using System.Collections.Generic;
using System.Numerics;
using AcDream.Core.Physics;
using AcDream.Core.Physics.Motion;
using DatReaderWriter.DBObjs;
using DatReaderWriter.Enums;
using DatReaderWriter.Types;

namespace AcDream.Core.Tests.Physics.Motion;

/// <summary>
/// R1-P4 — the frame-advance core: <c>update_internal</c> (0x005255d0),
/// <c>update</c> (0x00525b80), <c>advance_to_next_animation</c>
/// (0x005252b0), <c>execute_hooks</c> (0x00524830) — gaps
/// G3/G4/G5/G6/G8/G9/G19.
///
/// Skeleton per the ACE-verified structure (P0-pins.md): overshoot →
/// clamp to the RAW high/low frame + leftover carry + animDone →
/// per-crossed-frame pose/physics/hook loop → AnimDone gate
/// (list HEAD != first_cyclic) → advance (pose-out both directions,
/// forward wraps to first_cyclic, reverse wraps to the LIST TAIL) →
/// carry the leftover (P0 pin) → loop. NO safety cap, NO boundary
/// epsilon.
/// </summary>
public class CSequenceUpdateTests
{
    private sealed class MapLoader : IAnimationLoader
    {
        private readonly Dictionary<uint, Animation> _map = new();
        public void Add(uint id, Animation anim) => _map[id] = anim;
        public Animation? LoadAnimation(uint id) => _map.TryGetValue(id, out var a) ? a : null;
    }

    private sealed class RecordingHookQueue : IAnimHookQueue
    {
        public readonly List<string> Events = new();
        public void AddAnimHook(AnimationHook hook)
            => Events.Add($"hook:{((TaggedHook)hook).Tag}:{hook.Direction}");
        public void AddAnimDoneHook() => Events.Add("ANIMDONE");
    }

    /// <summary>Hook subclass carrying a test tag (frame index).</summary>
    private sealed class TaggedHook : AnimationHook
    {
        public string Tag = "";
        public override AnimationHookType HookType => (AnimationHookType)0;
    }

    /// <summary>numFrames frames; one Forward-direction tagged hook per frame.</summary>
    private static Animation MakeAnim(int numFrames, bool posFrames = false, string hookPrefix = "f")
    {
        var anim = new Animation();
        for (int f = 0; f < numFrames; f++)
        {
            var pf = new AnimationFrame(1u);
            pf.Frames.Add(new Frame { Origin = new Vector3(f, 0, 0), Orientation = Quaternion.Identity });
            pf.Hooks.Add(new TaggedHook { Tag = $"{hookPrefix}{f}", Direction = AnimationHookDir.Both });
            anim.PartFrames.Add(pf);
            if (posFrames)
                anim.PosFrames.Add(new Frame { Origin = new Vector3(1, 0, 0), Orientation = Quaternion.Identity });
        }
        return anim;
    }

    private static AnimData Ad(uint animId, float framerate = 30f, int low = 0, int high = -1)
    {
        QualifiedDataId<Animation> qid = animId;
        return new AnimData { AnimId = qid, LowFrame = low, HighFrame = high, Framerate = framerate };
    }

    private static (CSequence seq, RecordingHookQueue hooks) Cyclic(int frames, float framerate = 30f)
    {
        var loader = new MapLoader();
        loader.Add(1u, MakeAnim(frames));
        var seq = new CSequence(loader);
        var hooks = new RecordingHookQueue();
        seq.HookObj = hooks;
        seq.AppendAnimation(Ad(1u, framerate));
        return (seq, hooks);
    }

    // ── forward advance basics (G3) ─────────────────────────────────────

    [Fact]
    public void Forward_SingleTick_AdvancesOneFrame_FiresExitedFrameHook()
    {
        var (seq, hooks) = Cyclic(5);

        seq.Update(1.0 / 30.0, null);

        Assert.Equal(1.0, seq.FrameNumber, 9);
        Assert.Equal(new[] { "hook:f0:Both" }, hooks.Events);
    }

