using System;
using UnityEngine;

namespace IdleSpectator;

public static partial class InterestDirector
{
    private const float RelatedPersonalCombatCutSeconds = 3f;
    private const float PersonalCombatCutSeconds = 6f;

    private static bool CanSwitchTo(InterestCandidate candidate, float onCurrent, float sinceSwitch)
    {
        if (candidate == null)
        {
            return false;
        }

        // Same FixedDwell beat already watched on this subject - never cut back in.
        if (InterestVariety.IsBeatCooled(candidate))
        {
            InterestDropLog.Record("beat_cooldown", candidate.HappinessEffectId ?? candidate.AssetId ?? candidate.Key);
            return false;
        }

        if (candidate != _current && InterestVariety.IsEditorialReplayCooled(candidate))
        {
            InterestDropLog.Record("editorial_replay", candidate.Label ?? candidate.Key);
            return false;
        }
        if (candidate != _current && InterestVariety.IsExactReplayCooled(candidate))
        {
            InterestDropLog.Record("exact_replay", candidate.Label ?? candidate.Key);
            return false;
        }

        if (candidate != _current && InterestVariety.IsCombatRunBlocked(candidate))
        {
            InterestDropLog.Record("combat_run_budget", candidate.Label ?? candidate.Key);
            return false;
        }

        if (candidate != _current
            && !StoryScheduler.MayUseCombatShot(candidate))
        {
            InterestDropLog.Record(
                "episode_combat_budget",
                candidate.Label ?? candidate.Key);
            return false;
        }

        if (candidate != _current
            && !NarrativeExposureLedger.MayPresent(candidate))
        {
            InterestDropLog.Record(
                "combat_exposure_budget",
                candidate.Label ?? candidate.Key);
            return false;
        }

        if (_current == null)
        {
            return IsWorthWatchingNow(candidate, Time.unscaledTime, selectingDuringGrace: false);
        }

        float now = Time.unscaledTime;

        // Same fighter, new attack_target: do not cut Duel A-vs-B → A-vs-C mid-scrap.
        if (IsCombatPartnerSwapNoise(_current, candidate))
        {
            InterestDropLog.Record(
                "combat_partner_hold",
                $"cur={_current.Key} next={candidate.Key}");
            return false;
        }

        // Crisis signal tip (war / disaster / outbreak) owns the camera against Mass/Battle scraps.
        // Must run before crisis cut-in: a leftover war crisis can MatchCrisis(Mass) while a
        // small WarFront tip does not. Drop reason keeps war_theater_hold alias for harness.
        if (StoryPlanner.IsCrisisCameraSignal(_current)
            && candidate.Completion == InterestCompletionKind.CombatActive)
        {
            string holdReason = _current.Completion == InterestCompletionKind.WarFront
                ? "war_theater_hold"
                : "crisis_theater_hold";
            InterestDropLog.Record(
                holdReason,
                $"cur={_current.Key} next={candidate.Key} evt={candidate.EventStrength:0.#}");
            return false;
        }

        // Crisis-owned tips (esp. forced epilogue_crisis) may cut without score-margin wars
        // against aftermath / ambient peers that outscore the closer on raw EventStrength.
        if (StoryPlanner.CrisisActive
            && StoryPlanner.MatchesCrisis(candidate)
            && !StoryPlanner.MatchesCrisis(_current)
            && IsWorthWatchingNow(candidate, now, selectingDuringGrace: InQuietGrace))
        {
            return true;
        }

