using System;
using System.Collections.Generic;
using System.Linq;

namespace Wayne.Lib.StateEngine
{
    public class StateLookupEntry
    {
        #region Fields

        public string NextStateFactoryName { get; internal set; }
        public HistoryType HistoryType { get; private set; }

        #endregion

        #region Construction

        public StateLookupEntry(string nextStateFactoryName, HistoryType historyType)
        {
            NextStateFactoryName = nextStateFactoryName;
            HistoryType = historyType;
        }

        #endregion
    }


    /// <summary>
    /// StateTransitionLookup is used by the State machine to find the state to 
    /// change to when a transition occurs. It uses a dataset that contains the actual data.
    /// </summary>
    public class StateTransitionLookup
    {
        #region Fields

        private readonly StateTypeContainer stateTypeContainer;

        #endregion

        #region Construction

        /// <summary>
        /// Constructor
        /// </summary>
        public StateTransitionLookup(StateTypeContainer stateTypeContainer)
        {
            LookupTable = new Dictionary<string, Dictionary<object, StateLookupEntry>>();
            this.stateTypeContainer = stateTypeContainer;
        }

        public Dictionary<string, Dictionary<object, StateLookupEntry>> LookupTable { get; private set; }

        #endregion

        #region Method: GetNextState

        /// <summary>
        ///		Performs a Lookup for the next state when in the source state, and
        ///		are going to perform the specified transition
        /// </summary>
        /// <param name="sourceStateFactoryName">
        /// The state the state machine is in when performing transition
        /// </param>
        /// <param name="transition">
        /// The requested transition.
        /// </param>
        /// <returns>
        /// Returns the next state that should be entered based on the transition.
        /// </returns>
        public StateEntry GetNextState(string sourceStateFactoryName, Wayne.Lib.StateEngine.Transition transition)
        {
            if (transition == null)
                return null;

            StateLookupEntry stateLookupEntry;
            //Try look up with the current state name
            if (TryLookup(sourceStateFactoryName, transition.Type, out stateLookupEntry))
            {
                return new StateEntry(transition, stateLookupEntry.NextStateFactoryName, stateLookupEntry.HistoryType);
            }

            //If not matching with current state name, try lookup recursively with AnyState 
            if (sourceStateFactoryName != AnyState.FactoryName) //Unless we are already in recursion.
            {
                return GetNextState(AnyState.FactoryName, transition);
            }

            return null;
        }

        public bool TryLookup(string sourceStateFactoryName, object transitionType, out StateLookupEntry stateLookupEntry)
        {
            stateLookupEntry = null;
            Dictionary<object, StateLookupEntry> lookup1;
            if (LookupTable.TryGetValue(sourceStateFactoryName, out lookup1))
            {
                return lookup1.TryGetValue(transitionType, out stateLookupEntry);
            }
            return false;
        }

        #endregion

        #region Method: AddTransition

        /// <summary>
        /// Internal add transition.
        /// </summary>
        /// <param name="sourceStateFactoryName"></param>
        /// <param name="transitionType"></param>
        /// <param name="nextStateType"></param>
        /// <param name="historyType"></param>
        /// <param name="replace"></param>
        private void InternalAddTransition(string sourceStateFactoryName, object transitionType, string nextStateType, HistoryType historyType, bool replace)
        {
            if (historyType == HistoryType.Explicit)
                throw new StateEngineException("Cannot configure a transition to have a explicit history type. It is only used internally when working with explicit transitions");

            var stateLookup = GetTransitionsForState(sourceStateFactoryName);
            var exists = stateLookup.ContainsKey(transitionType);

            if (exists && !replace)
            {
                throw new ArgumentException(string.Format("The State-Transition combination \"{0}-{1}\" has already been defined.", sourceStateFactoryName, Transition.GetTransitionName(transitionType)));
            }
            if (!exists && replace)
            {
                throw new ArgumentException(string.Format("The State-Transition combination \"{0}-{1}\" is not defined.", sourceStateFactoryName, Transition.GetTransitionName(transitionType)));
            }

            StateLookupEntry lookupEntry = new StateLookupEntry(nextStateType, historyType);
            stateLookup[transitionType] = lookupEntry;
        }

        /// <summary>
        /// Returns a transition dictionary for the specified state. 
        /// </summary>
        /// <param name="sourceStateFactoryName"></param>
        /// <returns></returns>
        public Dictionary<object, StateLookupEntry> GetTransitionsForState(string sourceStateFactoryName)
        {
            Dictionary<object, StateLookupEntry> result;
            if (!LookupTable.TryGetValue(sourceStateFactoryName, out result))
            {
                LookupTable.Add(sourceStateFactoryName, result = new Dictionary<object, StateLookupEntry>());
            }
            return result;
        }

