using System.Numerics;

namespace AcDream.App.Rendering.Walk;

/// <summary>The composition context: the cell/building halves plus the
/// frame-level state retail keeps in globals (the CY near plane from
/// <c>Render::update_viewpoint</c>, and the active-view installation the
/// building clip consumes).</summary>
public interface IRetailFrameWalkContext : IWalkBuildingFrameContext
{
    WalkPlane CyPlane { get; }

    /// <summary><c>Render::set_view</c> at the frame level: install view
    /// <paramref name="index"/> of <paramref name="views"/> as the active
    /// clip context for subsequent building-polygon clips.</summary>
    void SetActiveView(WalkPortalView views, int index);

    float ViewportWidth { get; }
    float ViewportHeight { get; }
}

/// <summary>
/// Campaign FW1 — the frame walk root, composing the ported machinery into
/// retail's frame shapes (model:
/// docs/research/2026-08-30-fw-walk-pseudocode.md §1, §3-§5; oracle:
/// docs/research/2026-08-30-fw-walk-oracle/README.md):
///
/// <list type="bullet">
/// <item>Rooting (<c>SmartBox::RenderNormalMode</c> @0x00453aa0): the
/// CAMERA cell's low word &lt; 0x100 → outdoor root (default full-screen
/// view + the landscape walk); otherwise → <c>DrawInside</c>.</item>
/// <item>Outdoor (<c>LScape::draw</c> @0x00506330): visibility per view,
/// blocks far-to-near, per-block cells far-to-near, buildings at their
/// cell's turn with the two-pass portal machinery (punches + look-ins on
/// the OUTDOOR pview — the traces' <c>pv=009d4b08 ov=0</c>).</item>
/// <item>Interior (<c>PView::DrawInside</c> @0x005a5860 +
/// <c>DrawCells</c> @0x005a4840): the flood on the INTERIOR pview
/// (<c>pv=009d4a80</c>), then the landscape drawn THROUGH the exit views
/// when any survive (<c>ov&gt;0</c>).</item>
/// </list>
///
/// Two PView instances exist exactly as the live traces showed.
/// </summary>
public sealed class RetailFrameWalk
{
    private readonly WalkPView _interiorPView = new();
    // The outdoor pview never draws the landscape through its look-in
    // floods (the landscape is already drawn when buildings punch), so its
    // draw_landscape is FALSE and look-in DCs always read ov=0 — exactly
    // the pv=…/ov=0 pattern of every look-in in the oracle traces.
    private readonly WalkPView _outdoorPView = new() { DrawLandscape = false };
    private readonly WalkPortalView _defaultView = new();

    public WalkPView InteriorPView => _interiorPView;
    public WalkPView OutdoorPView => _outdoorPView;

    /// <summary>Retail global <c>alwaysDrawObjects</c> (.data default 1
    /// @0x00820ed4): cell contents draw for every cell of an in-view block
    /// regardless of per-cell visibility.</summary>
    public bool AlwaysDrawObjects = true;

    /// <summary>Retail global <c>Render::deg_mul</c> — DYNAMIC: the
    /// auto-tuner (<c>auto_update_deg_mul</c>) swings it with frame load
    /// (positive ⇒ degrade thresholds slide toward each level's max;
    /// negative ⇒ toward its min). The oracle captures pin ≈+0.99 for every
    /// fixture except doorway-still, whose capture ran under cdb load with
    /// the multiplier depressed (the recon session's live dump read −0.99
    /// under the same conditions).</summary>
    public float DegradeMultiplier = WalkBuilding.DefaultDegradeMultiplier;

    /// <summary>The per-frame root (<c>SmartBox::RenderNormalMode</c>).
    /// <paramref name="cameraCell"/> may be null only when the camera is
    /// outdoors.</summary>
    public void WalkFrame(
        uint cameraCellId, WalkCell? cameraCell, WalkLandscape landscape,
        IRetailFrameWalkContext ctx, IWalkEventSink sink)
    {
        if ((cameraCellId & 0xFFFF) < 0x100)
        {
            // Render::set_default_view @0x0054ef50: the full-screen quad view.
            _defaultView.ResetForPush();
            WalkCopyView.AppendFullViewportQuad(
                _defaultView, ctx.Rays, ctx.WorldViewpoint,
                ctx.ViewportWidth, ctx.ViewportHeight);
            DrawLandscape(landscape, _defaultView, ctx, sink);
        }
        else
        {
            DrawInside(
                cameraCell ?? throw new ArgumentNullException(nameof(cameraCell)),
                landscape, ctx, sink);
        }
    }

