using System;
using System.Collections.Generic;
using System.Linq;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows;
using System.Windows.Media;
using System.Windows.Input;

namespace SHJX.Service.WorkFlowEdit
{
    public class DiagramView : Canvas
    {
        private Pen _gridPen;

        static DiagramView()
        {
            FrameworkElement.DefaultStyleKeyProperty.OverrideMetadata(
                typeof(DiagramView), new FrameworkPropertyMetadata(typeof(DiagramView)));
        }

        #region Properties

        #region GridCellSize

        public static readonly DependencyProperty GridCellSizeProperty =
            DependencyProperty.Register("GridCellSize",
                                       typeof(Size),
                                       typeof(DiagramView),
                                       new FrameworkPropertyMetadata(new Size(10, 10)));

        public Size GridCellSize
        {
            get { return (Size)GetValue(GridCellSizeProperty); }
            set { SetValue(GridCellSizeProperty, value); }
        }

        #endregion

        #region ShowGrid

        public static readonly DependencyProperty ShowGridProperty =
            DependencyProperty.Register("ShowGrid",
                                       typeof(bool),
                                       typeof(DiagramView),
                                       new FrameworkPropertyMetadata(false));

        public bool ShowGrid
        {
            get { return (bool)GetValue(ShowGridProperty); }
            set { SetValue(ShowGridProperty, value); }
        }

        #endregion

        #region DocumentSize

        public static readonly DependencyProperty DocumentSizeProperty =
            DependencyProperty.Register("DocumentSize",
                                       typeof(Size),
                                       typeof(DiagramView),
                                       new FrameworkPropertyMetadata(new Size(2000, 2000)));

        public Size DocumentSize
        {
            get { return (Size)GetValue(DocumentSizeProperty); }
            set { SetValue(DocumentSizeProperty, value); }
        }

        #endregion

        #region Zoom

        public static readonly DependencyProperty ZoomProperty =
            DependencyProperty.Register("Zoom",
                                       typeof(double),
                                       typeof(DiagramView),
                                       new FrameworkPropertyMetadata(1.0, new PropertyChangedCallback(OnZoomChanged)));

        private static void OnZoomChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            var view = d as DiagramView;
            var zoom = (double)e.NewValue;
            view._gridPen = view.CreateGridPen();
            if (Math.Abs(zoom - 1) < 0.0001)
                view.LayoutTransform = null;
            else
                view.LayoutTransform = new ScaleTransform(zoom, zoom);
        }

        public double Zoom
        {
            get { return (double)GetValue(ZoomProperty); }
            set { SetValue(ZoomProperty, value); }
        }

        #endregion

        public Selection Selection { get; private set; }

        public IDiagramController Controller { get; set; }

        public IEnumerable<DiagramItem> Items
        {
            get { return Children.OfType<DiagramItem>(); }
        }

        private IInputTool _inputTool;
        public IInputTool InputTool
        {
            get { return _inputTool; }
            set
            {
                if (value == null)
                    throw new ArgumentNullException("value");
                _inputTool = value;
            }
        }

        private IMoveResizeTool _dragTool;
        public IMoveResizeTool DragTool
        {
            get { return _dragTool; }
            set
            {
                if (value == null)
                    throw new ArgumentNullException("value");
                _dragTool = value;
            }
        }

        private ILinkTool _linkTool;
        public ILinkTool LinkTool
        {
            get { return _linkTool; }
            set
            {
                _linkTool = value ?? throw new ArgumentNullException("value");
            }
        }

        public IDragDropTool DragDropTool { get; set; }

        private Adorner _dragAdorner;
        public Adorner DragAdorner
        {
            get { return _dragAdorner; }
            set
            {
                if (_dragAdorner != value)
                {
                    var adornerLayer = AdornerLayer.GetAdornerLayer(this);
                    if (_dragAdorner != null)
                        adornerLayer.Remove(_dragAdorner);
                    _dragAdorner = value;
                    if (_dragAdorner != null)
                        adornerLayer.Add(_dragAdorner);
                }
            }
        }

