// Copyright (c) Six Labors.
// Licensed under the Six Labors Split License.

using System.Numerics;
using System.Runtime.CompilerServices;
using Castle.Core.Configuration;
using SixLabors.ImageSharp.Advanced;
using SixLabors.ImageSharp.Memory;
using SixLabors.ImageSharp.PixelFormats;
using Xunit.Abstractions;

namespace SixLabors.ImageSharp.Tests.Helpers;

public class ParallelRowIteratorTests
{
    public delegate void RowIntervalAction<T>(RowInterval rows, Span<T> span);

    private readonly ITestOutputHelper output;

    public ParallelRowIteratorTests(ITestOutputHelper output)
    {
        this.output = output;
    }

    /// <summary>
    /// maxDegreeOfParallelism, minY, maxY, expectedStepLength, expectedLastStepLength
    /// </summary>
    public static TheoryData<int, int, int, int, int, int> IterateRows_OverMinimumPixelsLimit_Data =
        new()
        {
            { 1, 0, 100, -1, 100, 1 },
            { 2, 0, 9, 5, 4, 2 },
            { 4, 0, 19, 5, 4, 4 },
            { 2, 10, 19, 5, 4, 2 },
            { 4, 0, 200, 50, 50, 4 },
            { 4, 123, 323, 50, 50, 4 },
            { 4, 0, 1201, 301, 298, 4 },
            { 8, 10, 236, 29, 23, 8 },
            { 16, 0, 209, 14, 13, 15 },
            { 24, 0, 209, 9, 2, 24 },
            { 32, 0, 209, 7, 6, 30 },
            { 64, 0, 209, 4, 1, 53 },
        };

    [Theory]
    [MemberData(nameof(IterateRows_OverMinimumPixelsLimit_Data))]
    public void IterateRows_OverMinimumPixelsLimit_IntervalsAreCorrect(
        int maxDegreeOfParallelism,
        int minY,
        int maxY,
        int expectedStepLength,
        int expectedLastStepLength,
        int expectedNumberOfSteps)
    {
        ParallelExecutionSettings parallelSettings = new(
            maxDegreeOfParallelism,
            1,
            Configuration.Default.MemoryAllocator);

        Rectangle rectangle = new(0, minY, 10, maxY - minY);

        int actualNumberOfSteps = 0;

        void RowAction(RowInterval rows)
        {
            Assert.True(rows.Min >= minY);
            Assert.True(rows.Max <= maxY);

            int step = rows.Max - rows.Min;
            int expected = rows.Max < maxY ? expectedStepLength : expectedLastStepLength;

            Interlocked.Increment(ref actualNumberOfSteps);
            Assert.Equal(expected, step);
        }

        TestRowIntervalOperation operation = new(RowAction);

        ParallelRowIterator.IterateRowIntervals(
            rectangle,
            in parallelSettings,
            in operation);

        Assert.Equal(expectedNumberOfSteps, actualNumberOfSteps);
    }

    [Theory]
    [MemberData(nameof(IterateRows_OverMinimumPixelsLimit_Data))]
    public void IterateRows_OverMinimumPixelsLimit_ShouldVisitAllRows(
        int maxDegreeOfParallelism,
        int minY,
        int maxY,
        int expectedStepLength,
        int expectedLastStepLength,
        int expectedNumberOfSteps)
    {
        ParallelExecutionSettings parallelSettings = new(
            maxDegreeOfParallelism,
            1,
            Configuration.Default.MemoryAllocator);

        Rectangle rectangle = new(0, minY, 10, maxY - minY);

        int[] expectedData = Enumerable.Repeat(0, minY).Concat(Enumerable.Range(minY, maxY - minY)).ToArray();
        int[] actualData = new int[maxY];

        void RowAction(RowInterval rows)
        {
            for (int y = rows.Min; y < rows.Max; y++)
            {
                actualData[y] = y;
            }
        }

        TestRowIntervalOperation operation = new(RowAction);

        ParallelRowIterator.IterateRowIntervals(
            rectangle,
            in parallelSettings,
            in operation);

