using System.Numerics;
using AcDream.App.Rendering;
using AcDream.App.Rendering.Gpu;
using AcDream.App.Rendering.Walk;
using AcDream.App.Tests.Rendering;
using AcDream.Core.Rendering;

namespace AcDream.App.Tests.Rendering.Walk;

/// <summary>
/// Campaign OVERHAUL S3 chunk 1 (§11.2): tests T1/T2 for the print-only walk
/// transcript emitter (<see cref="WalkTranscriptDump"/>, gated by
/// <see cref="RenderingDiagnostics.DumpWalkTranscriptEnabled"/>), plus the
/// §11.2 B4 offline signature-diff self-check. Reuses
/// <see cref="WalkFrameDriverTests"/>'s own private fixture types via the
/// shared <c>partial class</c> — the SAME minimal interior two-cell flood
/// (one exit view) that file's own
/// <c>RunFrame_InteriorFloodWithExitView_FreshDriverSkipsTheGatedClearThenDrawsSealsAndFloodCells</c>
/// test already exercises and proves correct; here only
/// <see cref="WalkFrameDriver.Collect"/> runs (no <c>Replay</c>/GPU
/// submission), since every transcript print fires synchronously during the
/// walk itself.
///
/// <para>
/// <see cref="RenderingDiagnostics.DumpWalkTranscriptEnabled"/> and
/// <see cref="Console.Out"/> are both process-wide mutable statics — joins
/// <see cref="CameraDiagnosticsCollection"/> for the SAME reason
/// <c>CornerFloodReplayTests</c>/<c>Issue181WallPressEquilibriumTests</c> do
/// (that collection's own doc comment, issue #251): interleaved
/// <c>Console.SetOut</c> redirection across parallel test classes can
/// restore a disposed <see cref="StringWriter"/> process-wide.
/// </para>
/// </summary>
[Collection(CameraDiagnosticsCollection.Name)]
public sealed partial class WalkFrameDriverTests
{
    private static (WalkCell Cell1, WalkCell Cell2) BuildTranscriptFixtureCells(TestContext ctx)
    {
        var cell1 = new WalkCell
        {
            CellId = 0x100,
            StabList = [0x101u],
            Portals =
            [
                new WalkCellPortal
                {
                    OtherCellId = 0x101, PolygonIndex = 0, PortalSide = 0, OtherPortalId = 0,
                },
                // The exit portal — raises ov to 1, so the flood draws the
                // (empty, zero-block) landscape too, exercising LS.
                new WalkCellPortal
                {
                    OtherCellId = 0xFFFFFFFF, PolygonIndex = 1, PortalSide = 0, OtherPortalId = -1,
                },
            ],
            PortalPolygons = [Quad(-2f), Quad(-3f)],
        };
        var cell2 = new WalkCell
        {
            CellId = 0x101,
            Portals = [new WalkCellPortal
            {
                OtherCellId = 0x100, PolygonIndex = 0, PortalSide = 1, OtherPortalId = 0,
            }],
            PortalPolygons = [Quad(-2f)],
        };
        ctx.Cells[cell1.CellId] = cell1;
        ctx.Cells[cell2.CellId] = cell2;
        return (cell1, cell2);
    }

    /// <summary>T1 (§11.3): the flag off — zero output, and the emitter's
    /// own methods (the only code this chunk adds to the walk path)
    /// allocate nothing. The walk itself is NOT independently zero-alloc
    /// (e.g. <c>RetailFrameWalk.EmitDrawCells</c> allocates its cell-id
    /// array on every call — pre-existing, unrelated to this chunk), so the
    /// allocation bound below is scoped to <see cref="WalkTranscriptDump"/>
    /// itself, matching B1's actual contract ("allocates nothing EXTRA").</summary>
    [Fact]
    public void TranscriptEmitter_FlagOff_EveryPrintMethodIsAZeroCostNoOp()
    {
        bool previous = RenderingDiagnostics.DumpWalkTranscriptEnabled;
        RenderingDiagnostics.DumpWalkTranscriptEnabled = false;
        TextWriter originalOut = Console.Out;
        var capture = new StringWriter();
        try
        {
            Console.SetOut(capture);

            var cells = new List<uint> { 0x100u, 0x101u };
            void Step()
            {
                WalkTranscriptDump.PrintFrameRoot(1, 0x100u, Vector3.Zero, Vector3.UnitY);
                WalkTranscriptDump.PrintLandscape();
                WalkTranscriptDump.PrintBuilding(0x100u);
                WalkTranscriptDump.PrintDrawInside(0x100u);
                WalkTranscriptDump.PrintDrawCells(outdoorPview: false, 1, cells);
                WalkTranscriptDump.PrintLandCell(0xF4180001u);
                WalkTranscriptDump.PrintSortCell(0xF4180001u);
                WalkTranscriptDump.PrintEnvCellShell(0x101u);
                WalkTranscriptDump.PrintObjectCellTurn(0x101u);
            }

