using System.Text.RegularExpressions;
using AcDream.App.Physics;

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): source pins 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 STRUCTURE of the production source
    /// 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 LocalForcePositionTransactionIsNeverCalledFromThisFile()
        {
            string source = ReadSource("LiveEntityNetworkUpdateController.cs");

            // The name may still appear in a comment explaining what
            // replaced it (contract §"the deleted LocalForcePositionTransaction");
            // what must be gone is any actual call into it.
            Assert.DoesNotContain(
                "LocalForcePositionTransaction.Apply(",
                source,
                StringComparison.Ordinal);
        }

        [Fact]
        public void GenericTailWriteIsNeverDuplicatedForTheLocalForcePositionPath()
        {
            string source = ReadSource("LiveEntityNetworkUpdateController.cs");

            // 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.
            Assert.Single(
                Regex.Matches(source, @"entity\.SetPosition\(worldPos\);")
                    .Cast<Match>());
        }

        [Fact]
        public void CommittedOrDeferredCellReturnsBeforeReachingTheGenericTail()
        {
            string source = ReadSource("LiveEntityNetworkUpdateController.cs");

            // 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.
            Assert.Matches(
                new Regex(
                    @"ObserveAcceptedLocalPosition\(\s*"
                        + @"update\.Position\.LandblockId\);\s*return;",
                    RegexOptions.Singleline),
                source);
        }

        /// <summary>
        /// AP-140 (retired 2026-08-04): the accepted-Position routing gate
        /// for the free-flight/landing decision must select the hard snap on
        /// retail's CONTACT predicate
        /// (<c>InterpolationManager::adjust_offset</c> @0x00555D30 gates its
        /// whole body on <c>transient_state &amp; 1</c> @0x00555D52, and bit 0
        /// is <c>CONTACT_TS</c>), not on the client <c>Airborne</c> flag,
        /// which is <c>!Body.OnWalkable</c> — WALKABILITY, a strictly wider
        /// set that also captures a remote sliding on a steep face.
        ///
        /// <para>
        /// C4 route 4b-3's OnPosition collapse (2026-08-04) dissolved
        /// <c>OnPosition</c>'s former standalone player-remote LANDING
        /// TRANSITION block — which used to carry its own
        /// <c>if (!rmState.Body.InContact)</c> copy of this gate — into
        /// <c>ApplyRemoteContactRouting</c>'s free-flight carve-out, now the
        /// ONE site (for every guid) that decides this. The gate itself did
        /// not move in spirit, only in address: this pin follows it there.
        /// </para>
        ///
        /// <para>
        /// A source pin rather than a behavioural fixture for the reason this
        /// class already documents: the controller's dependency set is
        /// composition-only. The gate inside <c>ApplyRemoteContactRouting</c>
        /// — a static method, so reachable — IS covered behaviourally, in
        /// <c>LiveEntityNetworkRemoteSteadyStateIntegrationTests</c>. Restore
        /// <c>if (rmState.Airborne)</c> or <c>if (remote.Airborne)</c> here
        /// and this test fails.
        /// </para>
        /// </summary>
        [Fact]
        public void PlayerRemoteLandingSnapSelectsOnContactNotOnWalkability()
        {
            string source = ReadSource("LiveEntityNetworkUpdateController.cs");

            Assert.Contains(
                "if (!remote.Body.InContact)",
                source,
                StringComparison.Ordinal);
            // `rmState.Airborne` survives as a WRITE target and in prose (the
            // block's own comment explains why it is deliberately not cleared
            // there); what must never come back is reading it as the gate.
            Assert.DoesNotContain(
                "if (rmState.Airborne)",
                source,
                StringComparison.Ordinal);
            Assert.DoesNotContain(
                "if (remote.Airborne)",
                source,
                StringComparison.Ordinal);
        }

        private static string ReadSource(string fileName)
        {
            DirectoryInfo? directory = new(AppContext.BaseDirectory);
            while (directory is not null)
            {
                if (File.Exists(Path.Combine(directory.FullName, "AcDream.slnx")))
                {
                    return File.ReadAllText(Path.Combine(
                        directory.FullName,
                        "src",
                        "AcDream.App",
                        "Physics",
                        fileName));
                }

                directory = directory.Parent;
            }

            throw new DirectoryNotFoundException("Could not find AcDream.slnx.");
        }
    }
}