        Assert.Equal(expectedData, actualData);
    }

    [Theory]
    [MemberData(nameof(IterateRows_OverMinimumPixelsLimit_Data))]
    public void IterateRowsWithTempBuffer_OverMinimumPixelsLimit(
        int maxDegreeOfParallelism,
        int minY,
        int maxY,
        int expectedStepLength,
        int expectedLastStepLength,
        int expectedNumberOfSteps)
    {
        ParallelExecutionSettings parallelSettings = new(
            maxDegreeOfParallelism,
            1,
            Configuration.Default.MemoryAllocator);

        Rectangle rectangle = new(0, minY, 10, maxY - minY);

        int actualNumberOfSteps = 0;

        void RowAction(RowInterval rows, Span<Vector4> buffer)
        {
            Assert.True(rows.Min >= minY);
            Assert.True(rows.Max <= maxY);

            int step = rows.Max - rows.Min;
            int expected = rows.Max < maxY ? expectedStepLength : expectedLastStepLength;

            Interlocked.Increment(ref actualNumberOfSteps);
            Assert.Equal(expected, step);
        }

        TestRowIntervalOperation<Vector4> operation = new(RowAction);

        ParallelRowIterator.IterateRowIntervals<TestRowIntervalOperation<Vector4>, Vector4>(
            rectangle,
            in parallelSettings,
            in operation);

        Assert.Equal(expectedNumberOfSteps, actualNumberOfSteps);
    }

    [Theory]
    [MemberData(nameof(IterateRows_OverMinimumPixelsLimit_Data))]
    public void IterateRowsWithTempBuffer_OverMinimumPixelsLimit_ShouldVisitAllRows(
        int maxDegreeOfParallelism,
        int minY,
        int maxY,
        int expectedStepLength,
        int expectedLastStepLength,
        int expectedNumberOfSteps)
    {
        ParallelExecutionSettings parallelSettings = new(
            maxDegreeOfParallelism,
            1,
            Configuration.Default.MemoryAllocator);

        Rectangle rectangle = new(0, minY, 10, maxY - minY);

        int[] expectedData = Enumerable.Repeat(0, minY).Concat(Enumerable.Range(minY, maxY - minY)).ToArray();
        int[] actualData = new int[maxY];

        void RowAction(RowInterval rows, Span<Vector4> buffer)
        {
            for (int y = rows.Min; y < rows.Max; y++)
            {
                actualData[y] = y;
            }
        }

        TestRowIntervalOperation<Vector4> operation = new(RowAction);

        ParallelRowIterator.IterateRowIntervals<TestRowIntervalOperation<Vector4>, Vector4>(
            rectangle,
            in parallelSettings,
            in operation);

        Assert.Equal(expectedData, actualData);
    }

    public static TheoryData<int, int, int, int, int, int, int> IterateRows_WithEffectiveMinimumPixelsLimit_Data =
        new()
        {
            { 2, 200, 50, 2, 1, -1, 2 },
            { 2, 200, 200, 1, 1, -1, 1 },
            { 4, 200, 100, 4, 2, 2, 2 },
            { 4, 300, 100, 8, 3, 3, 2 },
            { 2, 5000, 1, 4500, 1, -1, 4500 },
            { 2, 5000, 1, 5000, 1, -1, 5000 },
            { 2, 5000, 1, 5001, 2, 2501, 2500 },
        };

    [Theory]
    [MemberData(nameof(IterateRows_WithEffectiveMinimumPixelsLimit_Data))]
    public void IterateRows_WithEffectiveMinimumPixelsLimit(
        int maxDegreeOfParallelism,
        int minimumPixelsProcessedPerTask,
        int width,
        int height,
        int expectedNumberOfSteps,
        int expectedStepLength,
        int expectedLastStepLength)
    {
        ParallelExecutionSettings parallelSettings = new(
            maxDegreeOfParallelism,
            minimumPixelsProcessedPerTask,
            Configuration.Default.MemoryAllocator);

