/*
 * Copyright (C) 2012-2018 CypherCore <http://github.com/CypherCore>
 * 
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

using Framework.Constants;
using Game.Entities;
using Game.Groups;
using System;
using System.Collections.Generic;
using System.Linq;

namespace Game.AI
{
    public class npc_escortAI : ScriptedAI
    {
        public npc_escortAI(Creature creature) : base(creature)
        {
            m_uiPlayerGUID = ObjectGuid.Empty;
            m_uiWPWaitTimer = 2500;
            m_uiPlayerCheckTimer = 1000;
            m_uiEscortState = eEscortState.None;
            MaxPlayerDistance = 50;
            m_pQuestForEscort = null;
            m_bIsActiveAttacker = true;
            m_bIsRunning = false;
            m_bCanInstantRespawn = false;
            m_bCanReturnToStart = false;
            DespawnAtEnd = true;
            DespawnAtFar = true;
            ScriptWP = false;
            HasImmuneToNPCFlags = false;
        }

        public override void AttackStart(Unit who)
        {
            if (!who)
                return;

            if (me.Attack(who, true))
            {
                if (me.GetMotionMaster().GetCurrentMovementGeneratorType() == MovementGeneratorType.Point)
                    me.GetMotionMaster().MovementExpired();

                if (IsCombatMovementAllowed())
                    me.GetMotionMaster().MoveChase(who);
            }
        }

        //see followerAI
        bool AssistPlayerInCombatAgainst(Unit who)
        {
            if (!who || !who.GetVictim())
                return false;

            //experimental (unknown) flag not present
            if (!me.GetCreatureTemplate().TypeFlags.HasAnyFlag(CreatureTypeFlags.CanAssist))
                return false;

            //not a player
            if (!who.GetVictim().GetCharmerOrOwnerPlayerOrPlayerItself())
                return false;

            //never attack friendly
            if (me.IsFriendlyTo(who))
                return false;

            //too far away and no free sight?
            if (me.IsWithinDistInMap(who, GetMaxPlayerDistance()) && me.IsWithinLOSInMap(who))
            {
                //already fighting someone?
                if (!me.GetVictim())
                {
                    AttackStart(who);
                    return true;
                }
                else
                {
                    who.SetInCombatWith(me);
                    me.AddThreat(who, 0.0f);
                    return true;
                }
            }

            return false;
        }

        public override void MoveInLineOfSight(Unit who)
        {
            if (me.HasReactState(ReactStates.Aggressive) && !me.HasUnitState(UnitState.Stunned) && who.isTargetableForAttack() && who.isInAccessiblePlaceFor(me))
            {
                if (HasEscortState(eEscortState.Escorting) && AssistPlayerInCombatAgainst(who))
                    return;

                if (!me.CanFly() && me.GetDistanceZ(who) > SharedConst.CreatureAttackRangeZ)
                    return;

                if (me.IsHostileTo(who))
                {
                    float fAttackRadius = me.GetAttackDistance(who);
                    if (me.IsWithinDistInMap(who, fAttackRadius) && me.IsWithinLOSInMap(who))
                    {
                        if (!me.GetVictim())
                        {
                            // Clear distracted state on combat
                            if (me.HasUnitState(UnitState.Distracted))
                            {
                                me.ClearUnitState(UnitState.Distracted);
                                me.GetMotionMaster().Clear();
                            }

                            AttackStart(who);
                        }
                        else if (me.GetMap().IsDungeon())
                        {
                            who.SetInCombatWith(me);
                            me.AddThreat(who, 0.0f);
                        }
                    }
                }
            }
        }

        public override void JustDied(Unit killer)
        {
            if (!HasEscortState(eEscortState.Escorting) || m_uiPlayerGUID.IsEmpty() || m_pQuestForEscort == null)
                return;
            
