// Copyright (c) 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.IO;

namespace ICSharpCode.NRefactory.VB.Ast
{
	/// <summary>
	/// Base class for statements.
	/// </summary>
	/// <remarks>
	/// This class is useful even though it doesn't provide any additional functionality:
	/// It can be used to communicate more information in APIs, e.g. "this subnode will always be a statement"
	/// </remarks>
	public abstract class Statement : AstNode
	{
		#region Null
		public new static readonly Statement Null = new NullStatement ();
		
		sealed class NullStatement : Statement
		{
			public override bool IsNull {
				get {
					return true;
				}
			}
			
			public override S AcceptVisitor<T, S> (IAstVisitor<T, S> visitor, T data)
			{
				return default (S);
			}
			
			protected internal override bool DoMatch(AstNode other, PatternMatching.Match match)
			{
				return other == null || other.IsNull;
			}
		}
		#endregion
		
		#region PatternPlaceholder
		public static implicit operator Statement(PatternMatching.Pattern pattern)
		{
			return pattern != null ? new PatternPlaceholder(pattern) : null;
		}
		
		sealed class PatternPlaceholder : Statement, PatternMatching.INode
		{
			readonly PatternMatching.Pattern child;
			
			public PatternPlaceholder(PatternMatching.Pattern child)
			{
				this.child = child;
			}
			
			public override S AcceptVisitor<T, S>(IAstVisitor<T, S> visitor, T data)
			{
				return visitor.VisitPatternPlaceholder(this, child, data);
			}
			
			protected internal override bool DoMatch(AstNode other, PatternMatching.Match match)
			{
				return child.DoMatch(other, match);
			}
			
			bool PatternMatching.INode.DoMatchCollection(Role role, PatternMatching.INode pos, PatternMatching.Match match, PatternMatching.BacktrackingInfo backtrackingInfo)
			{
				return child.DoMatchCollection(role, pos, match, backtrackingInfo);
			}
		}
		#endregion
		
		/// <summary>
		/// Gets the previous statement within the current block.
		/// This is usually equivalent to <see cref="PrevSibling"/>, but will skip any non-statements (e.g. comments)
		/// </summary>
		public Statement PreviousStatement {
			get {
				AstNode node = this;
				while ((node = node.PrevSibling) != null) {
					Statement stmt = node as Statement;
					if (stmt != null)
						return stmt;
				}
				return null;
			}
		}
		
		/// <summary>
		/// Gets the next statement within the current block.
		/// This is usually equivalent to <see cref="NextSibling"/>, but will skip any non-statements (e.g. comments)
		/// </summary>
		public Statement NextStatement {
			get {
				AstNode node = this;
				while ((node = node.NextSibling) != null) {
					Statement stmt = node as Statement;
					if (stmt != null)
						return stmt;
				}
				return null;
			}
		}
		
		public new Statement Clone()
		{
			return (Statement)base.Clone();
		}
		
		public Statement ReplaceWith(Func<Statement, Statement> replaceFunction)
		{
			if (replaceFunction == null)
				throw new ArgumentNullException("replaceFunction");
			return (Statement)base.ReplaceWith(node => replaceFunction((Statement)node));
		}
		
		// Make debugging easier by giving Statements a ToString() implementation
//		public override string ToString()
//		{
////			if (IsNull)
////				return "Null";
////			StringWriter w = new StringWriter();
////			AcceptVisitor(new OutputVisitor(w, new CSharpFormattingOptions()), null);
////			string text = w.ToString().TrimEnd().Replace("\t", "").Replace(w.NewLine, " ");
////			if (text.Length > 100)
////				return text.Substring(0, 97) + "...";
////			else
////				return text;
//			throw new NotImplementedException();
//		}
	}
}