// Copyright (c) CypherCore <http://github.com/CypherCore> All rights reserved.
// Licensed under the GNU GENERAL PUBLIC LICENSE. See LICENSE file in the project root for full license information.

using Framework.Constants;
using Game.Networking;
using System;
using System.Collections.Generic;
using System.Linq;

namespace Game.Entities
{
    public interface IUpdateField<T>
    {
        void SetValue(T value);
        T GetValue();
    }

    public interface IsUpdateFieldStructureTag<T>
    {
        void WriteCreate(WorldPacket data, T owner, Player receiver);
        void WriteUpdate(WorldPacket data, bool ignoreChangesMask, T owner, Player receiver);
    }
    public interface IHasChangesMask
    {
        void ClearChangesMask();
        UpdateMask GetUpdateMask();
    }

    public class UpdateFieldString : IUpdateField<string>
    {
        public string _value;
        public int BlockBit;
        public int Bit;

        public UpdateFieldString(int blockBit, int bit)
        {
            BlockBit = blockBit;
            Bit = bit;
            _value = "";
        }

        public static implicit operator string(UpdateFieldString updateField)
        {
            return updateField._value;
        }

        public int Size() { return _value.GetByteCount(); }

        public void SetValue(string value) { _value = value; }

        public string GetValue() { return _value; }
    }

    public class UpdateField<T> : IUpdateField<T> where T : new()
    {
        public T _value;
        public int BlockBit;
        public int Bit;

        public UpdateField(int blockBit, int bit)
        {
            BlockBit = blockBit;
            Bit = bit;
            _value = new T();
        }

        public static implicit operator T(UpdateField<T> updateField)
        {
            return updateField._value;
        }

        public void SetValue(T value) { _value = value; }

        public T GetValue() { return _value; }
    }

    public class OptionalUpdateField<T> : IUpdateField<T> where T : new()
    {
        bool _hasValue;
        public T _value;
        public int BlockBit;
        public int Bit;

        public OptionalUpdateField(int blockBit, int bit)
        {
            BlockBit = blockBit;
            Bit = bit;
        }

        public static implicit operator T(OptionalUpdateField<T> updateField)
        {
            return updateField._value;
        }

        public void SetValue(T value)
        {
            _hasValue = true;
            _value = value;
        }

        public T GetValue() { return _value; }

        public bool HasValue() { return _hasValue; }
    }

    public class UpdateFieldArrayString
    {
        public string[] _values;
        public int FirstElementBit;
        public int Bit;

        public UpdateFieldArrayString(uint size, int bit, int firstElementBit)
        {
            _values = new string[size];
            for (var i = 0; i < size; ++i)
                _values[i] = "";

            Bit = bit;
            FirstElementBit = firstElementBit;
        }

        public string this[int index]
        {
            get
            {
                return _values[index];
            }
            set
            {
                _values[index] = value;
            }
        }

        public int GetSize() { return _values.Length; }

        public IEnumerator<string> GetEnumerator()
        {
            foreach (var obj in _values)
                yield return obj;
        }
    }

    public class UpdateFieldArray<T> where T : new()
    {
        public T[] _values;
        public int FirstElementBit;
        public int Bit;

        public UpdateFieldArray(uint size, int bit, int firstElementBit)
        {
            _values = new T[size];
            for (var i = 0; i < size; ++i)
                _values[i] = new T();

            Bit = bit;
            FirstElementBit = firstElementBit;
        }

        public T this[int index]
        {
            get
            {
                return _values[index];
            }
            set
            {
                _values[index] = value;
            }
        }

        public int GetSize() { return _values.Length; }

        public T First(Func<T, bool> predicate)
        {
            return _values.First(predicate);
        }

        public int IndexOf(T value)
        {
            return Array.IndexOf(_values, value);
        }

        public IEnumerator<T> GetEnumerator()
        {
            foreach (var obj in _values)
                yield return obj;
        }
    }

    public class DynamicUpdateField<T> where T : new()
    {
        public List<T> _values = new();
        public List<uint> _updateMask = new();
        public int BlockBit;
        public int Bit;

        public DynamicUpdateField()
        {
            BlockBit = -1;
            Bit = -1;
        }
        public DynamicUpdateField(int blockBit, int bit)
        {
            BlockBit = blockBit;
            Bit = bit;
        }

        public int FindIndex(T value)
        {
            return _values.IndexOf(value);
        }

        public int FindIndexIf(Predicate<T> predicate)
        {
            return _values.FindIndex(predicate);
        }