        // Live fight: hold until cold (see who wins), unless something extremely urgent cuts in.
        // Same-arc theater refresh / absorb still allowed. WarFront on the same kingdom
        // theater may reclaim the chapter (Mass → War) without waiting for combat cold.
        if (CombatFightIsHot(_current, now)
            && !IsSameStoryArc(_current, candidate)
            && candidate.Completion != InterestCompletionKind.CombatActive)
        {
            bool warTheaterReclaim = candidate.Completion == InterestCompletionKind.WarFront
                                     && StickyScoreboard.SharesKingdomTheater(_current, candidate);
            if (warTheaterReclaim)
            {
                return IsWorthWatchingNow(candidate, now, selectingDuringGrace: false);
            }

            if (IsPersonalStoryInterrupt(candidate))
            {
                float personalDelay = TouchesCurrentPrincipal(candidate)
                    ? RelatedPersonalCombatCutSeconds
                    : PersonalCombatCutSeconds;
                if (onCurrent >= personalDelay
                    && IsWorthWatchingNow(candidate, now, selectingDuringGrace: false))
                {
                    InterestDropLog.Record(
                        "combat_story_cut",
                        $"cur={_current.Key} next={candidate.Key} on={onCurrent:0.#}");
                    return true;
                }
            }

            if (IsCombatUrgentPeer(_current, candidate))
            {
                InterestDropLog.Record(
                    "combat_urgent_cut",
                    $"cur={_current.Key} next={candidate.Key} evt={candidate.EventStrength:0.#}");
                return IsWorthWatchingNow(candidate, now, selectingDuringGrace: false);
            }

            InterestDropLog.Record(
                "combat_hold",
                $"cur={_current.Key} next={candidate.Key}");
            return false;
        }

        // Once an episode has a meaningful related development ready, let it reclaim the
        // camera from ordinary unrelated material after a brief visual settling beat.
        // Legitimate critical/payoff interruptions and live-combat holds remain protected.
        if (StoryScheduler.ActiveEpisode != null
            && onCurrent >= 0.75f)
        {
            NarrativeThread activeThread =
                NarrativeStoryStore.Thread(StoryScheduler.ActiveEpisode.ThreadId);
            NarrativeInterruptClass nextNarrativeClass =
                InterruptPolicy.Classify(candidate, StoryScheduler.ActiveEpisode, activeThread);
            NarrativeInterruptClass currentNarrativeClass =
                InterruptPolicy.Classify(_current, StoryScheduler.ActiveEpisode, activeThread);
            if (nextNarrativeClass == NarrativeInterruptClass.RelatedEscalation
                && !InterruptPolicy.MayInterrupt(currentNarrativeClass)
                && IsWorthWatchingNow(candidate, now, selectingDuringGrace: InQuietGrace))
            {
                InterestDropLog.Record(
                    "episode_reclaim",
                    $"cur={_current.Key} next={candidate.Key}");
                return true;
            }
        }

        bool inGrace = InQuietGrace;
        if (inGrace)
        {
            // Story aftermath / same-arc continuation may cut freely during quiet grace.
            if (IsSameStoryArc(_current, candidate)
                && IsWorthWatchingNow(candidate, now, selectingDuringGrace: true))
            {
                return true;
            }

            // Quiet grace after a sticky hold: only margin-worthy events may cut in.
            // Prevents family-join / love status from stealing a fight between swings.
            if (_current != null
                && (_current.Completion == InterestCompletionKind.CombatActive
                    || _current.Completion == InterestCompletionKind.StatusPhase
                    || _current.Completion == InterestCompletionKind.HappinessGrief
                    || IsStickyStoryScene(_current)))
            {
                float graceCur = _current.TotalScore;
                float graceNext = candidate.TotalScore;
                float onCurrentGrace = now - _currentStartedAt;
                ScoringWeights gw = InterestScoringConfig.W;
                float graceMargin = IsSoftStickyCluster(_current)
                    ? gw.cutInMargin
                    : Mathf.Max(
                        gw.cutInMargin,
                        gw.stickyCutInMargin > 0f ? gw.stickyCutInMargin : 50f);
                if (VarietyValveOpen(_current, onCurrentGrace) && IsVarietyValveCandidate(candidate))
                {
                    float valveMargin = gw.stickyVarietyValveMargin > 0f
                        ? gw.stickyVarietyValveMargin
                        : 20f;
                    graceMargin = Mathf.Min(graceMargin, valveMargin);
                    if (graceNext >= graceCur - gw.rotateSlack
                        && IsWorthWatchingNow(candidate, now, selectingDuringGrace: true))
                    {
                        return true;
                    }
                }