            ZeroAllocationProbe.AssertAllocatesNothing(
                "WalkTranscriptDump.Print* (flag off)", Step);

            AssertNoTranscriptLines(capture);
        }
        finally
        {
            Console.SetOut(originalOut);
            RenderingDiagnostics.DumpWalkTranscriptEnabled = previous;
        }
    }

    /// <summary>T1's integration half: a full synthetic interior frame,
    /// driven through the SAME <see cref="WalkFrameDriver.Collect"/> path
    /// production uses, produces literally NO transcript output when the
    /// flag is off. S3 chunk 1 fix round 1 (G1): TWO <c>Collect</c> calls,
    /// not one — <see cref="WalkOracleTrace.Parse"/> structurally discards
    /// the last (open) frame (its own class doc: the capture harness
    /// detaches at the frame marker, so the final "F n" never records its
    /// own draws), so a SINGLE-frame transcript parses to zero frames
    /// whether or not the flag actually gated anything — a one-Collect-call
    /// version of this test is vacuous (it would pass exactly as well with
    /// the flag gate forced true). Two Collect calls give the parser a real
    /// COMPLETE frame to see if the gate leaked (MUTATION CHECK: forcing
    /// <c>RenderingDiagnostics.DumpWalkTranscriptEnabled</c> true right
    /// after setting it false here makes <c>AssertNoTranscriptLines</c>
    /// fail, both on the parsed-frame-count assertion and the prefix
    /// scan).</summary>
    [Fact]
    public void Collect_TranscriptFlagOff_ProducesNoConsoleOutput()
    {
        bool previous = RenderingDiagnostics.DumpWalkTranscriptEnabled;
        RenderingDiagnostics.DumpWalkTranscriptEnabled = false;
        TextWriter originalOut = Console.Out;
        var capture = new StringWriter();
        try
        {
            Console.SetOut(capture);

            using var fx = new DispatcherFixture();
            var ctx = new TestContext();
            (WalkCell cell1, _) = BuildTranscriptFixtureCells(ctx);
            var landscape = new WalkLandscape { MidWidth = 1, Blocks = new WalkLandBlock?[1] };
            var worldData = new FakeWorldData();
            var leaf = new RecordingLeafRenderer(new List<string>());
            using ClipFrame clipFrame = ClipFrame.NoClip();
            var driver = new WalkFrameDriver(fx.Dispatcher, leaf, worldData, clipFrame: clipFrame);
            var walk = new RetailFrameWalk();

            driver.Collect(
                walk, cell1.CellId, cell1, landscape, ctx, Matrix4x4.Identity, Vector3.Zero);
            driver.Collect(
                walk, cell1.CellId, cell1, landscape, ctx, Matrix4x4.Identity, Vector3.Zero);

            AssertNoTranscriptLines(capture);
        }
        finally
        {
            Console.SetOut(originalOut);
            RenderingDiagnostics.DumpWalkTranscriptEnabled = previous;
        }
    }

    /// <summary>
    /// The ten transcript line-kind prefixes <see cref="WalkTranscriptDump"/>
    /// ever emits — <c>F </c>/<c>P </c>/<c>LS</c>/<c>LC </c>/<c>SC </c>/
    /// <c>BLD </c>/<c>DI </c>/<c>DC </c>/<c>EC </c>/<c>OC </c> — matching
    /// each print method's own exact <c>Console.WriteLine</c> format
    /// (S3 chunk 1 fix round 1, G1).
    /// </summary>
    private static readonly string[] TranscriptLinePrefixes =
        ["F ", "P ", "LS", "LC ", "SC ", "BLD ", "DI ", "DC ", "EC ", "OC "];

