using System;
using System.Numerics;

namespace AcDream.Core.Physics;

/// <summary>
/// L.2a slice 1 (2026-05-12) — runtime-toggleable physics probe flags.
/// Initialized from env vars at process start; flippable at runtime via
/// the DebugPanel mirror (or by direct assignment). Log call sites read
/// these statics so a checkbox toggle takes effect on the next resolve
/// without relaunching.
///
/// <para>
/// L.2d slice 1 (2026-05-13) adds <see cref="ProbeBuildingEnabled"/> +
/// the <see cref="LastBspHitPoly"/> diagnostic side-channel. Future
/// slices may fold the older <c>ACDREAM_DUMP_*</c> env vars into this
/// class for unified runtime toggling. Until then, those older flags
/// remain sticky-at-startup per their original implementation.
/// </para>
/// </summary>
public static class PhysicsDiagnostics
{
    /// <summary>
    /// When true, <see cref="PhysicsEngine.ResolveWithTransition"/> emits
    /// one structured <c>[resolve]</c> line per call: input + target +
    /// output position/cell, grounded state, contact-plane status,
    /// collision-normal validity, walkable polygon status, moving entity
    /// id. Initial state from <c>ACDREAM_PROBE_RESOLVE=1</c>.
    /// </summary>
    public static bool ProbeResolveEnabled { get; set; } =
        Environment.GetEnvironmentVariable("ACDREAM_PROBE_RESOLVE") == "1";

    /// <summary>
    /// When true, every change to <c>PlayerMovementController.CellId</c>
    /// emits one <c>[cell-transit]</c> line: old → new cell, current
    /// world position, reason tag (<c>resolver</c> / <c>teleport</c>).
    /// Initial state from <c>ACDREAM_PROBE_CELL=1</c>.
    /// </summary>
    public static bool ProbeCellEnabled { get; set; } =
        Environment.GetEnvironmentVariable("ACDREAM_PROBE_CELL") == "1";

    /// <summary>
    /// L.2d slice 1 (2026-05-13). When true, every BSP-shadow-entry hit
    /// attributed by <c>TransitionTypes.FindObjCollisions</c> emits a
    /// multi-line <c>[resolve-bldg]</c> entry: which part (partIdx vs 0),
    /// physics-BSP root radius vs visual AABB radius, world-space entity
    /// origin, and the specific hit polygon's vertices in both
    /// object-local and world space. Designed to distinguish the three
    /// L.2d hypotheses (wrong BSP loaded / over-registered parts /
    /// BSPQuery flaw) from a single Holtburg-doorway capture.
    ///
    /// <para>
    /// Also gates a one-time <c>[entity-source]</c> log line at every
    /// <c>ShadowObjects.Register(...)</c> call site in <c>GameWindow</c>
    /// — makes <c>entityId=0xA9B479</c> in a probe line greppable to its
    /// source registration within the same log file.
    /// </para>
    ///
    /// <para>
    /// Initial state from <c>ACDREAM_PROBE_BUILDING=1</c>. Mirrorable
    /// via <c>DebugVM.ProbeBuilding</c> when <c>ACDREAM_DEVTOOLS=1</c>.
    /// </para>
    ///
    /// <para>
    /// Spec: <c>docs/superpowers/specs/2026-05-13-l2d-cbuildingobj-collision-design.md</c>.
    /// </para>
    /// </summary>
    public static bool ProbeBuildingEnabled { get; set; } =
        Environment.GetEnvironmentVariable("ACDREAM_PROBE_BUILDING") == "1";

    /// <summary>
    /// L.2d slice 1 (2026-05-13). Diagnostic side-channel: the
    /// <see cref="ResolvedPolygon"/> that <see cref="BSPQuery"/>
    /// recorded for the most recent collision-normal write.
    /// <see cref="TransitionTypes.FindObjCollisions"/> clears this to
    /// <see langword="null"/> before each shadow-entry test and reads it
    /// back after, so emitting the <c>[resolve-bldg]</c> probe line can
    /// reference the actual hit poly without plumbing an out-param
    /// through BSPQuery's recursive private methods.
    ///
    /// <para>
    /// Written by <see cref="BSPQuery"/> only when
    /// <see cref="ProbeBuildingEnabled"/> is true, so this stays
    /// zero-cost in normal play. Cylinder collisions leave this
    /// <see langword="null"/> — the probe line emits
    /// <c>hitPoly: n/a (cylinder)</c> in that case.
    /// </para>
    ///
    /// <para>
    /// Not threadsafe — physics runs on a single thread. If that
    /// changes, this needs <c>[ThreadStatic]</c> or rethink. Deviation
    /// from spec component 4 (which described an out-param); the
    /// side-channel keeps BSPQuery's signature stable and the diagnostic
    /// path off the production code surface.
    /// </para>
    /// </summary>
    public static ResolvedPolygon? LastBspHitPoly { get; set; }

