// server/sim/content/bonds/addon/battle.js — battle side of the 15 add-on bonds (research 02 §3.9–§3.23).
//
// Every number comes from data/bonds.json (`env_gbuff_new` buff blackboards). ATK / DEF / max HP "+X%" are 直接乘算
// (support directMods: additive with every other percentage, PRTS 盟约记录). Effects only apply to the owning
// player's units (`unit.ownerId === playerId`): two players sharing a boss / 联防 field never buff each other.
// Layer-dependent values read the LIVE layers (`battle.getPlayer(pid).bonds[id].layers`): an IN_BATTLE layer gain
// (engine `layerGain` hook, which fires before the layers are written) schedules one deferred recompute per player.
//
//   精准 preciShip     members ATK +(base_atk + atk_per_stack·L); tier 2 (3 distinct): members + RANGED operators,
//                      which also ignore power_def_penetrate DEF / power_magic_resist_penetrate RES (defIgnorePct / resIgnorePct)
//   迅捷 swiftShip     member skill end → p = min(1, base_prob + prob_per_stack·L): +normal_sp SP; L ≥ power_bond_stack_cnt:
//                      every operator's skill end rolls p again for +power_sp (members roll both, research [ASSUMED])
//   灵巧 skillfulShip  aura: members + operators on their 4 (L ≥ 40: 8) adjacent tiles ASPD +(base + per·L), once per unit
//   奥术 arcaneShip    member arts damage → target arts taken ×(base + per·L) for weak_duration s; tier 2: ×power_weak_scale
//                      when the target is below hp_ratio at application. ONE instance per target whatever applies it — the
//                      two players of a pair field compete for it, the strongest wins (battle.applyStrongest, 同名效果取最高:
//                      PRTS 作战机制 "同名buff的默认叠加策略buff只能表现出一个"; 巴哈姆特 12316 first-hand: "共享型buff會跟對面搶
//                      如果對面層數比你高就不需要再特別激活直接吃他的奧術buff"). v2.5 kept one per player, so two players'
//                      instances multiplied (×5.4 × ×5.6 on a leader at ~250 layers, DESIGN §20.10). PRTS 盟约记录's own
//                      note "※同一单位仅可对同一目标同时施加1个该盟约法术伤害提升效果" (one instance per unit and target)
//                      fits it under the engine default (a newer same-named buff waits until the earlier ends, PRTS
//                      常见同名状态); strongest vs earliest is [ASSUMED]. Known deviation [ASSUMED]: an earlier revision
//                      (oldid 386936) forbade a unit re-applying while its own instance lasts; an equal hit here
//                      refreshes it to a fresh 3 s (slightly stronger). Re-measured after the 0.1.0 report
//                      "奥术盟约不生效": it works on the real and the browser path (test/sim/feedback1b-arcane.test.js);
//                      标准 never activates it (modeDataDict inactiveBondIdList)
//   坚守 steadShip     all operators max HP +(base + per·L); tier 2: 40 % of a non-member operator's damage is borne by
//                      the members on the field (split evenly, sourceless true damage — already mitigated), members’ thorns
//                      (base + per·L arts, sourceless but credited to the member hit, ≤ 1 per cd_duration per member;
//                      无来源 damage uses the chance and hits nobody, a 流失 never does — PRTS 备注 / 作战机制)
//                      + 脆弱 ×damage_scale for weak[limit] s
//   助力 deputShip     all operators DEF +(base + per·L), redeploy time ×(1 + respawn_time)
//   突袭 raidShip      member idle ≥ no_attack_duration s (or skill ready) with no enemy in range → "保留技力立即再部署"
//                      next to the most advanced ground enemy, on a free tile its position may be deployed on
//                      (grid.canStand: never the 深水区 — player report #3 after 0.1.0, members dropped into 战场#08's
//                      pool after an enemy wading in it; Battle.isReservedTile: never a tile a knocked-out operator
//                      lies on — player report F5, members landed on a fallen teammate): a real redeployment (retreat +
//                      free redeploy on the landing tile, full HP, `deploy` fires — 部署时 traits such as 史尔特尔,
//                      突袭手雷, 卡西米尔, 叙拉古) with its SP / charges kept (engine redeploy tile + keepSp); ATK/HP
//                      +(base + per·L) until it leaves the field; knocked out after a jump it lies where it fell and
//                      comes back there (the engine's rest tile, Battle._layBody — PRTS 卫戍协议/帮助 "原地留下一个
//                      “倒地干员”…自动部署至该位置"; its own home when it fell on another board piece's home);
//                      L ≥ power_bond_stack_cnt: every operator ASPD +power_attack_speed
//   不屈 indomShip     ground operator knocked out → p = min(1, base + per·L) immediate free redeploy where it lies
//                      (the engine's rest tile); tier 2: every operator on the field +sp SP
//   协防 emptyShip     all operators phys/arts taken ×(1 − damage_resistance); members dealt ×damage_scale_normal
//                      (elite ×damage_scale_extra)
//   独行 soloShip      the member(s) ATK +atk, HP +max_hp, +sp SP on every deploy
//   绝技 suntShip      tier 1: elite operators ATK +power_atk; tier 2: elites (and their summons) SP cost ×sp_ratio
//   远见 / 奇迹 / 投资人 / 调和 have no battle effect (prep side, membership in support/index.js).
//
// Hooks registered only when a bond needs them. Priorities: `hit` −20 (坚守 redirect, after other modifiers had their
// say), `death` 10 (不屈, the bond slot of the revive/redeploy convention); everything else 0.

