using System;
using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public enum Transition
{
    NullTransition = 0,
}
public enum StateID
{
    NullStateID = 0,
}
public abstract class FSMState
{
    protected Dictionary<Transition, StateID> map = new Dictionary<Transition, StateID>();
    protected StateID stateID;
    public StateID ID { get { return stateID; } }

    public void AddTransition(Transition trans, StateID id)
    {
        if (trans == Transition.NullTransition)
        {
            Debug.LogError("FSMState ERROR: NullTransition is not allowed for a real transition");
            return;
        }
        if (id == StateID.NullStateID)
        {
            Debug.LogError("FSMState ERROR: NullStateID is not allowed for a real ID");
            return;
        }
        if (map.ContainsKey(trans))
        {
            Debug.LogError("FSMState ERROR: State " + stateID.ToString() + " already has transition " + trans.ToString() +
                           "Impossible to assign to another state");
            return;
        }
        map.Add(trans, id);
    }
    public void DeleteTransition(Transition trans)
    {
        if (trans == Transition.NullTransition)
        {
            Debug.LogError("FSMState ERROR: NullTransition is not allowed");
            return;
        }
        if (map.ContainsKey(trans))
        {
            map.Remove(trans);
            return;
        }
        Debug.LogError("FSMState ERROR: Transition " + trans.ToString() + " passed to " + stateID.ToString() +
                       " was not on the state's transition list");
    }
    public StateID GetOutputState(Transition trans)
    {
        if (map.ContainsKey(trans))
        {
            return map[trans];
        }
        return StateID.NullStateID;
    }
    public virtual void DoBeforeEntering() { }
    public virtual void DoBeforeLeaving() { }
    public abstract void Reason(GameObject player, GameObject npc);
    public abstract void Act(GameObject player, GameObject npc);
    public class FSMSystem
    {
        private List<FSMState> states;
        private StateID currentStateID;
        public StateID CurrentStateID { get { return currentStateID; } }
        private FSMState currentState;
        public FSMState CurrentState { get { return currentState; } }

        public FSMSystem()
        {
            states = new List<FSMState>();
        }
        public void AddState(FSMState s)
        {
            if (s == null)
            {
                Debug.LogError("FSM ERROR: Null reference is not allowed");
            }
            if (states.Count == 0)
            {
                states.Add(s);
                currentState = s;
                currentStateID = s.ID;
                return;
            }
            foreach (FSMState state in states)
            {
                if (state.ID == s.ID)
                {
                    Debug.LogError("FSM ERROR: Impossible to add state " + s.ID.ToString() +
                                   " because state has already been added");
                    return;
                }
            }
            states.Add(s);
        }
        public void DeleteState(StateID id)
        {
            if (id == StateID.NullStateID)
            {
                Debug.LogError("FSM ERROR: NullStateID is not allowed for a real state");
                return;
            }
            foreach (FSMState state in states)
            {
                if (state.ID == id)
                {
                    states.Remove(state);
                    return;
                }
            }
            Debug.LogError("FSM ERROR: Impossible to delete state " + id.ToString() +
                           ". It was not on the list of states");
        }
        public void PerformTransition(Transition trans)
        {
            if (trans == Transition.NullTransition)
            {
                Debug.LogError("FSM ERROR: NullTransition is not allowed for a real transition");
                return;
            }
            StateID id = currentState.GetOutputState(trans);
            if (id == StateID.NullStateID)
            {
                Debug.LogError("FSM ERROR: State " + currentStateID.ToString() + " does not have a target state " +
                               " for transition " + trans.ToString());
                return;
            }
            currentStateID = id;
            foreach (FSMState state in states)
            {
                if (state.ID == currentStateID)
                {
                    currentState.DoBeforeLeaving();
                    currentState = state;
                    currentState.DoBeforeEntering();
                    break;
                }
            }
        }
    }
}