    /// <summary>
    /// B.6 slice 1 (2026-05-14) — baseline trace for the local-player
    /// server-initiated auto-walk path (issue #63). When true, the
    /// following events emit one-line <c>[autowalk-*]</c> logs:
    /// <list type="bullet">
    ///   <item><description><c>[autowalk-out]</c> on every <c>SendUse</c>
    ///     / <c>SendPickUp</c> the local player issues — these are the
    ///     packets that may trigger ACE's server-side <c>CreateMoveToChain</c>
    ///     when the target is out of <c>WithinUseRadius</c>.</description></item>
    ///   <item><description><c>[autowalk-mt]</c> on every inbound
    ///     <c>UpdateMotion</c> for the local player — captures the
    ///     <c>MovementType + MoveToPath + speed/runRate</c> ACE sends.</description></item>
    ///   <item><description><c>[autowalk-up]</c> on every inbound
    ///     <c>UpdatePosition</c> for the local player — answers "what's
    ///     ACE's broadcast cadence during auto-walk?"</description></item>
    /// </list>
    /// Initial state from <c>ACDREAM_PROBE_AUTOWALK=1</c>.
    ///
    /// <para>
    /// Spec: <c>docs/superpowers/specs/2026-05-14-phase-b6-design.md</c>
    /// §"Required investigation".
    /// </para>
    /// </summary>
    public static bool ProbeAutoWalkEnabled { get; set; } =
        Environment.GetEnvironmentVariable("ACDREAM_PROBE_AUTOWALK") == "1";

    /// <summary>
    /// 2026-05-16. Logs one line per `IsUseableTarget` call that takes
    /// the null-useability fallback path (creature pass / BF_DOOR pass /
    /// BF_LIFESTONE pass / etc.). Used to measure how often ACE's seed
    /// DB ships entities without `_useability` set — settles whether
    /// the fallback is live code or theoretical defense.
    ///
    /// <para>
    /// Retail has NO fallback; null/zero useability blocks Use entirely
    /// (acclient_2013_pseudo_c.txt:402923 ItemHolder::UseObject —
    /// IsUseable==0 falls through to "cannot be used" branch). Our
    /// fallback exists because ACE genuinely sends null for many seed
    /// weenies. The probe quantifies "many".
    /// </para>
    ///
    /// <para>Toggle via env var <c>ACDREAM_PROBE_USEABILITY_FALLBACK=1</c>
    /// or DebugPanel checkbox.</para>
    /// </summary>
    public static bool ProbeUseabilityFallbackEnabled { get; set; } =
        Environment.GetEnvironmentVariable("ACDREAM_PROBE_USEABILITY_FALLBACK") == "1";

    /// <summary>
    /// L.4-diag (2026-04-30) → promoted into <see cref="PhysicsDiagnostics"/>
    /// 2026-05-16 per CLAUDE.md "Code Structure Rules" §5 (diagnostic owner
    /// classes, not per-call-site env reads). Gates the <c>[steep-roof]</c>
    /// trace family that fires from four sites during the rooftop-bounce
    /// investigation:
    /// <list type="bullet">
    ///   <item><description><c>PhysicsEngine.ResolveWithTransition</c> —
    ///     <c>[steep-roof] KILL-VELOCITY-APPLIED</c> when retail-faithful
    ///     <c>kill_velocity</c> zeroes the body's velocity on steep-slope
    ///     impact.</description></item>
    ///   <item><description><c>TransitionTypes</c> (<c>FindEnvCollisions</c>
    ///     post-step) — per-frame plane-normal trace on the active
    ///     <see cref="CollisionInfo"/>.</description></item>
    ///   <item><description><c>PlayerMovementController</c> — two sites
    ///     emitting <c>[steep-roof]</c> + the per-frame bounce trace when
    ///     the post-collision velocity disagrees with retail.</description></item>
    /// </list>
    /// Initial state from <c>ACDREAM_DUMP_STEEP_ROOF=1</c>. Runtime-toggleable
    /// via the property setter; not yet wired to a DebugPanel checkbox (open
    /// follow-up if a debugging session calls for it).
    /// </summary>
    public static bool DumpSteepRoofEnabled { get; set; } =
        Environment.GetEnvironmentVariable("ACDREAM_DUMP_STEEP_ROOF") == "1";

