FSM.cs

using System;

namespace P8.StateMachine {

	public static class FSM< ImplMachine, ImplState >
		where ImplMachine : FSM< ImplMachine, ImplState >.Machine
		where ImplState   : FSM< ImplMachine, ImplState >.State
	{

		public abstract class Machine {
			public ImplState current = null;

			protected Machine() {
			}
			virtual public void setup( ImplState first ) {
				trans( first );
			}
			virtual public void update( float dt ) {
				current?.update( dt );
			}
			virtual public void trans( ImplState next ) {
				current?.exit( next );
				var prev = current;
				current = next;
				current?.enter( prev );
			}
		}

		public abstract class State {
			public float tCnt => _tCnt;		//!< 経過時刻
			
			protected State( ImplMachine parent ) {
				_parent = parent;
			}

			virtual public void enter( ImplState prev ) {
				_tCnt = 0;
			}
			virtual public void update( float dt ) {
				_tCnt += dt;
			}
			virtual public void exit( ImplState next ) {
			}

			protected ImplMachine _parent;
			protected float _tCnt;
			
			protected void trans( ImplState next ) => _parent.trans( next );
		}

	}

}