/*
 *                     GNU AFFERO GENERAL PUBLIC LICENSE
 *                       Version 3, 19 November 2007
 *  Copyright (C) 2007 Free Software Foundation, Inc. <https://fsf.org/>
 *  Everyone is permitted to copy and distribute verbatim copies
 *  of this license document, but changing it is not allowed.
 */

using Emgu.CV;
using Emgu.CV.CvEnum;
using System;
using System.Diagnostics;
using System.Threading.Tasks;
using UVtools.Core.FileFormats;
using UVtools.Core.Operations;

namespace UVtools.Core.Managers;

public class MatCacheManager : IDisposable
{
    /// <summary>
    /// Gets the slicer file
    /// </summary>
    public FileFormat SlicerFile { get; }

    /// <summary>
    /// Gets or sets the cache count of items to keep in memory
    /// </summary>
    public ushort CacheCount { get; set; }

    /// <summary>
    /// Gets the number of cached elements per a cache entry
    /// </summary>
    public byte ElementsPerCache { get; }

    /// <summary>
    /// Gets the starting layer index range
    /// </summary>
    public uint LayerIndexStart { get; }

    /// <summary>
    /// Gets the ending layer index range
    /// </summary>
    public uint LayerIndexEnd { get; }

    /// <summary>
    /// Gets the size of this collection
    /// </summary>
    public uint CollectionSize => LayerIndexEnd - LayerIndexStart + 1;

    /// <summary>
    /// Gets the image rotation to cache
    /// </summary>
    public RotateDirection Rotate { get; init; } = RotateDirection.None;

    /// <summary>
    /// Gets the image flip to cache
    /// </summary>
    public FlipDirection Flip { get; init; } = FlipDirection.None;

    /// <summary>
    /// Gets if striping anti-aliasing is enabled, cache will be threshold'ed
    /// </summary>
    public bool StripAntiAliasing { get; init; }

    /// <summary>
    /// Gets or sets the cache direction, false to go backwards, true to go forward
    /// </summary>
    public bool Direction { get; set; } = true;

    /// <summary>
    /// If enabled it will not calculate the cache index given a layer index, set this to true to use your own indexing without pair them with layers
    /// </summary>
    public bool UseRawIndexInsteadOfLayerIndex { get; init; }

    /// <summary>
    /// Gets or sets the auto dispose mode, it will dispose all mat's below of above passed index 
    /// </summary>
    public bool AutoDispose { get; set; } = false;

    /// <summary>
    /// Gets or sets the amount of last mats to keep cached when <see cref="AutoDispose"/> is enabled
    /// </summary>
    public ushort AutoDisposeKeepLast { get; set; } = 0;

    /// <summary>
    /// Gets the cache mat array
    /// </summary>
    private Mat[][] MatCache { get; }

    /// <summary>
    /// Gets or sets the action to trigger after cache the initial <see cref="Mat"/>
    /// </summary>
    public Action<Mat[]>? AfterCacheAction { get; set; }

    public MatCacheManager(FileFormat slicerFile, ushort cacheCount = 0, byte elementsPerCache = 1) : this(slicerFile, 0, slicerFile.LastLayerIndex, cacheCount, elementsPerCache)
    { }

    public MatCacheManager(FileFormat slicerFile, uint collectionSize, ushort cacheCount = 0, byte elementsPerCache = 1) : this(slicerFile, 0, collectionSize-1, cacheCount, elementsPerCache)
    { }

    public MatCacheManager(Operation operation, ushort cacheCount = 0, byte elementsPerCache = 1) : this(operation.SlicerFile, operation.LayerIndexStart, operation.LayerIndexEnd, cacheCount, elementsPerCache)
    {}

    public MatCacheManager(FileFormat slicerFile, uint layerIndexStart, uint layerIndexEnd, ushort cacheCount = 0, byte elementsPerCache = 1)
    {
        if (cacheCount == 0) cacheCount = (ushort)(Environment.ProcessorCount * 5);
        if (layerIndexEnd == 0) layerIndexEnd = slicerFile.LayerCount > 0 ? slicerFile.LayerCount - 1 : 0;
        SlicerFile = slicerFile;
        LayerIndexStart = layerIndexStart;
        LayerIndexEnd = layerIndexEnd;
        CacheCount = cacheCount;
        ElementsPerCache = elementsPerCache;
        MatCache = new Mat[CollectionSize][];

        if (layerIndexStart == 0) UseRawIndexInsteadOfLayerIndex = true;
    }

    /// <summary>
    /// Gets the cache index from a layer index, required when layer range is not 0 started
    /// </summary>
    /// <param name="layerIndex"></param>
    /// <returns></returns>
    private uint LayerIndexToCacheIndex(uint layerIndex)
    {
        return UseRawIndexInsteadOfLayerIndex ? layerIndex : layerIndex - LayerIndexStart;
    }

    /// <summary>
    /// Gets the layer index from the cache index, required when layer range is not 0 started
    /// </summary>
    /// <param name="index"></param>
    /// <returns></returns>
    private uint CacheIndexToLayerIndex(uint index)
    {
        return UseRawIndexInsteadOfLayerIndex ? index : index + LayerIndexStart;
    }

