using FluentAssertions;
using SatelliteProvider.Common.Imaging;
using SixLabors.ImageSharp;
using SixLabors.ImageSharp.PixelFormats;
using SixLabors.ImageSharp.Processing;

namespace SatelliteProvider.Tests;

public class TileGridStitcherTests : IDisposable
{
    private readonly string _tempDir;

    public TileGridStitcherTests()
    {
        _tempDir = Path.Combine(Path.GetTempPath(), $"stitcher_tests_{Guid.NewGuid():N}");
        Directory.CreateDirectory(_tempDir);
    }

    public void Dispose()
    {
        if (Directory.Exists(_tempDir))
        {
            Directory.Delete(_tempDir, recursive: true);
        }
        GC.SuppressFinalize(this);
    }

    private string CreateSolidTile(string name, int sizePixels, Rgb24 color)
    {
        var path = Path.Combine(_tempDir, $"{name}.png");
        using var img = new Image<Rgb24>(sizePixels, sizePixels);
        for (int y = 0; y < sizePixels; y++)
        {
            for (int x = 0; x < sizePixels; x++)
            {
                img[x, y] = color;
            }
        }
        img.SaveAsPng(path);
        return path;
    }

    [Fact]
    public async Task StitchAsync_PlacesEachTileAtCorrectGridOffset_AZ367_AC1()
    {
        // Arrange
        const int size = 8;
        var red = new Rgb24(200, 10, 10);
        var green = new Rgb24(10, 200, 10);
        var blue = new Rgb24(10, 10, 200);

        var redTile = CreateSolidTile("red", size, red);
        var greenTile = CreateSolidTile("green", size, green);
        var blueTile = CreateSolidTile("blue", size, blue);

        var tiles = new[]
        {
            new TilePlacement(10, 20, redTile),
            new TilePlacement(11, 20, greenTile),
            new TilePlacement(10, 21, blueTile),
        };

        // Act
        var result = await new TileGridStitcher().StitchAsync(
            tiles,
            tileSizePixels: size,
            deduplicateByTileCoords: false,
            swallowTileLoadErrors: false);

        // Assert
        using var img = result.Image;
        result.MinX.Should().Be(10);
        result.MinY.Should().Be(20);
        result.MaxX.Should().Be(11);
        result.MaxY.Should().Be(21);
        result.ImageWidth.Should().Be(2 * size);
        result.ImageHeight.Should().Be(2 * size);
        result.PlacedTiles.Should().HaveCount(3);
        result.MissingTiles.Should().BeEmpty();

        img[1, 1].Should().Be(red);
        img[size + 1, 1].Should().Be(green);
        img[1, size + 1].Should().Be(blue);
        img[size + 1, size + 1].Should().Be(default(Rgb24));
    }

    [Fact]
    public async Task StitchAsync_DeduplicatesAndSortsWhenRequested_AZ367()
    {
        // Arrange
        const int size = 4;
        var color = new Rgb24(123, 45, 67);
        var sameCellTileA = CreateSolidTile("dupA", size, color);
        var sameCellTileB = CreateSolidTile("dupB", size, color);
        var other = CreateSolidTile("other", size, color);

        var tiles = new[]
        {
            new TilePlacement(5, 5, sameCellTileA),
            new TilePlacement(5, 5, sameCellTileB),
            new TilePlacement(6, 5, other),
        };

        // Act
        var result = await new TileGridStitcher().StitchAsync(
            tiles,
            tileSizePixels: size,
            deduplicateByTileCoords: true,
            swallowTileLoadErrors: false);

        // Assert
        using var img = result.Image;
        result.PlacedTiles.Should().HaveCount(2);
        result.PlacedTiles.Select(p => (p.TileX, p.TileY))
            .Should().BeEquivalentTo(new[] { (5, 5), (6, 5) });
    }

    [Fact]
    public async Task StitchAsync_SwallowsLoadErrors_WhenFlagSet_AZ367()
    {
        // Arrange
        const int size = 4;
        var good = CreateSolidTile("good", size, new Rgb24(1, 2, 3));
        var ghost = Path.Combine(_tempDir, "missing.png");
        var sut = new TileGridStitcher();

        var tiles = new[]
        {
            new TilePlacement(0, 0, good),
            new TilePlacement(1, 0, ghost),
        };

        // Act
        var result = await sut.StitchAsync(
            tiles,
            tileSizePixels: size,
            deduplicateByTileCoords: false,
            swallowTileLoadErrors: true);

        // Assert
        using var img = result.Image;
        result.PlacedTiles.Should().HaveCount(1);
        result.MissingTiles.Should().ContainSingle()
            .Which.Reason.Should().Be(MissingTileReason.FileNotFound);
    }

