/*
 * 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.Collections;
using Framework.Constants;
using Framework.Database;
using Framework.Dynamic;
using Framework.GameMath;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using System.Text;

namespace Game.DataStorage
{
    class DBReader
    {
        private const int HeaderSize = 72 + 1 * 36;
        private const uint WDC2FmtSig = 0x32434457; // WDC2

        public static DB6Storage<T> Read<T>(string fileName, HotfixStatements preparedStatement, HotfixStatements preparedStatementLocale = 0) where T : new()
        {
            DB6Storage<T> storage = new DB6Storage<T>();

            if (!File.Exists(CliDB.DataPath + fileName))
            {
                Log.outError(LogFilter.ServerLoading, $"File {fileName} not found.");
                return storage;
            }

            DBReader reader = new DBReader();
            using (var stream = new FileStream(CliDB.DataPath + fileName, FileMode.Open))
            {
                if (!reader.Load(stream))
                {
                    Log.outError(LogFilter.ServerLoading, $"Error loading {fileName}.");
                    return storage;
                }
            }

            foreach (var b in reader._records)
                storage.Add((uint)b.Key, b.Value.As<T>());

            storage.LoadData(reader.Header.IdIndex, preparedStatement, preparedStatementLocale);

            Global.DB2Mgr.AddDB2(reader.Header.TableHash, storage);
            CliDB.LoadedFileCount++;
            return storage;
        }

        bool Load(Stream stream)
        {
            using (var reader = new BinaryReader(stream, Encoding.UTF8))
            {
                Header = new WDCHeader();
                Header.Signature = reader.ReadUInt32();
                if (Header.Signature != WDC2FmtSig)
                    return false;

                Header.RecordCount = reader.ReadUInt32();
                Header.FieldCount = reader.ReadUInt32();
                Header.RecordSize = reader.ReadUInt32();
                Header.StringTableSize = reader.ReadUInt32();
                Header.TableHash = reader.ReadUInt32();
                Header.LayoutHash = reader.ReadUInt32();
                Header.MinId = reader.ReadInt32();
                Header.MaxId = reader.ReadInt32();
                Header.Locale = reader.ReadInt32();
                Header.Flags = (HeaderFlags)reader.ReadUInt16();
                Header.IdIndex = reader.ReadUInt16();
                Header.TotalFieldCount = reader.ReadUInt32();
                Header.BitpackedDataOffset = reader.ReadUInt32();
                Header.LookupColumnCount = reader.ReadUInt32();
                Header.ColumnMetaSize = reader.ReadUInt32();
                Header.CommonDataSize = reader.ReadUInt32();
                Header.PalletDataSize = reader.ReadUInt32();
                Header.SectionsCount = reader.ReadUInt32();

                var sections = reader.ReadArray<SectionHeader>(Header.SectionsCount);

                // field meta data
                FieldMeta = reader.ReadArray<FieldMetaData>(Header.FieldCount);

                // column meta data 
                ColumnMeta = reader.ReadArray<ColumnMetaData>(Header.FieldCount);

                // pallet data
                PalletData = new Value32[ColumnMeta.Length][];
                for (int i = 0; i < ColumnMeta.Length; i++)
                {
                    if (ColumnMeta[i].CompressionType == DB2ColumnCompression.Pallet || ColumnMeta[i].CompressionType == DB2ColumnCompression.PalletArray)
                    {
                        PalletData[i] = reader.ReadArray<Value32>(ColumnMeta[i].AdditionalDataSize / 4);
                    }
                }

                // common data
                CommonData = new Dictionary<int, Value32>[ColumnMeta.Length];

                for (int i = 0; i < ColumnMeta.Length; i++)
                {
                    if (ColumnMeta[i].CompressionType == DB2ColumnCompression.Common)
                    {
                        Dictionary<int, Value32> commonValues = new Dictionary<int, Value32>();
                        CommonData[i] = commonValues;

