// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using System;
using System.Collections.Generic;
using System.Linq;

namespace Microsoft.AspNetCore.Razor.Language
{
	public abstract class TagHelperDescriptor : IEquatable<TagHelperDescriptor>
	{
		private IEnumerable<RazorDiagnostic> _allDiagnostics;
		private BoundAttributeDescriptor[] _editorRequiredAttributes;

		protected TagHelperDescriptor( string kind )
		{
			Kind = kind;
		}

		public string Kind { get; }

		public string Name { get; protected set; }

		public IReadOnlyList<TagMatchingRuleDescriptor> TagMatchingRules { get; protected set; }

		public string AssemblyName { get; protected set; }

		public IReadOnlyList<BoundAttributeDescriptor> BoundAttributes { get; protected set; }

		public IReadOnlyList<AllowedChildTagDescriptor> AllowedChildTags { get; protected set; }

		public string Documentation { get; protected set; }

		public string DisplayName { get; protected set; }

		public string TagOutputHint { get; protected set; }

		public bool CaseSensitive { get; protected set; }

		public IReadOnlyList<RazorDiagnostic> Diagnostics { get; protected set; }

		public IReadOnlyDictionary<string, string> Metadata { get; protected set; }

		// Hoisted / cached metadata
		private int? _hashCode;
		internal bool? IsComponentFullyQualifiedNameMatchCache { get; set; }
		internal bool? IsChildContentTagHelperCache { get; set; }
		internal ParsedTypeInformation? ParsedTypeInfo { get; set; }
		internal BoundAttributeDescriptor[] EditorRequiredAttributes
		{
			get
			{
				_editorRequiredAttributes ??= GetEditorRequiredAttributes( BoundAttributes );
				return _editorRequiredAttributes;
			}
		}

		public bool HasErrors
		{
			get
			{
				var allDiagnostics = GetAllDiagnostics();
				var errors = allDiagnostics.Any( diagnostic => diagnostic.Severity == RazorDiagnosticSeverity.Error );

				return errors;
			}
		}

		public virtual IEnumerable<RazorDiagnostic> GetAllDiagnostics()
		{
			if ( _allDiagnostics == null )
			{
				var allowedChildTagDiagnostics = AllowedChildTags.SelectMany( childTag => childTag.Diagnostics );
				var attributeDiagnostics = BoundAttributes.SelectMany( attribute => attribute.Diagnostics );
				var ruleDiagnostics = TagMatchingRules.SelectMany( rule => rule.GetAllDiagnostics() );
				var combinedDiagnostics = allowedChildTagDiagnostics
					.Concat( attributeDiagnostics )
					.Concat( ruleDiagnostics )
					.Concat( Diagnostics );
				_allDiagnostics = combinedDiagnostics.ToArray();
			}

			return _allDiagnostics;
		}

		public override string ToString()
		{
			return DisplayName ?? base.ToString();
		}

		public bool Equals( TagHelperDescriptor other )
		{
			return TagHelperDescriptorComparer.Default.Equals( this, other );
		}

		public override bool Equals( object obj )
		{
			return Equals( obj as TagHelperDescriptor );
		}

		public override int GetHashCode()
		{
			// TagHelperDescriptors are immutable instances and it should be safe to cache it's hashes once.
			_hashCode ??= TagHelperDescriptorComparer.Default.GetHashCode( this );
			return _hashCode.Value;
		}

		private static BoundAttributeDescriptor[] GetEditorRequiredAttributes( IReadOnlyList<BoundAttributeDescriptor> boundAttributeDescriptors )
		{
			List<BoundAttributeDescriptor> editorRequiredAttributes = null;
			var count = boundAttributeDescriptors.Count;
			for ( var i = 0; i < count; i++ )
			{
				var attribute = boundAttributeDescriptors[i];
				if ( attribute.IsEditorRequired )
				{
					editorRequiredAttributes ??= new();
					editorRequiredAttributes.Add( attribute );
				}
			}

			return editorRequiredAttributes?.ToArray() ?? Array.Empty<BoundAttributeDescriptor>();
		}

		internal readonly struct ParsedTypeInformation
		{
			public ParsedTypeInformation( bool success, StringSegment @namespace, StringSegment typeName )
			{
				Success = success;
				Namespace = @namespace;
				TypeName = typeName;
			}

			public bool Success { get; }
			public StringSegment Namespace { get; }
			public StringSegment TypeName { get; }
		}
	}
}
