// <copyright file="MklFourierTransformProvider.cs" company="Math.NET">
// Math.NET Numerics, part of the Math.NET Project
// https://numerics.mathdotnet.com
//
// Copyright (c) 2009-2018 Math.NET
//
// 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.
// </copyright>

#if NATIVE

using System;
using System.Threading;
using IStation.Numerics.Providers.Common.Mkl;
using Complex = System.Numerics.Complex;

namespace IStation.Numerics.Providers.FourierTransform.Mkl
{
    internal class MklFourierTransformProvider : IFourierTransformProvider, IDisposable
    {
        const int MinimumCompatibleRevision = 11;

        class Kernel
        {
            public IntPtr Handle;
            public int[] Dimensions;
            public FourierTransformScaling Scaling;
            public bool Real;
            public bool Single;
        }

        readonly string _hintPath;
        Kernel _kernel;

        /// <param name="hintPath">Hint path where to look for the native binaries</param>
        internal MklFourierTransformProvider(string hintPath)
        {
            _hintPath = hintPath;
        }

        /// <summary>
        /// Try to find out whether the provider is available, at least in principle.
        /// Verification may still fail if available, but it will certainly fail if unavailable.
        /// </summary>
        public bool IsAvailable()
        {
            return MklProvider.IsAvailable(hintPath: _hintPath);
        }

        /// <summary>
        /// Initialize and verify that the provided is indeed available. If not, fall back to alternatives like the managed provider
        /// </summary>
        public void InitializeVerify()
        {
            int revision = MklProvider.Load(hintPath: _hintPath);
            if (revision < MinimumCompatibleRevision)
            {
                throw new NotSupportedException(FormattableString.Invariant($"MKL Native Provider revision r{revision} is too old. Consider upgrading to a newer version. Revision r{MinimumCompatibleRevision} and newer are supported."));
            }

            // we only support exactly one major version, since major version changes imply a breaking change.
            int fftMajor = SafeNativeMethods.query_capability((int) ProviderCapability.FourierTransformMajor);
            int fftMinor = SafeNativeMethods.query_capability((int) ProviderCapability.FourierTransformMinor);
            if (!(fftMajor == 1 && fftMinor >= 0))
            {
                throw new NotSupportedException(FormattableString.Invariant($"MKL Native Provider not compatible. Expecting Fourier transform v1 but provider implements v{fftMajor}."));
            }
        }

        /// <summary>
        /// Frees memory buffers, caches and handles allocated in or to the provider.
        /// Does not unload the provider itself, it is still usable afterwards.
        /// </summary>
        public virtual void FreeResources()
        {
            Kernel kernel = Interlocked.Exchange(ref _kernel, null);
            if (kernel != null)
            {
                SafeNativeMethods.x_fft_free(ref kernel.Handle);
            }

            MklProvider.FreeResources();
        }

        public override string ToString()
        {
            return MklProvider.Describe();
        }

        Kernel Configure(int length, FourierTransformScaling scaling, bool real, bool single)
        {
            Kernel kernel = Interlocked.Exchange(ref _kernel, null);

            if (kernel == null)
            {
                kernel = new Kernel
                {
                    Dimensions = new[] {length},
                    Scaling = scaling,
                    Real = real,
                    Single = single
                };

                if (single)
                {
                    if (real) SafeNativeMethods.s_fft_create(out kernel.Handle, length, (float)ForwardScaling(scaling, length), (float)BackwardScaling(scaling, length));
                    else SafeNativeMethods.c_fft_create(out kernel.Handle, length, (float)ForwardScaling(scaling, length), (float)BackwardScaling(scaling, length));
                }
                else
                {
                    if (real) SafeNativeMethods.d_fft_create(out kernel.Handle, length, ForwardScaling(scaling, length), BackwardScaling(scaling, length));
                    else SafeNativeMethods.z_fft_create(out kernel.Handle, length, ForwardScaling(scaling, length), BackwardScaling(scaling, length));
                }