    /// <summary>
    /// Gets all cached mat's given an index
    /// </summary>
    /// <param name="layerIndex"></param>
    /// <returns></returns>
    public Mat[] Get(uint layerIndex)
    {
        uint index = LayerIndexToCacheIndex(layerIndex);
        if (MatCache[index] is null)
        {
            if (AutoDispose) // Dispose as go
            {
                ClearButKeep(layerIndex, AutoDisposeKeepLast);
            }
                
            int fromLayerIndex = (int)layerIndex;
            int toLayerIndex = (int)Math.Min(LayerIndexEnd+1, layerIndex + CacheCount);

            if (!Direction)
            {
                toLayerIndex = fromLayerIndex + 1;
                fromLayerIndex = Math.Max((int)LayerIndexStart, fromLayerIndex - CacheCount);
            }

            Parallel.For(fromLayerIndex, toLayerIndex, CoreSettings.ParallelOptions,
                currentLayerIndex =>
                {
                    var currentCacheIndex = LayerIndexToCacheIndex((uint)currentLayerIndex);
                    if (MatCache[currentCacheIndex] is not null) return; // Already cached
                    MatCache[currentCacheIndex] = new Mat[ElementsPerCache];
                    MatCache[currentCacheIndex][0] = SlicerFile[currentLayerIndex].LayerMat;

                    if (Flip != FlipDirection.None)
                    {
                        CvInvoke.Flip(MatCache[currentCacheIndex][0], MatCache[currentCacheIndex][0], (FlipType)Flip);
                    }

                    if (Rotate != RotateDirection.None)
                    {
                        CvInvoke.Rotate(MatCache[currentCacheIndex][0], MatCache[currentCacheIndex][0], (RotateFlags) Rotate);
                    }

                    if (StripAntiAliasing)
                    {
                        CvInvoke.Threshold(MatCache[currentCacheIndex][0], MatCache[currentCacheIndex][0], 127, byte.MaxValue, ThresholdType.Binary);
                    }

                    AfterCacheAction?.Invoke(MatCache[currentCacheIndex]);
                });
        }

        return MatCache[index];
    }

    public Mat Get(uint layerIndex, byte elementIndex)
    {
        return Get(layerIndex)[elementIndex];
    }

    public Mat Get1(uint layerIndex)
    {
        return Get(layerIndex)[0];
    }

    public (Mat mat1, Mat mat2) Get2(uint layerIndex)
    {
        var mats = Get(layerIndex);
        return (mats[0], mats[1]);
    }

    public (Mat mat1, Mat mat2, Mat mat3) Get3(uint layerIndex)
    {
        var mats = Get(layerIndex);
        return (mats[0], mats[1], mats[2]);
    }

        
    public void GetAndConsumeWork(uint layerIndex, Action<Mat[]> action)
    {
        try
        {
            action.Invoke(Get(layerIndex));
        }
        catch (Exception e)
        {
            Debug.WriteLine(e);
            throw;
        }
        finally
        {
            Consume(layerIndex);
        }
    }

    public void GetAndConsumeWork(uint layerIndex, Action<Mat> action)
    {
        try
        {
            action.Invoke(Get1(layerIndex));
        }
        catch (Exception e)
        {
            Debug.WriteLine(e);
            throw;
        }
        finally
        {
            Consume(layerIndex);
        }
    }

    public void GetAndConsumeWork(uint layerIndex, byte elementIndex, Action<Mat> action)
    {
        try
        {
            action.Invoke(Get(layerIndex)[elementIndex]);
        }
        catch (Exception e)
        {
            Debug.WriteLine(e);
            throw;
        }
        finally
        {
            Consume(layerIndex);
        }
    }

    /// <summary>
    /// Consume and dispose the cached Mats for given layer index
    /// </summary>
    /// <param name="layerIndex"></param>
    public void Consume(uint layerIndex)
    {
        var index = LayerIndexToCacheIndex(layerIndex);
        if(MatCache[index] is null) return;
        for (int i = 0; i < MatCache[index].Length; i++)
        {
            MatCache[index][i]?.Dispose();
        }
        MatCache[index] = null!;
    }

    /// <summary>
    /// Clears and dispose the cache but keep the selected index and optionally the last n indexes
    /// </summary>
    /// <param name="layerIndex"></param>
    /// <param name="keepLast"></param>
    public void ClearButKeep(uint layerIndex, ushort keepLast = 0)
    {
        if (Direction)
        {
            for (int i = (int)layerIndex - 1 - keepLast; i >= LayerIndexStart; i--) Consume((uint)i);
        }
        else
        {
            for (int i = (int)layerIndex + 1 + keepLast; i <= LayerIndexEnd; i++) Consume((uint)i);
        }
    }

    /// <summary>
    /// Clears and dispose all the cache
    /// </summary>
    public void Clear()
    {
        for (uint i = 0; i < MatCache.Length; i++)
        {
            Consume(CacheIndexToLayerIndex(i));
        }
    }

    /// <inheritdoc />
    public void Dispose()
    {
        Clear();
    }
}