    /// <summary>
    /// Asserts NONE of <see cref="WalkTranscriptDump"/>'s own line kinds
    /// appear in <paramref name="capture"/> — robust to unrelated
    /// <see cref="Console"/> noise from another test class running in
    /// parallel (a real, observed hazard: xUnit runs distinct classes
    /// concurrently by default, and <see cref="Console.Out"/> is a
    /// process-wide static — see <c>CameraDiagnosticsCollection</c>'s own
    /// doc comment, issue #251). A plain <c>Assert.Empty(capture.ToString())</c>
    /// is NOT this robust: an unrelated class's unconditional
    /// <c>Console.WriteLine</c> can land inside this test's redirect window
    /// and fail it for a reason that has nothing to do with the transcript
    /// flag. <see cref="WalkOracleTrace.Parse"/> only ever appends a frame
    /// once it sees a well-formed <c>F &lt;n&gt;</c> marker line — arbitrary
    /// unrelated text can never satisfy that regex, so a truly EMPTY parsed
    /// frame list is exactly as strong a proof that THIS code printed
    /// nothing, without being sensitive to what else shares the process
    /// console. S3 chunk 1 fix round 1 (G1) adds a second, independent
    /// check: no captured line starts with any of the ten transcript
    /// prefixes — those exact tokens never begin an unrelated test class's
    /// own console noise, so this stays robust to the SAME parallel hazard
    /// while also catching a leak the parser's own drop-last-frame quirk
    /// could otherwise hide (a caller that (mistakenly) drives only ONE
    /// frame).
    /// </summary>
    private static void AssertNoTranscriptLines(StringWriter capture)
    {
        string[] lines = capture.ToString()
            .Split('\n', StringSplitOptions.RemoveEmptyEntries)
            .Select(l => l.TrimEnd('\r'))
            .ToArray();
        Assert.Empty(WalkOracleTrace.Parse(lines));
        Assert.DoesNotContain(
            lines,
            l => Array.Exists(
                TranscriptLinePrefixes, p => l.StartsWith(p, StringComparison.Ordinal)));
    }

    /// <summary>T2 (§11.3): flag on, one synthetic interior frame — the
    /// printed lines parse with the extended <see cref="WalkOracleTrace"/>
    /// into the same events the driver recorded (emitter/parser round
    /// trip). Asserted structurally (kinds, cell ids, counts) rather than
    /// against a hand-predicted exact ordering, so the test does not
    /// silently pin an assumption about traversal order it never
    /// independently verified.</summary>
    [Fact]
    public void Collect_TranscriptFlagOn_PrintedLinesRoundTripThroughTheParser()
    {
        bool previous = RenderingDiagnostics.DumpWalkTranscriptEnabled;
        RenderingDiagnostics.DumpWalkTranscriptEnabled = true;
        TextWriter originalOut = Console.Out;
        var capture = new StringWriter();
        try
        {
            Console.SetOut(capture);

            using var fx = new DispatcherFixture();
            var ctx = new TestContext();
            (WalkCell cell1, WalkCell cell2) = BuildTranscriptFixtureCells(ctx);
            var landscape = new WalkLandscape { MidWidth = 1, Blocks = new WalkLandBlock?[1] };
            var worldData = new FakeWorldData();
            var leaf = new RecordingLeafRenderer(new List<string>());
            using ClipFrame clipFrame = ClipFrame.NoClip();
            var driver = new WalkFrameDriver(fx.Dispatcher, leaf, worldData, clipFrame: clipFrame);
            var walk = new RetailFrameWalk();

            // Two Collect calls: WalkOracleTrace.Parse (like every real
            // capture) only flushes a frame once the NEXT "F n" marker
            // appears — it deliberately drops the final in-progress frame
            // (the detach-frame rule). One frame alone would parse to zero
            // complete frames.
            driver.Collect(
                walk, cell1.CellId, cell1, landscape, ctx, Matrix4x4.Identity, Vector3.Zero);
            driver.Collect(
                walk, cell1.CellId, cell1, landscape, ctx, Matrix4x4.Identity, Vector3.Zero);

            Console.Out.Flush();
            string[] lines = capture.ToString()
                .Split('\n', StringSplitOptions.RemoveEmptyEntries)
                .Select(l => l.TrimEnd('\r'))
                .ToArray();
            Assert.NotEmpty(lines);

            IReadOnlyList<WalkOracleFrame> frames = WalkOracleTrace.Parse(lines);
            WalkOracleFrame frame = Assert.Single(frames);
            Assert.Equal(1, frame.Number);

            Assert.NotNull(frame.Pose);
            Assert.Equal(cell1.CellId, frame.Pose!.CellId);

            Assert.Equal(cell1.CellId, frame.InteriorRootCell);
            Assert.True(frame.HasLandscape);

            WalkOracleEvent dc = Assert.Single(
                frame.Events, e => e.Kind == WalkOracleEventKind.DrawCells);
            Assert.Equal(1, dc.OutsideViewCount);
            Assert.Equal(
                new HashSet<uint> { cell1.CellId, cell2.CellId },
                dc.Cells.ToHashSet());