    /// <summary><c>PView::DrawInside</c> + the event half of
    /// <c>DrawCells</c>. The geometry/object passes emit no walk events.</summary>
    public void DrawInside(
        WalkCell cell, WalkLandscape landscape,
        IRetailFrameWalkContext ctx, IWalkEventSink sink)
    {
        sink.Emit(WalkEvent.DrawInside(cell.CellId));
        cell.PushView();
        AddViews(cell.StabList, ctx);
        WalkCopyView.AppendFullViewportQuad(
            cell.TopView, ctx.Rays, ctx.WorldViewpoint,
            ctx.ViewportWidth, ctx.ViewportHeight);
        _interiorPView.ConstructView(cell, 0xFFFF, ctx.CellContext);

        EmitDrawCells(_interiorPView, sink);
        if (_interiorPView.OutsideView.ViewCount > 0)
            DrawLandscape(landscape, _interiorPView.OutsideView, ctx, sink);

        RemoveViews(cell.StabList, ctx);
        cell.PopView();
    }

    /// <summary><c>LScape::draw</c>: visibility per active view, then blocks
    /// far-to-near, cells far-to-near, buildings at their cell's turn.</summary>
    public void DrawLandscape(
        WalkLandscape landscape, WalkPortalView activeViews,
        IRetailFrameWalkContext ctx, IWalkEventSink sink)
    {
        sink.Emit(WalkEvent.Landscape());
        landscape.CalcDrawOrder();
        landscape.CheckBlocks(ctx.CyPlane, activeViews);

        for (int i = landscape.BlockDrawCount - 1; i >= 0; i--)
        {
            WalkLandBlock? block = landscape.Blocks[landscape.BlockDrawList[i]];
            if (block is null || block.InView == WalkBoundingType.Outside)
                continue;
            int cellCount = block.SideCellCount * block.SideCellCount;
            for (int k = 0; k < cellCount; k++)
            {
                int cellIndex = block.DrawArray[k];
                // RenderDeviceD3D::DrawBlock @0x005a19d9: DrawSortCell runs
                // when alwaysDrawObjects != 0 (retail .data default 1
                // @0x00820ed4) OR the cell IsInView; terrain (DrawLandCell)
                // emits no walk event.
                if (!AlwaysDrawObjects
                    && block.CellInView[cellIndex] == WalkBoundingType.Outside)
                {
                    continue;
                }
                // RenderDeviceD3D::DrawSortCell @0x0059f140 (decomp-
                // confirmed 2026-08-30): DrawBuilding(building) FIRST, then
                // DrawObjCell(cell) UNCONDITIONALLY — the building's turn
                // (shell + portal machinery) precedes this cell's own
                // outdoor-static turn.
                if (block.CellBuildings[cellIndex] is WalkBuilding building)
                    DrawBuilding(building, activeViews, ctx, sink);
                sink.OnLandscapeCellTurn((block.LandblockId & 0xFFFF0000u) | (uint)(cellIndex + 1));
            }
        }
    }

