Initial import

1 files changed, 177 insertions, 0 deletions

diff --git a/Xamarin.Forms.Core/NavigationModel.cs b/Xamarin.Forms.Core/NavigationModel.cs
new file mode 100644
index 00000000..4591d4a4
--- /dev/null
+++ b/Xamarin.Forms.Core/NavigationModel.cs
@@ -0,0 +1,177 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace Xamarin.Forms
+{
+	internal class NavigationModel
+	{
+		readonly List<Page> _modalStack = new List<Page>();
+		readonly List<List<Page>> _navTree = new List<List<Page>>();
+
+		public Page CurrentPage
+		{
+			get
+			{
+				if (_navTree.Any())
+					return _navTree.Last().Last();
+				return null;
+			}
+		}
+
+		public IEnumerable<Page> Modals
+		{
+			get { return _modalStack; }
+		}
+
+		public IEnumerable<Page> Roots
+		{
+			get
+			{
+				foreach (List<Page> list in _navTree)
+				{
+					yield return list[0];
+				}
+			}
+		}
+
+		public IReadOnlyList<IReadOnlyList<Page>> Tree
+		{
+			get { return _navTree; }
+		}
+
+		public void Clear()
+		{
+			_navTree.Clear();
+		}
+
+		public void InsertPageBefore(Page page, Page before)
+		{
+			List<Page> currentStack = _navTree.Last();
+			int index = currentStack.IndexOf(before);
+
+			if (index == -1)
+				throw new ArgumentException("before must be in the current navigation context");
+
+			currentStack.Insert(index, page);
+		}
+
+		public Page Pop(Page ancestralNav)
+		{
+			ancestralNav = AncestorToRoot(ancestralNav);
+			foreach (List<Page> stack in _navTree)
+			{
+				if (stack.Contains(ancestralNav))
+				{
+					if (stack.Count <= 1)
+						throw new InvalidNavigationException("Can not pop final item in stack");
+					Page result = stack.Last();
+					stack.Remove(result);
+					return result;
+				}
+			}
+
+			throw new InvalidNavigationException("Popped from unpushed item?");
+		}
+
+		public Page PopModal()
+		{
+			if (_navTree.Count <= 1)
+				throw new InvalidNavigationException("Can't pop modal without any modals pushed");
+			Page modal = _navTree.Last().First();
+			_modalStack.Remove(modal);
+			_navTree.Remove(_navTree.Last());
+			return modal;
+		}
+
+		public Page PopTopPage()
+		{
+			Page itemToRemove;
+			if (_navTree.Count == 1)
+			{
+				if (_navTree[0].Count > 1)
+				{
+					itemToRemove = _navTree[0].Last();
+					_navTree[0].Remove(itemToRemove);
+					return itemToRemove;
+				}
+				return null;
+			}
+			itemToRemove = _navTree.Last().Last();
+			_navTree.Last().Remove(itemToRemove);
+			if (!_navTree.Last().Any())
+			{
+				_navTree.RemoveAt(_navTree.Count - 1);
+			}
+			return itemToRemove;
+		}
+
+		public void PopToRoot(Page ancestralNav)
+		{
+			ancestralNav = AncestorToRoot(ancestralNav);
+			foreach (List<Page> stack in _navTree)
+			{
+				if (stack.Contains(ancestralNav))
+				{
+					if (stack.Count <= 1)
+						throw new InvalidNavigationException("Can not pop final item in stack");
+					stack.RemoveRange(1, stack.Count - 1);
+					return;
+				}
+			}
+
+			throw new InvalidNavigationException("Popped from unpushed item?");
+		}
+
+		public void Push(Page page, Page ancestralNav)
+		{
+			if (ancestralNav == null)
+			{
+				if (_navTree.Any())
+					throw new InvalidNavigationException("Ancestor must be provided for all pushes except first");
+				_navTree.Add(new List<Page> { page });
+				return;
+			}
+
+			ancestralNav = AncestorToRoot(ancestralNav);
+
+			foreach (List<Page> stack in _navTree)
+			{
+				if (stack.Contains(ancestralNav))
+				{
+					stack.Add(page);
+					return;
+				}
+			}
+
+			throw new InvalidNavigationException("Invalid ancestor passed");
+		}
+
+		public void PushModal(Page page)
+		{
+			_navTree.Add(new List<Page> { page });
+			_modalStack.Add(page);
+		}
+
+		public bool RemovePage(Page page)
+		{
+			bool found;
+			List<Page> currentStack = _navTree.Last();
+			var i = 0;
+			while (!(found = currentStack.Remove(page)) && i < _navTree.Count - 1)
+			{
+				currentStack = _navTree[i++];
+			}
+
+			return found;
+		}
+
+		Page AncestorToRoot(Page ancestor)
+		{
+			Page result = ancestor;
+			while (!Application.IsApplicationOrNull(result.RealParent))
+				result = (Page)result.RealParent;
+			return result;
+		}
+	}
+}
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