using System;
using System.Collections.Generic;
using System.Linq;
using SkiaSharp;
using StabilityMatrix.Core.Extensions;

namespace StabilityMatrix.Avalonia.Helpers;

public static class ImageProcessor
{
    /// <summary>
    /// Get the dimensions of a grid that can hold the given amount of images.
    /// </summary>
    public static (int rows, int columns) GetGridDimensionsFromImageCount(int count)
    {
        if (count <= 1) return (1, 1);
        if (count == 2) return (1, 2);
        
        // Prefer one extra row over one extra column,
        // the row count will be the floor of the square root
        // and the column count will be floor of count / rows
        var rows = (int) Math.Floor(Math.Sqrt(count));
        var columns = (int) Math.Floor((double) count / rows);
        return (rows, columns);
    }
    
    public static SKImage CreateImageGrid(
        IReadOnlyList<SKImage> images, 
        int spacing = 0)
    {
        var (rows, columns) = GetGridDimensionsFromImageCount(images.Count);

        var singleWidth = images[0].Width;
        var singleHeight = images[0].Height;
    
        // Make output image
        using var output = new SKBitmap(
            singleWidth * columns + spacing * (columns - 1), 
            singleHeight * rows + spacing * (rows - 1));
    
        // Draw images
        using var canvas = new SKCanvas(output);
        
        foreach (var (row, column) in 
                 Enumerable.Range(0, rows).Product(Enumerable.Range(0, columns)))
        {
            // Stop if we have drawn all images
            var index = row * columns + column;
            if (index >= images.Count) break;
            
            // Get image
            var image = images[index];
            
            // Draw image
            var destination = new SKRect(
                singleWidth * column + spacing * column,
                singleHeight * row + spacing * row,
                singleWidth * column + spacing * column + image.Width,
                singleHeight * row + spacing * row + image.Height);
            canvas.DrawImage(image, destination);
        }

        return SKImage.FromBitmap(output);
    }
}