using System.Numerics;
using AcDream.App.UI;

namespace AcDream.App.Studio;

// ─────────────────────────────────────────────────────────────────────────────
// DumpLayout — load a panel from the retail UI layout dump
//
// The dump stores every node's rect in ABSOLUTE screen coordinates (the
// panel's design position in the retail UI, not relative to its parent).
// Evidence: for the "inventory" panel, the root node is at x=500,y=138 and
// its direct children are also at x=500,y=161 — the child y=161 is only
// 23 pixels below the parent y=138, which makes sense as a child offset
// (the header row), not as the raw rect.  If the rects were parent-relative,
// (500,161) would place the child way off the window.
//
// DumpLayout converts absolute → parent-relative by computing:
//   child.Left = child.Rect.X - parent.Rect.X
//   child.Top  = child.Rect.Y - parent.Rect.Y
//
// The root node (ParentTraversalIndex == null) is placed at (0,0) so the
// whole tree sits at the UiHost origin rather than at the panel's retail
// screen position.
// ─────────────────────────────────────────────────────────────────────────────

/// <summary>
/// Builds a static <see cref="UiElement"/> tree from the retail UI layout dump
/// JSON.  The tree is a hierarchy of <see cref="DumpSpriteElement"/> (draws its
/// sprite) or plain <see cref="UiElement"/> containers (Group nodes), with each
/// node's <see cref="UiElement.EventId"/> set to the dump's element_id and
/// <see cref="UiElement.Name"/> set to the widget_kind string.
///
/// <para>This source is STATIC — no controllers, no FixtureProvider, no live
/// game data. It is a build reference for the UI Studio showing any of the 26
/// retail windows without needing the production panel wired up.</para>
/// </summary>
public static class DumpLayout
{
    /// <summary>
    /// Parse the dump at <paramref name="dumpPath"/>, find the panel whose slug
    /// matches <paramref name="slug"/>, and build a <see cref="UiElement"/> tree.
    ///
    /// <para>
    /// <paramref name="resolve"/> maps a RenderSurface id (0x06xxxxxx) to a
    /// (GL texture handle, native width, native height) triple — pass
    /// <c>RenderStack.ResolveChrome</c> from the studio, or a stub returning
    /// (1,1,1) for tests.
    /// </para>
    ///
    /// <para>Returns null and sets <paramref name="error"/> on failure.</para>
    /// </summary>
    public static UiElement? Load(
        string dumpPath,
        string slug,
        Func<uint, (uint, int, int)> resolve,
        out string? error)
    {
        // ── 1. Parse the dump JSON ────────────────────────────────────────
        var dump = UiDumpModel.Parse(dumpPath);
        if (dump is null)
        {
            error = $"[dump] Failed to parse '{dumpPath}'.";
            return null;
        }

        // ── 2. Find the requested panel ───────────────────────────────────
        var panel = dump.Panels.FirstOrDefault(
            p => string.Equals(p.Slug, slug, StringComparison.OrdinalIgnoreCase));
        if (panel is null)
        {
            error = $"[dump] Panel slug '{slug}' not found. " +
                    $"Available: {string.Join(", ", dump.Panels.Select(p => p.Slug))}";
            return null;
        }

        if (panel.Nodes.Count == 0)
        {
            error = $"[dump] Panel '{slug}' has no nodes.";
            return null;
        }

        // ── 3. Build a traversal-index → node lookup ──────────────────────
        var byIndex = new Dictionary<int, DumpNode>(panel.Nodes.Count);
        foreach (var n in panel.Nodes)
            byIndex[n.TraversalIndex] = n;

        // ── 4. Create UiElement objects for every node ────────────────────
        var elements = new Dictionary<int, UiElement>(panel.Nodes.Count);
        foreach (var node in panel.Nodes)
        {
            var el = BuildElement(node, resolve);
            elements[node.TraversalIndex] = el;
        }