        public bool HasChanged(int index)
        {
            return (_updateMask[UpdateMask.GetBlockIndex(index)] & UpdateMask.GetBlockFlag(index)) != 0;
        }

        public void WriteUpdateMask(WorldPacket data, int bitsForSize = 32)
        {
            data.WriteBits(_values.Count, bitsForSize);
            if (_values.Count > 32)
            {
                if (data.HasUnfinishedBitPack())
                    for (int block = 0; block < _values.Count / 32; ++block)
                        data.WriteBits(_updateMask[block], 32);
                else
                    for (int block = 0; block < _values.Count / 32; ++block)
                        data.WriteUInt32(_updateMask[block]);
            }

            else if (_values.Count == 32)
            {
                data.WriteBits(_updateMask.Last(), 32);
                return;
            }

            if ((_values.Count % 32) != 0)
                data.WriteBits(_updateMask.Last(), _values.Count % 32);
        }

        public void ClearChangesMask()
        {
            for (var i = 0; i < _updateMask.Count; ++i)
                _updateMask[i] = 0;
        }

        public void AddValue(T value)
        {
            MarkChanged(_values.Count);
            MarkAllUpdateMaskFields(value);

            _values.Add(value);
        }

        public void InsertValue(int index, T value)
        {
            _values.Insert(index, value);
            for (int i = index; i < _values.Count; ++i)
            {
                MarkChanged(i);
                // also mark all fields of value as changed
                MarkAllUpdateMaskFields(_values[i]);
            }
        }

        public void RemoveValue(int index)
        {
            // remove by shifting entire container - client might rely on values being sorted for certain fields
            _values.RemoveAt(index);
            for (int i = index; i < _values.Count; ++i)
            {
                MarkChanged(i);
                // also mark all fields of value as changed
                MarkAllUpdateMaskFields(_values[i]);
            }
            if ((_values.Count % 32) != 0)
                _updateMask[UpdateMask.GetBlockIndex(_values.Count)] &= (uint)~UpdateMask.GetBlockFlag(_values.Count);
            else
                _updateMask.RemoveAt(_updateMask.Count - 1);
        }

        void MarkAllUpdateMaskFields(T value)
        {
            if (value is IHasChangesMask)
                ((IHasChangesMask)value).GetUpdateMask().SetAll();
        }

        public void Clear()
        {
            _values.Clear();
            _updateMask.Clear();
        }

        public void MarkChanged(int index)
        {
            int block = UpdateMask.GetBlockIndex(index);
            if (block >= _updateMask.Count)
                _updateMask.Add(0);

            _updateMask[block] |= (uint)UpdateMask.GetBlockFlag(index);
        }

        public void ClearChanged(int index)
        {
            int block = UpdateMask.GetBlockIndex(index);
            if (block >= _updateMask.Count)
                _updateMask.Add(0);

            _updateMask[block] &= ~(uint)UpdateMask.GetBlockFlag(index);
        }

        public bool Empty()
        {
            return _values.Empty();
        }

        public int Size()
        {
            return _values.Count;
        }

        public T this[int index]
        {
            get
            {
                if (_values.Count <= index)
                    _values.Add(new T());

                return _values[index];
            }
            set
            {
                _values[index] = value;
            }
        }

        public static implicit operator List<T>(DynamicUpdateField<T> updateField)
        {
            return updateField._values;
        }

        public IEnumerator<T> GetEnumerator()
        {
            foreach (var obj in _values)
                yield return obj;
        }
    }

    public enum MapUpdateFieldState
    {
        Unchanged = 0,
        Changed = 1,
        Deleted = 2
    }

    public class MapUpdateField<K, V> where V : new()
    {
        Dictionary<K, (V, MapUpdateFieldState)> _values = new();
        public int BlockBit;
        public int Bit;

        public MapUpdateField(int blockBit, int bit)
        {
            BlockBit = blockBit;
            Bit = bit;
        }

        public bool Empty()
        {
            return _values.Empty();
        }

        public int Size()
        {
            return _values.Count;
        }

        public void TryAdd(K key)
        {
            if (!_values.ContainsKey(key))
                _values[key] = (new V(), MapUpdateFieldState.Changed);
        }

        public void Remove(K key)
        {
            _values.Remove(key);
        }

        public void MarkKeyForRemoval(K key)
        {
            var itr = _values.LookupByKey(key);
            if (itr.Item1 != null)
                itr.Item2 = MapUpdateFieldState.Deleted;
        }

        public (V, MapUpdateFieldState) Get(K key)
        {
            if (_values.TryGetValue(key, out var value))
                return value;