        /// <summary>
        /// Adds a transition from state of class TFromState to the class TToState, when the transitiontype 
        /// is inserted.
        /// </summary>
        /// <typeparam name="TFromState">Class type of the source state.</typeparam>
        /// <typeparam name="TToState">Class type of target state.</typeparam>
        /// <param name="transitionType">Transition type.</param>
        public void AddTransition<TFromState, TToState>(object transitionType)
            where TFromState : State
            where TToState : State
        {
            stateTypeContainer.Register<TFromState>();
            stateTypeContainer.Register<TToState>();

            InternalAddTransition(typeof(TFromState).FullName, transitionType, typeof(TToState).FullName, HistoryType.None, false);
        }

        /// <summary>
        /// Adds a transition from state of class fromStateFactoryName to the class toStateFactoryName, when the transitiontype 
        /// is inserted.
        /// </summary>
        /// <param name="fromStateFactoryName">String containig the factory name for the fromState.</param>
        /// <param name="toStateFactoryName">String containig the factory name for the toState.</param>
        /// <param name="transitionType">Transition type.</param>
        public void AddTransition(string fromStateFactoryName, string toStateFactoryName, object transitionType)
        {
            InternalAddTransition(fromStateFactoryName, transitionType, toStateFactoryName, HistoryType.None, false);
        }

        /// <summary>
        /// Adds a transition from state of class TFromState to the class TToState, when the transitiontype 
        /// is inserted.
        /// </summary>
        /// <typeparam name="TFromState">Class type of the source state.</typeparam>
        /// <typeparam name="TToState">Class type of target state.</typeparam>
        /// <param name="transitionType">Transition type.</param>
        /// <param name="historyType"></param>
        public void AddTransition<TFromState, TToState>(object transitionType, HistoryType historyType)
            where TFromState : State
            where TToState : State
        {
            stateTypeContainer.Register<TFromState>();
            stateTypeContainer.Register<TToState>();

            InternalAddTransition(typeof(TFromState).FullName, transitionType, typeof(TToState).FullName, historyType, false);
        }

        #endregion

        #region Method: ReplaceTransition (Specifying both From and To state)

        /// <summary>
        /// Replaces the existing transition from a state and the given TransitionType, to another state.
        /// </summary>
        /// <typeparam name="TFromOldState">Class type of the source state.</typeparam>
        /// <typeparam name="TToNewState">Class type of new target state.</typeparam>
        /// <param name="transitionType">Transition type.</param>
        public void ReplaceTransition<TFromOldState, TToNewState>(object transitionType)
            where TFromOldState : State
            where TToNewState : State
        {
            stateTypeContainer.Register<TFromOldState>();
            stateTypeContainer.Register<TToNewState>();
            InternalAddTransition(typeof(TFromOldState).FullName, transitionType, typeof(TToNewState).FullName, HistoryType.None, true);
        }

        /// <summary>
        /// Replaces the existing transition from a state and the given TransitionType, to another state.
        /// </summary>
        /// <param name="fromOldStateFactoryName">String containig the factory name for the fromState.</param>
        /// <param name="toNewStateFactoryName">String containig the factory name for the new toState.</param>
        /// <param name="transitionType">Transition type.</param>
        public void ReplaceTransition(string fromOldStateFactoryName, string toNewStateFactoryName, object transitionType)
        {
            InternalAddTransition(fromOldStateFactoryName, transitionType, toNewStateFactoryName, HistoryType.None, true);
        }

        /// <summary>
        /// Replaces the existing transition from a state and the given TransitionType, to another state.
        /// </summary>
        /// <typeparam name="TFromOldState">Class type of the source state.</typeparam>
        /// <typeparam name="TToNewState">Class type of new target state.</typeparam>
        /// <param name="transitionType">Transition type.</param>
        /// <param name="historyType"></param>
        public void ReplaceTransition<TFromOldState, TToNewState>(object transitionType, HistoryType historyType)
            where TFromOldState : State
            where TToNewState : State
        {
            stateTypeContainer.Register<TFromOldState>();
            stateTypeContainer.Register<TToNewState>();
            InternalAddTransition(typeof(TFromOldState).FullName, transitionType, typeof(TToNewState).FullName, historyType, true);
        }

        #endregion

        #region Method: ReplaceTransitions (Specifying only To state)

        /// <summary>
        /// Replaces all the existing transitions to the given OldToState to the NewToState.
        /// </summary>
        /// <typeparam name="TOldToState">Class type of old target state.</typeparam>
        /// <typeparam name="TNewToState">Class type of new target state.</typeparam>
        public void ReplaceTransitions<TOldToState, TNewToState>()
            where TOldToState : State
            where TNewToState : State
        {
            stateTypeContainer.Register<TOldToState>();
            stateTypeContainer.Register<TNewToState>();