        // ── 5. Wire parent–child relationships + set parent-relative coords ─
        UiElement? root = null;
        foreach (var node in panel.Nodes)
        {
            var el = elements[node.TraversalIndex];

            if (node.ParentTraversalIndex is null)
            {
                // Root node — place at (0,0) so the tree sits at the UiHost origin.
                // The panel's absolute rect offset is discarded here (it was the
                // retail design position inside the retail screen, which we don't need).
                el.Left = 0f;
                el.Top  = 0f;
                root    = el;
            }
            else
            {
                // Non-root: convert absolute → parent-relative by subtracting parent rect.
                //   child.Left = child.Rect.X - parent.Rect.X
                //   child.Top  = child.Rect.Y - parent.Rect.Y
                // This preserves the visual layout inside each group without placing the
                // entire panel at its retail screen origin.
                var parentNode = byIndex[node.ParentTraversalIndex.Value];
                el.Left = node.Rect.X - parentNode.Rect.X;
                el.Top  = node.Rect.Y - parentNode.Rect.Y;

                var parentEl = elements[node.ParentTraversalIndex.Value];
                parentEl.AddChild(el);
            }
        }

        if (root is null)
        {
            error = $"[dump] Panel '{slug}': no root node found (all nodes have a parent).";
            return null;
        }

        // Give the root the full panel dimensions (from the dump's width/height record).
        root.Width  = panel.Width;
        root.Height = panel.Height;

        error = null;
        return root;
    }

    // ── Private helpers ───────────────────────────────────────────────────────

    private static UiElement BuildElement(
        DumpNode node,
        Func<uint, (uint, int, int)> resolve)
    {
        uint imageId = UiDumpModel.PickImageId(node);
        var kind     = node.WidgetKind ?? "Group";

        UiElement el;
        if (imageId != 0 && !string.Equals(kind, "Group", StringComparison.OrdinalIgnoreCase))
        {
            // Sprite/Button/Scrollbar/Slider — create a sprite-drawing element.
            el = new DumpSpriteElement(imageId, resolve)
            {
                Name        = kind,
                ClickThrough = true,  // static mockup; no behavior
                Anchors      = AnchorEdges.None,
            };
        }
        else
        {
            // Group (or sprite without an image) — plain container, no own draw.
            el = new DumpGroupElement()
            {
                Name        = kind,
                ClickThrough = true,
                Anchors      = AnchorEdges.None,
            };
        }

        // EventId is set from the dump's element_id (cast to uint — the decimal
        // values in the JSON represent the same dat handle used at runtime).
        el.EventId = (uint)node.ElementId;
        el.Left    = node.Rect.X;   // overwritten by caller per root/child logic
        el.Top     = node.Rect.Y;
        el.Width   = node.Rect.Width;
        el.Height  = node.Rect.Height;

        return el;
    }
}

// ─────────────────────────────────────────────────────────────────────────────
// DumpSpriteElement — minimal element that draws a single sprite
// ─────────────────────────────────────────────────────────────────────────────

/// <summary>
/// Draws a single sprite at its native size tiled to fill <see cref="UiElement.Width"/>
/// × <see cref="UiElement.Height"/>. Used for Sprite/Button/Scrollbar/Slider nodes from
/// the retail UI dump.
///
/// <para>We do NOT reuse <see cref="AcDream.App.UI.Layout.UiDatElement"/> here because
/// that class requires an <c>ElementInfo</c> with a populated <c>StateMedia</c>
/// dictionary — the dat-import plumbing — which is not needed for a static dump
/// preview. A minimal subclass keeps the code simpler and the dependency surface
/// smaller.</para>
/// </summary>
internal sealed class DumpSpriteElement : UiElement
{
    private readonly uint _imageId;
    private readonly Func<uint, (uint tex, int w, int h)> _resolve;

    public DumpSpriteElement(uint imageId, Func<uint, (uint tex, int w, int h)> resolve)
    {
        _imageId = imageId;
        _resolve = resolve;
    }

    protected override void OnDraw(UiRenderContext ctx)
    {
        if (_imageId == 0) return;

        var (tex, tw, th) = _resolve(_imageId);
        if (tex == 0 || tw == 0 || th == 0) return;

        // Tile at native resolution (same as UiDatElement.OnDraw — UV-repeat on both
        // axes via GL_REPEAT, Width/tw and Height/th tile the texture).
        ctx.DrawSprite(tex, 0, 0, Width, Height,
            0, 0, Width / tw, Height / th, Vector4.One);
    }
}

// ─────────────────────────────────────────────────────────────────────────────
// DumpGroupElement — pure container (Group nodes from the dump)
// ─────────────────────────────────────────────────────────────────────────────

/// <summary>
/// Container element for dump Group nodes — no own draw, just hosts children.
/// Extending UiElement directly (no OnDraw override) gives transparent groups,
/// which matches Group nodes in the retail layout that have no background sprite.
/// </summary>
internal sealed class DumpGroupElement : UiElement
{
    // No OnDraw — completely transparent container.
}