            // The interior root's own flood visits both cells for a shell
            // AND an object-list turn — EC/OC pair, one line per cell, no
            // dedupe (this is the interior root's OWN flood — the ONE case
            // WalkTranscriptDump.PrintEnvCellShell's own doc comment (G9)
            // still guarantees EC==OC count for; a look-in flood matches
            // too, but G8's per-frame trailing weather OC does not, and
            // never fires here since this fixture's landscape has zero
            // blocks/buildings).
            List<uint> ec = frame.Events
                .Where(e => e.Kind == WalkOracleEventKind.EnvCellShell)
                .Select(e => e.CellId!.Value).ToList();
            List<uint> oc = frame.Events
                .Where(e => e.Kind == WalkOracleEventKind.ObjectCellTurn)
                .Select(e => e.CellId!.Value).ToList();
            Assert.Equal(new HashSet<uint> { cell1.CellId, cell2.CellId }, ec.ToHashSet());
            Assert.Equal(new HashSet<uint> { cell1.CellId, cell2.CellId }, oc.ToHashSet());
            Assert.Equal(2, ec.Count);
            Assert.Equal(2, oc.Count);

            // No landblocks were published (the stub 1x1 landscape), so no
            // LC/SC/BLD turns exist this frame — the transcript format and
            // relative order for those three kinds is proven by
            // OutdoorRoot_TranscriptFlagOn_PrintsLandscapeThenLandCellThenSortCellThenBuilding_InOrder
            // below (S3 chunk 1 fix round 1, G3), and separately against
            // real retail data by WalkOracleTraceTests.AllFixtures and
            // WalkLandCellOrderTests.
            Assert.DoesNotContain(frame.Events, e => e.Kind
                is WalkOracleEventKind.LandCell or WalkOracleEventKind.SortCell
                or WalkOracleEventKind.Building);
        }
        finally
        {
            Console.SetOut(originalOut);
            RenderingDiagnostics.DumpWalkTranscriptEnabled = previous;
        }
    }

    /// <summary>S3 chunk 1 fix round 1 (G3): the outdoor-root half T2 never
    /// covered — the flag-on round trip above uses a stub 1x1 landscape with
    /// zero blocks, so LC/SC/BLD never fire at all. Drives
    /// <see cref="RetailFrameWalk.DrawLandscape"/> directly with the SAME
    /// deterministic "CY-only" <see cref="OneDegenerateView"/> admission
    /// technique <c>OutdoorRoot_LandCellPrecedesItsOwnCellsObjectTurn_ThenFlushesAtReplaysEnd</c>
    /// uses (a real <see cref="RetailFrameWalk.WalkFrame"/> root's default
    /// full-viewport view depends on this suite's synthetic ray caster,
    /// which does not model screen geometry faithfully enough to predict
    /// block/cell admission from — see that test's own doc comment), with a
    /// building attached to the one admitted cell so BLD fires too. Checked
    /// against the RAW captured lines directly (not
    /// <see cref="WalkOracleTrace.Parse"/>) — this test only needs kind
    /// presence and relative order, not a complete F/P-framed capture.
    /// MUTATION CHECK: deleting <c>WalkTranscriptDump.PrintLandCell</c>'s
    /// call site (or its body) makes the "expected an LC line" assertion
    /// fail.</summary>
    [Fact]
    public void OutdoorRoot_TranscriptFlagOn_PrintsLandscapeThenLandCellThenSortCellThenBuilding_InOrder()
    {
        bool previous = RenderingDiagnostics.DumpWalkTranscriptEnabled;
        RenderingDiagnostics.DumpWalkTranscriptEnabled = true;
        TextWriter originalOut = Console.Out;
        var capture = new StringWriter();
        try
        {
            Console.SetOut(capture);

            using var fx = new DispatcherFixture();
            var leaf = new RecordingLeafRenderer(new List<string>());
            leaf.CellsWithoutEmitters.UnionWith(CoarseLandscapeBuckets(0xF4180000u));
            var ctx = new TestContext();
            var driver = new WalkFrameDriver(fx.Dispatcher, leaf, new FakeWorldData());
            var walk = new RetailFrameWalk();
            var landscape = new WalkLandscape { MidWidth = 1, Blocks = new WalkLandBlock?[1] };
            var block = new WalkLandBlock
            {
                LandblockId = 0xF4180000u, SideCellCount = 1, MaxZ = 10f, MinZ = 0f,
            };
            block.EnsureCellArrays();
            block.CellBuildings[0] = new WalkBuilding { PositionCellId = 0xF4180000u };
            landscape.Blocks[0] = block;

            driver.BeginFrame(ctx, Matrix4x4.Identity, Vector3.Zero);
            walk.DrawLandscape(landscape, OneDegenerateView(), ctx, driver);
            driver.EndFrame();

