using System;
using System.Collections.Generic;

namespace AcDream.App.UI;

/// <summary>
/// A toolbar-frame variant that snaps its height between two stops — collapsed (row 2 hidden) and
/// expanded (row 2 shown) — and toggles a set of "second-row" elements to match. Resized via the
/// bottom edge (the mount sets <see cref="UiElement.ResizableEdges"/> = Bottom); each tick it resolves
/// the dragged height to the nearer stop so the frame always rests collapsed or expanded — never a
/// half-row. Toolkit UX (keystone.dll has no decomp; the dat stacks both rows always) — see IA-17.
/// </summary>
public sealed class UiCollapsibleFrame : UiNineSlicePanel
{
    public UiCollapsibleFrame(Func<uint, (uint, int, int)> resolve) : base(resolve) { }

    public float CollapsedHeight { get; set; }
    public float ExpandedHeight  { get; set; }
    /// <summary>Elements shown only when expanded (the row-2 slot lists). Hidden when collapsed.</summary>
    public IReadOnlyList<UiElement> SecondRow { get; set; } = Array.Empty<UiElement>();

    /// <summary>True when the frame is at (or nearer) the expanded stop.</summary>
    public bool IsExpanded => Height >= (CollapsedHeight + ExpandedHeight) * 0.5f;

    protected override void OnTick(double deltaSeconds)
    {
        base.OnTick(deltaSeconds);
        if (ExpandedHeight <= CollapsedHeight) return;   // not configured yet — no snap
        bool expanded = IsExpanded;
        Height = expanded ? ExpandedHeight : CollapsedHeight;   // snap the dragged height to a stop
        for (int i = 0; i < SecondRow.Count; i++) SecondRow[i].Visible = expanded;
    }

    /// <summary>Test hook — OnTick is protected. Drives one snap+visibility reconcile.</summary>
    internal void TickForTest(double dt) => OnTick(dt);
}