                return graceNext >= graceCur + graceMargin
                       && IsWorthWatchingNow(candidate, now, selectingDuringGrace: true);
            }

            return IsWorthWatchingNow(candidate, now, selectingDuringGrace: true);
        }

        if (!IsWorthWatchingNow(candidate, now, selectingDuringGrace: false))
        {
            return false;
        }

        bool protectedScene = SessionProtected(now, onCurrent);
        ScoringWeights w = InterestScoringConfig.W;
        float curScore = _current.TotalScore;
        float nextScore = candidate.TotalScore;
        bool nextFill = InterestScoring.IsFillScore(nextScore);
        bool curAmbient = IsAmbientShot(_current);
        bool curFill = curAmbient || InterestScoring.IsFillScore(curScore);
        bool sticky = IsStickyStoryScene(_current);
        float cutMargin = sticky
            ? Mathf.Max(w.cutInMargin, w.stickyCutInMargin > 0f ? w.stickyCutInMargin : 50f)
            : w.cutInMargin;
        bool varietyValve = VarietyValveOpen(_current, onCurrent)
                            && IsVarietyValveCandidate(candidate);
        if (varietyValve)
        {
            float valveMargin = w.stickyVarietyValveMargin > 0f ? w.stickyVarietyValveMargin : 20f;
            cutMargin = Mathf.Min(cutMargin, valveMargin);
        }

        // Ambient fill: any real event may take the camera immediately (no min dwell).
        if (curAmbient && !nextFill && !IsAmbientShot(candidate))
        {
            return true;
        }

        // Prefer / MC: cut character-fill or soft-quiet linger without full score margin.
        // Never weakens sticky combat, war, crisis, or short-arc hard holds.
        if ((curFill || StoryPlanner.SoftFillQuietActive)
            && !sticky
            // Correlated short-story ownership outranks Saga Prefer/MC soft bias.
            // Otherwise the same MC's weak life noise can steal its own aftermath.
            && !StoryPlanner.OwnsCandidate(_current)
            && !StoryPlanner.CrisisActive
            && !CombatFightIsHot(_current, now)
            && _current.Completion != InterestCompletionKind.WarFront
            && !nextFill
            && !IsAmbientShot(candidate)
            && (LifeSagaRoster.TipTouchesPrefer(candidate) || LifeSagaRoster.TipTouchesMc(candidate)))
        {
            InterestDropLog.Record(
                "saga_ambient_cut",
                $"cur={_current.Key} next={candidate.Key}");
            return true;
        }

        // Soft family pack: yield to discrete unit events after a short hold.
        if (IsSoftStickyCluster(_current)
            && !IsSoftStickyCluster(candidate)
            && !nextFill
            && !IsAmbientShot(candidate)
            && onCurrent >= SoftClusterYieldSeconds
            && nextScore >= curScore - w.rotateSlack)
        {
            return true;
        }

        // Variety valve: after a long combat/war hold, one Story/Epic/lover/discovery cut.
        // Score-margin alone can never clear Mass (~150) with lover (~78); use class gate.
        if (varietyValve && !nextFill && !IsAmbientShot(candidate))
        {
            bool hotEnough = InterestScoring.IsHotScore(nextScore)
                             || nextScore >= curScore - w.rotateSlack;
            bool storyEnough = nextScore >= w.noticeScoreMin
                               || candidate.EventStrength >= w.noticeScoreMin;
            if (hotEnough || storyEnough)
            {
                InterestDropLog.Record(
                    "variety_valve",
                    $"cur={curScore:0.#} next={nextScore:0.#} on={onCurrent:0.#}");
                return true;
            }
        }