            Player player = GetPlayerForEscort();
            if (player)
            {
                Group group = player.GetGroup();
                if (group)
                {
                    for (GroupReference groupRef = group.GetFirstMember(); groupRef != null; groupRef = groupRef.next())
                    {
                        Player member = groupRef.GetSource();
                        if (member)
                            member.FailQuest(m_pQuestForEscort.Id);
                    }
                }
                else
                    player.FailQuest(m_pQuestForEscort.Id);
            }
        }

        public override void JustRespawned()
        {
            m_uiEscortState = eEscortState.None;

            if (!IsCombatMovementAllowed())
                SetCombatMovement(true);

            //add a small delay before going to first waypoint, normal in near all cases
            m_uiWPWaitTimer = 2500;

            if (me.getFaction() != me.GetCreatureTemplate().Faction)
                me.RestoreFaction();

            Reset();
        }

        void ReturnToLastPoint()
        {
            float x, y, z, o;
            me.GetHomePosition(out x, out y, out z, out o);
            me.GetMotionMaster().MovePoint(0xFFFFFF, x, y, z);
        }

        public override void EnterEvadeMode(EvadeReason why = EvadeReason.Other)
        {
            me.RemoveAllAuras();
            me.DeleteThreatList();
            me.CombatStop(true);
            me.SetLootRecipient(null);

            if (HasEscortState(eEscortState.Escorting))
            {
                AddEscortState(eEscortState.Returning);
                ReturnToLastPoint();
                Log.outDebug(LogFilter.Scripts, "EscortAI has left combat and is now returning to last point");
            }
            else
            {
                me.GetMotionMaster().MoveTargetedHome();
                if (HasImmuneToNPCFlags)
                    me.SetFlag(UnitFields.Flags, UnitFlags.ImmuneToNpc);
                Reset();
            }
        }

        bool IsPlayerOrGroupInRange()
        {
            Player player = GetPlayerForEscort();
            if (player)
            {
                Group group = player.GetGroup();
                if (group)
                {
                    for (GroupReference groupRef = group.GetFirstMember(); groupRef != null; groupRef = groupRef.next())
                    {
                        Player member = groupRef.GetSource();
                        if (member)
                            if (me.IsWithinDistInMap(member, GetMaxPlayerDistance()))
                                return true;
                    }
                }
                else if (me.IsWithinDistInMap(player, GetMaxPlayerDistance()))
                    return true;
            }

            return false;
        }

        public override void UpdateAI(uint diff)
        {
            //Waypoint Updating
            if (HasEscortState(eEscortState.Escorting) && !me.GetVictim() && m_uiWPWaitTimer != 0 && !HasEscortState(eEscortState.Returning))
            {
                if (m_uiWPWaitTimer <= diff)
                {
                    //End of the line
                    if (WPIndex == WaypointList.Count)
                    {
                        if (DespawnAtEnd)
                        {
                            Log.outDebug(LogFilter.Scripts, "EscortAI reached end of waypoints");

                            if (m_bCanReturnToStart)
                            {
                                float fRetX, fRetY, fRetZ;
                                me.GetRespawnPosition(out fRetX, out fRetY, out fRetZ);

                                me.GetMotionMaster().MovePoint(0xFFFFFE, fRetX, fRetY, fRetZ);

                                m_uiWPWaitTimer = 0;

                                Log.outDebug(LogFilter.Scripts, "EscortAI are returning home to spawn location: {0}, {1}, {2}, {3}", 0xFFFFFE, fRetX, fRetY, fRetZ);
                                return;
                            }

                            if (m_bCanInstantRespawn)
                            {
                                me.setDeathState(DeathState.JustDied);
                                me.Respawn();
                            }
                            else
                                me.DespawnOrUnsummon();

                            return;
                        }
                        else
                        {
                            Log.outDebug(LogFilter.Scripts, "EscortAI reached end of waypoints with Despawn off");
                            return;
                        }
                    }

                    if (!HasEscortState(eEscortState.Paused))
                    {
                        me.GetMotionMaster().MovePoint(GetCurrentWaypoint().id, GetCurrentWaypoint().x, GetCurrentWaypoint().y, GetCurrentWaypoint().z);
                        Log.outDebug(LogFilter.Scripts, "EscortAI start waypoint {0} ({1}, {2}, {3}).", GetCurrentWaypoint().id, GetCurrentWaypoint().x, GetCurrentWaypoint().y, GetCurrentWaypoint().z);