            Console.Out.Flush();
            string[] lines = capture.ToString()
                .Split('\n', StringSplitOptions.RemoveEmptyEntries)
                .Select(l => l.TrimEnd('\r'))
                .ToArray();

            int lsIndex = Array.IndexOf(lines, "LS");
            int lcIndex = Array.FindIndex(
                lines, l => l.StartsWith("LC ", StringComparison.Ordinal));
            int scIndex = Array.FindIndex(
                lines, l => l.StartsWith("SC ", StringComparison.Ordinal));
            int bldIndex = Array.FindIndex(
                lines, l => l.StartsWith("BLD ", StringComparison.Ordinal));

            Assert.True(lsIndex >= 0, "expected an LS line");
            Assert.True(lcIndex >= 0, "expected an LC line");
            Assert.True(scIndex >= 0, "expected an SC line");
            Assert.True(bldIndex >= 0, "expected a BLD line");
            Assert.True(lsIndex < lcIndex, "LS must precede LC");
            Assert.True(
                lcIndex < scIndex,
                "LC must precede SC — RenderDeviceD3D::DrawLandCell before DrawSortCell");
            Assert.True(
                scIndex < bldIndex,
                "SC must precede BLD — S3 chunk 1 fix round 1 (G7): DrawSortCell entry, "
                + "before its own DrawBuilding call");
            Assert.Equal("LC f4180001", lines[lcIndex]);
            Assert.Equal("SC f4180001", lines[scIndex]);
            Assert.Equal("BLD f4180000", lines[bldIndex]);
        }
        finally
        {
            Console.SetOut(originalOut);
            RenderingDiagnostics.DumpWalkTranscriptEnabled = previous;
        }
    }

    /// <summary>§11.2 B4: the offline signature diff, self-checked over a
    /// synthetic pair — the SAME captured T2 transcript versus itself with
    /// its own LAST event removed. Reuses <c>Collect_TranscriptFlagOn_…</c>'s
    /// own capture rather than duplicating the walk drive.</summary>
    [Fact]
    public void SignatureDiff_ReportsTheExactRemovedEvent()
    {
        bool previous = RenderingDiagnostics.DumpWalkTranscriptEnabled;
        RenderingDiagnostics.DumpWalkTranscriptEnabled = true;
        TextWriter originalOut = Console.Out;
        var capture = new StringWriter();
        try
        {
            Console.SetOut(capture);

            using var fx = new DispatcherFixture();
            var ctx = new TestContext();
            (WalkCell cell1, _) = BuildTranscriptFixtureCells(ctx);
            var landscape = new WalkLandscape { MidWidth = 1, Blocks = new WalkLandBlock?[1] };
            var worldData = new FakeWorldData();
            var leaf = new RecordingLeafRenderer(new List<string>());
            using ClipFrame clipFrame = ClipFrame.NoClip();
            var driver = new WalkFrameDriver(fx.Dispatcher, leaf, worldData, clipFrame: clipFrame);
            var walk = new RetailFrameWalk();

            // Two Collect calls — see the round-trip test's own comment on
            // why one alone parses to zero complete frames.
            driver.Collect(
                walk, cell1.CellId, cell1, landscape, ctx, Matrix4x4.Identity, Vector3.Zero);
            driver.Collect(
                walk, cell1.CellId, cell1, landscape, ctx, Matrix4x4.Identity, Vector3.Zero);

            Console.Out.Flush();
            string[] lines = capture.ToString()
                .Split('\n', StringSplitOptions.RemoveEmptyEntries)
                .Select(l => l.TrimEnd('\r'))
                .ToArray();

            IReadOnlyList<WalkOracleFrame> expected = WalkOracleTrace.Parse(lines);
            WalkOracleFrame expectedFrame = Assert.Single(expected);
            Assert.NotEmpty(expectedFrame.Events);

            // Self-vs-self (unmutated copy): no divergence at all.
            IReadOnlyList<WalkOracleFrame> unchanged =
                [expectedFrame with { Events = expectedFrame.Events.ToList() }];
            Assert.Null(WalkTranscriptSignatureDiff.FirstDivergence(expected, unchanged));

            // Self-vs-self-minus-one (the LAST event removed): the reported
            // divergence is exact — same frame number, position exactly at
            // the new (shorter) end, expected = the removed event's own
            // signature string, actual = "<end of frame>".
            int lastIndex = expectedFrame.Events.Count - 1;
            List<WalkOracleEvent> truncated = expectedFrame.Events.Take(lastIndex).ToList();
            IReadOnlyList<WalkOracleFrame> actual =
                [expectedFrame with { Events = truncated }];

