using System.Globalization;
using Avalonia.Data.Converters;
using Avalonia.Media;
using FileTime.App.Core.Models;
using FileTime.GuiApp.ViewModels;

namespace FileTime.GuiApp.Converters;

public class NamePartShrinkerConverter : IMultiValueConverter
{
    private const int PixelPerChar = 8;
    public object? Convert(IList<object?> values, Type targetType, object? parameter, CultureInfo culture)
    {
        if (values.Count > 0 && values[0] is IList<ItemNamePart> nameParts)
        {
            var attributeWidth = values[2] is bool b && b ? 340 : 0;
            var newNameParts = nameParts;
            if (values.Count > 1 && values[1] is double width && width > 0)
            {
                newNameParts = GetNamePartsForWidth(nameParts, width - attributeWidth);
            }

            return newNameParts.Select(p => new ItemNamePartViewModel(p.Text, p.IsSpecial ? TextDecorations.Underline : null)).ToList();
        }
        return null;
    }

    private static List<ItemNamePart> GetNamePartsForWidth(IList<ItemNamePart> nameParts, double maxWidth)
    {
        //Best case, we are in the range
        var textLength = nameParts.Select(p => p.Text.Length).Sum();
        if (textLength * PixelPerChar <= maxWidth)
        {
            return nameParts.ToList();
        }

        //Trying at least with the special parts
        var newNameParts = new ItemNamePart?[nameParts.Count];
        for (var i = 0; i < nameParts.Count; i++)
        {
            if (nameParts[i].IsSpecial)
            {
                newNameParts[i] = nameParts[i];
            }
        }

        return GetNamePartsForWidthOptimistic(nameParts, newNameParts, maxWidth);
    }

    private static List<ItemNamePart> GetNamePartsForWidthOptimistic(IList<ItemNamePart> nameParts, ItemNamePart?[] newNameParts, double maxWidth)
    {
        var trimmedIndexes = new List<int>();
        for (var i = 0; i < newNameParts.Length; i++)
        {
            if (newNameParts[i] == null)
            {
                trimmedIndexes.Add(i);
                newNameParts[i] = new ItemNamePart("...");
            }
        }

        var textLength = newNameParts.Select(p => p?.Text.Length ?? 0).Sum();
        if (textLength * PixelPerChar > maxWidth)
        {
            return GetNamePartsForWidthPessimistic(nameParts, maxWidth);
        }

        foreach (var trimmedIndex in trimmedIndexes)
        {
            var baseTextLength = newNameParts.Select((p, i) => i == trimmedIndex ? 0 : (p?.Text.Length ?? 0)).Sum();
            var proposedText = nameParts[trimmedIndex].Text;
            var trimmed = false;
            while ((baseTextLength + proposedText.Length + (trimmed ? 3 : 0)) * PixelPerChar > maxWidth)
            {
                proposedText = proposedText[0..^1];
                trimmed = true;
            }
            newNameParts[trimmedIndex] = new ItemNamePart(proposedText + (trimmed ? "..." : ""));
            if (trimmed) break;
        }

        return newNameParts.Where(f => f is not null).ToList()!;
    }

    private static List<ItemNamePart> GetNamePartsForWidthPessimistic(IList<ItemNamePart> nameParts, double maxWidth)
    {
        var newNameParts = new List<ItemNamePart>(nameParts);
        foreach (var namePart in nameParts)
        {
            var baseTextLength = newNameParts.Select(p => p.Text.Length).Sum();
            var proposedText = namePart.Text;
            var trimmed = false;

            while ((baseTextLength + 3) * PixelPerChar > maxWidth && proposedText != "")
            {
                proposedText = proposedText[0..^1];
                trimmed = true;
            }

            if (!string.IsNullOrWhiteSpace(proposedText)) newNameParts.Add(new ItemNamePart(proposedText, namePart.IsSpecial));
            if (trimmed) break;
        }
        if (newNameParts.Last().IsSpecial)
        {
            newNameParts.Add(new ItemNamePart("..."));
        }
        else
        {
            var last = newNameParts.Last();
            newNameParts[^1] = new ItemNamePart(last.Text + "...");
        }
        return newNameParts;
    }
}