using System.Reflection;
using System.Reflection.Emit;
using AcDream.App.Tests.Architecture;
using AcDream.App.Physics;
using AcDream.Core.World;
using AcDream.Runtime.Session;

namespace AcDream.App.Tests.Physics;

public sealed class LiveEntityNetworkBranchRoutingTests
{
    [Fact]
    public void Vector_ProjectileStopsCanonicalAndOrdinaryRoutes()
    {
        var calls = new List<string>();

        LiveEntityVectorRoute route = LiveEntityVectorRouter.Route(
            () => { calls.Add("projectile"); return true; },
            () => { calls.Add("canonical"); return true; },
            () => calls.Add("ordinary"));

        Assert.Equal(LiveEntityVectorRoute.Projectile, route);
        Assert.Equal(["projectile"], calls);
    }

    [Fact]
    public void Vector_CanonicalBodyRunsOnlyAfterProjectileDeclines()
    {
        var calls = new List<string>();

        LiveEntityVectorRoute route = LiveEntityVectorRouter.Route(
            () => { calls.Add("projectile"); return false; },
            () => { calls.Add("canonical"); return true; },
            () => calls.Add("ordinary"));

        Assert.Equal(LiveEntityVectorRoute.CanonicalBody, route);
        Assert.Equal(["projectile", "canonical"], calls);
    }

    [Fact]
    public void Vector_OrdinaryRemoteIsTheLastFallback()
    {
        var calls = new List<string>();

        LiveEntityVectorRoute route = LiveEntityVectorRouter.Route(
            () => { calls.Add("projectile"); return false; },
            () => { calls.Add("canonical"); return false; },
            () => calls.Add("ordinary"));

        Assert.Equal(LiveEntityVectorRoute.OrdinaryRemote, route);
        Assert.Equal(["projectile", "canonical", "ordinary"], calls);
    }

    // C4 route 2 (2026-08-03): LocalForcePositionTransaction and its
    // ForcePosition_* coverage here are RETIRED, not adapted — the class is
    // deleted outright (docs/research/2026-08-03-c4-route-2-contract.md
    // §"The contract" item 2). Its three jobs (ownership validation, the
    // blip/commit, and the exactly-once ack including the displaced-
    // authority case its trailing isCurrent() covered) are now properties of
    // the Runtime-owned RuntimeAcceptedPositionDriveController and are tested
    // there: tests/AcDream.Runtime.Tests/Session/RuntimeAcceptedPositionDriveControllerTests.cs.

    /// <summary>
    /// R8 review fix (2026-08-03): assembly checks for the generic-tail
    /// double-write guard in <c>LiveEntityNetworkUpdateController.OnPosition</c>.
    /// A full behavioral fixture is impractical here for the SAME reason
    /// <c>C3cF1ProductionWiringTests</c> gives — the controller's dependency
    /// set is composition-only (67+ collaborators wired only by
    /// <c>SessionPlayerComposition</c>) — so this follows that file's exact
    /// established pattern: assert the compiled call/return structure rather
    /// than construct the class. The Runtime-level behavioral
    /// coverage for the seam itself lives in
    /// RuntimeAcceptedPositionDriveControllerTests; these pins are what stop
    /// this App-layer call site from silently reintroducing the retired
    /// duplicate-write authority (the deleted LocalForcePositionTransaction
    /// pair + the generic render-tail writing the SAME accepted Position a
    /// second time — 670f307c's divergence class).
    /// </summary>
    public sealed class LiveEntityNetworkUpdateControllerForcePositionWiringTests
    {
        [Fact]
        public void GenericTailWriteIsNeverDuplicatedForTheLocalForcePositionPath()
        {
            // The generic render-tail's WorldEntity write is the ONE
            // remaining writer of an accepted Position — it must serve
            // remotes only, never a second local-player write alongside the
            // Runtime-committed one.
            MethodInfo genericTail = typeof(LiveEntityNetworkUpdateController)
                .GetMethod(
                    "TryApplyGenericRemoteRenderPose",
                    BindingFlags.Static | BindingFlags.NonPublic)
                ?? throw new MissingMethodException(
                    typeof(LiveEntityNetworkUpdateController).FullName,
                    "TryApplyGenericRemoteRenderPose");
            Assert.Single(
                CompiledCallGraph.Read(genericTail),
                call => call.Target.DeclaringType == typeof(WorldEntity)
                    && call.Target.Name == nameof(WorldEntity.SetPosition));
        }

        [Fact]
        public void CommittedOrDeferredCellReturnsBeforeReachingTheGenericTail()
        {
            // The Committed/DeferredCell branch must still return
            // immediately after its two preserved side effects — a missing
            // `return` here would fall through into the generic tail below
            // and resurrect the double-write.
            MethodInfo onPosition = typeof(LiveEntityNetworkUpdateController)
                .GetMethod(
                    "OnPosition",
                    BindingFlags.Instance | BindingFlags.Public)
                ?? throw new MissingMethodException(
                    typeof(LiveEntityNetworkUpdateController).FullName,
                    "OnPosition");
            IReadOnlyList<CompiledCall> calls = CompiledCallGraph.Read(onPosition);
            CompiledCall drive = Assert.Single(calls, call =>
                call.Target.DeclaringType
                    == typeof(RuntimeAcceptedPositionDriveController)
                && call.Target.Name == "TryExecuteAcceptedLocalPosition");
            CompiledCall observe = calls.First(call =>
                call.Offset > drive.Offset
                && call.Target.Name == "ObserveAcceptedLocalPosition");
            IReadOnlyList<CompiledInstruction> instructions =
                CompiledCallGraph.ReadInstructions(onPosition);
            int observeInstruction = instructions
                .Select((instruction, index) => (instruction, index))
                .Single(pair => pair.instruction.Offset == observe.Offset)
                .index;

            Assert.Equal(OpCodes.Ret, instructions[observeInstruction + 1].OpCode);
        }
    }
}