//-----------------------------------------------------------------------
//-----------------------------------------------------------------------
//     file="StringHashMultiplexer.cs"
//     Project: StgSharp
//     AuthorGroup: Nitload Space
//     Copyright (c) Nitload Space. All rights reserved.
//     
//     Permission is hereby granted, free of charge, to any person 
//     obtaining a copy of this software and associated documentation 
//     files (the “Software”), to deal in the Software without restriction, 
//     including without limitation the rights to use, copy, modify, merge,
//     publish, distribute, sublicense, and/or sell copies of the Software, 
//     and to permit persons to whom the Software is furnished to do so, 
//     subject to the following conditions:
//     
//     The above copyright notice and 
//     this permission notice shall be included in all copies 
//     or substantial portions of the Software.
//     
//     THE SOFTWARE IS PROVIDED “AS IS”, 
//     WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, 
//     INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
//     FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. 
//     IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, 
//     DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, 
//     ARISING FROM, OUT OF OR IN CONNECTION WITH 
//     THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//     
//-----------------------------------------------------------------------
//-----------------------------------------------------------------------
using System;
using System.Collections.Generic;
using System.Diagnostics.CodeAnalysis;
using System.Globalization;
using System.Runtime.CompilerServices;
using System.Text;
using System.Threading;

namespace StgSharp.Collections
{
    public sealed class StringHashMultiplexer : IHashMultiplexer<string>
    {

        private int _initCount, _remainedCount, _hashCache, _hashLast;
        private string _source, _sourceLast;

        public int RemainedMultiplexCount
        {
            get => _remainedCount;
            set => _initCount = value;
        }

        public void CacheHash( string obj, int count )
        {
            _hashCache = ForceComputeHash( obj );
            _initCount = count;
            _remainedCount = _initCount;
            _source = obj;
        }

        public bool Equals( string x, string y )
        {
            return x == y;
        }

        public void ExtendCache( int count )
        {
            _initCount += count;
            _remainedCount += count;
        }

        [MethodImpl( MethodImplOptions.AggressiveInlining )]
        public unsafe int ForceComputeHash( [NotNull] string obj )
        {
            int hash;
            fixed( char* cPtr = obj.AsSpan() ) {
                hash = InternalIO.Intrinsic.city_hash_simplify( cPtr, obj.Length );
            }
            return hash;
        }

        public int GetHashCode( string obj )
        {
            if( _remainedCount > 0 && ReferenceEquals( _source, obj ) )
            {
                _remainedCount--;
                return _hashCache;
            }
            if( ReferenceEquals( _sourceLast, obj ) ) {
                return _hashLast;
            }
            _sourceLast = obj;
            _hashLast = ForceComputeHash( obj );
            return _hashLast;
        }

    }

    public sealed class ConcurrentStringHashMultiplexer : IHashMultiplexer<string>, IDisposable
    {

        private bool disposedValue;
        private readonly ThreadLocal<StringHashMultiplexer> _multiplexers = 
            new( () => new StringHashMultiplexer() );

        public int RemainedMultiplexCount
        {
            get => _multiplexers.Value.RemainedMultiplexCount;
            set => _multiplexers.Value.RemainedMultiplexCount = value;
        }

        public void CacheHash( string obj, int count )
        {
            throw new NotImplementedException();
        }

        // ~ConcurrentStringHashMultiplexer()
        // {
        //     Dispose(disposing: false);
        // }

        public void Dispose()
        {
            Dispose( disposing: true );
            GC.SuppressFinalize( this );
        }

        public bool Equals( string x, string y )
        {
            return x == y;
        }

        public void ExtendCache( int count )
        {
            _multiplexers.Value.ExtendCache( count );
        }

        public unsafe int ForceComputeHash( [NotNull] string obj )
        {
            int hash;
            fixed( char* cPtr = obj.AsSpan() ) {
                hash = InternalIO.Intrinsic.city_hash_simplify( cPtr, obj.Length );
            }
            return hash;
        }

        public int GetHashCode( string obj )
        {
            return _multiplexers.Value.GetHashCode( obj );
        }

        private void Dispose( bool disposing )
        {
            if( !disposedValue )
            {
                if( disposing ) {
                    _multiplexers.Dispose();
                }

                disposedValue = true;
            }
        }

    }
}