using System;
using Xamarin.Forms;

namespace Samples
{
    public class BoxViewClockSample : ISample
    {
        public string Title => "Xamarin.Forms BoxViewClock";

        BoxViewClockPage page;

        public Ooui.Element CreateElement ()
        {
            //
            // Always return the same page because the code never stops the timer
            // and we don't want to create an unlimited number of them.
            //
            if (page == null)
                page = new BoxViewClockPage ();
            return page.GetOouiElement ();
        }

        class BoxViewClockPage : ContentPage
        {
            // Structure for storing information about the three hands.
            struct HandParams
            {
                public HandParams (double width, double height, double offset) : this ()
                {
                    Width = width;
                    Height = height;
                    Offset = offset;
                }

                public double Width { private set; get; }   // fraction of radius
                public double Height { private set; get; }  // ditto
                public double Offset { private set; get; }  // relative to center pivot
            }

            static readonly HandParams secondParams = new HandParams (0.02, 1.1, 0.85);
            static readonly HandParams minuteParams = new HandParams (0.05, 0.8, 0.9);
            static readonly HandParams hourParams = new HandParams (0.125, 0.65, 0.9);

            BoxView[] tickMarks = new BoxView[60];
            BoxView secondHand, minuteHand, hourHand;

            public BoxViewClockPage ()
            {
                AbsoluteLayout absoluteLayout = new AbsoluteLayout ();

                // Create the tick marks (to be sized and positioned later)
                for (int i = 0; i < tickMarks.Length; i++) {
                    tickMarks[i] = new BoxView {
                        Color = Color.Accent
                    };
                    absoluteLayout.Children.Add (tickMarks[i]);
                }

                // Create the three hands.
                absoluteLayout.Children.Add (hourHand =
                    new BoxView {
                        Color = Color.Accent
                    });
                absoluteLayout.Children.Add (minuteHand =
                    new BoxView {
                        Color = Color.Accent
                    });
                absoluteLayout.Children.Add (secondHand =
                    new BoxView {
                        Color = Color.Accent
                    });

                Content = absoluteLayout;

                // Attach a couple event handlers.
                Device.StartTimer (TimeSpan.FromMilliseconds (16), OnTimerTick);
                SizeChanged += OnPageSizeChanged;
            }

            void OnPageSizeChanged (object sender, EventArgs args)
            {
                // Size and position the 12 tick marks.
                Point center = new Point (this.Width / 2, this.Height / 2);
                double radius = 0.45 * Math.Min (this.Width, this.Height);

                for (int i = 0; i < tickMarks.Length; i++) {
                    double size = radius / (i % 5 == 0 ? 15 : 30);
                    double radians = i * 2 * Math.PI / tickMarks.Length;
                    double x = center.X + radius * Math.Sin (radians) - size / 2;
                    double y = center.Y - radius * Math.Cos (radians) - size / 2;
                    AbsoluteLayout.SetLayoutBounds (tickMarks[i], new Rectangle (x, y, size, size));

                    tickMarks[i].AnchorX = 0.51;        // Anchor settings necessary for Android
                    tickMarks[i].AnchorY = 0.51;
                    tickMarks[i].Rotation = 180 * radians / Math.PI;
                }

                // Function for positioning and sizing hands.
                Action<BoxView, HandParams> Layout = (boxView, handParams) => {
                    double width = handParams.Width * radius;
                    double height = handParams.Height * radius;
                    double offset = handParams.Offset;

                    AbsoluteLayout.SetLayoutBounds (boxView,
                        new Rectangle (center.X - 0.5 * width,
                                      center.Y - offset * height,
                                      width, height));

                    boxView.AnchorX = 0.51;
                    boxView.AnchorY = handParams.Offset;
                };

                Layout (secondHand, secondParams);
                Layout (minuteHand, minuteParams);
                Layout (hourHand, hourParams);
            }

            bool OnTimerTick ()
            {
                // Set rotation angles for hour and minute hands.
                DateTime dateTime = DateTime.Now;
                hourHand.Rotation = 30 * (dateTime.Hour % 12) + 0.5 * dateTime.Minute;
                minuteHand.Rotation = 6 * dateTime.Minute + 0.1 * dateTime.Second;

                // Do an animation for the second hand.
                double t = dateTime.Millisecond / 1000.0;
                if (t < 0.5) {
                    t = 0.5 * Easing.SpringIn.Ease (t / 0.5);
                }
                else {
                    t = 0.5 * (1 + Easing.SpringOut.Ease ((t - 0.5) / 0.5));
                }
                secondHand.Rotation = 6 * (dateTime.Second + t);
                return true;
            }
        }
    }
}