    [Fact]
    public void Forward_ExactBoundaryLanding_NoAdvance()
    {
        // Boundary test is STRICT (>): landing exactly at high_frame+0.0
        // integer positions must NOT advance (the G3 bug class: acdream's
        // old epsilon-shifted boundary reclassified these).
        var (seq, hooks) = Cyclic(5);
        seq.FrameNumber = 3.5;

        seq.Update(0.5 / 30.0, null); // lands exactly at 4.0 == high_frame

        Assert.Equal(4.0, seq.FrameNumber, 9);
        Assert.Equal(new[] { "hook:f3:Both" }, hooks.Events); // crossed 3→4
        Assert.DoesNotContain("ANIMDONE", hooks.Events);
    }

    [Fact]
    public void Forward_CyclicWrap_NoAnimDone_RestartsAtStartingFrame()
    {
        // Single cyclic node: overshoot wraps to itself via first_cyclic;
        // head == first_cyclic → NO AnimDoneHook (G5's structural gate).
        var (seq, hooks) = Cyclic(3);
        seq.FrameNumber = 2.0;

        seq.Update(1.0 / 30.0, null); // 2→3 > high(2) → clamp, advance, wrap

        Assert.Equal(0.0, seq.FrameNumber, 9);
        Assert.DoesNotContain("ANIMDONE", hooks.Events);
        Assert.Same(seq.FirstCyclic, seq.CurrAnim);
    }

    // ── multi-node fast-forward + the P0-pinned carry (G3/G5) ───────────

    [Fact]
    public void Forward_LinkToCycle_FiresAnimDone_AndCarriesLeftover()
    {
        // link (2 frames) + cycle (4 frames): a 0.1s tick (3 frames at
        // 30fps) exhausts the link (2 frames) and carries 1 frame of time
        // into the cycle. Retail order: link's crossed-frame hooks →
        // AnimDoneHook (head != first_cyclic) → cycle's crossed hooks.
        var loader = new MapLoader();
        loader.Add(1u, MakeAnim(2, hookPrefix: "link"));
        loader.Add(2u, MakeAnim(4, hookPrefix: "cyc"));
        var seq = new CSequence(loader);
        var hooks = new RecordingHookQueue();
        seq.HookObj = hooks;
        seq.AppendAnimation(Ad(1u)); // link — first_cyclic slides…
        seq.AppendAnimation(Ad(2u)); // …to the cycle

        seq.Update(0.1, null); // 3 frames of time

        // link: FrameNumber 0→3, clamp to high(1), leftover = 1 frame;
        // crossing fires link f0 only (floor(1)>0), then AnimDone, then
        // advance → cycle at starting(0); carry 1/30 → cycle 0→1 fires cyc f0.
        Assert.Equal(new[] { "hook:link0:Both", "ANIMDONE", "hook:cyc0:Both" }, hooks.Events);
        Assert.Equal(1.0, seq.FrameNumber, 6); // the carry (P0 pin) — zeroing would leave 0.0
        Assert.Same(seq.FirstCyclic, seq.CurrAnim); // now inside the cycle
    }

    // ── reverse playback (G3/G9) ────────────────────────────────────────

    [Fact]
    public void Reverse_DescendingHooks_BackwardDirection()
    {
        // Natively-reverse node (framerate −30): seeded at starting =
        // high+1 = 5. Each tick fires the hook of the frame being LEFT
        // (the pre-tick floor index), descending; the very first tick's
        // index (5 = high+1) is OOB → null part frame → no hook, exactly
        // the retail structure.
        var (seq, hooks) = Cyclic(5, framerate: -30f);
        Assert.Equal(5.0, seq.FrameNumber, 9); // get_starting_frame = high+1

        seq.Update(1.0 / 30.0, null); // 5→4 (leaves OOB index 5 — nothing)
        seq.Update(1.0 / 30.0, null); // 4→3 (leaves frame 4)
        seq.Update(1.0 / 30.0, null); // 3→2 (leaves frame 3)

        Assert.Equal(2.0, seq.FrameNumber, 9);
        Assert.Equal(new[] { "hook:f4:Both", "hook:f3:Both" }, hooks.Events);
    }