                        WaypointStart(GetCurrentWaypoint().id);

                        m_uiWPWaitTimer = 0;
                    }
                }
                else
                    m_uiWPWaitTimer -= diff;
            }

            //Check if player or any member of his group is within range
            if (HasEscortState(eEscortState.Escorting) && !m_uiPlayerGUID.IsEmpty() && !me.GetVictim() && !HasEscortState(eEscortState.Returning))
            {
                if (m_uiPlayerCheckTimer <= diff)
                {
                    if (DespawnAtFar && !IsPlayerOrGroupInRange())
                    {
                        Log.outDebug(LogFilter.Scripts, "EscortAI failed because player/group was to far away or not found");

                        if (m_bCanInstantRespawn)
                        {
                            me.setDeathState(DeathState.JustDied);
                            me.Respawn();
                        }
                        else
                            me.DespawnOrUnsummon();

                        return;
                    }

                    m_uiPlayerCheckTimer = 1000;
                }
                else
                    m_uiPlayerCheckTimer -= diff;
            }

            UpdateEscortAI(diff);
        }

        void UpdateEscortAI(uint diff)
        {
            if (!UpdateVictim())
                return;

            DoMeleeAttackIfReady();
        }

        public override void MovementInform(MovementGeneratorType moveType, uint pointId)
        {
            if (moveType != MovementGeneratorType.Point || !HasEscortState(eEscortState.Escorting))
                return;

            //Combat start position reached, continue waypoint movement
            if (pointId == 0xFFFFFF)
            {
                Log.outDebug(LogFilter.Scripts, "EscortAI has returned to original position before combat");

                me.SetWalk(!m_bIsRunning);
                RemoveEscortState(eEscortState.Returning);

                if (m_uiWPWaitTimer == 0)
                    m_uiWPWaitTimer = 1;
            }
            else if (pointId == 0xFFFFFE)
            {
                Log.outDebug(LogFilter.Scripts, "EscortAI has returned to original home location and will continue from beginning of waypoint list.");

                WPIndex = 0;
                m_uiWPWaitTimer = 1;
            }
            else
            {
                //Make sure that we are still on the right waypoint
                if (GetCurrentWaypoint().id != pointId)
                {
                    Log.outDebug(LogFilter.Server, "TSCR ERROR: EscortAI reached waypoint out of order {0}, expected {1}, creature entry {2}", pointId, GetCurrentWaypoint().id, me.GetEntry());
                    return;
                }

                Log.outDebug(LogFilter.Scripts, "EscortAI Waypoint {0} reached", GetCurrentWaypoint().id);

                //Call WP function
                WaypointReached(GetCurrentWaypoint().id);

                m_uiWPWaitTimer = GetCurrentWaypoint().WaitTimeMs + 1;

                ++WPIndex;
            }
        }

        public void AddWaypoint(uint id, float x, float y, float z, uint waitTime = 0)
        {
            Escort_Waypoint t = new Escort_Waypoint(id, x, y, z, waitTime);

            WaypointList.Add(t);
            ScriptWP = true;
        }

        void FillPointMovementListForCreature()
        {
            var movePoints = Global.ScriptMgr.GetPointMoveList(me.GetEntry());
            if (movePoints.Empty())
                return;

            foreach (var pointMove in movePoints)
            {
                Escort_Waypoint point = new Escort_Waypoint(pointMove.uiPointId, pointMove.fX, pointMove.fY, pointMove.fZ, pointMove.uiWaitTime);
                WaypointList.Add(point);
            }
        }

        public void SetRun(bool on = true)
        {
            if (on)
            {
                if (!m_bIsRunning)
                    me.SetWalk(false);
                else
                    Log.outDebug(LogFilter.Scripts, "EscortAI attempt to set run mode, but is already running.");
            }
            else
            {
                if (m_bIsRunning)
                    me.SetWalk(true);
                else
                    Log.outDebug(LogFilter.Scripts, "EscortAI attempt to set walk mode, but is already walking.");
            }

