using Annulus;
using Azimuth;
using System;

namespace Glass.Testbed
{
    /// <summary>
    /// One named UI experiment.
    /// </summary>
    public abstract class TestCase
    {
        // Margin separates a thing from its neighbour; Gutter separates one band of the layout from the next.
        public const int Margin = 8;
        public const int Gutter = 12;

        public string Name { get; }

        public Panel Root { get; }

        protected TestCase(string name)
        {
            Name = name;

            // Invisible rather than null: a null material reaches NullRenderer, which BlacklightRenderer throws on.
            Root = new Panel { Material = Material.Invisible, DebugName = name };
        }

        public Rect ClientRect => Rect.FromPositionAndSize(Vector.Zero, Root.ClientRect.Size);

        protected RectAggregator ContentAggregator;

        public Rect ContentBounds => ContentAggregator.Rect;

        public void Add(Control control)
        {
            Root.ChildControls.Add(control);
        }

        public T NewChild<T>(string debugName = null) where T : Control, new()
        {
            return Root.ChildControls.NewChild<T>(debugName);
        }

        private void PlaceCaption(TextMaterial material, Rect row)
        {
            Panel caption = material.BuildControl(Constraints.Unbounded);
            caption.Bounds = row;
            Add(caption);
        }

        /// <summary>
        /// Adds a row to this case's content sized to the caption's own text, and puts the caption in it.
        /// </summary>
        protected void AddCaption(StringView text)
        {
            TextMaterial material = Widgets.Caption(text);
            PlaceCaption(material, ContentAggregator.NewRow(material, margin: 4));
        }

        /// <summary>
        /// Takes the row off <paramref name="remaining"/> instead, for a caption inside a rect the case has already
        /// claimed rather than one at the end of its content.
        /// </summary>
        protected void AddCaption(StringView text, ref Rect remaining)
        {
            TextMaterial material = Widgets.Caption(text);
            PlaceCaption(material, remaining.NewRow(material, margin: 4));
        }

        /// <summary>
        /// Lays this case out within <paramref name="area"/>.  Runs once.
        /// </summary>
        /// <remarks>
        /// Not the constructor, because the area isn't known until the tab strip has been built and measured,
        /// and the tab strip is built from the cases.
        /// </remarks>
        public void Build(Rect area)
        {
            Root.Bounds = area;

            // Seeded with the client width so a full-width row still spans the window, but with no height, so a case
            // is free to grow past the bottom of it.
            ContentAggregator = new RectAggregator(
                Rect.FromPositionAndSize(Vector.Zero, new Vector(ClientRect.Width, 0)), new Vector(Gutter, Gutter));

            Populate();

            Root.Bounds = Rect.FromPositionAndSize(area.TopLeft, ContentBounds.Size);
        }

        /// <summary>
        /// Fills this case with whatever it is demonstrating.
        /// </summary>
        protected abstract void Populate();

        /// <summary>
        /// Runs each time this case is shown, so one a user can leave in some other state resets itself.
        /// </summary>
        protected virtual void Setup()
        {
        }

        /// <summary>
        /// Runs each tick this case is the shown one, for a case with something moving in it.
        /// </summary>
        public virtual void Update(TimeSpan elapsed)
        {
        }

        public void Show(ControlContainer host)
        {
            host.Add(Root);
            Setup();
        }

        public void Hide(ControlContainer host)
        {
            host.Remove(Root);
        }
    }
}