using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Media;

namespace MapControl
{
    public class ImageSourceTile(int zoomLevel, int x, int y, int columnCount)
        : Tile(zoomLevel, x, y, columnCount)
    {
        public event EventHandler Completed;

        public ImageSource ImageSource { get; set; }

        public override async Task LoadImageAsync(Func<Task<ImageSource>> loadImageFunc)
        {
            ImageSource = await loadImageFunc().ConfigureAwait(false);

            Completed?.Invoke(this, EventArgs.Empty);
        }
    }

    public class DrawingTileMatrixLayer(WmtsTileMatrix wmtsTileMatrix, int zoomLevel) : UIElement
    {
        public WmtsTileMatrix WmtsTileMatrix => wmtsTileMatrix;

        public TileMatrix TileMatrix { get; private set; } = new TileMatrix(zoomLevel, 1, 1, 0, 0);

        public IEnumerable<ImageSourceTile> Tiles { get; private set; } = [];

        public DrawingGroup Drawing { get; } = new DrawingGroup { Transform = new MatrixTransform() };

        protected override void OnRender(DrawingContext drawingContext)
        {
            drawingContext.DrawDrawing(Drawing);
        }

        public void UpdateRenderTransform(ViewTransform viewTransform)
        {
            // Tile matrix origin in pixels.
            //
            var tileMatrixOrigin = new Point(WmtsTileMatrix.TileWidth * TileMatrix.XMin, WmtsTileMatrix.TileHeight * TileMatrix.YMin);

            ((MatrixTransform)Drawing.Transform).Matrix =
                viewTransform.GetTileLayerTransform(WmtsTileMatrix.Scale, WmtsTileMatrix.TopLeft, tileMatrixOrigin);
        }

        public bool UpdateTiles(ViewTransform viewTransform, double viewWidth, double viewHeight)
        {
            // Tile matrix bounds in pixels.
            //
            var bounds = viewTransform.GetTileMatrixBounds(WmtsTileMatrix.Scale, WmtsTileMatrix.TopLeft, viewWidth, viewHeight);

            // Tile X and Y bounds.
            //
            var xMin = (int)Math.Floor(bounds.X / WmtsTileMatrix.TileWidth);
            var yMin = (int)Math.Floor(bounds.Y / WmtsTileMatrix.TileHeight);
            var xMax = (int)Math.Floor((bounds.X + bounds.Width) / WmtsTileMatrix.TileWidth);
            var yMax = (int)Math.Floor((bounds.Y + bounds.Height) / WmtsTileMatrix.TileHeight);

            if (!WmtsTileMatrix.HasFullHorizontalCoverage)
            {
                // Set X range limits.
                //
                xMin = Math.Max(xMin, 0);
                xMax = Math.Min(Math.Max(xMax, 0), WmtsTileMatrix.MatrixWidth - 1);
            }

            // Set Y range limits.
            //
            yMin = Math.Max(yMin, 0);
            yMax = Math.Min(Math.Max(yMax, 0), WmtsTileMatrix.MatrixHeight - 1);

            if (TileMatrix.XMin == xMin && TileMatrix.YMin == yMin &&
                TileMatrix.XMax == xMax && TileMatrix.YMax == yMax)
            {
                // No change of the TileMatrix and the Tiles collection.
                //
                return false;
            }

            TileMatrix = new TileMatrix(TileMatrix.ZoomLevel, xMin, yMin, xMax, yMax);

            Drawing.Children.Clear();
            CreateTiles();

            return true;
        }

        private void CreateTiles()
        {
            var tiles = new List<ImageSourceTile>();

            for (var y = TileMatrix.YMin; y <= TileMatrix.YMax; y++)
            {
                for (var x = TileMatrix.XMin; x <= TileMatrix.XMax; x++)
                {
                    var tile = Tiles.FirstOrDefault(t => t.X == x && t.Y == y);

                    if (tile == null)
                    {
                        tile = new ImageSourceTile(TileMatrix.ZoomLevel, x, y, WmtsTileMatrix.MatrixWidth);

                        var equivalentTile = Tiles.FirstOrDefault(t => t.ImageSource != null && t.Column == tile.Column && t.Row == tile.Row);

                        if (equivalentTile != null)
                        {
                            tile.IsPending = false;
                            tile.ImageSource = equivalentTile.ImageSource;
                        }
                        else
                        {
                            tile.Completed += OnTileCompleted;
                        }
                    }

                    if (tile.ImageSource != null)
                    {
                        DrawTile(tile);
                    }

                    tiles.Add(tile);
                }
            }

            Tiles = tiles;
        }

        private void DrawTile(ImageSourceTile tile)
        {
            var width = WmtsTileMatrix.TileWidth;
            var height = WmtsTileMatrix.TileHeight;
            var x = width * (tile.X - TileMatrix.XMin);
            var y = height * (tile.Y - TileMatrix.YMin);

            Drawing.Children.Add(new ImageDrawing(tile.ImageSource, new Rect(x, y, width, height)));
        }

        private void OnTileCompleted(object sender, EventArgs e)
        {
            var tile = (ImageSourceTile)sender;

            tile.Completed -= OnTileCompleted;

            if (tile.X >= TileMatrix.XMin && tile.X <= TileMatrix.XMax &&
                tile.Y >= TileMatrix.YMin && tile.Y <= TileMatrix.YMax &&
                tile.ImageSource != null)
            {
                _ = Dispatcher.InvokeAsync(() => DrawTile(tile));
            }
        }
    }
}