            return default;
        }

        public (K, V) FindIf(Predicate<V> predicate)
        {
            var itr = _values.First(pair => { return predicate(pair.Value.Item1); });
            if (itr.Key != null)
                return (itr.Key, itr.Value.Item1);

            return default;
        }

        public IEnumerator<KeyValuePair<K, (V, MapUpdateFieldState)>> GetEnumerator()
        {
            foreach (var obj in _values)
                yield return obj;
        }

        public List<K> GetKeys() { return _values.Keys.ToList(); }

        public List<(V, MapUpdateFieldState)> GetValues() { return _values.Values.ToList(); }
    }

    public class VariantUpdateField(int blockBit, int bit)
    {
        public object _value;

        public int BlockBit = blockBit;
        public int Bit = bit;

        public bool Is<T>() { return _value is T; }

        public T Get<T>() where T : class, new()
        {
            if (Is<T>())
                return _value as T;

            return null;
        }

        public void Visit(Action<dynamic> visitor)
        {
            visitor(_value);
        }

        public void ConstructValue<T>() where T : class, new()
        {
            _value = new T();
        }
    }

    public abstract class HasChangesMask : IHasChangesMask
    {
        public int ChangeMaskLength;

        public UpdateMask _changesMask;
        public int _blockBit;
        public int Bit;

        public HasChangesMask(int blockBit, TypeId bit, int changeMask)
        {
            _blockBit = blockBit;
            Bit = (int)bit;
            ChangeMaskLength = changeMask;
            _changesMask = new UpdateMask(changeMask);
        }

        public HasChangesMask(int changeMask)
        {
            ChangeMaskLength = changeMask;
            _changesMask = new UpdateMask(changeMask);
        }

        public abstract void ClearChangesMask();

        public UpdateMask GetUpdateMask()
        {
            return _changesMask;
        }

        public void ClearChanged<U>(UpdateField<U> updateField) where U : new()
        {
            _changesMask.Reset(updateField.Bit);
        }

        public void ClearChanged<U>(UpdateFieldArray<U> updateField, int index) where U : new()
        {
            if (updateField.FirstElementBit >= 0)
                _changesMask.Reset(updateField.FirstElementBit + index);
        }

        public void ClearChanged<U>(DynamicUpdateField<U> updateField, int index) where U : new()
        {
            _changesMask.Reset(Bit);
            updateField.ClearChanged(index);
        }

        public void ClearChangesMask<U>(UpdateField<U> updateField) where U : new()
        {
            if (typeof(IHasChangesMask).IsAssignableFrom(typeof(U)))
                ((IHasChangesMask)updateField._value).ClearChangesMask();
        }

        public void ClearChangesMask(UpdateFieldString updateField) { }

        public void ClearChangesMask<K, V>(MapUpdateField<K, V> field) where V : new()
        {
            foreach (var key in field.GetKeys())
            {
                var value = field.Get(key);
                switch (value.Item2)
                {
                    case MapUpdateFieldState.Unchanged:
                        break;
                    case MapUpdateFieldState.Changed:
                        if (typeof(HasChangesMask).IsAssignableFrom(typeof(K)))
                            ((IHasChangesMask)key).ClearChangesMask();

                        if (typeof(HasChangesMask).IsAssignableFrom(typeof(V)))
                            ((IHasChangesMask)value.Item1).ClearChangesMask();

                        value.Item2 = MapUpdateFieldState.Unchanged;
                        break;
                    case MapUpdateFieldState.Deleted:
                        field.Remove(key);
                        continue;
                    default:
                        break;
                }
            }
        }

        public void ClearChangesMask<U>(OptionalUpdateField<U> updateField) where U : new()
        {
            if (typeof(IHasChangesMask).IsAssignableFrom(typeof(U)) && updateField.HasValue())
                ((IHasChangesMask)updateField._value).ClearChangesMask();
        }

        public void ClearChangesMask<U>(UpdateFieldArray<U> updateField) where U : new()
        {
            if (typeof(IHasChangesMask).IsAssignableFrom(typeof(U)))
            {
                for (int i = 0; i < updateField.GetSize(); ++i)
                    ((IHasChangesMask)updateField[i]).ClearChangesMask();
            }
        }

        public void ClearChangesMask(UpdateFieldArrayString updateField) { }

        public void ClearChangesMask<U>(DynamicUpdateField<U> updateField) where U : new()
        {
            if (typeof(IHasChangesMask).IsAssignableFrom(typeof(U)))
            {
                for (int i = 0; i < updateField.Size(); ++i)
                    ((IHasChangesMask)updateField[i]).ClearChangesMask();

