous page!';
	}

	else if ($numberOfPeopleGettingOff > $peopleOnBus)
	{
		$errors['invalid'] = "The values inserted are not valid. Go back to the previous page!";
	}

    else
    {
    	//$result['capacity'] = "The bus has a capacity of $busMaxCapacity";

		// Question 1: Capacity is less than total people
		if ($peopleCurrentlyOnBus > $busMaxCapacity)
		{
			$difference = $peopleCurrentlyOnBus - $busMaxCapacity;

			$gotOn = $numberOfPeopleGettingOn - $difference;
			$result['comment'] = "$gotOn got on the bus, but $difference could not get on";
			$result['freeSeats'] = $busMaxCapacity - $gotOn;
			$result['takenSeat'] = $peopleCurrentlyOnBus;
		}

		//Question 2: Spare seats
		else if ($peopleCurrentlyOnBus < $busMaxCapacity)
		{
			$spareSeats = $busMaxCapacity - $peopleCurrentlyOnBus;
			//echo "$peopleCurrentlyOnBus people got on the bus, and there were $spareSeats spare seats";
		}

		// Question 3: Total capacity = total people
		else
		{
			//echo "$numberOfPeopleGettingOn people tried to get on the bus";
			//echo "<br>";
			//echo "Everyone could get on the bus yay";
		}

    }

	header("content-type:application/json");
	echo json_encode($result);


	// present the result


?>