    /// <summary>
    /// Indoor walking Phase 1 (2026-05-19). When true, emits one
    /// <c>[indoor-bsp]</c> line per <see cref="BSPQuery.FindCollisions"/>
    /// call made from <see cref="Transition.FindEnvCollisions"/>'s indoor
    /// cell-BSP branch. Captures the cell id, sphere local position,
    /// resulting <see cref="TransitionState"/>, and the hit poly's id,
    /// local-normal, and side-type — pinpoints why indoor collision
    /// returns spurious collisions (#84) and helps cross-check the
    /// outdoor-in approach path (#85).
    ///
    /// <para>
    /// While true, this also un-gates the diagnostic
    /// <see cref="LastBspHitPoly"/> side-channel inside
    /// <see cref="BSPQuery"/> — see the OR'd condition at every poly
    /// write site. Zero-cost when off.
    /// </para>
    ///
    /// <para>
    /// Initial state from <c>ACDREAM_PROBE_INDOOR_BSP=1</c>.
    /// Runtime-toggleable via DebugPanel.
    /// </para>
    ///
    /// <para>
    /// Spec: <c>docs/superpowers/specs/2026-05-19-indoor-walking-phase1-bsp-cluster-design.md</c>.
    /// </para>
    /// </summary>
    public static bool ProbeIndoorBspEnabled { get; set; } =
        Environment.GetEnvironmentVariable("ACDREAM_PROBE_INDOOR_BSP") == "1";

    /// <summary>
    /// Indoor walking Phase D follow-up (2026-05-19). When true, emits one
    /// <c>[cell-cache]</c> line each time <see cref="PhysicsDataCache.CacheCellStruct"/>
    /// caches a new EnvCell. Reports per-cell polygon counts and BSP root
    /// structure so the caller can cross-reference with <c>[indoor-bsp]</c>
    /// lines to distinguish between:
    /// <list type="bullet">
    ///   <item><description>Empty data (physicsPolyCount=0 or resolvedCount=0)
    ///     — candidate (a)/(c) in the poly=n/a investigation.</description></item>
    ///   <item><description>Non-zero polygon counts but bspRootPolyCount=0 at
    ///     root + tree has children — correct structure for non-leaf root,
    ///     leaves hold the poly refs; not a bug.</description></item>
    ///   <item><description>Non-zero polygon counts but bspRootPolyCount=0 at
    ///     root AND root is a leaf (bspRootHasChildren=false) — BSP leaf with
    ///     zero poly refs, candidate (b)/(d).</description></item>
    /// </list>
    /// This diagnostic fires at most once per EnvCell (cache is no-op after
    /// first population). It does NOT have a DebugPanel mirror yet — this is
    /// a one-shot capture tool, not a persistent toggle. Promote to full
    /// infrastructure after the root cause is identified.
    ///
    /// <para>Initial state from <c>ACDREAM_PROBE_CELL_CACHE=1</c>.</para>
    /// </summary>
    public static bool ProbeCellCacheEnabled { get; set; } =
        Environment.GetEnvironmentVariable("ACDREAM_PROBE_CELL_CACHE") == "1";

    /// <summary>
    /// ContactPlane retention spike (2026-05-20). When true, every write to
    /// <c>CollisionInfo.ContactPlane{,Valid,CellId,IsWater}</c> and
    /// <c>LastKnownContactPlane{,Valid,CellId,IsWater}</c> emits one
    /// <c>[cp-write]</c> line: field, old → new value, caller method (walked
    /// from the stack), and source line. Maps the per-frame lifecycle of the
    /// contact plane to confirm/refute the hypothesis that
    /// <c>FindEnvCollisions</c> indoor branch is rewriting CP every frame
    /// instead of retaining it across frames.
    ///
    /// <para>
    /// Only logs when the value actually changes (suppresses no-op writes to
    /// reduce log volume). Initial state from
    /// <c>ACDREAM_PROBE_CONTACT_PLANE=1</c>. Spike-only — remove once the fix
    /// lands and the diagnostic value is captured.
    /// </para>
    /// </summary>
    public static bool ProbeContactPlaneEnabled { get; set; } =
        Environment.GetEnvironmentVariable("ACDREAM_PROBE_CONTACT_PLANE") == "1";