                updateField.ClearChangesMask();
            }
        }

        public void ClearChangesMask(VariantUpdateField field)
        {
            if (field._value != null && typeof(IHasChangesMask).IsAssignableFrom(field._value.GetType()))
                ((IHasChangesMask)field._value).ClearChangesMask();
        }

        public dynamic ModifyValueOld(dynamic value, int bit, int blockBit)
        {
            _changesMask.Set(blockBit);
            _changesMask.Set(bit);
            return value;
        }

        public UpdateField<U> ModifyValue<U>(UpdateField<U> updateField) where U : new()
        {
            MarkChanged(updateField);
            return updateField;
        }

        public UpdateFieldString ModifyValue(UpdateFieldString updateField)
        {
            MarkChanged(updateField);
            return updateField;
        }

        public MapUpdateField<K, V> ModifyValue<K, V>(MapUpdateField<K, V> updateField) where V : new()
        {
            MarkChanged(updateField);
            return updateField;
        }

        public V ModifyValue<K, V>(MapUpdateField<K, V> updateField, K key) where V : new()
        {
            MarkChanged(updateField);
            updateField.TryAdd(key);
            return updateField.Get(key).Item1;
        }

        public OptionalUpdateField<U> ModifyValue<U>(OptionalUpdateField<U> updateField) where U : new()
        {
            MarkChanged(updateField);
            return updateField;
        }

        public ref U ModifyValue<U>(UpdateFieldArray<U> updateField, int index) where U : new()
        {
            MarkChanged(updateField, index);
            return ref updateField._values[index];
        }

        public ref string ModifyValue(UpdateFieldArrayString updateField, int index)
        {
            MarkChanged(updateField, index);
            return ref updateField._values[index];
        }

        public DynamicUpdateField<U> ModifyValue<U>(DynamicUpdateField<U> updateField) where U : new()
        {
            _changesMask.Set(updateField.BlockBit);
            _changesMask.Set(updateField.Bit);
            return updateField;
        }

        public DynamicUpdateFieldSetter<U> ModifyValue<U>(DynamicUpdateField<U> updateField, int index) where U : new()
        {
            if (index >= updateField._values.Count)
            {
                // fill with zeros until reaching desired slot
                updateField._values.Resize((uint)index + 1);
                updateField._updateMask.Resize((uint)(updateField._values.Count + 31) / 32);
            }

            _changesMask.Set(updateField.BlockBit);
            _changesMask.Set(updateField.Bit);
            updateField.MarkChanged(index);

            return new DynamicUpdateFieldSetter<U>(updateField, index);
        }

        public DynamicUpdateFieldSetter<U> ModifyValue<U>(UpdateFieldArray<DynamicUpdateField<U>> updateField, int index, int dynamicIndex) where U : new()
        {
            if (dynamicIndex >= updateField[index].Size())
            {
                // fill with zeros until reaching desired slot
                updateField[index]._values.Resize((uint)dynamicIndex + 1);
                updateField[index]._updateMask.Resize((uint)(updateField[index]._values.Count + 31) / 32);
            }

            _changesMask.Set(updateField.Bit);
            if (updateField.FirstElementBit >= 0)
                _changesMask.Set(updateField.FirstElementBit);

            updateField[index].MarkChanged(dynamicIndex);

            return new DynamicUpdateFieldSetter<U>(updateField[index], dynamicIndex);
        }

        public V ModifyValue<V>(VariantUpdateField field) where V : class, new()
        {
            if (!field.Is<V>())
                field.ConstructValue<V>();

            if (field.BlockBit >= 0)
                _changesMask.Set(field.BlockBit);

            _changesMask.Set(Bit);
            return field.Get<V>();
        }

        public void MarkChanged<U>(UpdateField<U> updateField) where U : new()
        {
            _changesMask.Set(updateField.BlockBit);
            _changesMask.Set(updateField.Bit);
        }

        public void MarkChanged<K, V>(MapUpdateField<K, V> updateField) where V : new()
        {
            if (updateField.BlockBit >= 0)
                _changesMask.Set(updateField.BlockBit);