        // Same-arc refresh (combat/hatch/grief keys) may replace without full margin.
        if (sticky && IsSameStoryArc(_current, candidate) && nextScore >= curScore - w.rotateSlack)
        {
            return true;
        }

        // StoryPlanner hard-arc / crisis hold against unrelated peers.
        float storyHold = Mathf.Max(
            StoryPlanner.ArcHoldMargin(_current, candidate),
            StoryPlanner.CrisisHoldMargin(_current, candidate));
        if (storyHold > 0f)
        {
            cutMargin = Mathf.Max(cutMargin, storyHold);
        }

        // Instant score-margin cut - no settle grace, no MinDwell block.
        // Soft clusters use the normal cut-in margin (not stickyCutInMargin).
        float effectiveMargin = IsSoftStickyCluster(_current) ? w.cutInMargin : cutMargin;
        if (nextScore >= curScore + effectiveMargin)
        {
            return true;
        }

        if ((sticky || storyHold > 0f) && !IsSoftStickyCluster(_current) && nextScore < curScore + cutMargin)
        {
            InterestDropLog.Record(
                "below_margin",
                $"sticky cur={curScore:0.#} next={nextScore:0.#} need={cutMargin:0.#}"
                + (varietyValve ? " valve" : "")
                + (storyHold > 0f ? " story" : ""));
        }

        // Fill never cuts a protected non-fill session without margin (already failed above).
        if (nextFill && !curFill && protectedScene)
        {
            return false;
        }

        float fillRotate = _minDwell < MinDwellSeconds * 0.5f ? _curiosityRotate : w.fillRotateSeconds;
        if (nextFill && curFill && onCurrent < fillRotate)
        {
            return false;
        }

        // Protected / sticky EventLed hold: only margin or same-arc (handled above).
        if ((protectedScene || sticky) && !curAmbient)
        {
            return false;
        }

        // Peer rotate / stronger score after MinDwell when unprotected or on fill.
        if (nextScore > curScore && onCurrent >= MinDwellFor(_current) && sinceSwitch >= _switchCooldown)
        {
            return true;
        }

        return onCurrent >= MinDwellFor(_current)
               && sinceSwitch >= _switchCooldown
               && nextScore >= curScore - w.rotateSlack;
    }

    /// <summary>Soft multi-actor holds that must yield to discrete unit events.</summary>
    private const float SoftClusterYieldSeconds = 4f;

    private static bool IsSoftStickyCluster(InterestCandidate c) =>
        c != null && c.Completion == InterestCompletionKind.FamilyPack;

    /// <summary>
    /// True when a peer may interrupt a live fight: sticky score margin, or catalog epic-world
    /// EventStrength with a smaller urgent margin (disasters / kingdom fall, not lovers).
    /// </summary>
    private static bool IsCombatUrgentPeer(InterestCandidate current, InterestCandidate next)
    {
        if (current == null || next == null)
        {
            return false;
        }

        if (InterestScoring.IsFillScore(next.TotalScore) || IsAmbientShot(next))
        {
            return false;
        }

        ScoringWeights w = InterestScoringConfig.W;
        float stickyMargin = w.stickyCutInMargin > 0f ? w.stickyCutInMargin : 50f;
        if (next.TotalScore >= current.TotalScore + stickyMargin)
        {
            return true;
        }