import { absoluteRangeKeys, canTargetEnemy } from '../../../targeting.js';
import { localOrder, localBefore } from '../../../dir.js';
import { isHpLoss } from '../../../damage.js';
import {
  num, bondRecord, buffParams, bondTier, bondLayers, isMember, isElite, isGroundOp, onField, playerOps, passiveBuff,
  fxOn, N4, N8, bodyInKeys, directMods,
} from '../../support/index.js';

export const ID = Object.freeze({
  preci: 'preciShip', swift: 'swiftShip', skillful: 'skillfulShip', arcane: 'arcaneShip', stead: 'steadShip',
  deput: 'deputShip', raid: 'raidShip', indom: 'indomShip', empty: 'emptyShip', solo: 'soloShip', sunt: 'suntShip',
});
export const KEY = Object.freeze({
  preci: 'bond:preciShip', stead: 'bond:steadShip', deput: 'bond:deputShip', skillful: 'bond:skillfulShip',
  raid: 'bond:raidShip', raidAspd: 'bond:raidShip:aspd', empty: 'bond:emptyShip', emptyDmg: 'bond:emptyShip:dmg',
  solo: 'bond:soloShip', sunt: 'bond:suntShip', arcane: 'bond:arcaneShip',
});
/** Bonds whose battle values depend on layers (recomputed on in-battle gains). */
const LAYERED = new Set([ID.preci, ID.swift, ID.skillful, ID.arcane, ID.stead, ID.deput, ID.raid, ID.indom]);
const STEAD_CD = 'bond:steadShip:cd';
const AURA_POLL = 0.25;
const RAID_POLL = 0.25;
const RAID_SEARCH = 2; // landing tiles within this Chebyshev distance of the target enemy

/** 奥术 vulnerability mods for a multiplier (battle.applyStrongest). */
const arcaneMods = (v) => ({ artsTakenMul: v });

/** `env_gbuff_new` blackboard of a bond (numbers only). */
export function bondBb(bondId) {
  return buffParams(bondRecord(bondId), 'env_gbuff_new') ?? {};
}
/** 迅捷 / 不屈 proc chance p = min(1, base_prob + prob_per_stack·L). */
export const procChance = (bb, L) => Math.max(0, Math.min(1, num(bb.base_prob) + num(bb.prob_per_stack) * L));
const prob = procChance;