        Rectangle rectangle = new(0, 0, width, height);

        int actualNumberOfSteps = 0;

        void RowAction(RowInterval rows)
        {
            Assert.True(rows.Min >= 0);
            Assert.True(rows.Max <= height);

            int step = rows.Max - rows.Min;
            int expected = rows.Max < height ? expectedStepLength : expectedLastStepLength;

            Interlocked.Increment(ref actualNumberOfSteps);
            Assert.Equal(expected, step);
        }

        TestRowIntervalOperation operation = new(RowAction);

        ParallelRowIterator.IterateRowIntervals(
            rectangle,
            in parallelSettings,
            in operation);

        Assert.Equal(expectedNumberOfSteps, actualNumberOfSteps);
    }

    [Theory]
    [MemberData(nameof(IterateRows_WithEffectiveMinimumPixelsLimit_Data))]
    public void IterateRowsWithTempBuffer_WithEffectiveMinimumPixelsLimit(
        int maxDegreeOfParallelism,
        int minimumPixelsProcessedPerTask,
        int width,
        int height,
        int expectedNumberOfSteps,
        int expectedStepLength,
        int expectedLastStepLength)
    {
        ParallelExecutionSettings parallelSettings = new(
            maxDegreeOfParallelism,
            minimumPixelsProcessedPerTask,
            Configuration.Default.MemoryAllocator);

        Rectangle rectangle = new(0, 0, width, height);

        int actualNumberOfSteps = 0;

        void RowAction(RowInterval rows, Span<Vector4> buffer)
        {
            Assert.True(rows.Min >= 0);
            Assert.True(rows.Max <= height);

            int step = rows.Max - rows.Min;
            int expected = rows.Max < height ? expectedStepLength : expectedLastStepLength;

            Interlocked.Increment(ref actualNumberOfSteps);
            Assert.Equal(expected, step);
        }

        TestRowIntervalOperation<Vector4> operation = new(RowAction);

        ParallelRowIterator.IterateRowIntervals<TestRowIntervalOperation<Vector4>, Vector4>(
            rectangle,
            in parallelSettings,
            in operation);

        Assert.Equal(expectedNumberOfSteps, actualNumberOfSteps);
    }

    public static readonly TheoryData<int, int, int, int, int, int, int> IterateRectangularBuffer_Data =
        new()
        {
            { 8, 582, 453, 10, 10, 291, 226 }, // boundary data from DetectEdgesTest.DetectEdges_InBox
            { 2, 582, 453, 10, 10, 291, 226 },
            { 16, 582, 453, 10, 10, 291, 226 },
            { 16, 582, 453, 10, 10, 1, 226 },
            { 16, 1, 453, 0, 10, 1, 226 },
        };

    [Theory]
    [MemberData(nameof(IterateRectangularBuffer_Data))]
    public void IterateRectangularBuffer(
        int maxDegreeOfParallelism,
        int bufferWidth,
        int bufferHeight,
        int rectX,
        int rectY,
        int rectWidth,
        int rectHeight)
    {
        MemoryAllocator memoryAllocator = Configuration.Default.MemoryAllocator;

        using (Buffer2D<Point> expected = memoryAllocator.Allocate2D<Point>(bufferWidth, bufferHeight, AllocationOptions.Clean))
        using (Buffer2D<Point> actual = memoryAllocator.Allocate2D<Point>(bufferWidth, bufferHeight, AllocationOptions.Clean))
        {
            Rectangle rect = new(rectX, rectY, rectWidth, rectHeight);

            void FillRow(int y, Buffer2D<Point> buffer)
            {
                for (int x = rect.Left; x < rect.Right; x++)
                {
                    buffer[x, y] = new Point(x, y);
                }
            }

            // Fill Expected data:
            for (int y = rectY; y < rect.Bottom; y++)
            {
                FillRow(y, expected);
            }

            // Fill actual data using IterateRows:
            ParallelExecutionSettings settings = new(maxDegreeOfParallelism, memoryAllocator);

            void RowAction(RowInterval rows)
            {
                this.output.WriteLine(rows.ToString());
                for (int y = rows.Min; y < rows.Max; y++)
                {
                    FillRow(y, actual);
                }
            }

            TestRowIntervalOperation operation = new(RowAction);

