//-----------------------------------------------------------------------
// -----------------------------------------------------------------------
// file="Random"
// Project: StgSharp
// AuthorGroup: Nitload
// Copyright (c) Nitload. 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.Mathematics;

using System;
using System.Collections.Generic;
using System.Data;
using System.Numerics;
using System.Reflection;
using System.Runtime.CompilerServices;
using System.Security.Cryptography;
using System.Text;

namespace StgSharp.Mathematics
{
    public static unsafe partial class Scalar
    {

        private static byte[] randomSeed;

        internal static float currentSeed
#if DEBUG    
            = 0.5f;

        #else
        = Abs(System.DateTime.UtcNow.GetHashCode());
        #endif

        /// <summary>
        ///   returns a random float number between 0 and 1.
        /// </summary>
        /// <returns>
        ///
        /// </returns>
        public static unsafe float LowProceisionRandom()
        {
            float seed = currentSeed;

            float sample = Scalar.Pow(Scalar.SeedSqrt(seed), 2);
            float sample2 = (sample - seed) / seed;
            sample2 = Scalar.Abs(sample2);

            if (sample == 1) {
                sample = sample2;
            }

            currentSeed = sample;
            sample2 *= 1000000;

            float result = sample2 - ((int)sample2);
            if (result == 0)
            {
                currentSeed = sample2 + 0.1f;
                result = Scalar.LowProceisionRandom();
            }
            return result;
        }

        /// <summary>
        ///
        /// </summary>
        /// <returns>
        ///
        /// </returns>
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static T Random<T>() where T : unmanaged, IConvertible, INumber<T>

        {
            if (randomSeed == null)
            {
                randomSeed = new byte[64];
                string originSeed =
                    ($"{((Assembly.GetEntryAssembly() == null) ? (Assembly.GetAssembly(typeof(World))!) :
                    Assembly.GetEntryAssembly())}") + ($"{DateTime.UtcNow.ToString("o")}");
                randomSeed = SHA256.HashData(Encoding.UTF8.GetBytes(originSeed));
            }
            randomSeed = SHA256.HashData(randomSeed);
            fixed (byte* bptr = randomSeed) {
                return *(T*)bptr;
            }
        }

        /// <summary>
        ///   Generates a random seed in int value.
        /// </summary>
        /// <returns>
        ///
        /// </returns>
        public static unsafe int RandomSeed()
        {
            float seedValue1 = LowProceisionRandom();
            float seedValue2 = LowProceisionRandom();
            uint seedValueBits = *(uint*)&seedValue1;

            float seedValue = seedValueBits * seedValue2;

            return *(int*)&seedValue;
        }

    }
}