// =====================================================================================================================
// per-player state

function makeState(battle, p) {
  const pid = p.playerId;
  const ops = playerOps(battle, pid);
  const st = { pid, ops, tiers: {}, bb: {}, members: {} };
  for (const id of Object.values(ID)) {
    const t = bondTier(battle, pid, id);
    if (t <= 0) continue;
    st.tiers[id] = t;
    st.bb[id] = bondBb(id);
    st.members[id] = new Set(ops.filter((u) => isMember(battle, u, id)));
  }
  return st;
}
const L = (battle, st, id) => bondLayers(battle, st.pid, id);

// =====================================================================================================================
// match-long passives (re-applied on layer changes; passiveBuff replaces by key → idempotent)

function applyPassives(battle, st) {
  const t = st.tiers;
  if (t[ID.preci]) {
    const bb = st.bb[ID.preci];
    const wide = t[ID.preci] >= 2;
    const mods = directMods({ atk: num(bb.base_atk) + num(bb.atk_per_stack) * L(battle, st, ID.preci) });
    if (wide) { mods.defIgnorePct = num(bb.power_def_penetrate); mods.resIgnorePct = num(bb.power_magic_resist_penetrate); }
    for (const u of st.ops) {
      if (st.members[ID.preci].has(u) || (wide && u.def?.position === 'RANGED')) passiveBuff(battle, u, KEY.preci, mods);
    }
  }
  if (t[ID.stead]) {
    const bb = st.bb[ID.stead];
    const mods = directMods({ hp: num(bb.base_max_hp) + num(bb.max_hp_per_stack) * L(battle, st, ID.stead) });
    for (const u of st.ops) passiveBuff(battle, u, KEY.stead, mods);
  }
  if (t[ID.deput]) {
    const bb = st.bb[ID.deput];
    const mods = directMods({ def: num(bb.base_def) + num(bb.def_per_stack) * L(battle, st, ID.deput) }, { redeployMul: Math.max(0, 1 + num(bb.respawn_time)) });
    for (const u of st.ops) passiveBuff(battle, u, KEY.deput, mods);
  }
  if (t[ID.raid]) {
    const bb = st.bb[ID.raid];
    const lv = L(battle, st, ID.raid);
    const milestone = num(bb.power_bond_stack_cnt, Infinity);
    if (lv >= milestone) {
      const mods = { aspd: num(bb.power_attack_speed) };
      for (const u of st.ops) passiveBuff(battle, u, KEY.raidAspd, mods);
      if (!st.raidMilestone) { st.raidMilestone = true; for (const u of st.members[ID.raid]) if (onField(u)) { fxOn(battle, 'bondMilestone', u, KEY.raid, 'aspd'); break; } }
    }
    st.raidMods = raidMods(bb, lv);
    for (const u of st.members[ID.raid]) {
      const b = u.findBuff(KEY.raid);
      if (b) { b.mods = st.raidMods; u.markDirty(); }
    }
  }
  if (t[ID.arcane]) {
    const bb = st.bb[ID.arcane];
    const m = num(bb.base_damage_scale, 1) + num(bb.damage_scale_per_stack) * L(battle, st, ID.arcane);
    st.arcaneMul = Math.max(0, m);
    st.arcaneLowMul = Math.max(0, m * num(bb.power_weak_scale, 1));
  }
  if (t[ID.skillful]) {
    const bb = st.bb[ID.skillful];
    const lv = L(battle, st, ID.skillful);
    const v = num(bb.base_attack_speed) + num(bb.attack_speed_per_stack) * lv;
    if (!st.auraMods || st.auraMods.aspd !== v) st.auraMods = { aspd: v };
    st.auraWide = lv >= num(bb.power_bond_stack_cnt, Infinity);
  }
}

function raidMods(bb, lv) {
  const mods = directMods({
    atk: num(bb.base_atk) + num(bb.atk_per_stack) * lv,
    hp: num(bb.base_max_hp) + num(bb.max_hp_per_stack) * lv,
  });
  const aspd = num(bb.base_attack_speed) + num(bb.attack_speed_per_stack) * lv;
  if (aspd) mods.aspd = aspd;
  return mods;
}