            m_bIsRunning = on;
        }

        /// todo get rid of this many variables passed in function.
        public void Start(bool isActiveAttacker = true, bool run = false, ObjectGuid playerGUID = default(ObjectGuid), Quest quest = null, bool instantRespawn = false, bool canLoopPath = false, bool resetWaypoints = true)
        {
            if (me.GetVictim())
            {
                Log.outError(LogFilter.Server, "TSCR ERROR: EscortAI (script: {0}, creature entry: {1}) attempts to Start while in combat", me.GetScriptName(), me.GetEntry());
                return;
            }

            if (HasEscortState(eEscortState.Escorting))
            {
                Log.outError(LogFilter.Scripts, "EscortAI (script: {0}, creature entry: {1}) attempts to Start while already escorting", me.GetScriptName(), me.GetEntry());
                return;
            }

            if (!ScriptWP && resetWaypoints) // sd2 never adds wp in script, but tc does
            {
                if (!WaypointList.Empty())
                    WaypointList.Clear();
                FillPointMovementListForCreature();
            }

            if (WaypointList.Empty())
            {
                Log.outError(LogFilter.Scripts, "EscortAI (script: {0}, creature entry: {1}) starts with 0 waypoints (possible missing entry in script_waypoint. Quest: {2}).",
                    me.GetScriptName(), me.GetEntry(), quest != null ? quest.Id : 0);
                return;
            }

            //set variables
            m_bIsActiveAttacker = isActiveAttacker;
            m_bIsRunning = run;

            m_uiPlayerGUID = playerGUID;
            m_pQuestForEscort = quest;

            m_bCanInstantRespawn = instantRespawn;
            m_bCanReturnToStart = canLoopPath;

            if (m_bCanReturnToStart && m_bCanInstantRespawn)
                Log.outDebug(LogFilter.Scripts, "EscortAI is set to return home after waypoint end and instant respawn at waypoint end. Creature will never despawn.");

            if (me.GetMotionMaster().GetCurrentMovementGeneratorType() == MovementGeneratorType.Waypoint)
            {
                me.GetMotionMaster().MovementExpired();
                me.GetMotionMaster().MoveIdle();
                Log.outDebug(LogFilter.Scripts, "EscortAI start with WAYPOINT_MOTION_TYPE, changed to MoveIdle.");
            }

            //disable npcflags
            me.SetUInt64Value(UnitFields.NpcFlags, (ulong)NPCFlags.None);
            if (me.HasFlag(UnitFields.Flags, UnitFlags.ImmuneToNpc))
            {
                HasImmuneToNPCFlags = true;
                me.RemoveFlag(UnitFields.Flags, UnitFlags.ImmuneToNpc);
            }

            Log.outDebug(LogFilter.Scripts, "EscortAI started with {0} waypoints. ActiveAttacker = {1}, Run = {2}, PlayerGUID = {3}", WaypointList.Count, m_bIsActiveAttacker, m_bIsRunning, m_uiPlayerGUID);

            WPIndex = 0;

            //Set initial speed
            if (m_bIsRunning)
                me.SetWalk(false);
            else
                me.SetWalk(true);

            AddEscortState(eEscortState.Escorting);
        }

        public void SetEscortPaused(bool on)
        {
            if (!HasEscortState(eEscortState.Escorting))
                return;

            if (on)
                AddEscortState(eEscortState.Paused);
            else
                RemoveEscortState(eEscortState.Paused);
        }

        bool SetNextWaypoint(uint pointId, float x, float y, float z, float orientation)
        {
            me.UpdatePosition(x, y, z, orientation);
            return SetNextWaypoint(pointId, false, true);
        }

        bool SetNextWaypoint(uint pointId, bool setPosition, bool resetWaypointsOnFail)
        {
            if (!WaypointList.Empty())
                WaypointList.Clear();

            FillPointMovementListForCreature();

            if (WaypointList.Empty())
                return false;

            int size = WaypointList.Count;
            Escort_Waypoint waypoint = new Escort_Waypoint(0, 0, 0, 0, 0);
            do
            {
                waypoint = WaypointList.FirstOrDefault();
                WaypointList.RemoveAt(0);
                if (waypoint.id == pointId)
                {
                    if (setPosition)
                        me.UpdatePosition(waypoint.x, waypoint.y, waypoint.z, me.GetOrientation());