    /// <summary><c>RenderDeviceD3D::DrawBuilding</c> @0x0059f2a0 at the walk
    /// level: the BLD event fires at ENTRY (before the degrade check — the
    /// oracle traces' breakpoint sat there, so this stays unconditional for
    /// conformance). The ENTIRE rest of the body — the alpha barrier, the
    /// portal pass, and the shell draw — sits inside retail's
    /// <c>if (part-&gt;gfxobj[part-&gt;deg_level] != 0)</c> @0x0059f2d3; a
    /// degraded-out slot draws NOTHING beyond the BLD event.
    /// <c>HasGeometry</c> + a non-null <c>SelectDrawingBsp</c> together model
    /// that one gate. Inside the gate, retail's own order
    /// (@0x0059f30b–0x0059f345) is <c>D3DPolyRender::FlushAlphaList(0f)</c> →
    /// <c>CPhysicsPart::Draw(parts, 1)</c> (the PORTAL flavor — the two-pass
    /// punch/look-in walk below) → <c>CPhysicsPart::Draw(parts, 0)</c> (the
    /// plain mesh — the building's own SHELL) → flag reset: the alpha
    /// barrier and the portal pass both precede the shell draw, not follow
    /// it.</summary>
    public void DrawBuilding(
        WalkBuilding building, WalkPortalView activeViews,
        IRetailFrameWalkContext ctx, IWalkEventSink sink)
    {
        sink.Emit(WalkEvent.Building(building.PositionCellId));
        if (!building.HasGeometry) return;
        // Retail walks the CURRENT degrade level's drawing BSP
        // (part->gfxobj[deg_level]); a degraded-out slot skips everything
        // after publishing the portal list.
        WalkBspNode? bsp = building.SelectDrawingBsp(
            ctx.ViewerDistanceTo(building),
            degradeMultiplier: DegradeMultiplier);
        if (bsp is null) return;

        // Additive (Campaign FW3.2b-1): the alpha barrier
        // (D3DPolyRender::FlushAlphaList(0f) @0x0059f30b) — gated by the
        // SAME part->gfxobj[deg_level]!=0 check as everything below it, so
        // this fires only now that both HasGeometry and the bsp lookup have
        // passed.
        sink.OnBuildingTurn(building);

        int viewCount = Math.Max(activeViews.ViewCount, 0);
        var passSink = new PortalPassSink(building, sink);
        Vector3 viewpoint = ctx.ViewpointInBuilding(building);
        for (int v = 0; v < viewCount; v++)
        {
            ctx.SetActiveView(activeViews, v);
            WalkBuildingPortals.BuildDrawPortalsOnly(
                bsp, 1, viewpoint,
                (portalRef, pass) => WalkBuildingPortals.DrawPortal(
                    _outdoorPView, building, portalRef, pass, ctx, passSink));
            WalkBuildingPortals.BuildDrawPortalsOnly(
                bsp, 2, viewpoint,
                (portalRef, pass) => WalkBuildingPortals.DrawPortal(
                    _outdoorPView, building, portalRef, pass, ctx, passSink));
        }

        // Additive (Campaign FW3.2b-1): CPhysicsPart::Draw(parts, 0)
        // @0x0059f331 — the building's own shell mesh — runs AFTER the
        // portal walk completes (CPhysicsPart::Draw(parts, 1) just above),
        // not before it.
        sink.OnBuildingShellTurn(building);
    }

    private void EmitDrawCells(WalkPView pview, IWalkEventSink sink)
    {
        uint[] cells = new uint[pview.CellDrawList.Count];
        for (int i = 0; i < cells.Length; i++)
            cells[i] = pview.CellDrawList[i].CellId;
        sink.Emit(WalkEvent.DrawCells(pview.OutsideView.ViewCount, cells));
    }

    private void AddViews(uint[] stabList, IRetailFrameWalkContext ctx)
    {
        foreach (uint id in stabList)
            ctx.GetVisible(id)?.PushView();
    }

    private void RemoveViews(uint[] stabList, IRetailFrameWalkContext ctx)
    {
        foreach (uint id in stabList)
            ctx.GetVisible(id)?.PopView();
    }

    private sealed class PortalPassSink(WalkBuilding building, IWalkEventSink sink)
        : WalkBuildingPortals.IWalkPortalPassSink
    {
        public void OnPunch(WalkPolygon polygon)
        {
            // The far-Z punch is a depth-only GPU submission (FW2's ordered
            // stream); the oracle traces do not log it. Additive (Campaign
            // FW3.2b-1): forward to the richer sink so a driver can flush +
            // draw the punch fan — building-local space, world transform is
            // the driver's job (WalkProductionFrameContext-style lookup).
            sink.OnPunchGeometry(building, polygon);
        }

        public void OnDrawCells(WalkPView pview)
        {
            uint[] cells = new uint[pview.CellDrawList.Count];
            for (int i = 0; i < cells.Length; i++)
                cells[i] = pview.CellDrawList[i].CellId;
            sink.Emit(WalkEvent.DrawCells(pview.OutsideView.ViewCount, cells));
        }
    }
}