using NUnit.Framework;

namespace Chernobyl.StateMachine
{
    public class StateExtensionsTests
    {
        [Test, Description("A test to ensure that StateExtensions.IsActive(IState) " +
            "returns true when an IState is active and false when it is inactive.")]
        public void IsActiveTest()
        {
            IState state = new State();
            
            Assert.False(state.IsActive(), "The IState.IsActive(IState) should " +
                "return false as the IState is inactive.");

            state.ParentState = new State();

            Assert.True(state.IsActive(), "The IState.IsActive(IState) should " +
                "return true as the IState is active.");
        }

        [Test, Description("A test to ensure that " + 
            "StateExtensions.CheckedLeftAdd(IState, EventHandler) invokes " +
            "the EventHandler passed to it if the IState is active.")]
        public void CheckedEnteredAddInvokeWhenActive()
        {
            IState state = new State();
            state.ParentState = new State();
            state.CheckedEnteredAdd((sender, e) => Assert.Pass());
        }

        [Test, Description("A test to ensure that " +
            "StateExtensions.CheckedLeftAdd(IState, EventHandler) does not invoke " +
            "the EventHandler passed to it if the IState is active.")]
        public void CheckedEnteredAddDoesNotInvokeWhenInactive()
        {
            IState state = new State();
            state.CheckedEnteredAdd((sender, e) => Assert.Fail("The event handler " +
                "should not have been invoked."));
        }

        [Test, Description("A test to ensure that " +
            "StateExtensions.CheckedLeftAdd(IState, EventHandler) does not invoke " +
            "the EventHandler passed to it if the IState is active.")]
        public void CheckedLeftAddDoesNotInvokeWhenActive()
        {
            IState state = new State();
            state.ParentState = new State();
            state.CheckedLeftAdd((sender, e) => Assert.Fail("The event handler " +
                "should not have been invoked."));
        }

        [Test, Description("A test to ensure that " +
            "StateExtensions.CheckedLeftAdd(IState, EventHandler) invokes " +
            "the EventHandler passed to it if the IState is inactive.")]
        public void CheckedLeftAddInvokeWhenInactive()
        {
            IState state = new State();
            state.CheckedLeftAdd((sender, e) => Assert.Pass());
        }

        [Test, Description("A test to ensure the StateExtensions.EnterWith(IState, IState) " + 
            "method properly makes a one state the child of another when the " + 
            "parent's IState.Entered event is raised.")]
        public void EnterWithTest()
        {
            IState grandParent = new State();
            IState parent = new State();
            IState child = new State();

            parent.EnterWith(child);

            Assert.AreEqual(null, child.ParentState, "The IState.ParentState of " + 
                "the child was set before the parent state was activated.");

            parent.ParentState = grandParent;

            Assert.AreEqual(parent, child.ParentState, "The IState.ParentState of " +
                "the child was not set after the parent state was activated.");
        }
    }
}