133 lines
3.8 KiB
C#
133 lines
3.8 KiB
C#
// Copyright (c) 2012-2022 Wojciech Figat. All rights reserved.
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using System;
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using System.Collections.Generic;
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namespace FlaxEngine.Utilities
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{
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/// <summary>
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/// State machine logic pattern
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/// </summary>
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public abstract class StateMachine
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{
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/// <summary>
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/// The current state.
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/// </summary>
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protected State currentState;
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/// <summary>
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/// The states.
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/// </summary>
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protected readonly List<State> states = new List<State>();
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/// <summary>
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/// Gets the current state.
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/// </summary>
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public State CurrentState => currentState;
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/// <summary>
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/// Occurs when state is being changed.
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/// </summary>
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public event Action StateChanging;
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/// <summary>
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/// Occurs when state gets changed.
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/// </summary>
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public event Action StateChanged;
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/// <summary>
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/// Gets the states (read-only).
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/// </summary>
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public IReadOnlyList<State> States => states;
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/// <summary>
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/// Gets state of given type.
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/// </summary>
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/// <typeparam name="TStateType">The type of the state.</typeparam>
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public State GetState<TStateType>()
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{
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return states.Find(x => x.GetType() == typeof(TStateType));
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}
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/// <summary>
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/// Goes to the state.
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/// </summary>
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/// <typeparam name="TStateType">The type of the state.</typeparam>
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/// <exception cref="InvalidOperationException">Cannot find state of given type.</exception>
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public void GoToState<TStateType>()
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{
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var state = states.Find(x => x.GetType() == typeof(TStateType));
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if (state == null)
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throw new InvalidOperationException($"Cannot find state {typeof(TStateType)}.");
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GoToState(state);
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}
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/// <summary>
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/// Goes to the state.
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/// </summary>
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/// <param name="state">The target state.</param>
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/// <exception cref="ArgumentNullException">state</exception>
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public virtual void GoToState(State state)
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{
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if (state == null)
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throw new ArgumentNullException(nameof(state));
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// Prevent from entering the same state
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if (state == currentState)
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return;
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// Check if cannot leave current state
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if (currentState != null && !currentState.CanExit(state))
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return;
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// Check if cannot enter new state
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if (!state.CanEnter())
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return;
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// Change state
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SwitchState(state);
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}
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/// <summary>
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/// Adds the state.
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/// </summary>
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/// <param name="state">The state.</param>
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public virtual void AddState(State state)
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{
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if (state.owner == this)
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throw new InvalidOperationException("Cannot add already registered state.");
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states.Add(state);
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state.owner = this;
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}
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/// <summary>
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/// Removes the state.
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/// </summary>
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/// <param name="state">The state.</param>
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public virtual void RemoveState(State state)
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{
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if (state.owner == null)
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throw new InvalidOperationException("Cannot remove unregistered state.");
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states.Remove(state);
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state.owner = null;
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}
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/// <summary>
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/// Switches the state.
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/// </summary>
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/// <param name="nextState">Then next state.</param>
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protected virtual void SwitchState(State nextState)
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{
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StateChanging?.Invoke();
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currentState?.OnExit(nextState);
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currentState = nextState;
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currentState?.OnEnter();
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StateChanged?.Invoke();
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}
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}
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}
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