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AspClassic.Parser/Tree.cs

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+#define DEBUG
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.Diagnostics;
+
+namespace AspClassic.Parser;
+
+/// <summary>
+/// The root class of all trees.
+/// </summary>
+public abstract class Tree
+{
+	private readonly TreeType _Type;
+
+	private readonly Span _Span;
+
+	private Tree _Parent;
+
+	private ReadOnlyCollection<Tree> _Children;
+
+	/// <summary>
+	/// The type of the tree.
+	/// </summary>
+	public TreeType Type => _Type;
+
+	/// <summary>
+	/// The location of the tree.
+	/// </summary>
+	/// <remarks>
+	/// The span ends at the first character beyond the tree
+	/// </remarks>
+	public Span Span => _Span;
+
+	/// <summary>
+	/// The parent of the tree. Nothing if the root tree.
+	/// </summary>
+	public Tree Parent => _Parent;
+
+	/// <summary>
+	/// The children of the tree.
+	/// </summary>
+	public ReadOnlyCollection<Tree> Children
+	{
+		get
+		{
+			if (_Children == null)
+			{
+				List<Tree> ChildList = new List<Tree>();
+				GetChildTrees(ChildList);
+				_Children = new ReadOnlyCollection<Tree>(ChildList);
+			}
+			return _Children;
+		}
+	}
+
+	/// <summary>
+	/// Whether the tree is 'bad'.
+	/// </summary>
+	public virtual bool IsBad => false;
+
+	protected Tree(TreeType type, Span span)
+	{
+		Debug.Assert(type >= TreeType.SyntaxError && type <= TreeType.File);
+		_Type = type;
+		_Span = span;
+	}
+
+	protected void SetParent(Tree child)
+	{
+		if (child != null)
+		{
+			child._Parent = this;
+		}
+	}
+
+	protected void SetParents<T>(IList<T> children) where T : Tree
+	{
+		if (children == null)
+		{
+			return;
+		}
+		foreach (Tree Child in children)
+		{
+			SetParent(Child);
+		}
+	}
+
+	protected static void AddChild(IList<Tree> childList, Tree child)
+	{
+		if (child != null)
+		{
+			childList.Add(child);
+		}
+	}
+
+	protected static void AddChildren<T>(IList<Tree> childList, ReadOnlyCollection<T> children) where T : Tree
+	{
+		if (children == null)
+		{
+			return;
+		}
+		foreach (Tree Child in children)
+		{
+			childList.Add(Child);
+		}
+	}
+
+	protected virtual void GetChildTrees(IList<Tree> childList)
+	{
+	}
+}