using AcDream.App.UI;
using Xunit;

namespace AcDream.App.Tests.UI;

public class DragDropSpineTests
{
    // A spy handler used across the spine tests.
    private sealed class SpyHandler : IItemListDragHandler
    {
        public bool AcceptResult = true;
        public (UiItemList list, UiItemSlot cell, ItemDragPayload payload)? LastOver;
        public (UiItemList list, UiItemSlot cell, ItemDragPayload payload)? LastDrop;

        public bool OnDragOver(UiItemList list, UiItemSlot cell, ItemDragPayload p)
        { LastOver = (list, cell, p); return AcceptResult; }

        public void HandleDropRelease(UiItemList list, UiItemSlot cell, ItemDragPayload p)
        { LastDrop = (list, cell, p); }
    }

    [Fact]
    public void Payload_holdsAllFields()
    {
        var src = new UiItemSlot();
        var p = new ItemDragPayload(0x5001u, ItemDragSource.ShortcutBar, 3, src);
        Assert.Equal(0x5001u, p.ObjId);
        Assert.Equal(ItemDragSource.ShortcutBar, p.SourceKind);
        Assert.Equal(3, p.SourceSlot);
        Assert.Same(src, p.SourceCell);
    }

    [Fact]
    public void UiItemList_registerDragHandler_roundtrips()
    {
        var list = new UiItemList(_ => (0u, 0, 0));
        Assert.Null(list.DragHandler);
        var h = new SpyHandler();
        list.RegisterDragHandler(h);
        Assert.Same(h, list.DragHandler);
    }

    // ── UiItemSlot drag-source payload/ghost ────────────────────────────────
    [Fact]
    public void GetDragPayload_emptyCell_isNull()
        => Assert.Null(new UiItemSlot().GetDragPayload());

    [Fact]
    public void GetDragPayload_boundCell_snapshotsFields()
    {
        var cell = new UiItemSlot { SlotIndex = 4, SourceKind = ItemDragSource.ShortcutBar };
        cell.SetItem(0x5001u, 0x99u);
        var p = Assert.IsType<ItemDragPayload>(cell.GetDragPayload());
        Assert.Equal(0x5001u, p.ObjId);
        Assert.Equal(ItemDragSource.ShortcutBar, p.SourceKind);
        Assert.Equal(4, p.SourceSlot);
        Assert.Same(cell, p.SourceCell);
    }

    [Fact]
    public void GetDragGhost_emptyCell_isNull()
        => Assert.Null(new UiItemSlot().GetDragGhost());

    [Fact]
    public void GetDragGhost_boundCell_returnsIconTuple()
    {
        var cell = new UiItemSlot { Width = 32, Height = 32 };
        cell.SetItem(0x5001u, 0x99u);
        var g = cell.GetDragGhost();
        Assert.NotNull(g);
        Assert.Equal(0x99u, g!.Value.tex);
        Assert.Equal(32, g.Value.w);
        Assert.Equal(32, g.Value.h);
    }

    // ── cell drop-target: DragEnter overlay + DropReleased dispatch ──────────
    private static (UiItemList list, UiItemSlot cell, SpyHandler h) ListWithHandler()
    {
        var list = new UiItemList(_ => (1u, 1, 1)); // non-zero resolve so overlay draw is harmless
        var h = new SpyHandler();
        list.RegisterDragHandler(h);
        return (list, list.Cell, h);
    }

    private static ItemDragPayload SomePayload()
        => new(0x5001u, ItemDragSource.ShortcutBar, 0, new UiItemSlot());

    [Fact]
    public void DragEnter_setsAcceptOverlay_whenHandlerAccepts()
    {
        var (_, cell, h) = ListWithHandler();
        h.AcceptResult = true;
        cell.OnEvent(new UiEvent(0u, cell, UiEventType.DragEnter, Payload: SomePayload()));
        Assert.Equal(UiItemSlot.DragAcceptState.Accept, cell.DragAcceptVisual);
    }

    [Fact]
    public void DragEnter_setsRejectOverlay_whenHandlerRejects()
    {
        var (_, cell, h) = ListWithHandler();
        h.AcceptResult = false;
        cell.OnEvent(new UiEvent(0u, cell, UiEventType.DragEnter, Payload: SomePayload()));
        Assert.Equal(UiItemSlot.DragAcceptState.Reject, cell.DragAcceptVisual);
    }

    [Fact]
    public void DragOver_resetsOverlayToNeutral()
    {
        var (_, cell, h) = ListWithHandler();
        cell.OnEvent(new UiEvent(0u, cell, UiEventType.DragEnter, Payload: SomePayload()));
        cell.OnEvent(new UiEvent(0u, cell, UiEventType.DragOver, Payload: SomePayload()));
        Assert.Equal(UiItemSlot.DragAcceptState.None, cell.DragAcceptVisual);
    }

    [Fact]
    public void DropReleased_accepted_dispatchesToHandler()
    {
        var (list, cell, h) = ListWithHandler();
        var p = SomePayload();
        cell.OnEvent(new UiEvent(0u, cell, UiEventType.DropReleased, Data0: 1, Payload: p));
        Assert.NotNull(h.LastDrop);
        Assert.Same(list, h.LastDrop!.Value.list);
        Assert.Same(cell, h.LastDrop.Value.cell);
        Assert.Same(p, h.LastDrop.Value.payload);
    }

    [Fact]
    public void DropReleased_notAccepted_skipsDispatch()
    {
        var (_, cell, h) = ListWithHandler();
        cell.OnEvent(new UiEvent(0u, cell, UiEventType.DropReleased, Data0: 0, Payload: SomePayload()));
        Assert.Null(h.LastDrop);
    }
}