    [Fact]
    public async Task StitchAsync_PropagatesLoadErrors_WhenFlagFalse_AZ367()
    {
        // Arrange — corrupt file (text bytes pretending to be PNG)
        const int size = 4;
        var good = CreateSolidTile("good", size, new Rgb24(1, 2, 3));
        var corrupt = Path.Combine(_tempDir, "corrupt.png");
        await File.WriteAllTextAsync(corrupt, "this is not a png file");

        var tiles = new[]
        {
            new TilePlacement(0, 0, good),
            new TilePlacement(1, 0, corrupt),
        };

        // Act
        Func<Task> act = () => new TileGridStitcher().StitchAsync(
            tiles,
            tileSizePixels: size,
            deduplicateByTileCoords: false,
            swallowTileLoadErrors: false);

        // Assert
        await act.Should().ThrowAsync<Exception>();
    }

    [Fact]
    public async Task StitchAsync_EmptyTiles_ThrowsInvalidOperation_AZ367()
    {
        // Arrange
        var sut = new TileGridStitcher();

        // Act
        Func<Task> act = () => sut.StitchAsync(
            Array.Empty<TilePlacement>(),
            tileSizePixels: 256,
            deduplicateByTileCoords: false,
            swallowTileLoadErrors: false);

        // Assert
        await act.Should().ThrowAsync<InvalidOperationException>();
    }

    [Fact]
    public async Task StitchAsync_NonPositiveTileSize_ThrowsArgumentOutOfRange_AZ367()
    {
        // Arrange
        var sut = new TileGridStitcher();
        var tiles = new[] { new TilePlacement(0, 0, "/nope") };

        // Act
        Func<Task> act = () => sut.StitchAsync(tiles, 0, false, false);

        // Assert
        await act.Should().ThrowAsync<ArgumentOutOfRangeException>();
    }

    [Fact]
    public void DrawCross_PaintsHorizontalAndVerticalArms_AtCenter_AZ367_AC1()
    {
        // Arrange
        const int width = 20;
        using var img = new Image<Rgb24>(width, width);
        var red = new Rgb24(255, 0, 0);
        var sut = new TileGridStitcher();

        // Act
        sut.DrawCross(img, new Point(10, 10), red, armLength: 4, thickness: 2);

        // Assert — horizontal arm pixels
        img[6, 10].Should().Be(red);
        img[14, 10].Should().Be(red);
        img[10, 6].Should().Be(red);
        img[10, 14].Should().Be(red);
        // Pixel outside the arm length stays default
        img[5, 10].Should().Be(default(Rgb24));
        img[10, 5].Should().Be(default(Rgb24));
    }

    [Fact]
    public void DrawCross_ProducesIdenticalOutputToInlinedPreRefactorCross_AZ367_AC2()
    {
        // Arrange — replicate the route stitcher's pre-refactor DrawCross
        const int width = 200;
        const int height = 200;
        var color = new Rgb24(255, 0, 0);
        const int armLength = 50;
        const int thickness = 10;
        var center = new Point(100, 100);

        using var newImg = new Image<Rgb24>(width, height);
        using var oldImg = new Image<Rgb24>(width, height);

        // Act — new path through TileGridStitcher
        new TileGridStitcher().DrawCross(newImg, center, color, armLength, thickness);

        // Act — old path inlined
        int halfThickness = thickness / 2;
        for (int dx = -armLength; dx <= armLength; dx++)
        {
            for (int t = -halfThickness; t <= halfThickness; t++)
            {
                int x = center.X + dx;
                int y = center.Y + t;
                if (x >= 0 && x < width && y >= 0 && y < height)
                    oldImg[x, y] = color;
            }
        }
        for (int dy = -armLength; dy <= armLength; dy++)
        {
            for (int t = -halfThickness; t <= halfThickness; t++)
            {
                int x = center.X + t;
                int y = center.Y + dy;
                if (x >= 0 && x < width && y >= 0 && y < height)
                    oldImg[x, y] = color;
            }
        }

        // Assert — every pixel identical
        for (int y = 0; y < height; y++)
        {
            for (int x = 0; x < width; x++)
            {
                newImg[x, y].Should().Be(oldImg[x, y], $"pixel ({x},{y}) must match pre-refactor cross");
            }
        }
    }

    [Fact]
    public void DrawRectangleBorder_DrawsTopBottomLeftRightWalls_AZ367_AC1()
    {
        // Arrange
        const int size = 40;
        using var img = new Image<Rgb24>(size, size);
        var yellow = new Rgb24(255, 255, 0);
        var sut = new TileGridStitcher();

        // Act
        sut.DrawRectangleBorder(img, new Rectangle(5, 5, 30, 30), yellow, thickness: 3);