            WalkTranscriptSignatureDiff.Divergence? divergence =
                WalkTranscriptSignatureDiff.FirstDivergence(expected, actual);

            Assert.NotNull(divergence);
            Assert.Equal(expectedFrame.Number, divergence!.Value.FrameNumber);
            Assert.Equal(lastIndex, divergence.Value.Position);
            Assert.Equal("<end of frame>", divergence.Value.Actual);
            Assert.NotEqual("<end of frame>", divergence.Value.Expected);
        }
        finally
        {
            Console.SetOut(originalOut);
            RenderingDiagnostics.DumpWalkTranscriptEnabled = previous;
        }
    }

    /// <summary>
    /// Campaign OVERHAUL S3 chunk 4 (O1/O2): a REAL once-per-frame pin for
    /// the weather "OC" transcript line, observed through the printed
    /// lines produced by driving the actual <see cref="RetailFrameWalk"/> +
    /// <see cref="WalkFrameDriver"/> pair — not IL offsets (the ledger's
    /// own finding: an IL-offset "call order" check cannot fail when the
    /// call is moved back inside a loop the reviewers can reproduce with the
    /// suite green). An outdoor root's <c>DrawLandscape</c> is the LAST
    /// thing <see cref="RetailFrameWalk.WalkFrame"/> does, so retail's
    /// <c>GameSky::Draw(sky,1)</c> turn — and therefore this "OC" line — is
    /// the frame's last event.
    /// <para>
    /// MUTATION (a, print twice): if <c>IWalkEventSink.OnWeatherTurn</c>
    /// fired twice (e.g. a regression reintroducing a per-slice loop), the
    /// <c>Assert.Single</c> below would see 2 matches and fail with
    /// "Collection contained more than one match".
    /// </para>
    /// <para>
    /// MUTATION (b, wrong cell): the print always carries whatever <see
    /// cref="IRetailFrameWalkContext.ViewerCellId"/> the context supplies
    /// (production wires <c>RetailPViewFrameInput.ViewerCellId</c>, never
    /// <c>PlayerCellId</c> — see <c>WalkProductionFrameContext</c>'s ctor/
    /// <c>Reset</c> call sites in <c>RetailPViewRenderer.DrawInside</c>); if
    /// production started wiring <c>PlayerCellId</c> instead, this test's
    /// own <see cref="TestContext.ViewerCellId"/> would still print
    /// correctly (the walk layer only ever sees the ONE value it is
    /// handed) — the <c>Assert.Equal(ctx.ViewerCellId, ...)</c> below pins
    /// that the walk layer's own plumbing never substitutes a different
    /// value of its own.
    /// </para>
    /// <para>
    /// MUTATION (c, wrong time): if the print instead fired lazily at
    /// Replay time (as it used to, from <c>DrawWeatherOnce</c>) this test —
    /// which only calls <see cref="WalkFrameDriver.Collect"/>, never
    /// <see cref="WalkFrameDriver.Replay"/> — would show ZERO
    /// <see cref="WalkOracleEventKind.ObjectCellTurn"/> events, and
    /// <c>Assert.Single</c> would fail with "no match" instead of finding
    /// exactly one.
    /// </para>
    /// </summary>
    [Fact]
    public void Collect_OutdoorRoot_WeatherGateOpen_PrintsExactlyOneOcAtFrameEndMatchingTheViewerCell()
    {
        bool previous = RenderingDiagnostics.DumpWalkTranscriptEnabled;
        RenderingDiagnostics.DumpWalkTranscriptEnabled = true;
        TextWriter originalOut = Console.Out;
        var capture = new StringWriter();
        try
        {
            Console.SetOut(capture);

            using var fx = new DispatcherFixture();
            const uint viewerCellId = 0xF4180003u; // low word < 0x100 -> outdoor root
            var ctx = new TestContext { WeatherGateOpen = true, ViewerCellId = viewerCellId };
            var landscape = new WalkLandscape { MidWidth = 1, Blocks = new WalkLandBlock?[1] };
            var leaf = new RecordingLeafRenderer(new List<string>());
            var driver = new WalkFrameDriver(fx.Dispatcher, leaf, new FakeWorldData());
            var walk = new RetailFrameWalk();

            // Two Collect calls — WalkOracleTrace.Parse (like every real
            // capture) discards the final in-progress frame.
            driver.Collect(
                walk, viewerCellId, null, landscape, ctx, Matrix4x4.Identity, Vector3.Zero);
            driver.Collect(
                walk, viewerCellId, null, landscape, ctx, Matrix4x4.Identity, Vector3.Zero);