    [Fact]
    public void Reverse_AdvanceWrapsToListTail()
    {
        // Two nodes A(reverse),B(forward): exhausting A backward wraps
        // curr_anim to the LIST TAIL (B) — retail's asymmetric wrap (G9).
        var loader = new MapLoader();
        loader.Add(1u, MakeAnim(3, hookPrefix: "a"));
        loader.Add(2u, MakeAnim(4, hookPrefix: "b"));
        var seq = new CSequence(loader);
        var hooks = new RecordingHookQueue();
        seq.HookObj = hooks;
        seq.AppendAnimation(Ad(1u, framerate: -30f)); // A — curr seeds here
        seq.AppendAnimation(Ad(2u));                  // B = first_cyclic = tail
        seq.FrameNumber = 0.5;                        // mid-window of A

        seq.Update(0.02, null); // frametime = −0.6 → crosses low(0)

        // After the reverse advance, curr must have left A via the TAIL
        // wrap (B), whatever the carry then does within B.
        Assert.NotNull(seq.CurrAnim);
        Assert.Equal(3, seq.CurrAnim!.HighFrame); // B (4 frames → high 3)
    }

    // ── stationary / degenerate (G8 + else-branch) ──────────────────────

    [Fact]
    public void ZeroFramerate_PhysicsOnlyAndReturn()
    {
        var (seq, hooks) = Cyclic(3, framerate: 0f);
        seq.SetVelocity(new Vector3(2, 0, 0));
        var frame = new Frame { Origin = Vector3.Zero, Orientation = Quaternion.Identity };

        seq.Update(0.5, frame);

        // frametime == 0 → apply_physics(frame, elapsed, elapsed) then return.
        Assert.Equal(1.0f, frame.Origin.X, 5);
        Assert.Empty(hooks.Events);
        Assert.Equal(0.0, seq.FrameNumber, 9);
    }

    [Fact]
    public void EmptyList_Update_AppliesAccumulatedPhysics()
    {
        // update (0x00525b80): empty anim_list + frame != null →
        // apply_physics(frame, elapsed, elapsed) — free-fall/knockback
        // with no animation (G8).
        var seq = new CSequence(new MapLoader());
        seq.SetVelocity(new Vector3(0, 3, 0));
        var frame = new Frame { Origin = Vector3.Zero, Orientation = Quaternion.Identity };

        seq.Update(2.0, frame);

        Assert.Equal(6.0f, frame.Origin.Y, 5);
    }

    // ── root motion into the caller Frame (G7 wiring half) ──────────────

    [Fact]
    public void Forward_PosFrames_CombinedIntoCallerFrame()
    {
        // Each crossed frame combines the node's pos_frame into the caller
        // Frame (retail root motion): 2 crossed frames → +2 X.
        var loader = new MapLoader();
        loader.Add(1u, MakeAnim(5, posFrames: true));
        var seq = new CSequence(loader);
        seq.AppendAnimation(Ad(1u));
        var frame = new Frame { Origin = Vector3.Zero, Orientation = Quaternion.Identity };

        seq.Update(2.0 / 30.0, frame); // crosses frames 0 and 1

        Assert.Equal(2.0f, frame.Origin.X, 5);
        Assert.Equal(2.0, seq.FrameNumber, 9);
    }

    // ── update entry contract (G19) ─────────────────────────────────────

    [Fact]
    public void Update_RunsApricot_TrimmingConsumedLinkNodes()
    {
        // After the link→cycle advance, apricot (called by update) frees
        // the consumed link node.
        var loader = new MapLoader();
        loader.Add(1u, MakeAnim(2, hookPrefix: "link"));
        loader.Add(2u, MakeAnim(4, hookPrefix: "cyc"));
        var seq = new CSequence(loader);
        seq.AppendAnimation(Ad(1u));
        seq.AppendAnimation(Ad(2u));
        Assert.Equal(2, seq.Count);

        seq.Update(0.1, null); // exhausts the link, advances into the cycle

        Assert.Equal(1, seq.Count); // link trimmed by apricot
        Assert.Same(seq.FirstCyclic, seq.CurrAnim);
    }
}