        // King / leadership deaths sit under the epic floor (king_killed=88) but must cut
        // live scraps - soak missed a king slaying while parked on a Duel thrash.
        if (IsLeadershipDeathPeer(next))
        {
            return true;
        }

        float epicMin = w.combatUrgentEventStrengthMin > 0f
            ? w.combatUrgentEventStrengthMin
            : 95f;
        float urgentMargin = w.combatUrgentCutInMargin > 0f
            ? w.combatUrgentCutInMargin
            : 20f;
        return next.EventStrength >= epicMin
               && next.TotalScore >= current.TotalScore + urgentMargin;
    }

    private static bool IsPersonalStoryInterrupt(InterestCandidate candidate)
    {
        if (candidate == null
            || candidate.Completion == InterestCompletionKind.CombatActive
            || candidate.Completion == InterestCompletionKind.WarFront
            || InterestScoring.IsFillScore(candidate.TotalScore)
            || IsAmbientShot(candidate))
        {
            return false;
        }

        if (candidate.Completion == InterestCompletionKind.HappinessGrief)
        {
            return true;
        }

        NarrativeDevelopmentKind kind =
            candidate.NarrativePresentation?.DevelopmentKind
            ?? NarrativeDevelopmentKind.Unknown;
        if (kind == NarrativeDevelopmentKind.BondFormed
            || kind == NarrativeDevelopmentKind.BondBroken
            || kind == NarrativeDevelopmentKind.ChildBorn
            || kind == NarrativeDevelopmentKind.Death
            || kind == NarrativeDevelopmentKind.Recovery)
        {
            return true;
        }

        string text = ((candidate.AssetId ?? "") + " "
                       + (candidate.HappinessEffectId ?? "") + " "
                       + (candidate.Category ?? "") + " "
                       + (candidate.Verb ?? "")).ToLowerInvariant();
        return ContainsPersonalToken(
            text,
            "child",
            "baby",
            "born",
            "parent",
            "lover",
            "love",
            "partner",
            "family",
            "grief",
            "mourn",
            "kiss",
            "marri");
    }

    private static bool TouchesCurrentPrincipal(InterestCandidate candidate)
    {
        if (_current == null || candidate == null)
        {
            return false;
        }

        long currentId = _current.SubjectId != 0
            ? _current.SubjectId
            : EventFeedUtil.SafeId(_current.FollowUnit);
        if (currentId == 0)
        {
            return false;
        }

        if (candidate.SubjectId == currentId
            || candidate.RelatedId == currentId
            || candidate.PairOwnerId == currentId
            || candidate.PairPartnerId == currentId)
        {
            return true;
        }

        for (int i = 0; i < candidate.ParticipantIds.Count; i++)
        {
            if (candidate.ParticipantIds[i] == currentId)
            {
                return true;
            }
        }

        return false;
    }

    private static bool ContainsPersonalToken(string text, params string[] tokens)
    {
        if (string.IsNullOrEmpty(text) || tokens == null)
        {
            return false;
        }

        for (int i = 0; i < tokens.Length; i++)
        {
            if (text.IndexOf(tokens[i], StringComparison.Ordinal) >= 0)
            {
                return true;
            }
        }

        return false;
    }

    public static bool HarnessProbePersonalCombatInterrupt(out string detail)
    {
        var birth = new InterestCandidate
        {
            AssetId = "add_child",
            Category = "Family",
            TotalScore = 80f
        };
        var love = new InterestCandidate
        {
            HappinessEffectId = "fell_in_love",
            Category = "Relationship",
            TotalScore = 75f
        };
        var routine = new InterestCandidate
        {
            HappinessEffectId = "just_slept",
            Category = "Activity",
            TotalScore = 70f
        };
        var building = new InterestCandidate
        {
            AssetId = "building_complete",
            Category = "Building",
            TotalScore = 80f
        };
        bool birthCuts = IsPersonalStoryInterrupt(birth);
        bool loveCuts = IsPersonalStoryInterrupt(love);
        bool routineWaits = !IsPersonalStoryInterrupt(routine);
        bool buildingWaits = !IsPersonalStoryInterrupt(building);
        bool ok = birthCuts && loveCuts && routineWaits && buildingWaits;
        detail = "personal=" + birthCuts + "/" + loveCuts
                 + " waits=" + routineWaits + "/" + buildingWaits
                 + " pass=" + ok;
        return ok;
    }