        // Assert — corners are yellow
        img[5, 5].Should().Be(yellow);
        img[34, 5].Should().Be(yellow);
        img[5, 34].Should().Be(yellow);
        img[34, 34].Should().Be(yellow);
        // Interior pixel (beyond 3-px wall) stays untouched
        img[20, 20].Should().Be(default(Rgb24));
    }

    [Fact]
    public void DrawRectangleBorder_ProducesIdenticalOutputToInlinedPreRefactorBorder_AZ367_AC2()
    {
        // Arrange — replicate the route stitcher's pre-refactor DrawRectangleBorder
        const int width = 100;
        const int height = 100;
        var color = new Rgb24(255, 255, 0);
        const int thickness = 5;
        int x1 = 10, y1 = 15, x2 = 80, y2 = 70;

        using var newImg = new Image<Rgb24>(width, height);
        using var oldImg = new Image<Rgb24>(width, height);

        // Act — new path uses Rectangle (inclusive bounds (x1,y1)..(x2,y2))
        new TileGridStitcher().DrawRectangleBorder(
            newImg,
            new Rectangle(x1, y1, x2 - x1 + 1, y2 - y1 + 1),
            color,
            thickness);

        // Act — old path inlined
        for (int t = 0; t < thickness; t++)
        {
            for (int x = x1; x <= x2; x++)
            {
                int topY = y1 + t;
                int bottomY = y2 - t;
                if (x >= 0 && x < width && topY >= 0 && topY < height)
                    oldImg[x, topY] = color;
                if (x >= 0 && x < width && bottomY >= 0 && bottomY < height)
                    oldImg[x, bottomY] = color;
            }
            for (int y = y1; y <= y2; y++)
            {
                int leftX = x1 + t;
                int rightX = x2 - t;
                if (leftX >= 0 && leftX < width && y >= 0 && y < height)
                    oldImg[leftX, y] = color;
                if (rightX >= 0 && rightX < width && y >= 0 && y < height)
                    oldImg[rightX, y] = color;
            }
        }

        // Assert — every pixel identical
        for (int y = 0; y < height; y++)
        {
            for (int x = 0; x < width; x++)
            {
                newImg[x, y].Should().Be(oldImg[x, y], $"pixel ({x},{y}) must match pre-refactor border");
            }
        }
    }

    [Fact]
    public async Task StitchAsync_OutputMatchesInlinedPreRefactorRegionStitch_AZ367_AC2()
    {
        // Arrange — three solid tiles at the same coords pre/post refactor
        const int size = 8;
        var c1 = new Rgb24(10, 20, 30);
        var c2 = new Rgb24(40, 50, 60);
        var c3 = new Rgb24(70, 80, 90);

        var p1 = CreateSolidTile("p1", size, c1);
        var p2 = CreateSolidTile("p2", size, c2);
        var p3 = CreateSolidTile("p3", size, c3);

        var coords = new[]
        {
            (TileX: 100, TileY: 200, Path: p1),
            (TileX: 101, TileY: 200, Path: p2),
            (TileX: 100, TileY: 201, Path: p3),
        };

        var placements = coords.Select(c => new TilePlacement(c.TileX, c.TileY, c.Path)).ToList();

        // Act — new path
        var result = await new TileGridStitcher().StitchAsync(
            placements,
            tileSizePixels: size,
            deduplicateByTileCoords: false,
            swallowTileLoadErrors: false);

        // Act — old path inlined (region stitcher pre-refactor)
        var minX = coords.Min(t => t.TileX);
        var maxX = coords.Max(t => t.TileX);
        var minY = coords.Min(t => t.TileY);
        var maxY = coords.Max(t => t.TileY);
        var imageWidth = (maxX - minX + 1) * size;
        var imageHeight = (maxY - minY + 1) * size;
        using var oldImg = new Image<Rgb24>(imageWidth, imageHeight);
        foreach (var (x, y, filePath) in coords)
        {
            using var tileImg = await Image.LoadAsync<Rgb24>(filePath);
            var destX = (x - minX) * size;
            var destY = (y - minY) * size;
            oldImg.Mutate(ctx => ctx.DrawImage(tileImg, new Point(destX, destY), 1f));
        }

        // Assert
        using var newImg = result.Image;
        newImg.Width.Should().Be(oldImg.Width);
        newImg.Height.Should().Be(oldImg.Height);
        for (int y = 0; y < newImg.Height; y++)
        {
            for (int x = 0; x < newImg.Width; x++)
            {
                newImg[x, y].Should().Be(oldImg[x, y], $"pixel ({x},{y}) must match pre-refactor stitch");
            }
        }
    }
}