                return kernel;
            }

            if (kernel.Dimensions.Length != 1 || kernel.Dimensions[0] != length || kernel.Scaling != scaling || kernel.Real != real || kernel.Single != single)
            {
                SafeNativeMethods.x_fft_free(ref kernel.Handle);

                if (single)
                {
                    if (real) SafeNativeMethods.s_fft_create(out kernel.Handle, length, (float)ForwardScaling(scaling, length), (float)BackwardScaling(scaling, length));
                    else SafeNativeMethods.c_fft_create(out kernel.Handle, length, (float)ForwardScaling(scaling, length), (float)BackwardScaling(scaling, length));
                }
                else
                {
                    if (real) SafeNativeMethods.d_fft_create(out kernel.Handle, length, ForwardScaling(scaling, length), BackwardScaling(scaling, length));
                    else SafeNativeMethods.z_fft_create(out kernel.Handle, length, ForwardScaling(scaling, length), BackwardScaling(scaling, length));
                }

                kernel.Dimensions = new[] {length};
                kernel.Scaling = scaling;
                kernel.Real = real;
                kernel.Single = single;
                return kernel;
            }

            return kernel;
        }

        Kernel Configure(int[] dimensions, FourierTransformScaling scaling, bool single)
        {
            if (dimensions.Length == 1)
            {
                return Configure(dimensions[0], scaling, false, single);
            }

            Kernel kernel = Interlocked.Exchange(ref _kernel, null);

            if (kernel == null)
            {
                kernel = new Kernel
                {
                    Dimensions = dimensions,
                    Scaling = scaling,
                    Real = false,
                    Single = single
                };

                long length = 1;
                for (int i = 0; i < dimensions.Length; i++)
                {
                    length *= dimensions[i];
                }

                if (single)
                {
                    SafeNativeMethods.c_fft_create_multidim(out kernel.Handle, dimensions.Length, dimensions, (float)ForwardScaling(scaling, length), (float)BackwardScaling(scaling, length));
                }
                else
                {
                    SafeNativeMethods.z_fft_create_multidim(out kernel.Handle, dimensions.Length, dimensions, ForwardScaling(scaling, length), BackwardScaling(scaling, length));
                }

                return kernel;
            }

            bool mismatch = kernel.Dimensions.Length != dimensions.Length || kernel.Scaling != scaling || kernel.Real != false || kernel.Single != single;
            if (!mismatch)
            {
                for (int i = 0; i < dimensions.Length; i++)
                {
                    if (dimensions[i] != kernel.Dimensions[i])
                    {
                        mismatch = true;
                        break;
                    }
                }
            }

            if (mismatch)
            {
                long length = 1;
                for (int i = 0; i < dimensions.Length; i++)
                {
                    length *= dimensions[i];
                }

                SafeNativeMethods.x_fft_free(ref kernel.Handle);

                if (single)
                {
                    SafeNativeMethods.c_fft_create_multidim(out kernel.Handle, dimensions.Length, dimensions, (float)ForwardScaling(scaling, length), (float)BackwardScaling(scaling, length));
                }
                else
                {
                    SafeNativeMethods.z_fft_create_multidim(out kernel.Handle, dimensions.Length, dimensions, ForwardScaling(scaling, length), BackwardScaling(scaling, length));
                }

                kernel.Dimensions = dimensions;
                kernel.Scaling = scaling;
                kernel.Real = false;
                kernel.Single = single;
                return kernel;
            }

            return kernel;
        }

        void Release(Kernel kernel)
        {
            Kernel existing = Interlocked.Exchange(ref _kernel, kernel);
            if (existing != null)
            {
                SafeNativeMethods.x_fft_free(ref existing.Handle);
            }
        }

        public void Forward(Complex32[] samples, FourierTransformScaling scaling)
        {
            Kernel kernel = Configure(samples.Length, scaling, false, true);
            SafeNativeMethods.c_fft_forward(kernel.Handle, samples);
            Release(kernel);
        }