        public bool IsDragging { get { return DragAdorner != null; } }

        #endregion

        public DiagramView()
        {
            _gridPen = CreateGridPen();
            Selection = new Selection();
            InputTool = new InputTool(this);
            DragTool = new MoveResizeTool(this);
            LinkTool = new LinkTool(this);
            BindCommands();
            Focusable = true;

            this.LayoutUpdated += new EventHandler(DiagramView_LayoutUpdated);
        }

        void DiagramView_LayoutUpdated(object sender, EventArgs e)
        {
            foreach (var n in Children.OfType<Node>())
                n.UpdatePosition();
        }

        public DiagramItem FindItem(object modelElement)
        {
            return Items.FirstOrDefault(p => p.ModelElement == modelElement);
        }

        protected override void OnMouseDown(MouseButtonEventArgs e)
        {
            InputTool.OnMouseDown(e);
            base.OnMouseDown(e);
            Focus();
        }

        protected override void OnMouseMove(MouseEventArgs e)
        {
            InputTool.OnMouseMove(e);
            base.OnMouseMove(e);
        }

        protected override void OnMouseUp(MouseButtonEventArgs e)
        {
            InputTool.OnMouseUp(e);
            base.OnMouseUp(e);
        }

        protected override void OnPreviewKeyDown(KeyEventArgs e)
        {
            InputTool.OnPreviewKeyDown(e);
            base.OnPreviewKeyDown(e);
        }

        protected override void OnDragEnter(DragEventArgs e)
        {
            if (DragDropTool != null)
                DragDropTool.OnDragEnter(e);
            base.OnDragEnter(e);
        }

        protected override void OnDragLeave(DragEventArgs e)
        {
            if (DragDropTool != null)
                DragDropTool.OnDragLeave(e);
            base.OnDragLeave(e);
        }

        protected override void OnDragOver(DragEventArgs e)
        {
            if (DragDropTool != null)
                DragDropTool.OnDragOver(e);
            base.OnDragOver(e);
        }

        protected override void OnDrop(DragEventArgs e)
        {
            if (DragDropTool != null)
                DragDropTool.OnDrop(e);
            base.OnDrop(e);
        }

        protected override Size MeasureOverride(Size constraint)
        {
            base.MeasureOverride(DocumentSize);
            return DocumentSize;
        }

        protected override void OnRender(DrawingContext dc)
        {
            var rect = new Rect(0, 0, RenderSize.Width, RenderSize.Height);
            dc.DrawRectangle(Background, null, rect);
            if (ShowGrid && GridCellSize.Width > 0 && GridCellSize.Height > 0)
                DrawGrid(dc, rect);
        }

        protected virtual void DrawGrid(DrawingContext dc, Rect rect)
        {
            //using .5 forces wpf to draw a single pixel line
            for (var i = 0.5; i < rect.Height; i += GridCellSize.Height)
                dc.DrawLine(_gridPen, new Point(0, i), new Point(rect.Width, i));
            for (var i = 0.5; i < rect.Width; i += GridCellSize.Width)
                dc.DrawLine(_gridPen, new Point(i, 0), new Point(i, rect.Height));
        }

        protected virtual Pen CreateGridPen()
        {
            return new Pen(Brushes.LightGray, (1 / Zoom));
        }

        private void BindCommands()
        {
            CommandBindings.Add(new CommandBinding(ApplicationCommands.Cut, ExecuteCommand, CanExecuteCommand));
            CommandBindings.Add(new CommandBinding(ApplicationCommands.Copy, ExecuteCommand, CanExecuteCommand));
            CommandBindings.Add(new CommandBinding(ApplicationCommands.Paste, ExecuteCommand, CanExecuteCommand));
            CommandBindings.Add(new CommandBinding(ApplicationCommands.Delete, ExecuteCommand, CanExecuteCommand));
        }

        private void ExecuteCommand(object sender, ExecutedRoutedEventArgs e)
        {
            if (Controller != null)
                Controller.ExecuteCommand(e.Command, e.Parameter);
            if (e.Command == ApplicationCommands.Delete)
                Selection.Clear();
        }

        private void CanExecuteCommand(object sender, CanExecuteRoutedEventArgs e)
        {
            if (Controller != null)
                e.CanExecute = Controller.CanExecuteCommand(e.Command, e.Parameter);
        }
    }
}