/** Layer-independent passives (协防 / 独行 / 绝技), applied once. */
function applyStatic(battle, st) {
  const t = st.tiers;
  if (t[ID.empty]) {
    const bb = st.bb[ID.empty];
    const taken = Math.max(0, 1 - num(bb.damage_resistance));
    for (const u of st.ops) {
      passiveBuff(battle, u, KEY.empty, { physTakenMul: taken, artsTakenMul: taken });
      if (st.members[ID.empty].has(u)) {
        passiveBuff(battle, u, KEY.emptyDmg, { dmgDealtMul: num(isElite(u) ? bb.damage_scale_extra : bb.damage_scale_normal, 1) });
      }
    }
  }
  if (t[ID.solo]) {
    const bb = st.bb[ID.solo];
    const mods = directMods({ atk: num(bb.atk), hp: num(bb.max_hp) });
    for (const u of st.members[ID.solo]) passiveBuff(battle, u, KEY.solo, mods);
  }
  if (t[ID.sunt]) {
    const bb = st.bb[ID.sunt];
    const mods = directMods({ atk: num(bb.power_atk) });
    for (const u of st.ops) {
      if (!isElite(u)) continue;
      passiveBuff(battle, u, KEY.sunt, mods);
      if (t[ID.sunt] >= 2) suntSpCost(u, bb);
    }
  }
}

function suntSpCost(u, bb) {
  const sk = u && u.skill;
  if (!sk || sk.noSkill || u.mem[KEY.sunt]) return;
  u.mem[KEY.sunt] = true;
  sk.spCostMul = sk.spCostMul * num(bb.sp_ratio, 1);
}

// =====================================================================================================================
// 灵巧 aura

function updateAura(battle, st) {
  const mods = st.auraMods;
  if (!mods) return;
  const next = st.auraNext ?? (st.auraNext = new Set());
  next.clear();
  const offs = st.auraWide ? N8 : N4;
  for (const m of st.members[ID.skillful]) {
    if (!onField(m)) continue;
    next.add(m);
    for (const [dr, dc] of offs) {
      const a = battle.unitAt(m.tileR + dr, m.tileC + dc);
      if (a && a.kind === 'op' && a.ownerId === st.pid && onField(a)) next.add(a);
    }
  }
  const cur = st.aura ?? (st.aura = new Set());
  for (const u of cur) if (!next.has(u)) battle.removeBuff(u, KEY.skillful);
  for (const u of next) {
    const b = u.findBuff(KEY.skillful);
    if (!b) battle.addBuff(u, { key: KEY.skillful, mods });
    else if (b.mods !== mods) { b.mods = mods; u.markDirty(); }
  }
  st.aura = next;
  st.auraNext = cur;
}

// =====================================================================================================================
// 突袭 relocation

function raidTile(battle, u, e) {
  const er = Math.round(e.y), ec = Math.round(e.x);
  const ranged = u.def?.position === 'RANGED';
  const grid = u.rangeGrid || [[0, 0]];
  const ext = num(u.s.rangeExtend);
  let best = null, bs = null;
  for (let dr = -RAID_SEARCH; dr <= RAID_SEARCH; dr++) {
    for (let dc = -RAID_SEARCH; dc <= RAID_SEARCH; dc++) {
      const r = er + dr, c = ec + dc;
      if (!battle.grid.inRect(r, c) || battle.isReservedTile(r, c)) continue;
      if (!battle.grid.canStand(r, c, { ranged })) continue;
      const covers = bodyInKeys(e, absoluteRangeKeys(grid, r, c, u.dir, ext)) ? 0 : 1;
      const d = Math.max(Math.abs(dr), Math.abs(dc)) + 0.01 * (Math.abs(dr) + Math.abs(dc));
      // last tie-break: the offset in the unit's facing-RIGHT frame (sim/dir.js localOrder; for a RIGHT-facing unit the
      // plain tile-key order), so the landing tile turns with its direction
      const s0 = covers, s1 = d, s2 = localOrder(dr, dc, u.dir);
      if (!bs || s0 < bs[0] || (s0 === bs[0] && (s1 < bs[1] - 1e-9 || (Math.abs(s1 - bs[1]) <= 1e-9 && localBefore(s2, bs[2]))))) { best = [r, c, covers === 0]; bs = [s0, s1, s2]; }
    }
  }
  return best; // [row, col, targetInRange]
}