    /// <summary>
    /// Politics leadership death spectacles (live WorldLog / catalog ids), not lovers.
    /// </summary>
    private static bool IsLeadershipDeathPeer(InterestCandidate c)
    {
        if (c == null)
        {
            return false;
        }

        string id = (c.AssetId ?? "").ToLowerInvariant();
        if (id.IndexOf("king_killed", StringComparison.Ordinal) >= 0
            || id.IndexOf("king_dead", StringComparison.Ordinal) >= 0
            || id.IndexOf("king_died", StringComparison.Ordinal) >= 0
            || id.IndexOf("leader_killed", StringComparison.Ordinal) >= 0
            || id.IndexOf("favorite_killed", StringComparison.Ordinal) >= 0)
        {
            return true;
        }

        if (!string.Equals(c.Category, "Politics", StringComparison.OrdinalIgnoreCase))
        {
            return false;
        }

        return id.IndexOf("kill", StringComparison.Ordinal) >= 0
               || id.IndexOf("dead", StringComparison.Ordinal) >= 0
               || id.IndexOf("died", StringComparison.Ordinal) >= 0
               || id.IndexOf("slain", StringComparison.Ordinal) >= 0;
    }

    /// <summary>
    /// Sticky combat/war has held long enough that Story/Epic/lover/discovery may cut in.
    /// Live CombatActive scraps never open the valve - hold until the fight goes cold.
    /// </summary>
    private static bool VarietyValveOpen(InterestCandidate scene, float onCurrent) =>
        !_varietyValveUsed
        && VarietyValveTimeReady(scene, onCurrent)
        && !CombatFightIsHot(scene, Time.unscaledTime);

    private static bool IsStickyStoryScene(InterestCandidate c)
    {
        if (c == null)
        {
            return false;
        }

        // FamilyPack is a soft cluster - not hard sticky (see IsSoftStickyCluster).
        if (c.Completion == InterestCompletionKind.CombatActive
            || c.Completion == InterestCompletionKind.WarFront
            || c.Completion == InterestCompletionKind.PlotActive
            || c.Completion == InterestCompletionKind.StatusPhase
            || c.Completion == InterestCompletionKind.StatusOutbreak
            || c.Completion == InterestCompletionKind.HappinessGrief)
        {
            return true;
        }

        // Hatch FixedDwell is a story beat - hold against weak peers.
        if (!string.IsNullOrEmpty(c.HappinessEffectId)
            && (string.Equals(c.HappinessEffectId, "just_got_out_of_egg", StringComparison.OrdinalIgnoreCase)
                || string.Equals(c.HappinessEffectId, "just_hatched", StringComparison.OrdinalIgnoreCase)))
        {
            return true;
        }

        if (!string.IsNullOrEmpty(c.Key)
            && (c.Key.StartsWith("combat:", StringComparison.Ordinal)
                || c.Key.StartsWith("hatch:", StringComparison.Ordinal)))
        {
            return true;
        }

        return false;
    }

    private static bool IsSameStoryArc(InterestCandidate current, InterestCandidate next)
    {
        if (current == null || next == null)
        {
            return false;
        }

        if (!string.IsNullOrEmpty(current.Key)
            && !string.IsNullOrEmpty(next.Key)
            && string.Equals(current.Key, next.Key, StringComparison.Ordinal))
        {
            return true;
        }

        // Hatch: same subject beat may refresh without full margin.
        if (!string.IsNullOrEmpty(current.Key)
            && !string.IsNullOrEmpty(next.Key)
            && SameKeyPrefix(current.Key, next.Key, "hatch:"))
        {
            return true;
        }

        // Combat: only the same unordered pair (or escalate of that scrap) is same-arc.
        // Different combat:pair keys used to soft-cut and thrash Duel partners.
        if (current.Completion == InterestCompletionKind.CombatActive
            && next.Completion == InterestCompletionKind.CombatActive
            && IsSameCombatPairArc(current, next))
        {
            return true;
        }

