// Copyright (c) The Perspex Project. All rights reserved.
// Licensed under the MIT license. See licence.md file in the project root for full license information.

using System.Collections.Generic;
using System.Linq;
using Perspex.Collections;
using Perspex.Controls.Presenters;
using Perspex.Controls.Templates;
using Perspex.Input;
using Perspex.LogicalTree;
using Perspex.UnitTests;
using Xunit;

namespace Perspex.Controls.UnitTests
{
    public class TreeViewTests
    {
        [Fact]
        public void Items_Should_Be_Created()
        {
            var target = new TreeView
            {
                Template = CreateTreeViewTemplate(),
                Items = CreateTestTreeData(),
                DataTemplates = CreateNodeDataTemplate(),
            };

            ApplyTemplates(target);

            Assert.Equal(new[] { "Root" }, ExtractItemHeader(target, 0));
            Assert.Equal(new[] { "Child1", "Child2" }, ExtractItemHeader(target, 1));
            Assert.Equal(new[] { "Grandchild2a" }, ExtractItemHeader(target, 2));
        }

        [Fact]
        public void Root_ItemContainerGenerator_Containers_Should_Be_Root_Containers()
        {
            var target = new TreeView
            {
                Template = CreateTreeViewTemplate(),
                Items = CreateTestTreeData(),
                DataTemplates = CreateNodeDataTemplate(),
            };

            ApplyTemplates(target);

            var container = (TreeViewItem)target.ItemContainerGenerator.Containers.Single().ContainerControl;
            var header = (TextBlock)container.Header;
            Assert.Equal("Root", header.Text);
        }

        [Fact]
        public void Root_TreeContainerFromItem_Should_Return_Descendent_Item()
        {
            var tree = CreateTestTreeData();
            var target = new TreeView
            {
                Template = CreateTreeViewTemplate(),
                Items = tree,
                DataTemplates = CreateNodeDataTemplate(),
            };

            // For TreeViewItem to find its parent TreeView, OnAttachedToLogicalTree needs
            // to be called, which requires an IStyleRoot.
            var root = new TestRoot();
            root.Child = target;

            ApplyTemplates(target);

            var container = target.ItemContainerGenerator.Index.ContainerFromItem(
                tree[0].Children[1].Children[0]);

            Assert.NotNull(container);

            var header = ((TreeViewItem)container).Header;
            var headerContent = ((TextBlock)header).Text;

            Assert.Equal("Grandchild2a", headerContent);
        }

        [Fact]
        public void Clicking_Item_Should_Select_It()
        {
            var tree = CreateTestTreeData();
            var target = new TreeView
            {
                Template = CreateTreeViewTemplate(),
                Items = tree,
                DataTemplates = CreateNodeDataTemplate(),
            };

            var visualRoot = new TestRoot();
            visualRoot.Child = target;
            ApplyTemplates(target);

            var item = tree[0].Children[1].Children[0];
            var container = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(item);

            Assert.NotNull(container);

            container.RaiseEvent(new PointerPressedEventArgs
            {
                RoutedEvent = InputElement.PointerPressedEvent,
                MouseButton = MouseButton.Left,
            });

            Assert.Equal(item, target.SelectedItem);
            Assert.True(container.IsSelected);
        }

        [Fact]
        public void Setting_SelectedItem_Should_Set_Container_Selected()
        {
            var tree = CreateTestTreeData();
            var target = new TreeView
            {
                Template = CreateTreeViewTemplate(),
                Items = tree,
                DataTemplates = CreateNodeDataTemplate(),
            };

            var visualRoot = new TestRoot();
            visualRoot.Child = target;
            ApplyTemplates(target);

            var item = tree[0].Children[1].Children[0];
            var container = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(item);

            Assert.NotNull(container);

            target.SelectedItem = item;

            Assert.True(container.IsSelected);
        }

        [Fact]
        public void LogicalChildren_Should_Be_Set()
        {
            var target = new TreeView
            {
                Template = CreateTreeViewTemplate(),
                Items = new[] { "Foo", "Bar", "Baz " },
            };

            ApplyTemplates(target);

            var result = target.GetLogicalChildren()
                .OfType<TreeViewItem>()
                .Select(x => x.Header)
                .OfType<TextBlock>()
                .Select(x => x.Text)
                .ToList();