                        for (int j = 0; j < ColumnMeta[i].AdditionalDataSize / 8; j++)
                            commonValues[reader.ReadInt32()] = reader.Read<Value32>();
                    }
                }

                for (int sectionIndex = 0; sectionIndex < Header.SectionsCount; sectionIndex++)
                {
                    reader.BaseStream.Position = sections[sectionIndex].FileOffset;

                    byte[] recordsData;
                    Dictionary<long, string> stringsTable = null;
                    List<Tuple<int, short>> offsetmap = null;
                    if (!Header.HasOffsetTable())
                    {
                        // records data
                        recordsData = reader.ReadBytes((int)(sections[sectionIndex].NumRecords * Header.RecordSize));

                        Array.Resize(ref recordsData, recordsData.Length + 8); // pad with extra zeros so we don't crash when reading

                        // string data
                        stringsTable = new Dictionary<long, string>();

                        for (int i = 0; i < sections[sectionIndex].StringTableSize;)
                        {
                            long oldPos = reader.BaseStream.Position;

                            stringsTable[oldPos] = reader.ReadCString();

                            i += (int)(reader.BaseStream.Position - oldPos);
                        }
                    }
                    else
                    {
                        // sparse data with inlined strings
                        recordsData = reader.ReadBytes(sections[sectionIndex].SparseTableOffset - sections[sectionIndex].FileOffset);

                        if (reader.BaseStream.Position != sections[sectionIndex].SparseTableOffset)
                            throw new Exception("reader.BaseStream.Position != sections[sectionIndex].SparseTableOffset");

                        offsetmap = new List<Tuple<int, short>>();
                        for (int i = 0; i < (Header.MaxId - Header.MinId + 1); i++)
                        {
                            int offset = reader.ReadInt32();
                            short length = reader.ReadInt16();

                            if (offset == 0 || length == 0)
                                continue;

                            offsetmap.Add(new Tuple<int, short>(offset, length));
                        }
                    }

                    // index data
                    int[] indexData = reader.ReadArray<int>((uint)(sections[sectionIndex].IndexDataSize / 4));

                    // duplicate rows data
                    Dictionary<int, int> copyData = new Dictionary<int, int>();

                    for (int i = 0; i < sections[sectionIndex].CopyTableSize / 8; i++)
                        copyData[reader.ReadInt32()] = reader.ReadInt32();

                    // reference data
                    ReferenceData refData = null;

                    if (sections[sectionIndex].ParentLookupDataSize > 0)
                    {
                        refData = new ReferenceData
                        {
                            NumRecords = reader.ReadInt32(),
                            MinId = reader.ReadInt32(),
                            MaxId = reader.ReadInt32()
                        };

                        refData.Entries = new Dictionary<int, int>();
                        ReferenceEntry[] entries = reader.ReadArray<ReferenceEntry>((uint)refData.NumRecords);
                        foreach (var entry in entries)
                            if (!refData.Entries.ContainsKey(entry.Index))
                                refData.Entries[entry.Index] = entry.Id;
                    }
                    else
                    {
                        refData = new ReferenceData
                        {
                            Entries = new Dictionary<int, int>()
                        };
                    }

                    BitReader bitReader = new BitReader(recordsData);

                    for (int i = 0; i < Header.RecordCount; ++i)
                    {
                        bitReader.Position = 0;
                        if (offsetmap != null)
                            bitReader.Offset = offsetmap[i].Item1 - sections[sectionIndex].FileOffset;
                        else
                            bitReader.Offset = i * (int)Header.RecordSize;

                        bool hasRef = refData.Entries.TryGetValue(i, out int refId);

                        var rec = new WDC2Row(this, bitReader, sections[sectionIndex].FileOffset, sections[sectionIndex].IndexDataSize != 0 ? indexData[i] : -1, hasRef ? refId : -1, stringsTable);