            ReplaceTransitions(typeof(TOldToState).FullName, typeof(TNewToState).FullName);
        }

        /// <summary>
        /// Replaces all the existing transitions to the given OldToState to the NewToState.
        /// </summary>
        /// <param name="oldToStateFactoryName">String containig the factory name for the old ToState.</param>
        /// <param name="newToStateFactoryName">String containig the factory name for the new ToState.</param>
        public void ReplaceTransitions(string oldToStateFactoryName, string newToStateFactoryName)
        {
            LookupTable.Values
                .SelectMany(x => x.Values)
                .Where(x => x.NextStateFactoryName == oldToStateFactoryName)
                .ForEach(x => x.NextStateFactoryName = newToStateFactoryName);
        }

        #endregion

        #region Method: IntersectTransition

        /// <summary>
        /// Puts a state in-between two states that has a transition between them.
        /// </summary>
        /// <typeparam name="TFromState"></typeparam>
        /// <typeparam name="TIntersectingState"></typeparam>
        /// <typeparam name="TOldToState"></typeparam>
        /// <param name="transitionType"></param>
        public void IntersectTransition<TFromState, TIntersectingState, TOldToState>(object transitionType)
            where TFromState : State
            where TIntersectingState : State
            where TOldToState : State
        {
            stateTypeContainer.Register<TFromState>();
            stateTypeContainer.Register<TIntersectingState>();
            stateTypeContainer.Register<TOldToState>();

            IntersectTransition<TFromState, TIntersectingState, TOldToState>(transitionType, transitionType);
        }

        /// <summary>
        /// Puts a state in-between two states that has a transition between them.
        /// </summary>
        /// <typeparam name="TFromState"></typeparam>
        /// <typeparam name="TIntersectingState"></typeparam>
        /// <typeparam name="TOldToState"></typeparam>
        /// <param name="fromTransitionType"></param>
        /// <param name="toTransitionType"></param>
        public void IntersectTransition<TFromState, TIntersectingState, TOldToState>(object fromTransitionType, object toTransitionType)
            where TFromState : State
            where TIntersectingState : State
            where TOldToState : State
        {
            stateTypeContainer.Register<TFromState>();
            stateTypeContainer.Register<TIntersectingState>();
            stateTypeContainer.Register<TOldToState>();

            StateLookupEntry dummy;
            if (!TryLookup(typeof(TFromState).FullName, fromTransitionType, out dummy))
            {
                throw new StateEngineException(string.Format("No previous Transition {0}, from {1} to {2} exists to intersect.", Transition.GetTransitionName(fromTransitionType), typeof(TFromState).FullName, typeof(TOldToState).FullName));
            }

            //If the Transition TFromState to TOldState with toTransitionType doesn't exist throw an Error.
            ReplaceTransition<TFromState, TIntersectingState>(fromTransitionType);
            AddTransition<TIntersectingState, TOldToState>(toTransitionType);
        }

        #endregion

        #region Method: ReplaceState

        /// <summary>
        /// Replaces all the existing transitions to the given OldToState to the NewToState.
        /// Also adds the transitions from the OldToState to also from the NewToState.
        /// </summary>
        /// <typeparam name="TOldToState">Class type of old target state.</typeparam>
        /// <typeparam name="TNewToState">Class type of new target state.</typeparam>
        public void ReplaceState<TOldToState, TNewToState>()
            where TOldToState : State
            where TNewToState : State
        {
            stateTypeContainer.Register<TOldToState>();
            stateTypeContainer.Register<TNewToState>();

            ReplaceState(typeof(TOldToState).FullName, typeof(TNewToState).FullName, false);
        }

        /// <summary>
        /// Replaces all the existing transitions to the given OldToState to the NewToState.
        /// Also adds the transitions from the OldToState to also from the NewToState.
        /// </summary>
        /// <param name="removeAllTransitionsFromState">Default=false. Should all existing transitions *From* this state be removed?</param>
        /// <typeparam name="TOldToState">Class type of old target state.</typeparam>
        /// <typeparam name="TNewToState">Class type of new target state.</typeparam>
        public void ReplaceState<TOldToState, TNewToState>(bool removeAllTransitionsFromState)
            where TOldToState : State
            where TNewToState : State
        {
            stateTypeContainer.Register<TOldToState>();
            stateTypeContainer.Register<TNewToState>();

            ReplaceState(typeof(TOldToState).FullName, typeof(TNewToState).FullName, removeAllTransitionsFromState);
        }

