//-----------------------------------------------------------------------
// -----------------------------------------------------------------------
// file="RandomGenerator.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 StgSharp.HighPerformance;

using System;
using System.IO;
using System.Runtime.CompilerServices;
using System.Text;
using System.Xml.Serialization;

namespace StgSharp.Data
{
    public unsafe class RandomGenerator
    {

        private byte[] currentKey;
        private readonly byte[] originKey;

        public RandomGenerator() : this(DateTime.UtcNow.ToBinary()) { }

        public RandomGenerator(object source)
        {
            ArgumentNullException.ThrowIfNull(source);
            XmlSerializer s = new(source.GetType());
            using (StringWriter sw = new())
            {
                s.Serialize(sw, source);
                string data = sw.ToString();
                originKey = Encoding.Unicode.GetBytes(data);
            }
            currentKey = [0,0,0,0];
            fixed (byte* o = originKey, c = currentKey) {
                *(int*)c = UnsafeCompute.CityHashSimplify((char*)o, 0, originKey.Length / 2);
            }
            TotalGeneratedRandom = 0;
        }

        public int TotalGeneratedRandom
        {
[MethodImpl(MethodImplOptions.AggressiveInlining)]
            get;
[MethodImpl(MethodImplOptions.AggressiveInlining)]
            private set;
        }

        public unsafe int GenRandomInt()
        {
            uint source = PrivateRand();
            TotalGeneratedRandom++;
            M64 m = new M64();
            m.Member<uint>(0) = source;
            m.Member<uint>(1) = source;
            return (m << (TotalGeneratedRandom % 32)).Member<int>(1);
        }

        public byte GenRandomInt8()
        {
            TotalGeneratedRandom++;
            if (TotalGeneratedRandom % 4 == 0) {
                PrivateRand();
            }
            return currentKey[TotalGeneratedRandom % 4];
        }

        public float GenRandomSingle()
        {
            TotalGeneratedRandom++;

            while (true)
            {
                uint
                    temp0 = PrivateRand(),
                    temp1 = PrivateRand();

                if (temp0 * temp1 != 0)
                {
                    float ret = temp0 % temp1 * 1.0f / temp1;
                    if (ret < 0.335f)
                    {
                        ret = ret * ((ret * (-0.7811934f)) + 1.4489113f);
                    } else
                    {
                        ret = (ret * ((ret * (-0.1158368f)) + 1.0580600f)) + 0.0590584f;
                    }
                    if (ret > 1)
                    {
                        continue;
                    }
                    return ret;
                }
            }
        }

        public void Reset()
        {
            currentKey = originKey;
            TotalGeneratedRandom = 0;
        }

        private unsafe uint PrivateRand()
        {
            uint ret;
            fixed (byte* bptr = currentKey)
            {
                *(int*)bptr = UnsafeCompute.CityHashSimplify((char*)bptr, currentKey.Length / 2);
                ret = *(uint*)bptr;
            }

            // Console.WriteLine(ret.ToString(16));
            return ret;
        }

    }
}