        // Mass → War reclaim on the same kingdom pair (never War → Mass soft-cut).
        if (current.Completion == InterestCompletionKind.CombatActive
            && next.Completion == InterestCompletionKind.WarFront
            && StickyScoreboard.SharesKingdomTheater(current, next))
        {
            return true;
        }

        if (current.Completion == InterestCompletionKind.WarFront
            && next.Completion == InterestCompletionKind.WarFront
            && StickyScoreboard.SharesKingdomTheater(current, next))
        {
            return true;
        }

        if (current.Completion == InterestCompletionKind.HappinessGrief
            && next.Completion == InterestCompletionKind.HappinessGrief
            && current.SubjectId != 0
            && current.SubjectId == next.SubjectId)
        {
            return true;
        }

        // StoryPlanner aftermath / epilogue of the active climax.
        if (StoryPlanner.IsContinuationOf(current, next))
        {
            return true;
        }

        return false;
    }

    /// <summary>
    /// True when next is the same 1v1 pair or a multi escalate of the current scrap.
    /// </summary>
    private static bool IsSameCombatPairArc(InterestCandidate current, InterestCandidate next)
    {
        if (current == null || next == null)
        {
            return false;
        }

        if (!string.IsNullOrEmpty(current.Key)
            && !string.IsNullOrEmpty(next.Key)
            && string.Equals(current.Key, next.Key, StringComparison.Ordinal))
        {
            return true;
        }

        CollectCombatActorIds(current, out long curA, out long curB);
        CollectCombatActorIds(next, out long nextA, out long nextB);
        bool samePair = curA != 0
                        && curB != 0
                        && nextA != 0
                        && nextB != 0
                        && ((curA == nextA && curB == nextB) || (curA == nextB && curB == nextA));
        if (samePair)
        {
            return true;
        }

        // Duel → Mass/Battle escalate: shared fighter + larger theater.
        bool nextMulti = next.ParticipantCount >= 3
                         || string.Equals(next.AssetId, "live_battle", StringComparison.OrdinalIgnoreCase)
                         || HasStickyCollectiveMulti(next);
        if (!nextMulti)
        {
            return false;
        }

        return SharesCombatFighterId(current, nextA)
               || SharesCombatFighterId(current, nextB)
               || SharesCombatFighterId(next, curA)
               || SharesCombatFighterId(next, curB);
    }

    /// <summary>
    /// Peer Duel tips for the same scrap fighter (new attack_target) must not cut the hold.
    /// </summary>
    private static bool IsCombatPartnerSwapNoise(InterestCandidate current, InterestCandidate next)
    {
        if (current == null
            || next == null
            || current.Completion != InterestCompletionKind.CombatActive
            || next.Completion != InterestCompletionKind.CombatActive)
        {
            return false;
        }

        // Multi escalate / different theater is not partner-swap noise.
        bool nextMulti = next.ParticipantCount >= 3
                         || HasStickyCollectiveMulti(next)
                         || (string.Equals(next.AssetId, "live_battle", StringComparison.OrdinalIgnoreCase)
                             && next.ParticipantCount > 2);
        if (nextMulti && !IsThinPairCombat(next))
        {
            return false;
        }

        CollectCombatActorIds(current, out long curA, out long curB);
        CollectCombatActorIds(next, out long nextA, out long nextB);
        if (curA == 0 && curB == 0
            && current.TheaterLeadId == 0
            && current.PairOwnerId == 0
            && current.SubjectId == 0)
        {
            return false;
        }

