using XGame.Framework.Network.Protobuf;
using System.Collections.Generic;

namespace XGame.Framework.Network
{
    public static class ProtobufUtils
    {
        /// <summary>
        /// 为了优化性能，返回的字节流头部预留10个字节给外部使用，外部可以把头部信息写入到这10个预留的位置中
        /// 实际是8个字节用于头部,2个字节在body存body长度,因此与proto无关的字节数为前10字节
        /// </summary>
        private const int HeadOffset = 10;
        public static readonly CodedOutputStream CodedOutput = new CodedOutputStream();
        public static readonly CodedInputStream CodedInput = new CodedInputStream();

        public static BytesWrapper CreateBytesWrapper(IMsgParser parsor)
        {
            CodedOutput.Buffer = SessionBufferPool.Acquire();
            CodedOutput.Reset(HeadOffset);
            parsor.WriteTo(CodedOutput);
            return BytesWrapperPool.Acquire(CodedOutput.Buffer, HeadOffset, (int)CodedOutput.Position - HeadOffset);
        }

        public static void ParseFrom(byte[] bytes, int offset, int size, IMsgParser parser)
        {
            CodedInput.Reset(bytes, offset, size);
            parser.MergeFrom(CodedInput);
            CodedInput.CheckReadEndOfStreamTag();
        }

        public static void WriteTo<T>(CodedOutputStream output, FieldCodec<T> codec, List<T> ls)
        {
            if (ls == null || ls.Count == 0)
                return;

            var writer = codec.ValueWriter;
            var tag = codec.Tag;
            if (codec.PackedRepeatedField)
            {
                uint size = (uint)CalculatePackedDataSize(codec, ls);
                output.WriteTag(tag);
                output.WriteRawVarint32(size);
                for (int i = 0, count = ls.Count; i < count; i++)
                {
                    writer(output, ls[i]);
                }
            }
            else
            {
                for (int i = 0, count = ls.Count; i < count; i++)
                {
                    output.WriteTag(tag);
                    writer(output, ls[i]);
                }
            }
        }

        private static int CalculatePackedDataSize<T>(FieldCodec<T> codec, List<T> ls)
        {
            int fixedSize = codec.FixedSize;
            if (fixedSize == 0)
            {
                var calculator = codec.ValueSizeCalculator;
                int tmp = 0;
                for (int i = 0, count = ls.Count; i < count; i++)
                {
                    tmp += calculator(ls[i]);
                }
                return tmp;
            }
            else
            {
                return fixedSize * ls.Count;
            }
        }
        public static void AddEntriesFrom<T>(CodedInputStream input, FieldCodec<T> codec,
           List<T> ls)
        {
            uint tag = input.LastTag;
            var reader = codec.ValueReader;
            if (FieldCodec<T>.IsPackedRepeatedField(tag))
            {
                int length = input.ReadLength();
                if (length > 0)
                {
                    int oldLimit = input.PushLimit(length);
                    while (!input.ReachedLimit)
                    {
                        ls.Add(reader(input));
                    }
                    input.PopLimit(oldLimit);
                }
            }
            else
            {
                do
                {
                    ls.Add(reader(input));
                } while (input.MaybeConsumeTag(tag));
            }
        }

        public static int CalculateSize<T>(FieldCodec<T> codec, List<T> ls)
        {
            if (ls == null)
            {
                return 0;
            }
            int count = ls.Count;
            if (ls.Count == 0)
            {
                return 0;
            }
            uint tag = codec.Tag;
            if (codec.PackedRepeatedField)
            {
                int dataSize = CalculatePackedDataSize(codec, ls);
                return CodedOutputStream.ComputeRawVarint32Size(tag) +
                    CodedOutputStream.ComputeLengthSize(dataSize) +
                    dataSize;
            }
            else
            {
                var sizeCalculator = codec.ValueSizeCalculator;
                int size = count * CodedOutputStream.ComputeRawVarint32Size(tag);
                for (int i = 0; i < count; i++)
                {
                    size += sizeCalculator(ls[i]);
                }
                return size;
            }
        }

        public static void AddEntriesFrom<TKey, TValue>(CodedInputStream input, MapFieldCodec<TKey, TValue> codec, Dictionary<TKey, TValue> map)
        {
            var adapter = new MapFieldCodec<TKey, TValue>.MessageAdapter(codec);
            do
            {
                adapter.Reset();
                input.ReadMessage(adapter);
                map.Add(adapter.Key, adapter.Value);
            } while (input.MaybeConsumeTag(codec.MapTag));
        }

        public static void WriteTo<TKey, TValue>(CodedOutputStream output, MapFieldCodec<TKey, TValue> codec, Dictionary<TKey, TValue> map)
        {
            var message = new MapFieldCodec<TKey, TValue>.MessageAdapter(codec);
            foreach (var entry in map)
            {
                message.Key = entry.Key;
                message.Value = entry.Value;
                output.WriteTag(codec.MapTag);
                output.WriteMessage(message);
            }
        }

        public static int CalculateSize<TKey, TValue>(MapFieldCodec<TKey, TValue> codec, Dictionary<TKey, TValue> map)
        {
            var message = new MapFieldCodec<TKey, TValue>.MessageAdapter(codec);
            int size = 0;
            foreach (var entry in map)
            {
                message.Key = entry.Key;
                message.Value = entry.Value;
                size += CodedOutputStream.ComputeRawVarint32Size(codec.MapTag);
                size += CodedOutputStream.ComputeMessageSize(message);
            }
            return size;
        }
    }
}