// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using System.Collections.Concurrent;
using System.Diagnostics.CodeAnalysis;
using Microsoft.FluentUI.AspNetCore.Components;
 
namespace Aspire.Dashboard.Model;
 
public sealed class IconResolver
{
    private sealed record IconKey(string IconName, IconSize DesiredIconSize, IconVariant IconVariant);
    private static readonly List<IconSize> s_iconSizes = [IconSize.Size16, IconSize.Size20, IconSize.Size24];
    private readonly ConcurrentDictionary<IconKey, Icon?> _iconCache = new();
    private readonly ILogger<IconResolver> _logger;
 
    public IconResolver(ILogger<IconResolver> logger)
    {
        _logger = logger;
    }
 
    public Icon? ResolveIconName(string iconName, IconSize? desiredIconSize, IconVariant? iconVariant)
    {
        // Icons.GetInstance isn't efficient. Cache icon lookup.
        return _iconCache.GetOrAdd(new IconKey(iconName, desiredIconSize ?? IconSize.Size20, iconVariant ?? IconVariant.Regular), key =>
        {
            // Try to get the desired size.
            CustomIcon? icon;
            if (TryGetIconCore(key, key.DesiredIconSize, out icon))
            {
                return icon;
            }
 
            var iconSizesTried = new List<IconSize>
            {
                key.DesiredIconSize
            };
 
            // Some icons aren't available in all sizes. Try until we find a match. Prefer size bigger than desired.
            if (key.DesiredIconSize <= IconSize.Size16 && TryGetIcon(iconSizesTried, key, IconSize.Size16, out icon))
            {
                return icon;
            }
            if (key.DesiredIconSize <= IconSize.Size20 && TryGetIcon(iconSizesTried, key, IconSize.Size20, out icon))
            {
                return icon;
            }
            if (key.DesiredIconSize <= IconSize.Size24 && TryGetIcon(iconSizesTried, key, IconSize.Size24, out icon))
            {
                return icon;
            }
 
            // Usually icons are always available in bigger sizes and smaller sizes are removed.
            // This is because it isn't possible to scale down the detail. For example, BrainCircuit has a size 20 icon, but not a size 16 icon.
            // There are some rare icons that only have smaller sizes, For example, CodePyRectangle only has size 16 icon.
            // To handle the situation where we ask for a bigger than available icon, fall back to try any remaining icon sizes, including smaller.
            foreach (var size in s_iconSizes)
            {
                if (TryGetIcon(iconSizesTried, key, size, out icon))
                {
                    return icon;
                }
            }
 
            _logger.LogWarning("Icon '{IconName}' (variant: {IconVariant}, size: {IconSize}) could not be resolved.", key.IconName, key.IconVariant, key.DesiredIconSize);
            return null;
        });
 
        static bool TryGetIcon(List<IconSize> triedSizes, IconKey key, IconSize size, [NotNullWhen(true)] out CustomIcon? icon)
        {
            if (triedSizes.Contains(size))
            {
                icon = null;
                return false;
            }
 
            triedSizes.Add(size);
            return TryGetIconCore(key, size, out icon);
        }
    }
 
    private static bool TryGetIconCore(IconKey key, IconSize size, [NotNullWhen(true)] out CustomIcon? icon)
    {
        var iconInfo = new IconInfo
        {
            Name = key.IconName,
            Variant = key.IconVariant,
            Size = size
        };
 
        return iconInfo.TryGetInstance(out icon);
    }
}