        // Mass/Battle held on a theater lead: peer Duel with a new attack_target is noise.
        if (!IsThinPairCombat(current) && !IsNamedPairCombatOwnership(current))
        {
            if (IsThinPairCombat(next) && SharesCombatOwnerOrLead(current, nextA, nextB))
            {
                return true;
            }

            return false;
        }

        if (!IsThinPairCombat(next))
        {
            return false;
        }

        // Same unordered pair with flipped Follow (Duel A vs B ↔ B vs A) is ownership noise.
        // Same-subject refreshes may still soft-cut; A↔B tip order must hold while both live.
        bool sameUnorderedPair = curA != 0
                                 && curB != 0
                                 && nextA != 0
                                 && nextB != 0
                                 && ((curA == nextA && curB == nextB)
                                     || (curA == nextB && curB == nextA));
        if (sameUnorderedPair)
        {
            long curSub = current.SubjectId != 0
                ? current.SubjectId
                : (current.PairOwnerId != 0
                    ? current.PairOwnerId
                    : EventFeedUtil.SafeId(current.FollowUnit));
            long nextSub = next.SubjectId != 0
                ? next.SubjectId
                : EventFeedUtil.SafeId(next.FollowUnit);
            if (curSub != 0 && nextSub != 0 && curSub != nextSub)
            {
                return true;
            }

            return false;
        }

        // Shared fighter + different partner = attack_target thrash.
        return SharesCombatOwnerOrLead(current, nextA, nextB)
               || SharesCombatFighterId(current, nextA)
               || SharesCombatFighterId(current, nextB);
    }

    private static bool SharesCombatOwnerOrLead(InterestCandidate current, long nextA, long nextB)
    {
        if (current == null)
        {
            return false;
        }

        long lead = current.TheaterLeadId != 0
            ? current.TheaterLeadId
            : (current.PairOwnerId != 0 ? current.PairOwnerId : current.SubjectId);
        if (lead == 0)
        {
            lead = EventFeedUtil.SafeId(current.FollowUnit);
        }

        return lead != 0 && (lead == nextA || lead == nextB);
    }

    private static bool IsThinPairCombat(InterestCandidate c)
    {
        if (c == null)
        {
            return false;
        }

        if (c.HasCombatPairLock || c.ParticipantCount <= 2)
        {
            return true;
        }

        string tip = c.Label ?? "";
        if (tip.StartsWith("Duel", StringComparison.OrdinalIgnoreCase)
            || tip.IndexOf(" is fighting", StringComparison.OrdinalIgnoreCase) >= 0)
        {
            return true;
        }

        string key = c.Key ?? "";
        return key.StartsWith("combat:pair:", StringComparison.Ordinal)
               || (key.StartsWith("combat:", StringComparison.Ordinal)
                   && key.IndexOf(":pair:", StringComparison.Ordinal) < 0
                   && !string.Equals(c.AssetId, "live_battle", StringComparison.OrdinalIgnoreCase));
    }

    private static void CollectCombatActorIds(InterestCandidate c, out long a, out long b)
    {
        a = 0;
        b = 0;
        if (c == null)
        {
            return;
        }

        a = c.PairOwnerId != 0 ? c.PairOwnerId : c.SubjectId;
        b = c.PairPartnerId != 0 ? c.PairPartnerId : c.RelatedId;
        if (a == 0)
        {
            a = EventFeedUtil.SafeId(c.FollowUnit);
        }

        if (b == 0)
        {
            b = EventFeedUtil.SafeId(c.RelatedUnit);
        }
    }

    private static bool SharesCombatFighterId(InterestCandidate c, long id)
    {
        if (c == null || id == 0)
        {
            return false;
        }

        CollectCombatActorIds(c, out long a, out long b);
        return id == a || id == b;
    }

    private static bool SameKeyPrefix(string a, string b, string prefix)
    {
        if (string.IsNullOrEmpty(a) || string.IsNullOrEmpty(b) || string.IsNullOrEmpty(prefix))
        {
            return false;
        }

        if (!a.StartsWith(prefix, StringComparison.Ordinal)
            || !b.StartsWith(prefix, StringComparison.Ordinal))
        {
            return false;
        }

        return string.Equals(a, b, StringComparison.Ordinal);
    }
}