            ParallelRowIterator.IterateRowIntervals(
                rect,
                settings,
                in operation);

            // Assert:
            TestImageExtensions.CompareBuffers(expected, actual);
        }
    }

    [Theory]
    [InlineData(0, 10)]
    [InlineData(10, 0)]
    [InlineData(-10, 10)]
    [InlineData(10, -10)]
    public void IterateRowsRequiresValidRectangle(int width, int height)
    {
        ParallelExecutionSettings parallelSettings = default(ParallelExecutionSettings);

        Rectangle rect = new(0, 0, width, height);

        void RowAction(RowInterval rows)
        {
        }

        TestRowIntervalOperation operation = new(RowAction);

        ArgumentOutOfRangeException ex = Assert.Throws<ArgumentOutOfRangeException>(
            () => ParallelRowIterator.IterateRowIntervals(rect, in parallelSettings, in operation));

        Assert.Contains(width <= 0 ? "Width" : "Height", ex.Message);
    }

    [Theory]
    [InlineData(0, 10)]
    [InlineData(10, 0)]
    [InlineData(-10, 10)]
    [InlineData(10, -10)]
    public void IterateRowsWithTempBufferRequiresValidRectangle(int width, int height)
    {
        ParallelExecutionSettings parallelSettings = default(ParallelExecutionSettings);

        Rectangle rect = new(0, 0, width, height);

        void RowAction(RowInterval rows, Span<Rgba32> memory)
        {
        }

        TestRowIntervalOperation<Rgba32> operation = new(RowAction);

        ArgumentOutOfRangeException ex = Assert.Throws<ArgumentOutOfRangeException>(
            () => ParallelRowIterator.IterateRowIntervals<TestRowIntervalOperation<Rgba32>, Rgba32>(rect, in parallelSettings, in operation));

        Assert.Contains(width <= 0 ? "Width" : "Height", ex.Message);
    }

    [Fact]
    public void CanIterateWithoutIntOverflow()
    {
        ParallelExecutionSettings parallelSettings = ParallelExecutionSettings.FromConfiguration(Configuration.Default);
        const int max = 100_000;

        Rectangle rect = new(0, 0, max, max);
        int intervalMaxY = 0;
        void RowAction(RowInterval rows, Span<Rgba32> memory) => intervalMaxY = Math.Max(rows.Max, intervalMaxY);

        TestRowOperation operation = new();
        TestRowIntervalOperation<Rgba32> intervalOperation = new(RowAction);

        ParallelRowIterator.IterateRows(Configuration.Default, rect, in operation);
        Assert.Equal(max - 1, operation.MaxY.Value);

        ParallelRowIterator.IterateRowIntervals<TestRowIntervalOperation<Rgba32>, Rgba32>(rect, in parallelSettings, in intervalOperation);
        Assert.Equal(max, intervalMaxY);
    }

    private readonly struct TestRowOperation : IRowOperation
    {
        public TestRowOperation()
        {
        }

        public StrongBox<int> MaxY { get; } = new();

        public void Invoke(int y)
        {
            lock (this.MaxY)
            {
                this.MaxY.Value = Math.Max(y, this.MaxY.Value);
            }
        }
    }

    private readonly struct TestRowIntervalOperation : IRowIntervalOperation
    {
        private readonly Action<RowInterval> action;

        public TestRowIntervalOperation(Action<RowInterval> action)
            => this.action = action;

        public int GetRequiredBufferLength(Rectangle bounds)
            => bounds.Width;

        public void Invoke(in RowInterval rows) => this.action(rows);
    }

    private readonly struct TestRowIntervalOperation<TBuffer> : IRowIntervalOperation<TBuffer>
        where TBuffer : unmanaged
    {
        private readonly RowIntervalAction<TBuffer> action;

        public TestRowIntervalOperation(RowIntervalAction<TBuffer> action)
            => this.action = action;

        public int GetRequiredBufferLength(Rectangle bounds)
            => bounds.Width;

        public void Invoke(in RowInterval rows, Span<TBuffer> span)
            => this.action(rows, span);
    }
}