/// <summary>
/// <inheritdoc/>
/// <remarks>
/// This is the appropriate action for <see cref="T:VendingMachine.WaitUserSelectionState"/> i.e. when the machine is ready for the user to select an item.
/// <list type="bullet">
/// <item>
/// <description>
/// Case 1. Checks the total machine inventory and if it is empty, it transitions back to <see cref="T:VendingMachine.SoldOutState"/>.
/// Machine needs a refill.
/// </description>
/// </item>
/// <item>
/// <description>
/// Case 2. Checks if there is sufficient stock of the selected item and transitions the state to <see cref="T:VendingMachine.WaitCoinState"/>.
/// User is in a position to insert the coins.
/// </description>
/// </item>
/// <item>
/// <description>
/// Case 3. If there is no stock left for the selected item it transitions back to <see cref="T:VendingMachine.WaitUserSelectionState"/>.
/// This allows the user to reselect a different item.
/// </description>
/// </item>
/// </list>
/// </remarks>
/// </summary>
/// <param name="itemName">Name of the product</param>
public void SelectItem(string itemName)
{
// Machine's inventory is Zero. Everything is sold out. Make the state transition to the sold out state
if (_machine.TotalItemCount == 0)
{
_machine.State = _machine.GetSoldOutState;
return;
}
// check if the machine has enough stock of the selected item
if (_machine.GetItemCount(itemName) > 0)
{
// tell the machine to update the selected product in transaction
_machine.AddItem(itemName);
_machine.DisplayMessage(string.Format("You selected {0} with a value of {1} ", _machine.SelectedItem.Name, _machine.SelectedItem.Price));
// change the state to "wait for coins".
_machine.State = _machine.GetWaitCoinState;
// display an appropriate message to the user
_machine.DisplayMessage(string.Format("Please insert coins to buy '{0}'", _machine.SelectedItem.Name));
}
else
{
// Sufficient stock is not available. Hence, change the state to wait selection state
// such that the user can select a different drink. Notify this to the user.
_machine.State = _machine.GetUserSelectItemState;
throw new ApplicationException(string.Format("Sorry, '{0}' is not available. Please select a different drink.",
_machine.SelectedItem.Name));
}
}