                        if (sections[sectionIndex].IndexDataSize != 0)
                            _records.Add(indexData[i], rec);
                        else
                            _records.Add(rec.Id, rec);
                    }

                    foreach (var copyRow in copyData)
                    {
                        var rec = _records[copyRow.Value].Clone();
                        rec.Id = copyRow.Key;
                        _records.Add(copyRow.Key, rec);
                    }
                }
            }

            return true;            
        }

        internal WDCHeader Header;
        internal FieldMetaData[] FieldMeta;
        internal ColumnMetaData[] ColumnMeta;
        internal Value32[][] PalletData;
        internal Dictionary<int, Value32>[] CommonData;

        Dictionary<int, WDC2Row> _records = new Dictionary<int, WDC2Row>();
    }

    class WDC2Row
    {
        private BitReader _data;
        private int _dataOffset;
        private int _recordsOffset;
        private int _refId;
        private bool _dataHasId;

        public int Id { get; set; }

        private FieldMetaData[] _fieldMeta;
        private ColumnMetaData[] _columnMeta;
        private Value32[][] _palletData;
        private Dictionary<int, Value32>[] _commonData;
        private Dictionary<long, string> _stringsTable;

        public WDC2Row(DBReader reader, BitReader data, int recordsOffset, int id, int refId, Dictionary<long, string> stringsTable)
        {
            _data = data;
            _recordsOffset = recordsOffset;
            _refId = refId;

            _dataOffset = _data.Offset;

            _fieldMeta = reader.FieldMeta;
            _columnMeta = reader.ColumnMeta.ToArray();
            _palletData = reader.PalletData;
            _commonData = reader.CommonData;
            _stringsTable = stringsTable;

            if (id != -1)
                Id = id;
            else
            {
                int idFieldIndex = reader.Header.IdIndex;
                _data.Position = _columnMeta[idFieldIndex].RecordOffset;

                Id = GetFieldValue<int>(idFieldIndex);
                _dataHasId = true;
            }
        }

        T GetFieldValue<T>(int fieldIndex) where T : unmanaged
        {
            var columnMeta = _columnMeta[fieldIndex];
            switch (columnMeta.CompressionType)
            {
                case DB2ColumnCompression.None:
                    int bitSize = 32 - _fieldMeta[fieldIndex].Bits;
                    if (bitSize > 0)
                        return _data.Read<T>(bitSize);
                    else
                        return _data.Read<T>(columnMeta.Immediate.BitWidth);
                case DB2ColumnCompression.Immediate:
                    return _data.Read<T>(columnMeta.Immediate.BitWidth);
                case DB2ColumnCompression.SignedImmediate:
                    return _data.ReadSigned<T>(columnMeta.Immediate.BitWidth);
                case DB2ColumnCompression.Common:
                    if (_commonData[fieldIndex].TryGetValue(Id, out Value32 val))
                        return val.As<T>();
                    else
                        return columnMeta.Common.DefaultValue.As<T>();
                case DB2ColumnCompression.Pallet:
                case DB2ColumnCompression.PalletArray: //need for SummonProperties.db2
                    uint palletIndex = _data.Read<uint>(columnMeta.Pallet.BitWidth);
                    return _palletData[fieldIndex][palletIndex].As<T>();
            }
            throw new Exception(string.Format("Unexpected compression type {0}", _columnMeta[fieldIndex].CompressionType));
        }

        T[] GetFieldValueArray<T>(int fieldIndex, int arraySize) where T : unmanaged
        {
            var columnMeta = _columnMeta[fieldIndex];

            switch (columnMeta.CompressionType)
            {
                case DB2ColumnCompression.None:
                    int bitSize = 32 - _fieldMeta[fieldIndex].Bits;

