using AcDream.App.Rendering.Walk;

namespace AcDream.App.Tests.Rendering.Walk;

/// <summary>
/// S3 chunk 3 (§9.3 T1): <see cref="LandWalkOrder"/> +
/// <see cref="WalkLandscape.CalcDrawOrder"/> +
/// <see cref="WalkLandscapeAssembler.SideCellCountForRing"/> reproduce frame
/// 2's <c>LC</c> and <c>SC</c> sequences of BOTH OH cathedral captures
/// exactly — order, block membership, and per-block LOD side all pinned in
/// one pass, at the depth the two owner-verified transcripts (S3 §9.1 R2)
/// recorded them.
///
/// <para>Viewer: block <c>f4/18</c>, sq cell <c>(1, 1)</c> (the frame-2 `P`
/// line: x 36.6, y 24.0 — <c>floor(36.6/24)=1</c>, <c>floor(24.0/24)=1</c>).
/// Grid radius <see cref="WalkLandscapeAssembler.MidRadius"/> (25) — the
/// captured blocks span Chebyshev ring 24 (§9.1 R2 fact i), comfortably
/// inside it. Only the SET of blocks/cells the transcript itself visited is
/// placed on the grid (a real 51×51 window's un-streamed slots stay null
/// exactly the same way in production — <see cref="WalkLandscape.DrawLandscape"/>
/// skips a null/Outside slot regardless of why it's empty); each block's
/// <see cref="WalkLandBlock.CellInView"/> is set DIRECTLY from the
/// transcript's own LC membership (this test is an ORDER pin, not a second
/// visibility-math proof — that is <c>WalkVisibilityMathTests</c>'s
/// job) so <see cref="WalkLandscape.CalcDrawOrder"/> is the ONLY production
/// order machinery under test.</para>
/// </summary>
public sealed class WalkLandCellOrderTests
{
    private const int ViewerBlockX = 0xf4;
    private const int ViewerBlockY = 0x18;
    private const int ViewerSqX = 1;
    private const int ViewerSqY = 1;

    [Theory]
    [InlineData("cathedral-arrival")]
    [InlineData("cathedral-leak")]
    public void Frame2_ProducedLandCellSequence_MatchesTheCapturedRetailOrderExactly(
        string fixtureName)
    {
        IReadOnlyList<WalkOracleFrame> frames = WalkOracleTrace.Load(
            "docs/research/2026-09-01-overhaul/oh-capture", fixtureName + ".walk");
        WalkOracleFrame frame2 = Assert.Single(frames, f => f.Number == 2);

        List<WalkOracleEvent> landCellEvents = frame2.Events
            .Where(e => e.Kind is WalkOracleEventKind.LandCell or WalkOracleEventKind.SortCell)
            .ToList();
        Assert.NotEmpty(landCellEvents);

        // Extract the block visit order (first-appearance order = retail's
        // OWN far-to-near block sequence) and, per block, its side (from
        // the observed SC cell count — every SC-visited block emits
        // side² SC turns under AlwaysDrawObjects, R1) and its LC membership.
        var blockOrder = new List<uint>();
        var blockSeen = new HashSet<uint>();
        var sideByBlock = new Dictionary<uint, int>();
        var scCountByBlock = new Dictionary<uint, int>();
        var lcMembersByBlock = new Dictionary<uint, HashSet<uint>>();

        foreach (WalkOracleEvent e in landCellEvents)
        {
            uint cellId = e.CellId!.Value;
            uint blockPrefix = cellId & 0xFFFF0000u;
            uint lodId = cellId & 0xFFFFu;
            if (blockSeen.Add(blockPrefix))
            {
                blockOrder.Add(blockPrefix);
                lcMembersByBlock[blockPrefix] = new HashSet<uint>();
            }

            if (e.Kind == WalkOracleEventKind.SortCell)
            {
                scCountByBlock[blockPrefix] = scCountByBlock.GetValueOrDefault(blockPrefix) + 1;
            }
            else
            {
                lcMembersByBlock[blockPrefix].Add(lodId);
            }
        }

        foreach ((uint blockPrefix, int scCount) in scCountByBlock)
        {
            int side = (int)Math.Round(Math.Sqrt(scCount));
            Assert.Equal(scCount, side * side);
            sideByBlock[blockPrefix] = side;

