// Copyright (c) 2010 AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
// This code is distributed under MIT X11 license (for details please see \doc\license.txt)

using System;
using System.Collections.Generic;
using System.Linq;
using ICSharpCode.NRefactory.TypeSystem;
using ICSharpCode.NRefactory.TypeSystem.Implementation;

namespace ICSharpCode.NRefactory.CSharp.Resolver
{
	/// <summary>
	/// Represents a scope that contains "using" statements.
	/// This is either the file itself, or a namespace declaration.
	/// </summary>
	public class UsingScope : AbstractFreezable
	{
		readonly IProjectContent projectContent;
		readonly UsingScope parent;
		DomRegion region;
		string namespaceName = "";
		IList<ITypeOrNamespaceReference> usings;
		IList<KeyValuePair<string, ITypeOrNamespaceReference>> usingAliases;
		IList<string> externAliases;
		//IList<UsingScope> childScopes;
		
		protected override void FreezeInternal()
		{
			if (usings == null || usings.Count == 0)
				usings = EmptyList<ITypeOrNamespaceReference>.Instance;
			else
				usings = Array.AsReadOnly(usings.ToArray());
			
			if (usingAliases == null || usingAliases.Count == 0)
				usingAliases = EmptyList<KeyValuePair<string, ITypeOrNamespaceReference>>.Instance;
			else
				usingAliases = Array.AsReadOnly(usingAliases.ToArray());
			
			externAliases = FreezeList(externAliases);
			//childScopes = FreezeList(childScopes);
			
			// In current model (no child scopes), it makes sense to freeze the parent as well
			// to ensure the whole lookup chain is immutable.
			// But we probably shouldn't do this if we add back childScopes.
			if (parent != null)
				parent.Freeze();
			
			base.FreezeInternal();
		}
		
		/// <summary>
		/// Creates a new root using scope.
		/// </summary>
		public UsingScope(IProjectContent projectContent)
		{
			if (projectContent == null)
				throw new ArgumentNullException("projectContent");
			this.projectContent = projectContent;
		}
		
		/// <summary>
		/// Creates a new nested using scope.
		/// </summary>
		/// <param name="parent">The parent using scope.</param>
		/// <param name="namespaceName">The full namespace name.</param>
		public UsingScope(UsingScope parent, string namespaceName)
		{
			if (parent == null)
				throw new ArgumentNullException("parent");
			if (namespaceName == null)
				throw new ArgumentNullException("namespaceName");
			this.parent = parent;
			this.projectContent = parent.projectContent;
			this.namespaceName = namespaceName;
		}
		
		public UsingScope Parent {
			get { return parent; }
		}
		
		public IProjectContent ProjectContent {
			get { return projectContent; }
		}
		
		public DomRegion Region {
			get { return region; }
			set {
				CheckBeforeMutation();
				region = value;
			}
		}
		
		public string NamespaceName {
			get { return namespaceName; }
			set {
				if (value == null)
					throw new ArgumentNullException("NamespaceName");
				CheckBeforeMutation();
				namespaceName = value;
			}
		}
		
		public IList<ITypeOrNamespaceReference> Usings {
			get {
				if (usings == null)
					usings = new List<ITypeOrNamespaceReference>();
				return usings;
			}
		}
		
		public IList<KeyValuePair<string, ITypeOrNamespaceReference>> UsingAliases {
			get {
				if (usingAliases == null)
					usingAliases = new List<KeyValuePair<string, ITypeOrNamespaceReference>>();
				return usingAliases;
			}
		}
		
		public IList<string> ExternAliases {
			get {
				if (externAliases == null)
					externAliases = new List<string>();
				return externAliases;
			}
		}
		
//		public IList<UsingScope> ChildScopes {
//			get {
//				if (childScopes == null)
//					childScopes = new List<UsingScope>();
//				return childScopes;
//			}
//		}
		
		/// <summary>
		/// Gets whether this using scope has an alias (either using or extern)
		/// with the specified name.
		/// </summary>
		public bool HasAlias(string identifier)
		{
			if (usingAliases != null) {
				foreach (var pair in usingAliases) {
					if (pair.Key == identifier)
						return true;
				}
			}
			return externAliases != null && externAliases.Contains(identifier);
		}
	}
}