using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using BuzzGUI.Interfaces;

namespace BuzzGUI.Common
{
	public class ManagedActionStack : IActionStack
	{
		class ActionRef
		{
			public IAction Action { get; set; }
			public int Group { get; set; }
		}

		List<ActionRef> actions = new List<ActionRef>();
		int position;

		int groupCounter;
		int groupDepth;

		public IEnumerable<IAction> Actions { get { return actions.Select(a => a.Action); } }

		public void Do(IAction a)
		{
			if (groupDepth == 0) groupCounter++;

			a.Do();

			while (actions.Count > position)
				actions.RemoveAt(actions.Count - 1);

			actions.Add(new ActionRef() { Action = a, Group = groupCounter });
			position++;

			if (PostDoOrUndoGroup != null)
				PostDoOrUndoGroup(new[] { a }, true);
		}

		public bool CanUndo { get { return position > 0; } }
		public bool CanRedo { get { return actions.Count > 0 && position < actions.Count; } }

		public void Undo()
		{
			if (position < 1) return;

			int g = actions[position - 1].Group;
			int startpos = position - 1;

			do
			{
				actions[position - 1].Action.Undo();
				position--;
			} while (position >= 1 && actions[position - 1].Group == g);

			if (PostDoOrUndoGroup != null)
				PostDoOrUndoGroup(actions.Skip(position).Take(startpos - position + 1).Reverse().Select(a => a.Action), false);

		}

		public void Redo()
		{
			if (position >= actions.Count) return;

			int g = actions[position].Group;
			int startpos = position;

			do
			{
				actions[position].Action.Do();
				position++;
			} while (position < actions.Count && actions[position].Group == g);

			if (PostDoOrUndoGroup != null)
				PostDoOrUndoGroup(actions.Skip(startpos).Take(position - startpos).Select(a => a.Action), true);
		}

		public void BeginActionGroup()
		{
			if (groupDepth == 0)
				groupCounter++;
			
			groupDepth++;
		}

		public void EndActionGroup()
		{
			groupDepth--;
			
			if (groupDepth <= 0)
				groupDepth = 0;
		}

		public event Action<IEnumerable<IAction>, bool> PostDoOrUndoGroup;
			
	}
}