                    T[] arr1 = new T[arraySize];

                    for (int i = 0; i < arr1.Length; i++)
                    {
                        if (bitSize > 0)
                            arr1[i] = _data.Read<T>(bitSize);
                        else
                            arr1[i] = _data.Read<T>(columnMeta.Immediate.BitWidth);
                    }

                    return arr1;
                case DB2ColumnCompression.Immediate:
                    T[] arr2 = new T[arraySize];

                    for (int i = 0; i < arr2.Length; i++)
                        arr2[i] = _data.Read<T>(columnMeta.Immediate.BitWidth);

                    return arr2;
                case DB2ColumnCompression.SignedImmediate:
                    T[] arr4 = new T[arraySize];

                    for (int i = 0; i < arr4.Length; i++)
                        arr4[i] = _data.ReadSigned<T>(columnMeta.Immediate.BitWidth);

                    return arr4;
                case DB2ColumnCompression.PalletArray:
                    int cardinality = columnMeta.Pallet.Cardinality;

                    if (arraySize != cardinality)
                        throw new Exception("Struct missmatch for pallet array field?");

                    uint palletArrayIndex = _data.Read<uint>(columnMeta.Pallet.BitWidth);

                    T[] arr3 = new T[cardinality];

                    for (int i = 0; i < arr3.Length; i++)
                        arr3[i] = _palletData[fieldIndex][i + cardinality * (int)palletArrayIndex].As<T>();

                    return arr3;
            }
            throw new Exception(string.Format("Unexpected compression type {0}", columnMeta.CompressionType));
        }

        public T As<T>() where T : new()
        {
            _data.Position = 0;
            _data.Offset = _dataOffset;

            int fieldIndex = 0;
            T obj = new T();

            foreach (var f in typeof(T).GetFields())
            {
                Type type = f.FieldType;

                if (f.Name == "Id" && !_dataHasId)
                {
                    f.SetValue(obj, (uint)Id);
                    continue;
                }

                if (fieldIndex >= _fieldMeta.Length)
                {
                    if (_refId != -1)
                        f.SetValue(obj, (uint)_refId);
                    continue;
                }

                if (type.IsArray)
                {
                    Type arrayElementType = type.GetElementType();
                    if (arrayElementType.IsEnum)
                        arrayElementType = arrayElementType.GetEnumUnderlyingType();

                    Array atr = (Array)f.GetValue(obj);
                    switch (Type.GetTypeCode(arrayElementType))
                    {
                        case TypeCode.SByte:
                            f.SetValue(obj, GetFieldValueArray<sbyte>(fieldIndex, atr.Length));
                            break;
                        case TypeCode.Byte:
                            f.SetValue(obj, GetFieldValueArray<byte>(fieldIndex, atr.Length));
                            break;
                        case TypeCode.Int16:
                            f.SetValue(obj, GetFieldValueArray<short>(fieldIndex, atr.Length));
                            break;
                        case TypeCode.UInt16:
                            f.SetValue(obj, GetFieldValueArray<ushort>(fieldIndex, atr.Length));
                            break;
                        case TypeCode.Int32:
                            f.SetValue(obj, GetFieldValueArray<int>(fieldIndex, atr.Length));
                            break;
                        case TypeCode.UInt32:
                            f.SetValue(obj, GetFieldValueArray<uint>(fieldIndex, atr.Length));
                            break;
                        case TypeCode.UInt64:
                            f.SetValue(obj, GetFieldValueArray<ulong>(fieldIndex, atr.Length));
                            break;
                        case TypeCode.Single:
                            f.SetValue(obj, GetFieldValueArray<float>(fieldIndex, atr.Length));
                            break;
                        case TypeCode.String:
                            string[] array = new string[atr.Length];

                            if (_stringsTable == null)
                            {
                                for (int i = 0; i < array.Length; i++)
                                    array[i] = _data.ReadCString();
                            }
                            else
                            {
                                var pos = _recordsOffset + _data.Offset + (_data.Position >> 3);

                                int[] strIdx = GetFieldValueArray<int>(fieldIndex, atr.Length);

                                for (int i = 0; i < array.Length; i++)
                                    array[i] = _stringsTable[pos + i * 4 + strIdx[i]];
                            }

                            f.SetValue(obj, array);
                            break;
                        case TypeCode.Object:
                            if (arrayElementType == typeof(Vector3))
                            {
                                float[] pos = GetFieldValueArray<float>(fieldIndex, atr.Length * 3);