function raidTargets(battle, u, pid) {
  const own = [], other = [];
  for (const e of battle.enemies) {
    if (e.isFlying || !canTargetEnemy(u, e, { canHitFly: false })) continue;
    (e.ownerId === pid ? own : other).push(e);
  }
  const list = own.length ? own : other;
  const dist = new Map(list.map((e) => [e, num(battle.remainingDistance ? battle.remainingDistance(e) : 0)]));
  list.sort((a, b) => dist.get(a) - dist.get(b) || a.id - b.id);
  return list;
}

function raidPoll(battle, st) {
  const bb = st.bb[ID.raid];
  const idle = num(bb.no_attack_duration, 10);
  for (const u of st.members[ID.raid]) {
    if (!onField(u) || !u.canAct) continue;
    const since = Math.max(u.lastAttackAt ?? -Infinity, u.deployedAt ?? -Infinity, u.mem[KEY.raid] ?? -Infinity);
    const ready = !!(u.skill && u.skill.ready && !(u.skill.active && u.skill.isTimed));
    const idleOk = battle.time - since >= idle - 1e-9;
    if (!(ready || idleOk)) continue;
    if (battle.enemiesInKeys(u.rangeKeys || [], u, u.profile).length) continue;
    const targets = raidTargets(battle, u, st.pid);
    for (let i = 0; i < targets.length && i < 8; i++) {
      const tile = raidTile(battle, u, targets[i]);
      if (!tile) continue;
      // the "skill ready" path has no idle gate: only jump where the target is in range, else a ready skill that never
      // finds a target would redeploy (and fire every 部署时 effect) every poll
      if (!idleOk && !tile[2]) continue;
      const res = raidRedeploy(battle, u, tile[0], tile[1]);
      if (!res) continue;
      u.mem[KEY.raid] = battle.time;
      if (res === 'raid') {
        battle.addBuff(u, { key: KEY.raid, mods: st.raidMods });
        fxOn(battle, 'blink', u, KEY.raid, 'relocate', { target: targets[i].id });
      }
      break;
    }
  }
}

/**
 * "保留技力立即再部署": retreat the unit and redeploy it for free on (r, c) with its SP / charges kept (engine redeploy
 * `tile` + `keepSp`: restored before the `deploy` handlers run; the board tile stays its home). Should the landing fail
 * (raidTile skips taken, reserved and body tiles, so only content refusing it), the unit goes straight back to its home
 * tile (never stranded off the field).
 * Returns 'raid' | 'home' | false.
 */
function raidRedeploy(battle, u, r, c) {
  battle.retreat(u, { reason: 'raid' });
  if (u.alive) return false;
  if (battle.redeploy(u, { free: true, tile: [r, c], keepSp: true })) return 'raid';
  return battle.redeploy(u, { free: true, keepSp: true }) ? 'home' : false;
}

// =====================================================================================================================
// install

export function install(battle) {
  if (!battle || !Array.isArray(battle.players) || !battle.players.length) return;
  const states = [];
  for (const p of battle.players) {
    const st = makeState(battle, p);
    if (Object.keys(st.tiers).length) states.push(st);
  }
  if (!states.length) return;
  const byPid = Object.create(null);
  for (const st of states) { byPid[st.pid] = st; applyPassives(battle, st); applyStatic(battle, st); }
  const has = (id, tier = 1) => states.some((st) => (st.tiers[id] ?? 0) >= tier);

  // live layers
  if (states.some((st) => Object.keys(st.tiers).some((id) => LAYERED.has(id)))) {
    battle.on('layerGain', (c) => {
      const st = byPid[c.playerId];
      if (!st || !st.tiers[c.bondId] || !LAYERED.has(c.bondId) || st.pending) return;
      st.pending = true;
      battle.after(0, () => {
        st.pending = false;
        applyPassives(battle, st);
        if (st.tiers[ID.skillful]) updateAura(battle, st);
      });
    });
  }