        /// <summary>
        /// Replaces all the existing transitions to the given OldToState to the NewToState.
        /// Also adds the transitions from the OldToState to also from the NewToState.
        /// </summary>
        /// <param name="oldToStateFactoryName">String containig the factory name for the old ToState.</param>
        /// <param name="newToStateFactoryName">String containig the factory name for the new ToState.</param>
        public void ReplaceState(string oldToStateFactoryName, string newToStateFactoryName)
        {
            ReplaceState(oldToStateFactoryName, newToStateFactoryName, false);
        }

        /// <summary>
        /// Replaces all the existing transitions to the given OldToState to the NewToState.
        /// Also adds the transitions from the OldToState to also from the NewToState.
        /// Note: 'OverrideState' also exists, to be used e.g. when replacing state that transists to itself
        /// </summary>
        /// <param name="oldToStateFactoryName">The factory name for the old ToState.</param>
        /// <param name="newToStateFactoryName">The factory name for the new ToState.</param>
        /// <param name="removeAllTransitionsFromState">Default=false. Should all existing transitions *From* this state be removed?</param>
        public void ReplaceState(string oldToStateFactoryName, string newToStateFactoryName, bool removeAllTransitionsFromState)
        {
            var transitionsForState = GetTransitionsForState(oldToStateFactoryName);

            //Get a list of the self-ref transitions
            var selfRefTransitions = transitionsForState
                .Where(x => x.Value.NextStateFactoryName == oldToStateFactoryName)
                .ToArray();

            //Update all transitions going FROM the old state
            var transitions = transitionsForState;
            LookupTable.Remove(oldToStateFactoryName);
            if (!removeAllTransitionsFromState)
            {
                LookupTable.Add(newToStateFactoryName, transitions);
            }


            //Update all transitions going TO the old state.
            LookupTable.Values
                .SelectMany(x => x.Values)
                .Where(x => x.NextStateFactoryName == oldToStateFactoryName)
                .ForEach(x => x.NextStateFactoryName = newToStateFactoryName);

            //Warning : 
            //Add super-weird old broken self links for backwards compatibility
            selfRefTransitions.ForEach(t =>
            {
                transitionsForState.Remove(t.Key);
                InternalAddTransition(oldToStateFactoryName, t.Key, newToStateFactoryName, t.Value.HistoryType, false);
            });
        }

        #endregion

        #region Method: OverrideState

        /// <summary>
        /// Makes an override of a state.
        /// This could be used when you have made an inheritance of a state and want to replace the old one.
        /// </summary>
        /// <typeparam name="TOldState">The state to override.</typeparam>
        /// <typeparam name="TNewState">The overrider.</typeparam>
        public void OverrideState<TOldState, TNewState>()
            where TOldState : State
            where TNewState : State
        {
            stateTypeContainer.Register<TOldState>();
            stateTypeContainer.Register<TNewState>();

            string oldToStateFactoryName = typeof(TOldState).FullName;
            string newToStateFactoryName = typeof(TNewState).FullName;

            OverrideState(oldToStateFactoryName, newToStateFactoryName);
        }

        /// <summary>
        /// Makes an override of a state.
        /// This could be used when you have made an inheritance of a state and want to replace the old one.
        /// </summary>
        /// <param name="oldToStateFactoryName"></param>
        /// <param name="newToStateFactoryName"></param>
        public void OverrideState(string oldToStateFactoryName, string newToStateFactoryName)
        {
            //Update all transitions going FROM the old state
            var transitions = GetTransitionsForState(oldToStateFactoryName);
            LookupTable.Remove(oldToStateFactoryName);
            LookupTable.Add(newToStateFactoryName, transitions);

            //Update all transitions going TO the old state.
            LookupTable.Values
                .SelectMany(x => x.Values)
                .Where(x => x.NextStateFactoryName == oldToStateFactoryName)
                .ForEach(x => x.NextStateFactoryName = newToStateFactoryName);
        }

        #endregion

        #region Methods: GetLists
        /// <summary>
        /// Returns a list of state factory names that is in the lookup table.
        /// </summary>
        /// <param name="includeAnyStates">Should the AnyStates be included?</param>
        public string[] GetStateNameList(bool includeAnyStates)
        {
            var stateNames = LookupTable.Keys                
                .Concat(LookupTable
                    .Values
                    .SelectMany(dict => dict.Values.Select(entry => entry.NextStateFactoryName)))
                .Distinct();

            if (!includeAnyStates)
            {
                stateNames = stateNames.Where(x => x != AnyState.FactoryName);
            }

            return stateNames.ToArray();
        }

        #endregion
    }
}