                                Vector3[] vectors = new Vector3[atr.Length];
                                for (var i = 0; i < atr.Length; ++i)
                                    vectors[i] = new Vector3(pos[i * 3], pos[(i * 3) + 1], pos[(i * 3) + 2]);

                                f.SetValue(obj, vectors);
                            }
                            break;
                        default:
                            throw new Exception("Unhandled array type: " + arrayElementType.Name);
                    }
                }
                else
                {
                    if (type.IsEnum)
                        type = type.GetEnumUnderlyingType();

                    switch (Type.GetTypeCode(type))
                    {
                        case TypeCode.Single:
                            f.SetValue(obj, GetFieldValue<float>(fieldIndex));
                            break;
                        case TypeCode.Int64:
                            f.SetValue(obj, GetFieldValue<long>(fieldIndex));
                            break;
                        case TypeCode.UInt64:
                            f.SetValue(obj, GetFieldValue<ulong>(fieldIndex));
                            break;
                        case TypeCode.Int32:
                            f.SetValue(obj, GetFieldValue<int>(fieldIndex));
                            break;
                        case TypeCode.UInt32:
                            f.SetValue(obj, GetFieldValue<uint>(fieldIndex));
                            break;
                        case TypeCode.Int16:
                            f.SetValue(obj, GetFieldValue<short>(fieldIndex));
                            break;
                        case TypeCode.UInt16:
                            f.SetValue(obj, GetFieldValue<ushort>(fieldIndex));
                            break;
                        case TypeCode.Byte:
                            f.SetValue(obj, GetFieldValue<byte>(fieldIndex));
                            break;
                        case TypeCode.SByte:
                            f.SetValue(obj, GetFieldValue<sbyte>(fieldIndex));
                            break;
                        case TypeCode.String:
                            if (_stringsTable == null)
                            {
                                f.SetValue(obj, _data.ReadCString());
                            }
                            else
                            {
                                var pos = _recordsOffset + _data.Offset + (_data.Position >> 3);
                                int ofs = GetFieldValue<int>(fieldIndex);
                                f.SetValue(obj, _stringsTable[pos + ofs]);
                            }
                            break;
                        case TypeCode.Object:
                            if (type == typeof(LocalizedString))
                            {
                                LocalizedString localized = new LocalizedString();
                                if (_stringsTable == null)
                                {
                                    localized[LocaleConstant.enUS] = _data.ReadCString();
                                }
                                else
                                {
                                    var pos = _recordsOffset + _data.Offset + (_data.Position >> 3);
                                    int ofs = GetFieldValue<int>(fieldIndex);
                                    localized[LocaleConstant.enUS] = _stringsTable[pos + ofs];
                                }

                                f.SetValue(obj, localized);
                            }
                            else if (type == typeof(Vector2))
                            {
                                float[] pos = GetFieldValueArray<float>(fieldIndex, 2);
                                f.SetValue(obj, new Vector2(pos));
                            }
                            else if (type == typeof(Vector3))
                            {
                                float[] pos = GetFieldValueArray<float>(fieldIndex, 3);
                                f.SetValue(obj, new Vector3(pos));
                            }
                            else if (type == typeof(FlagArray128))
                            {
                                uint[] flags = GetFieldValueArray<uint>(fieldIndex, 4);
                                f.SetValue(obj, new FlagArray128(flags));
                            }
                            break;
                    }
                }

                fieldIndex++;
            }

            return obj;
        }

        public WDC2Row Clone()
        {
            return (WDC2Row)MemberwiseClone();
        }
    }

    public class WDCHeader
    {
        public bool HasIndexTable()
        {
            return Convert.ToBoolean(Flags & HeaderFlags.IndexMap);
        }

        public bool HasOffsetTable()
        {
            return Convert.ToBoolean(Flags & HeaderFlags.OffsetMap);
        }

        public uint Signature;
        public uint RecordCount;
        public uint FieldCount;
        public uint RecordSize;
        public uint StringTableSize;

        public uint TableHash;
        public uint LayoutHash;
        public int MinId;
        public int MaxId;
        public int Locale;
        public HeaderFlags Flags;
        public int IdIndex;
        public uint TotalFieldCount;
        public uint BitpackedDataOffset;
        public uint LookupColumnCount;
        public uint ColumnMetaSize;
        public uint CommonDataSize;
        public uint PalletDataSize;
        public uint SectionsCount;
    }