    /// <summary>
    /// Indoor walking ISSUES #83 H-disambiguation spike (2026-05-21).
    /// When true, two diagnostic emissions activate:
    /// <list type="bullet">
    ///   <item><description>One <c>[walk-miss]</c> line per
    ///     <see cref="Transition.TryFindIndoorWalkablePlane"/> MISS
    ///     event, dumping foot world/local position, the nearest
    ///     walkable polygon in the cell (with XY-containment flag and
    ///     vertical gap), and whether the LandCell terrain at the same
    ///     XY would have grounded the player.</description></item>
    ///   <item><description>One <c>[floor-polys]</c> line per indoor
    ///     cell cached, enumerating each walkable-eligible polygon's
    ///     id, normal Z, local-XY bounding box, and plane Z at the
    ///     bbox center.</description></item>
    /// </list>
    /// Together these answer H1 (multi-cell iteration missing) vs H2
    /// (probe distance too short) vs H3 (poly absent /
    /// <c>walkable_hits_sphere</c> rejection) for the ISSUES #83
    /// stuck-falling bug. Spike-only — remove once the root cause is
    /// identified and the fix lands.
    ///
    /// <para>
    /// Initial state from <c>ACDREAM_PROBE_WALK_MISS=1</c>.
    /// No DebugPanel mirror — one-shot diagnostic.
    /// </para>
    ///
    /// <para>
    /// Spec: <c>docs/superpowers/specs/2026-05-21-indoor-walk-miss-probe-design.md</c>.
    /// </para>
    /// </summary>
    public static bool ProbeWalkMissEnabled { get; set; } =
        Environment.GetEnvironmentVariable("ACDREAM_PROBE_WALK_MISS") == "1";

    public static void LogCpBoolWrite(string field, bool oldValue, bool newValue)
    {
        var caller = GetCpCallerName();
        Console.WriteLine(System.FormattableString.Invariant(
            $"[cp-write] {field}: {oldValue} -> {newValue} caller={caller}"));
    }

    public static void LogCpPlaneWrite(string field, Plane oldPlane, Plane newPlane)
    {
        var caller = GetCpCallerName();
        Console.WriteLine(System.FormattableString.Invariant(
            $"[cp-write] {field}: n=({oldPlane.Normal.X:F3},{oldPlane.Normal.Y:F3},{oldPlane.Normal.Z:F3}) D={oldPlane.D:F3} -> n=({newPlane.Normal.X:F3},{newPlane.Normal.Y:F3},{newPlane.Normal.Z:F3}) D={newPlane.D:F3} caller={caller}"));
    }

    public static void LogCpCellIdWrite(string field, uint oldValue, uint newValue)
    {
        var caller = GetCpCallerName();
        Console.WriteLine(System.FormattableString.Invariant(
            $"[cp-write] {field}: 0x{oldValue:X8} -> 0x{newValue:X8} caller={caller}"));
    }

    /// <summary>
    /// Walks the stack to identify the first frame outside <c>CollisionInfo</c>
    /// and <c>PhysicsDiagnostics</c> — that's the actual caller writing the
    /// ContactPlane field. Format: <c>TypeName.MethodName:line</c> when file
    /// info is available, else just <c>TypeName.MethodName</c>. Walked with
    /// <c>fileNeeded=true</c> only when the probe flag is on, so zero cost
    /// when off.
    /// </summary>
    private static string GetCpCallerName()
    {
        // Skip 2: this method + the LogCp*Write helper that called it.
        var st = new System.Diagnostics.StackTrace(2, fNeedFileInfo: true);
        for (int i = 0; i < st.FrameCount; i++)
        {
            var f = st.GetFrame(i);
            var m = f?.GetMethod();
            if (m is null) continue;
            var typeName = m.DeclaringType?.Name ?? "?";
            if (typeName == "CollisionInfo" || typeName == "PhysicsDiagnostics") continue;
            int line = f?.GetFileLineNumber() ?? 0;
            return line > 0 ? $"{typeName}.{m.Name}:{line}" : $"{typeName}.{m.Name}";
        }
        return "?";
    }
}