using System.Windows.Input;

namespace System.Windows.Forms
{
    public partial class ListBox : ListControl
    {
        public const int NoMatches = -1;

        protected new CustomControls.OwnerDrawListBox control { get; }

        public SelectedObjectCollection SelectedItems { get; }

        private SelectedIndexCollection selectedIndices;
        public SelectedIndexCollection SelectedIndices
        {
            get
            {
                if (selectedIndices == null)
                    BuildSelectedIndices();
                return selectedIndices;
            }
        }

        public int ItemHeight
        {
            get => (int)(control.ItemHeight * DpiScale);
            set => control.ItemHeight = (int)(value / DpiScale);
        }

        private DrawMode drawMode;
        public DrawMode DrawMode
        {
            get => drawMode;
            set
            {
                drawMode = value;
                control.OwnerDraw = value != DrawMode.Normal;
            }
        }

        private SelectionMode selectionMode;
        public SelectionMode SelectionMode
        {
            get => selectionMode;
            set
            {
                selectionMode = value;
                control.SelectionMode = value switch
                {
                    SelectionMode.MultiSimple => Windows.Controls.SelectionMode.Multiple,
                    SelectionMode.MultiExtended => Windows.Controls.SelectionMode.Extended,
                    _ => Windows.Controls.SelectionMode.Single
                };
            }
        }

        public int TopIndex
        {
            get => SelectedIndex;
            set
            {
                if (value != -1)
                    control.ScrollIntoView(Items[value]);
            }
        }

        private bool horizontalScrollbar;
        public bool HorizontalScrollbar
        {
            get => horizontalScrollbar;
            set
            {
                horizontalScrollbar = value;
                control.SetValue(Windows.Controls.ScrollViewer.HorizontalScrollBarVisibilityProperty, value ? Windows.Controls.ScrollBarVisibility.Visible : Windows.Controls.ScrollBarVisibility.Hidden);
            }
        }

        // these 3 are ignored
        public bool UseTabStops { get; set; }
        public int ColumnWidth { get; set; }
        public bool MultiColumn { get; set; }

        public event DrawItemEventHandler DrawItem;
        public event MeasureItemEventHandler MeasureItem;

        private void ListBox_MouseDown(object sender, MouseButtonEventArgs e)
        {
            var element = control.InputHitTest(e.GetPosition(control));
            if (element is FrameworkElement itm && itm.DataContext != null)
            {
                // fire event when clicked on the item (otherwise it will be skipped)
                OnMouseDown(Helper.GetMouseEventArgs(control, e));
            }
        }

        private void BuildSelectedIndices()
        {
            selectedIndices = new SelectedIndexCollection(this);
            for (int i = 0; i < control.SelectedItems.Count; i++)
            {
                var item = control.SelectedItems[i];
                selectedIndices.AddInternal(control.Items.IndexOf(item));
            }
        }

        protected virtual void OnDrawItem(DrawItemEventArgs e) => DrawItem?.Invoke(this, e);

        protected virtual void OnMeasureItem(MeasureItemEventArgs e) => MeasureItem?.Invoke(this, e);

        protected override void OnSelectionChanged(EventArgs e)
        {
            base.OnSelectionChanged(e);
            control.ScrollIntoView(SelectedItem);
            selectedIndices = null;
        }

        public void ClearSelected()
        {
            control.SelectedItems.Clear();
        }

        public void SetSelected(int index, bool selected)
        {
            var item = Items[index];
            if (selected)
                control.SelectedItems.Add(item);
            else
                control.SelectedItems.Remove(item);
        }

        public int IndexFromPoint(int x, int y)
        {
            object item = null;
            var element = control.InputHitTest(new Point(x / DpiScale, y / DpiScale));
            if (element is FrameworkElement itm)
            {
                item = itm.DataContext;
            }
            return item == null ? -1 : Items.IndexOf(item);
        }

        public int IndexFromPoint(Drawing.Point pos) => IndexFromPoint(pos.X, pos.Y);

        public ListBox()
        {
            control = new();
            SetControl(control);
            SelectedItems = new SelectedObjectCollection(control.SelectedItems);
            control.DrawItem += (sender, e) => OnDrawItem(e);
            control.MeasureItem += (sender, e) => OnMeasureItem(e);
            // use this instead of PreviewMouseDown! do not allow unhandled event to bubble/tunnel/whatever
            control.AddHandler(UIElement.MouseDownEvent, new MouseButtonEventHandler(ListBox_MouseDown), true);
            // std Control code does not work for these events
            control.MouseDoubleClick += (s, e) =>
            {
                OnMouseDoubleClick(Helper.GetMouseEventArgs(control, e));
                OnDoubleClick(EventArgs.Empty);
            };

            HorizontalScrollbar = false;
            Width = 120;
            Height = 96;
        }
    }
}