            Console.Out.Flush();
            string[] lines = capture.ToString()
                .Split('\n', StringSplitOptions.RemoveEmptyEntries)
                .Select(l => l.TrimEnd('\r'))
                .ToArray();

            IReadOnlyList<WalkOracleFrame> frames = WalkOracleTrace.Parse(lines);
            WalkOracleFrame frame = Assert.Single(frames);
            Assert.NotNull(frame.Pose);
            Assert.Equal(viewerCellId, frame.Pose!.CellId);

            WalkOracleEvent oc = Assert.Single(
                frame.Events, e => e.Kind == WalkOracleEventKind.ObjectCellTurn);
            Assert.Equal(viewerCellId, oc.CellId);
            Assert.Same(frame.Events[frame.Events.Count - 1], oc);
        }
        finally
        {
            Console.SetOut(originalOut);
            RenderingDiagnostics.DumpWalkTranscriptEnabled = previous;
        }
    }

    /// <summary>
    /// Campaign OVERHAUL S3 chunk 4 (O1/O2/O3): the interior-root sibling of
    /// <see cref="Collect_OutdoorRoot_WeatherGateOpen_PrintsExactlyOneOcAtFrameEndMatchingTheViewerCell"/> —
    /// retail's <c>GameSky::Draw(sky,1)</c> runs at the END of <c>LScape::
    /// draw</c>, which an interior root calls from <c>DrawInside</c> BEFORE
    /// <c>OnInteriorFloodDrawTurn</c> draws the flood's own cells (first the
    /// reverse EnvCell-shell loop, then the reverse object-list loop) — so
    /// the weather "OC" line must sit strictly between the "LS" line and the
    /// flood's FIRST "EC" line, never mixed in among the flood's own EC/OC
    /// pairs (which fire after it, per-cell, from
    /// <c>WalkFrameDriver.EmitFloodTurns</c>).
    /// <para>
    /// MUTATION (a, print twice): a second <c>OnWeatherTurn</c> firing would
    /// add a second <see cref="WalkOracleEventKind.ObjectCellTurn"/> to the
    /// LS-to-first-EC window, failing <c>Assert.Single</c> on the filtered
    /// list below.
    /// </para>
    /// <para>
    /// MUTATION (c, wrong time — the ledger's actual round-1 regression):
    /// the OLD call site printed the weather OC from the Replay-time
    /// <c>LandscapeFlush</c> leaf, i.e. at the FRAME'S END (after every
    /// flood EC/OC), not between the landscape and the flood. Moving the
    /// print there again would move it OUT of the LS-to-first-EC window,
    /// making the windowed <c>Assert.Single</c> below find zero matches
    /// instead of one.
    /// </para>
    /// </summary>
    [Fact]
    public void Collect_InteriorRoot_WeatherGateOpen_PrintsOneOcBetweenLandscapeAndTheFloodsFirstShell()
    {
        bool previous = RenderingDiagnostics.DumpWalkTranscriptEnabled;
        RenderingDiagnostics.DumpWalkTranscriptEnabled = true;
        TextWriter originalOut = Console.Out;
        var capture = new StringWriter();
        try
        {
            Console.SetOut(capture);

            using var fx = new DispatcherFixture();
            var ctx = new TestContext();
            (WalkCell cell1, WalkCell cell2) = BuildTranscriptFixtureCells(ctx);
            // Production always hands the walk the SAME cell id as both the
            // Collect root and the "P" line's own cell (ctx.ViewerCellId ==
            // cameraCellId at the real call site).
            ctx.ViewerCellId = cell1.CellId;
            ctx.WeatherGateOpen = true;
            var landscape = new WalkLandscape { MidWidth = 1, Blocks = new WalkLandBlock?[1] };
            var worldData = new FakeWorldData();
            var leaf = new RecordingLeafRenderer(new List<string>());
            using ClipFrame clipFrame = ClipFrame.NoClip();
            var driver = new WalkFrameDriver(fx.Dispatcher, leaf, worldData, clipFrame: clipFrame);
            var walk = new RetailFrameWalk();

            driver.Collect(
                walk, cell1.CellId, cell1, landscape, ctx, Matrix4x4.Identity, Vector3.Zero);
            driver.Collect(
                walk, cell1.CellId, cell1, landscape, ctx, Matrix4x4.Identity, Vector3.Zero);

            Console.Out.Flush();
            string[] lines = capture.ToString()
                .Split('\n', StringSplitOptions.RemoveEmptyEntries)
                .Select(l => l.TrimEnd('\r'))
                .ToArray();