            // Cross-check against the LOD-by-ring pyramid the ownership
            // map's R2 names explicitly (ring 0-1 -> 8, ring 2 -> 4, ring
            // 3-4 -> 2, ring >= 5 -> 1) — an independent confirmation that
            // the transcript's own per-block cell count matches production's
            // ring rule, not just an internally-consistent side count.
            int bx = (int)(blockPrefix >> 24) & 0xFF;
            int by = (int)(blockPrefix >> 16) & 0xFF;
            int ring = Math.Max(Math.Abs(bx - ViewerBlockX), Math.Abs(by - ViewerBlockY));
            Assert.Equal(WalkLandscapeAssembler.SideCellCountForRing(ring), side);
        }

        // Build the synthetic grid: only the transcript-visited blocks are
        // populated (production leaves everything else null too), each at
        // its REAL grid offset from the viewer block, with the REAL side
        // WalkLandscapeAssembler.SideCellCountForRing computed above.
        const int midWidth = WalkLandscapeAssembler.GridWidth;
        const int midRadius = WalkLandscapeAssembler.MidRadius;
        var landscape = new WalkLandscape
        {
            MidWidth = midWidth,
            Blocks = new WalkLandBlock?[midWidth * midWidth],
            ViewerBlockX = midRadius,
            ViewerBlockY = midRadius,
            ViewerCellX = ViewerSqX,
            ViewerCellY = ViewerSqY,
        };

        foreach (uint blockPrefix in blockOrder)
        {
            int bx = (int)(blockPrefix >> 24) & 0xFF;
            int by = (int)(blockPrefix >> 16) & 0xFF;
            int gridX = bx - ViewerBlockX + midRadius;
            int gridY = by - ViewerBlockY + midRadius;
            Assert.InRange(gridX, 0, midWidth - 1);
            Assert.InRange(gridY, 0, midWidth - 1);

            int side = sideByBlock[blockPrefix];
            var block = new WalkLandBlock
            {
                LandblockId = blockPrefix, SideCellCount = side, MaxZ = 0f, MinZ = 0f,
            };
            block.EnsureCellArrays();
            HashSet<uint> lcMembers = lcMembersByBlock[blockPrefix];
            for (int cellIndex = 0; cellIndex < side * side; cellIndex++)
            {
                int coarseX = cellIndex / side;
                int coarseY = cellIndex % side;
                uint retailLodId = (uint)(coarseX * 8 + coarseY + 1);
                block.CellInView[cellIndex] = lcMembers.Contains(retailLodId)
                    ? WalkBoundingType.EntirelyInside
                    : WalkBoundingType.Outside;
            }
            block.InView = WalkBoundingType.PartiallyInside;   // admitted; never Outside
            landscape.Blocks[gridX * midWidth + gridY] = block;
        }

        // LandWalkOrder.GetBlockOrder + FillCellOrderFarToNear (the ONLY
        // production order machinery under test — CheckBlocks is
        // deliberately not called; CellInView above is authoritative).
        landscape.CalcDrawOrder();

        var producedLc = new List<uint>();
        var producedSc = new List<uint>();
        for (int i = landscape.BlockDrawCount - 1; i >= 0; i--)
        {
            WalkLandBlock? block = landscape.Blocks[landscape.BlockDrawList[i]];
            if (block is null)
                continue;

            int cellCount = block.SideCellCount * block.SideCellCount;
            for (int k = 0; k < cellCount; k++)
            {
                int cellIndex = block.DrawArray[k];
                int coarseX = cellIndex / block.SideCellCount;
                int coarseY = cellIndex % block.SideCellCount;
                uint fullId = block.LandblockId | (uint)(coarseX * 8 + coarseY + 1);
                if (block.CellInView[cellIndex] != WalkBoundingType.Outside)
                    producedLc.Add(fullId);
                producedSc.Add(fullId);   // AlwaysDrawObjects: every cell of an admitted block.
            }
        }

        List<uint> expectedLc = landCellEvents
            .Where(e => e.Kind == WalkOracleEventKind.LandCell)
            .Select(e => e.CellId!.Value)
            .ToList();
        List<uint> expectedSc = landCellEvents
            .Where(e => e.Kind == WalkOracleEventKind.SortCell)
            .Select(e => e.CellId!.Value)
            .ToList();

        Assert.Equal(expectedSc, producedSc);
        Assert.Equal(expectedLc, producedLc);
    }
}