  // 灵巧 aura (deploy / death immediately, relocations through a cheap poll)
  if (has(ID.skillful)) {
    const aura = states.filter((st) => st.tiers[ID.skillful]);
    const refresh = (pid) => { for (const st of aura) if (pid == null || st.pid === pid) updateAura(battle, st); };
    battle.on('battleStart', () => refresh(null));
    battle.on('deploy', (c) => { if (c.unit && c.unit.kind === 'op' && byPid[c.unit.ownerId]?.tiers[ID.skillful]) refresh(c.unit.ownerId); });
    battle.on('death', (c) => { if (c.unit && c.unit.kind === 'op' && byPid[c.unit.ownerId]?.tiers[ID.skillful]) refresh(c.unit.ownerId); });
    battle.every(AURA_POLL, () => refresh(null));
  }

  // 突袭
  if (has(ID.raid)) {
    const raid = states.filter((st) => st.tiers[ID.raid] && st.members[ID.raid].size);
    if (raid.length) {
      battle.every(RAID_POLL, () => { for (const st of raid) raidPoll(battle, st); });
    }
  }

  // 迅捷
  if (has(ID.swift)) {
    battle.on('skillEnd', (c) => {
      const u = c.unit;
      if (!u || u.kind !== 'op' || c.reason === 'death' || !u.alive || !u.skill) return;
      const st = byPid[u.ownerId];
      if (!st || !st.tiers[ID.swift]) return;
      const bb = st.bb[ID.swift];
      const lv = L(battle, st, ID.swift);
      const p = prob(bb, lv);
      let gained = 0;
      if (st.members[ID.swift].has(u) && battle.rng() < p) gained += u.skill.gainSp(num(bb.normal_sp), 'bond');
      if (lv >= num(bb.power_bond_stack_cnt, Infinity) && battle.rng() < p) gained += u.skill.gainSp(num(bb.power_sp), 'bond');
      if (gained > 0) fxOn(battle, 'sp', u, 'bond:swiftShip', 'proc', { n: gained });
    });
  }

  // 独行 (SP on every deploy) / 绝技 (summons of elites)
  const soloOrSunt = has(ID.solo) || has(ID.sunt, 2);
  if (soloOrSunt) {
    battle.on('deploy', (c) => {
      const u = c.unit;
      if (!u || (u.kind !== 'op' && u.kind !== 'token')) return;
      const st = byPid[u.ownerId];
      if (!st) return;
      if (u.kind === 'op' && st.tiers[ID.solo] && st.members[ID.solo].has(u) && u.skill) {
        const n = num(st.bb[ID.solo].sp);
        if (n > 0) u.skill.gainSp(n, 'init');
      }
      if (u.kind === 'token' && (st.tiers[ID.sunt] ?? 0) >= 2 && isElite(u.ownerUnit)) suntSpCost(u, st.bb[ID.sunt]);
    });
  }

  // 不屈
  if (has(ID.indom)) {
    battle.on('death', (c) => {
      const u = c.unit;
      if (c.reason !== 'killed' || !isGroundOp(u)) return;
      const st = byPid[u.ownerId];
      if (!st || !st.tiers[ID.indom]) return;
      const bb = st.bb[ID.indom];
      if (st.tiers[ID.indom] >= 2) {
        const sp = num(bb.sp);
        if (sp > 0) for (const o of st.ops) if (onField(o) && o.skill) o.skill.gainSp(sp, 'bond');
      }
      if (u.alive || u.removed || u.mem[ID.indom] === battle.time) return;
      if (battle.rng() < prob(bb, L(battle, st, ID.indom))) {
        u.mem[ID.indom] = battle.time;
        if (battle.redeploy(u, { free: true })) fxOn(battle, 'revive', u, 'bond:indomShip', 'redeploy');
      }
    }, { priority: 10 });
  }