        public void Forward(Complex[] samples, FourierTransformScaling scaling)
        {
            Kernel kernel = Configure(samples.Length, scaling, false, false);
            SafeNativeMethods.z_fft_forward(kernel.Handle, samples);
            Release(kernel);
        }

        public void Backward(Complex32[] spectrum, FourierTransformScaling scaling)
        {
            Kernel kernel = Configure(spectrum.Length, scaling, false, true);
            SafeNativeMethods.c_fft_backward(kernel.Handle, spectrum);
            Release(kernel);
        }

        public void Backward(Complex[] spectrum, FourierTransformScaling scaling)
        {
            Kernel kernel = Configure(spectrum.Length, scaling, false, false);
            SafeNativeMethods.z_fft_backward(kernel.Handle, spectrum);
            Release(kernel);
        }

        public void ForwardReal(float[] samples, int n, FourierTransformScaling scaling)
        {
            Kernel kernel = Configure(n, scaling, true, true);
            SafeNativeMethods.s_fft_forward(kernel.Handle, samples);
            Release(kernel);
        }

        public void ForwardReal(double[] samples, int n, FourierTransformScaling scaling)
        {
            Kernel kernel = Configure(n, scaling, true, false);
            SafeNativeMethods.d_fft_forward(kernel.Handle, samples);
            Release(kernel);
        }

        public void BackwardReal(float[] spectrum, int n, FourierTransformScaling scaling)
        {
            Kernel kernel = Configure(n, scaling, true, true);
            SafeNativeMethods.s_fft_backward(kernel.Handle, spectrum);
            Release(kernel);

            spectrum[n] = 0f;
        }

        public void BackwardReal(double[] spectrum, int n, FourierTransformScaling scaling)
        {
            Kernel kernel = Configure(n, scaling, true, false);
            SafeNativeMethods.d_fft_backward(kernel.Handle, spectrum);
            Release(kernel);

            spectrum[n] = 0d;
        }

        public void ForwardMultidim(Complex32[] samples, int[] dimensions, FourierTransformScaling scaling)
        {
            Kernel kernel = Configure(dimensions, scaling, true);
            SafeNativeMethods.c_fft_forward(kernel.Handle, samples);
            Release(kernel);
        }

        public void ForwardMultidim(Complex[] samples, int[] dimensions, FourierTransformScaling scaling)
        {
            Kernel kernel = Configure(dimensions, scaling, false);
            SafeNativeMethods.z_fft_forward(kernel.Handle, samples);
            Release(kernel);
        }

        public void BackwardMultidim(Complex32[] spectrum, int[] dimensions, FourierTransformScaling scaling)
        {
            Kernel kernel = Configure(dimensions, scaling, true);
            SafeNativeMethods.c_fft_backward(kernel.Handle, spectrum);
            Release(kernel);
        }

        public void BackwardMultidim(Complex[] spectrum, int[] dimensions, FourierTransformScaling scaling)
        {
            Kernel kernel = Configure(dimensions, scaling, false);
            SafeNativeMethods.z_fft_backward(kernel.Handle, spectrum);
            Release(kernel);
        }

        static double ForwardScaling(FourierTransformScaling scaling, long length)
        {
            switch (scaling)
            {
                case FourierTransformScaling.SymmetricScaling:
                    return Math.Sqrt(1.0/length);
                case FourierTransformScaling.ForwardScaling:
                    return 1.0/length;
                default:
                    return 1.0;
            }
        }

        static double BackwardScaling(FourierTransformScaling scaling, long length)
        {
            switch (scaling)
            {
                case FourierTransformScaling.SymmetricScaling:
                    return Math.Sqrt(1.0/length);
                case FourierTransformScaling.BackwardScaling:
                    return 1.0/length;
                default:
                    return 1.0;
            }
        }

        public void Dispose()
        {
            FreeResources();
        }
    }
}

#endif