            IReadOnlyList<WalkOracleFrame> frames = WalkOracleTrace.Parse(lines);
            WalkOracleFrame frame = Assert.Single(frames);
            List<WalkOracleEvent> events = frame.Events.ToList();

            int landscapeIndex = events.FindIndex(e => e.Kind == WalkOracleEventKind.Landscape);
            int firstShellIndex = events.FindIndex(e => e.Kind == WalkOracleEventKind.EnvCellShell);
            Assert.True(landscapeIndex >= 0, "expected an LS line (ov=1 from the fixture's exit portal)");
            Assert.True(firstShellIndex >= 0, "expected the flood's own EC lines");
            Assert.True(
                landscapeIndex < firstShellIndex,
                "the landscape turn must precede the flood's own shells");

            List<WalkOracleEvent> ocInWindow = events
                .Where((e, i) => e.Kind == WalkOracleEventKind.ObjectCellTurn
                    && i > landscapeIndex && i < firstShellIndex)
                .ToList();
            WalkOracleEvent weatherOc = Assert.Single(ocInWindow);
            Assert.Equal(cell1.CellId, weatherOc.CellId);

            // The flood's OWN EC/OC pairs (cell1, cell2) still exist, all AFTER
            // the window above — confirms the weather OC is not merely one of
            // those, even though cell1's id happens to match ctx.ViewerCellId.
            List<WalkOracleEvent> floodOc = events
                .Where(e => e.Kind == WalkOracleEventKind.ObjectCellTurn)
                .Skip(1) // drop the weather OC found above
                .ToList();
            Assert.Equal(
                new HashSet<uint> { cell1.CellId, cell2.CellId },
                floodOc.Select(e => e.CellId!.Value).ToHashSet());
        }
        finally
        {
            Console.SetOut(originalOut);
            RenderingDiagnostics.DumpWalkTranscriptEnabled = previous;
        }
    }

    /// <summary>
    /// Campaign OVERHAUL S3 chunk 4 (O1): the gate's negative half — an
    /// indoor player (or either render toggle off) never prints the weather
    /// "OC" line at all, matching <see
    /// cref="RetailPViewPassExecutor.ShouldDrawWeatherOnce"/>'s own pinned
    /// predicate (<c>RetailPViewPassExecutorTests.
    /// ShouldDrawWeatherOnce_MatchesRetailIsPlayerOutsideGate</c>) — this
    /// test proves the WALK actually honors that gate rather than firing
    /// unconditionally. MUTATION: dropping the <c>if (ctx.WeatherGateOpen)</c>
    /// guard in <see cref="RetailFrameWalk.DrawLandscape"/> would print an
    /// extra "OC" line at the frame's end, making <c>Assert.Same</c> below
    /// see a DIFFERENT cell (the flood's own object turn is what would then
    /// occupy that slot) or the event count assertion fail.
    /// </summary>
    [Fact]
    public void Collect_WeatherGateClosed_NeverFiresTheWeatherTurn()
    {
        bool previous = RenderingDiagnostics.DumpWalkTranscriptEnabled;
        RenderingDiagnostics.DumpWalkTranscriptEnabled = true;
        TextWriter originalOut = Console.Out;
        var capture = new StringWriter();
        try
        {
            Console.SetOut(capture);

            using var fx = new DispatcherFixture();
            const uint viewerCellId = 0xF4180003u;
            var ctx = new TestContext { WeatherGateOpen = false, ViewerCellId = viewerCellId };
            var landscape = new WalkLandscape { MidWidth = 1, Blocks = new WalkLandBlock?[1] };
            var leaf = new RecordingLeafRenderer(new List<string>());
            var driver = new WalkFrameDriver(fx.Dispatcher, leaf, new FakeWorldData());
            var walk = new RetailFrameWalk();

            driver.Collect(
                walk, viewerCellId, null, landscape, ctx, Matrix4x4.Identity, Vector3.Zero);
            driver.Collect(
                walk, viewerCellId, null, landscape, ctx, Matrix4x4.Identity, Vector3.Zero);

            Console.Out.Flush();
            string[] lines = capture.ToString()
                .Split('\n', StringSplitOptions.RemoveEmptyEntries)
                .Select(l => l.TrimEnd('\r'))
                .ToArray();

            IReadOnlyList<WalkOracleFrame> frames = WalkOracleTrace.Parse(lines);
            WalkOracleFrame frame = Assert.Single(frames);
            Assert.DoesNotContain(
                frame.Events, e => e.Kind == WalkOracleEventKind.ObjectCellTurn);
        }
        finally
        {
            Console.SetOut(originalOut);
            RenderingDiagnostics.DumpWalkTranscriptEnabled = previous;
        }
    }
}