  // 坚守 (tier 2) redirect + thorns, 奥术 vulnerability
  const stead = has(ID.stead, 2);
  const arcane = has(ID.arcane);
  if (stead) {
    battle.on('hit', (c) => {
      const t = c.target, dmg = c.dmg;
      if (!t || t.side !== 'ally' || t.kind !== 'op' || !dmg || dmg.cancel || dmg.steadShare || dmg.steadCut || dmg.type === 'element') return;
      const st = byPid[t.ownerId];
      if (!st || (st.tiers[ID.stead] ?? 0) < 2 || st.members[ID.stead].has(t)) return;
      let any = false;
      for (const m of st.members[ID.stead]) if (onField(m)) { any = true; break; }
      if (!any) return;
      const ratio = Math.max(0, Math.min(1, num(st.bb[ID.stead].damage_resistance)));
      if (!(ratio > 0) || ratio >= 1) return;
      dmg.mul *= 1 - ratio;
      dmg.steadCut = ratio;
    }, { priority: -20 });
  }
  if (stead || arcane) {
    battle.on('damaged', (c) => {
      const t = c.target, dmg = c.dmg;
      if (!t || !dmg) return;
      if (t.side === 'ally') {
        if (!stead || t.kind !== 'op') return;
        const st = byPid[t.ownerId];
        if (!st || (st.tiers[ID.stead] ?? 0) < 2) return;
        if (dmg.steadCut) {
          const ratio = dmg.steadCut;
          dmg.steadCut = 0;
          const share = (num(c.amount) / (1 - ratio)) * ratio;
          if (!(share > 0)) return;
          const on = [];
          for (const m of st.members[ID.stead]) if (onField(m)) on.push(m);
          // the share is already mitigated and already carries the attacker's damage multipliers: deal it sourceless
          // (the member's own damage-taken modifiers and shields still apply), never re-scaled by the attacker
          for (const m of on) {
            const d = battle.makeDamage({ amount: share / on.length, type: 'true', canDodge: false, tags: ['bond:stead:share'] });
            d.steadShare = true;
            battle.dealDamage(null, m, d);
          }
          return;
        }
        // a 流失 never uses a thorn chance (PRTS 作战机制 "生命流失不会触发反伤"); 无来源 damage does, hitting nobody (备注
        // "可被无来源伤害消耗反伤机会")
        if (dmg.steadShare || dmg.steadThorn || c.type === 'element' || isHpLoss(dmg) || !st.members[ID.stead].has(t)) return;
        const bb = st.bb[ID.stead];
        const last = t.mem[STEAD_CD] ?? -Infinity;
        if (battle.time - last < num(bb.cd_duration) - 1e-9) return;
        t.mem[STEAD_CD] = battle.time;
        const src = c.source;
        if (!src || src.side !== 'enemy' || !src.alive) return;
        // "伤害来源受到(850+10×L)点法术伤害": 无来源 (no attacker multipliers, hooks see no source) but credited to the
        // member hit — its player's stats and shared-pool tally count it, like an element burst (v2.5: no credit at all,
        // up to 19 % of a co-op leader's pool and 88 % of a solo one went unattributed, DESIGN §20.10)
        const d = battle.makeDamage({ amount: num(bb.base_damage_value) + num(bb.damage_value_per_stack) * L(battle, st, ID.stead), type: 'arts', canDodge: false, sourceless: true });
        d.steadThorn = true;
        battle.dealDamage(t, src, d);
        if (src.alive) battle.applyStatus(src, 'fragile', { duration: num(bb['weak[limit]'], 5), value: num(bb.damage_scale, 1) - 1, source: t });
        return;
      }
      if (!arcane || c.type !== 'arts' || t.side !== 'enemy' || !t.alive) return;
      const src = c.source;
      if (!src || src.kind !== 'op') return;
      const st = byPid[src.ownerId];
      if (!st || !st.tiers[ID.arcane] || !st.members[ID.arcane].has(src)) return;
      const bb = st.bb[ID.arcane];
      const low = st.tiers[ID.arcane] >= 2 && t.hpRatio < num(bb.hp_ratio);
      // one 奥术 instance per target, the strongest (both players of a pair field included): see the header
      battle.applyStrongest(t, KEY.arcane, { duration: num(bb.weak_duration, 3), value: low ? st.arcaneLowMul : st.arcaneMul, mods: arcaneMods, source: src });
    });
  }
}