            _changesMask.Set(updateField.Bit);
        }

        public void MarkChanged<U>(OptionalUpdateField<U> updateField) where U : new()
        {
            _changesMask.Set(updateField.BlockBit);
            _changesMask.Set(updateField.Bit);
        }

        public void MarkChanged(UpdateFieldString updateField)
        {
            _changesMask.Set(updateField.BlockBit);
            _changesMask.Set(updateField.Bit);
        }

        public void MarkChanged<U>(UpdateFieldArray<U> updateField, int index) where U : new()
        {
            _changesMask.Set(updateField.Bit);
            if (updateField.FirstElementBit >= 0)
                _changesMask.Set(updateField.FirstElementBit + index);
        }

        public void MarkChanged(UpdateFieldArrayString updateField, int index)
        {
            _changesMask.Set(updateField.Bit);
            if (updateField.FirstElementBit >= 0)
                _changesMask.Set(updateField.FirstElementBit + index);
        }

        public void WriteCompleteDynamicFieldUpdateMask(int size, WorldPacket data, int bitsForSize = 32)
        {
            data.WriteBits(size, bitsForSize);
            if (size > 32)
            {
                if (data.HasUnfinishedBitPack())
                    for (int block = 0; block < size / 32; ++block)
                        data.WriteBits(0xFFFFFFFFu, 32);
                else
                    for (int block = 0; block < size / 32; ++block)
                        data.WriteUInt32(0xFFFFFFFFu);
            }
            else if (size == 32)
            {
                data.WriteBits(0xFFFFFFFFu, 32);
                return;
            }

            if ((size % 32) != 0)
                data.WriteBits(0xFFFFFFFFu, size % 32);
        }

        public void WriteMapFieldCreate<K, V, T>(MapUpdateField<K, V> map, WorldPacket data, T owner, Player receiver) where V : new()
        {
            data.WriteInt32(map.Size());
            foreach (var (k, (v, _)) in map)
            {
                if (typeof(IsUpdateFieldStructureTag<T>).IsAssignableFrom(typeof(K)))
                    ((IsUpdateFieldStructureTag<T>)k).WriteCreate(data, owner, receiver);
                else
                    data.Write(k);

                if (typeof(IsUpdateFieldStructureTag<T>).IsAssignableFrom(typeof(V)))
                    ((IsUpdateFieldStructureTag<T>)v).WriteCreate(data, owner, receiver);
                else
                    data.Write(v);
            }
        }

        public void WriteMapFieldUpdate<K, V, T>(MapUpdateField<K, V> map, WorldPacket data, bool ignoreChangesMask, T owner, Player receiver) where V : new()
        {
            data.WriteUInt8((byte)(ignoreChangesMask ? 1 : 0));
            if (ignoreChangesMask)
                WriteMapFieldCreate(map, data, owner, receiver);
            else
            {
                ushort changesCount = 0;
                WorldPacket tempBuffer = new();

                foreach (var (k, (v, state)) in map)
                {
                    if (state == MapUpdateFieldState.Unchanged)
                        continue;

                    ++changesCount;

                    if (typeof(IsUpdateFieldStructureTag<T>).IsAssignableFrom(typeof(K)))
                        ((IsUpdateFieldStructureTag<T>)k).WriteUpdate(tempBuffer, true /*ignoreChangesMask*/, owner, receiver);
                    else
                        tempBuffer.Write(k);

                    tempBuffer.WriteUInt8((byte)state);
                    if (state == MapUpdateFieldState.Deleted)
                        continue;

                    if (typeof(IsUpdateFieldStructureTag<T>).IsAssignableFrom(typeof(V)))
                        ((IsUpdateFieldStructureTag<T>)v).WriteUpdate(tempBuffer, true /*ignoreChangesMask*/, owner, receiver); // client bug replaces unchanged values with 0/default so send everything as if it changed
                    else
                        tempBuffer.Write(v);
                }

                data.WriteUInt16(changesCount);
                data.WriteBytes(tempBuffer);
            }
        }

        public UpdateMask GetStaticUpdateMask()
        {
            return new UpdateMask(ChangeMaskLength);
        }
    }

    public class DynamicUpdateFieldSetter<T> : IUpdateField<T> where T : new()
    {
        DynamicUpdateField<T> _dynamicUpdateField;
        int _index;

        public DynamicUpdateFieldSetter(DynamicUpdateField<T> dynamicUpdateField, int index)
        {
            _dynamicUpdateField = dynamicUpdateField;
            _index = index;
        }

        public void SetValue(T value)
        {
            _dynamicUpdateField[_index] = value;
        }

        public T GetValue() { return _dynamicUpdateField[_index]; }

        public static implicit operator T(DynamicUpdateFieldSetter<T> dynamicUpdateFieldSetter)
        {
            return dynamicUpdateFieldSetter.GetValue();
        }
    }
}