            Assert.Equal(new[] { "Foo", "Bar", "Baz " }, result);
        }

        [Fact]
        public void Removing_Item_Should_Remove_Itself_And_Children_From_Index()
        {
            var tree = CreateTestTreeData();
            var target = new TreeView
            {
                Template = CreateTreeViewTemplate(),
                DataTemplates = CreateNodeDataTemplate(),
                Items = tree,
            };

            var root = new TestRoot();
            root.Child = target;
            ApplyTemplates(target);

            Assert.Equal(4, target.ItemContainerGenerator.Index.Items.Count());

            tree[0].Children.RemoveAt(1);

            Assert.Equal(2, target.ItemContainerGenerator.Index.Items.Count());
        }

        [Fact]
        public void DataContexts_Should_Be_Correctly_Set()
        {
            var items = new object[]
            {
                "Foo",
                new Node { Value = "Bar" },
                new TextBlock { Text = "Baz" },
                new TreeViewItem { Header = "Qux" },
            };

            var target = new TreeView
            {
                Template = CreateTreeViewTemplate(),
                DataContext = "Base",
                DataTemplates = new DataTemplates
                {
                    new FuncDataTemplate<Node>(x => new Button { Content = x })
                },
                Items = items,
            };

            ApplyTemplates(target);

            var dataContexts = target.Presenter.Panel.Children
                .Cast<Control>()
                .Select(x => x.DataContext)
                .ToList();

            Assert.Equal(
                new object[] { items[0], items[1], "Base", "Base" },
                dataContexts);
        }

        private void ApplyTemplates(TreeView tree)
        {
            tree.ApplyTemplate();
            tree.Presenter.ApplyTemplate();
            ApplyTemplates(tree.Presenter.Panel.Children);
        }

        private void ApplyTemplates(IEnumerable<IControl> controls)
        {
            foreach (TreeViewItem control in controls)
            {
                control.Template = CreateTreeViewItemTemplate();
                control.ApplyTemplate();
                control.Presenter.ApplyTemplate();
                ApplyTemplates(control.Presenter.Panel.Children);
            }
        }

        private IList<Node> CreateTestTreeData()
        {
            return new PerspexList<Node>
            {
                new Node
                {
                    Value = "Root",
                    Children = new PerspexList<Node>
                    {
                        new Node
                        {
                            Value = "Child1",
                        },
                        new Node
                        {
                            Value = "Child2",
                            Children = new PerspexList<Node>
                            {
                                new Node
                                {
                                    Value = "Grandchild2a",
                                },
                            },
                        },
                    }
                }
            };
        }

        private DataTemplates CreateNodeDataTemplate()
        {
            return new DataTemplates
            {
                new FuncTreeDataTemplate<Node>(
                    x => new TextBlock { Text = x.Value },
                    x => x.Children),
            };
        }

        private IControlTemplate CreateTreeViewTemplate()
        {
            return new FuncControlTemplate<TreeView>(parent => new ItemsPresenter
            {
                Name = "PART_ItemsPresenter",
                [~ItemsPresenter.ItemsProperty] = parent[~ItemsControl.ItemsProperty],
            });
        }

        private IControlTemplate CreateTreeViewItemTemplate()
        {
            return new FuncControlTemplate<TreeViewItem>(parent => new ItemsPresenter
            {
                Name = "PART_ItemsPresenter",
                [~ItemsPresenter.ItemsProperty] = parent[~ItemsControl.ItemsProperty],
            });
        }

        private List<string> ExtractItemHeader(TreeView tree, int level)
        {
            return ExtractItemContent(tree.Presenter.Panel, 0, level)
                .Select(x => x.Header)
                .OfType<TextBlock>()
                .Select(x => x.Text)
                .ToList();
        }

        private IEnumerable<TreeViewItem> ExtractItemContent(IPanel panel, int currentLevel, int level)
        {
            foreach (TreeViewItem container in panel.Children)
            {
                if (container.Template == null)
                {
                    container.Template = CreateTreeViewItemTemplate();
                    container.ApplyTemplate();
                }

                if (currentLevel == level)
                {
                    yield return container;
                }
                else
                {
                    foreach (var child in ExtractItemContent(container.Presenter.Panel, currentLevel + 1, level))
                    {
                        yield return child;
                    }
                }
            }
        }

        private class Node
        {
            public string Value { get; set; }
            public IPerspexList<Node> Children { get; set; }
        }
    }
}