using System;
using System.Collections.Generic;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.DependencyInjection.Extensions;
using Microsoft.Maui.Hosting;
using Microsoft.Maui.Hosting.Internal;
 
namespace Microsoft.Maui.Hosting
{
	public static class FontsMauiAppBuilderExtensions
	{
		/// <summary>
		/// Configures the <see cref="MauiAppBuilder"/> with fonts.
		/// </summary>
		/// <param name="builder">The <see cref="MauiAppBuilder"/> to configure.</param>
		/// <returns>The configured <see cref="MauiAppBuilder"/>.</returns>
		public static MauiAppBuilder ConfigureFonts(this MauiAppBuilder builder)
		{
			builder.ConfigureFonts(configureDelegate: null);
			return builder;
		}
 
		/// <summary>
		/// Configures the <see cref="MauiAppBuilder"/> with a specified delegate <paramref name="configureDelegate"/> to register fonts in the application.
		/// </summary>
		/// <param name="builder">The <see cref="MauiAppBuilder"/> to configure.</param>
		/// <param name="configureDelegate">A configuration delegate that can register fonts in the provided <see cref="IFontCollection"/>.</param>
		/// <returns>The configured <see cref="MauiAppBuilder"/>.</returns>
		public static MauiAppBuilder ConfigureFonts(this MauiAppBuilder builder, Action<IFontCollection>? configureDelegate)
		{
			builder.Services.TryAddSingleton<IEmbeddedFontLoader>(svc => new EmbeddedFontLoader(svc));
			builder.Services.TryAddSingleton<IFontRegistrar>(svc => new FontRegistrar(svc.GetRequiredService<IEmbeddedFontLoader>(), svc));
			builder.Services.TryAddSingleton<IFontManager>(svc => new FontManager(svc.GetRequiredService<IFontRegistrar>(), svc));
			if (configureDelegate != null)
			{
				builder.Services.AddSingleton<FontsRegistration>(new FontsRegistration(configureDelegate));
			}
			builder.Services.TryAddEnumerable(ServiceDescriptor.Transient<IMauiInitializeService, FontInitializer>());
			return builder;
		}
 
 
		internal class FontsRegistration
		{
			private readonly Action<IFontCollection> _registerFonts;
 
			public FontsRegistration(Action<IFontCollection> registerFonts)
			{
				_registerFonts = registerFonts;
			}
 
			internal void AddFonts(IFontCollection fonts)
			{
				_registerFonts(fonts);
			}
		}
 
		internal class FontInitializer : IMauiInitializeService
		{
			private readonly IEnumerable<FontsRegistration> _fontsRegistrations;
			readonly IFontRegistrar _fontRegistrar;
 
			public FontInitializer(IEnumerable<FontsRegistration> fontsRegistrations, IFontRegistrar fontRegistrar)
			{
				_fontsRegistrations = fontsRegistrations;
				_fontRegistrar = fontRegistrar;
			}
 
			public void Initialize(IServiceProvider __)
			{
				if (_fontsRegistrations != null)
				{
					var fontsBuilder = new FontCollection();
 
					// Run all the user-defined registrations
					foreach (var font in _fontsRegistrations)
					{
						font.AddFonts(fontsBuilder);
					}
 
					// Register the fonts in the registrar
					foreach (var font in fontsBuilder)
					{
						if (font.Assembly == null)
							_fontRegistrar.Register(font.Filename, font.Alias);
						else
							_fontRegistrar.Register(font.Filename, font.Alias, font.Assembly);
					}
				}
			}
		}
	}
}