/// <summary>
/// <inheritdoc/>
/// <remarks>
/// The current state is the <see cref="T:VendingMachine.SoldState"/>. This means that the user has paid.
/// The following scenarios are possible in this case :-
/// <list type="bullet">
/// <item>
/// <description>
/// Case 1. Machine does not have exact change to tender. Hence, refund the user money and set the transition state to
/// <see cref="T:VendingMachine.WaitUserSelectionState"/>
/// </description>
/// </item>
/// <item>
/// <description>
/// Case 2. Everything is fine. Ask the machine to release the drink.
/// </description>
/// </item>
/// <item>
/// <description>
/// Case 3. After releasing the item, check if the machine owes any amount to the user. If yes, then,
/// the state is changed to <see cref="T:VendingMachine.DispenseChangeState"/>
/// </description>
/// </item>
/// <item>
/// <description>
/// Case 4. After releasing the item, checks if the machine has enough inventory and it owes nothing to the user.
/// Transitions the state to <see cref="T:VendingMachine.WaitUserSelectionState"/>
/// </description>
/// </item>
/// <item>
/// <description>
/// Case 5. After releasing the item, check the total inventory count.
/// If its zero, then transition the state to <see cref="T:VendingMachine.SoldOutState"/>
/// </description>
/// </item>
/// </list>
/// </remarks>
/// </summary>
public void DispenseItem()
{
// Machine does not have exact change to tender, hence do not dispense the item
// Change back the state to user selection state, refund the money and show an appropriate message to the user.
if (String.IsNullOrEmpty(_machine.TenderChange()))
{
var refund = _machine.RefundMoney();
_machine.State = _machine.GetUserSelectItemState;
throw new ApplicationException(string.Format("Machine does not have sufficient change. Please tender exact change. Please collect your inserted amount{0}", refund));
}
_machine.ReleaseItem();
_machine.DisplayMessage("Item has been dispensed. Please do not forget to collect it.");
// machine has to refund
if (_machine.CustomerBalance < 0)
{
_machine.State = _machine.GetDispenseChangeState;
}
// Machine has enough products and has nothing to refund back to the user
if (_machine.TotalItemCount > 0 && _machine.CustomerBalance == 0)
{
_machine.State = _machine.GetUserSelectItemState;
}
// Machine is empty. Everything is sold out. Hence, change the state to SoldOut
if (_machine.TotalItemCount == 0)
{
_machine.State = _machine.GetSoldOutState;
throw new ApplicationException("Sorry, the machine is out of stock.");
}
}