                    WPIndex = 0;
                    return true;
                }
            }
            while (!WaypointList.Empty());

            // we failed.
            // we reset the waypoints in the start; if we pulled any, reset it again
            if (resetWaypointsOnFail && size != WaypointList.Count)
            {
                if (!WaypointList.Empty())
                    WaypointList.Clear();

                FillPointMovementListForCreature();
            }

            return false;
        }

        public bool GetWaypointPosition(uint pointId, ref float x, ref float y, ref float z)
        {            
            var waypoints = Global.ScriptMgr.GetPointMoveList(me.GetEntry());
            if (waypoints.Empty())
                return false;

            foreach (var point in waypoints)
            {
                if (point.uiPointId == pointId)
                {
                    x = point.fX;
                    y = point.fY;
                    z = point.fZ;
                    return true;
                }
            }

            return false;
        }

        public virtual void WaypointReached(uint pointId) { }
        public virtual void WaypointStart(uint pointId) { }

        public bool HasEscortState(eEscortState escortState) { return m_uiEscortState.HasAnyFlag(escortState); }
        public override bool IsEscorted() { return m_uiEscortState.HasAnyFlag(eEscortState.Escorting); }

        public void SetMaxPlayerDistance(float newMax) { MaxPlayerDistance = newMax; }
        public float GetMaxPlayerDistance() { return MaxPlayerDistance; }

        public void SetDespawnAtEnd(bool despawn) { DespawnAtEnd = despawn; }
        public void SetDespawnAtFar(bool despawn) { DespawnAtFar = despawn; }
        public bool GetAttack() { return m_bIsActiveAttacker; }//used in EnterEvadeMode override
        public void SetCanAttack(bool attack) { m_bIsActiveAttacker = attack; }
        public ObjectGuid GetEventStarterGUID() { return m_uiPlayerGUID; }

        public Player GetPlayerForEscort() { return Global.ObjAccessor.GetPlayer(me, m_uiPlayerGUID); }

        void AddEscortState(eEscortState escortState) { m_uiEscortState |= escortState; }
        void RemoveEscortState(eEscortState escortState) { m_uiEscortState &= ~escortState; }

        ObjectGuid m_uiPlayerGUID;
        uint m_uiWPWaitTimer;
        uint m_uiPlayerCheckTimer;
        eEscortState m_uiEscortState;
        float MaxPlayerDistance;

        Quest m_pQuestForEscort;                     //generally passed in Start() when regular escort script.

        List<Escort_Waypoint> WaypointList = new List<Escort_Waypoint>();
        Escort_Waypoint GetCurrentWaypoint()
        {
            return WaypointList[WPIndex];
        }
        int WPIndex;

        bool m_bIsActiveAttacker;                           //obsolete, determined by faction.
        bool m_bIsRunning;                                  //all creatures are walking by default (has flag MOVEMENTFLAG_WALK)
        bool m_bCanInstantRespawn;                          //if creature should respawn instantly after escort over (if not, database respawntime are used)
        bool m_bCanReturnToStart;                           //if creature can walk same path (loop) without despawn. Not for regular escort quests.
        bool DespawnAtEnd;
        bool DespawnAtFar;
        bool ScriptWP;
        bool HasImmuneToNPCFlags;
    }

    public class Escort_Waypoint
    {
        public Escort_Waypoint(uint _id, float _x, float _y, float _z, uint _w)
        {
            id = _id;
            x = _x;
            y = _y;
            z = _z;
            WaitTimeMs = _w;
        }

        public uint id;
        public float x;
        public float y;
        public float z;
        public uint WaitTimeMs;
    }

    public enum eEscortState
    {
        None = 0x000,                        //nothing in progress
        Escorting = 0x001,                        //escort are in progress
        Returning = 0x002,                        //escort is returning after being in combat
        Paused = 0x004                         //will not proceed with waypoints before state is removed
    }
}