    [StructLayout(LayoutKind.Sequential, Pack = 1)]
    public struct FieldMetaData
    {
        public short Bits;
        public ushort Offset;

        public int ByteCount
        {
            get
            {
                int value = (32 - Bits) >> 3;
                return (value < 0 ? Math.Abs(value) + 4 : value);
            }
        }

        public int BitCount
        {
            get
            {
                int bitSize = 32 - Bits;
                if (bitSize < 0)
                    bitSize = (bitSize * -1) + 32;
                return bitSize;
            }
        }

        public FieldMetaData(short bits, ushort offset)
        {
            Bits = bits;
            Offset = offset;
        }
    }

    [StructLayout(LayoutKind.Explicit)]
    public struct ColumnMetaData
    {
        [FieldOffset(0)]
        public ushort RecordOffset;
        [FieldOffset(2)]
        public ushort Size;
        [FieldOffset(4)]
        public uint AdditionalDataSize;
        [FieldOffset(8)]
        public DB2ColumnCompression CompressionType;
        [FieldOffset(12)]
        public ColumnCompressionData_Immediate Immediate;
        [FieldOffset(12)]
        public ColumnCompressionData_Pallet Pallet;
        [FieldOffset(12)]
        public ColumnCompressionData_Common Common;
    }

    public struct ColumnCompressionData_Immediate
    {
        public int BitOffset;
        public int BitWidth;
        public int Flags; // 0x1 signed
    }

    public struct ColumnCompressionData_Pallet
    {
        public int BitOffset;
        public int BitWidth;
        public int Cardinality;
    }

    public struct ColumnCompressionData_Common
    {
        public Value32 DefaultValue;
        public int B;
        public int C;
    }

    [StructLayout(LayoutKind.Sequential, Pack = 1)]
    public struct SectionHeader
    {
        public long TactKeyLookup;
        public int FileOffset;
        public int NumRecords;
        public int StringTableSize;
        public int CopyTableSize;
        public int SparseTableOffset; // CatalogDataOffset, absolute value, {uint offset, ushort size}[MaxId - MinId + 1]
        public int IndexDataSize; // int indexData[IndexDataSize / 4]
        public int ParentLookupDataSize; // uint NumRecords, uint minId, uint maxId, {uint id, uint index}[NumRecords], questionable usefulness...
    }

    [StructLayout(LayoutKind.Sequential, Pack = 1)]
    public struct SparseEntry
    {
        public int Offset;
        public ushort Size;
    }

    public struct ReferenceEntry
    {
        public int Id;
        public int Index;
    }

    public class ReferenceData
    {
        public int NumRecords { get; set; }
        public int MinId { get; set; }
        public int MaxId { get; set; }
        public Dictionary<int, int> Entries { get; set; }
    }

    public struct Value32
    {
        private uint Value;

        public T As<T>() where T : unmanaged
        {
            return Unsafe.As<uint, T>(ref Value);
        }
    }

    public class LocalizedString
    {
        public bool HasString(LocaleConstant locale = SharedConst.DefaultLocale)
        {
            return !string.IsNullOrEmpty(stringStorage[(int)locale]);
        }

        public string this[LocaleConstant locale]
        {
            get
            {
                return stringStorage[(int)locale] ?? "";
            }
            set
            {
                stringStorage[(int)locale] = value;
            }
        }

        StringArray stringStorage = new StringArray((int)LocaleConstant.Total);
    }
}