/**
 * balance.test.js — is the game FAIR?  [SPRINT6 gate 1; jointly owned, Lane B holds the pen]
 *
 * Every other suite asks "does this system do what it says". This one asks the
 * only question a player cares about: **can the night be won, through the real
 * shop, and does winning require the things the design says it should.**
 *
 * It is deliberately a browser suite. The scoring chain it has to drive —
 * skyfx's hail/rain exposure over the bed — needs `document`, so it cannot run
 * in node like B's other suites. Driving the REAL chain is the point: a balance
 * test that reimplements the drain measures a copy and proves nothing.
 *
 * The shape of every assert here is:
 *   1. build a loadout through RiggingSession, so the $80 shop is real money;
 *   2. fly the real storm JSON over an in-band quad from the real yard;
 *   3. integrate the real exposure helpers into the real garden drain;
 *   4. judge with main.js's own win rule (hp >= 50 && corners lost < 2).
 *
 * Measured 2026-07-18 on merged main (weights hail 5.0 / rain 0.25, drain 0.9,
 * downdraftOfTotal 0.45). The numbers in the comments are what the levers move —
 * if you change a weight and a line here goes red, that IS the balance moving,
 * which is exactly what this file is for.
 */

import { RiggingSession } from '../rigging.js';
import { SailRig } from '../sail.js';
import { createSkyFx } from '../skyfx.js';
import { createWind, loadStorm } from '../weather.js';
import { HARDWARE, FIXED_DT, START_BUDGET } from '../contracts.js';

const [CARABINER, SHACKLE, RATED] = HARDWARE;

/** main.js's rule, duplicated ONLY here so a balance failure names the rule it broke. */
const WIN = (hp, lost) => hp >= 50 && lost < 2;
const GARDEN_DRAIN = 0.9;   // main.js
const W_HAIL = 5.0;         // main.js, decision 13 — integration weights
const W_RAIN = 0.25;

/**
 * The yard is READ FROM world.js, never copied.
 *
 * The first draft of this file hardcoded the anchor table from a THREADS entry
 * and got it badly wrong — the dressed yard has the house at x=±3, not ±5, and
 * the decision-2 branch anchors nowhere near where I'd guessed. It flew a
 * fictional yard and reported the wild night unwinnable (hp 36) while the real
 * one wins at hp 99. That is the same failure as Sprint 3's 16.7° reference rig:
 * a number I invented, proving something true about nothing. A balance suite in
 * particular cannot afford it — the yard IS the balance. So: build the real
 * world, take its anchors, and freeze only the sway.
 *
 * Sway is frozen deliberately: tree anchors wander with the wind, and a balance
 * failure that came from a gust rocking a branch would be a fact about world.js,
 * not about whether the shop can buy a winnable rig.
 */
async function buildYard() {
  const THREE = await import('../../vendor/three.module.js');
  const { createWorld } = await import('../world.js');
  const scene = new THREE.Scene();
  const calm = {
    sample: (p, t, o) => (o || new THREE.Vector3()).set(0, 0, 4),
    speedAt: () => 4, rainAt: () => 0, rainMmPerHour: () => 0,
    gustTelegraph: () => null, setSheltersFromTrees() {}, eventsBetween: () => [],
  };
  const world = createWorld(scene, { wind: calm });
  if (world.dress) { try { await world.dress(); } catch { /* graybox anchors are enough */ } }
  const anchors = world.anchors.map((a) => {
    const pos = { x: a.pos.x, y: a.pos.y, z: a.pos.z };
    return { id: a.id, type: a.type, pos, sway: () => pos };
  });
  return { anchors, bed: world.gardenBed, heightAt: world.heightAt };
}

/**
 * THE LINE for storm_02: the best bed-covering quad the dressed yard offers
 * (~41 m², ~63% of the bed). Only reachable because of A's decision-2 branch
 * anchors — before those landed, the integrator measured no winnable line at all,
 * and this quad is the difference.
 */
// Integrator update at the Sprint-6 merge: this suite and A's p4 anchor crossed
// mid-air. The quad below was the best PRE-p4 cover and its p1 corner pulls
// 7.4 kN — unholdable at any price (B's own blocker analysis, kept in THREADS).
// A's p4 supplies the missing north-west corner; their measured winning line is
// t2+p3+p4+t2b, four shackles + a spare ($75), hp 58 with 1 lost. That line is
// what THE LINE now flies. The old quad stays as the geometry control below.
const COVER_QUAD = ['t2', 'p3', 'p4', 't2b'];
const PRE_P4_QUAD = ['p1', 't1b', 't1c', 't2b'];
/** A rig that holds fine and shades nothing — the decision-13 control. */
const MISS_QUAD = ['h1', 'h2', 'h3', 't1'];

/**
 * Buy a loadout through the real shop. Returns null if $80 doesn't stretch to it.
 * `tension` defaults to the dial's own neutral (1.0 — RiggingSession's
 * DEFAULT_TENSION) rather than a number this file picked, so a loadout here is a
 * loadout a player could actually walk out of prep with. Gate 0 swept 0.6-1.0
 * and storm_02's verdict never moved, but the default should still be the
 * game's.
 */
function shop(yard, ids, hw, spares = 0, tension = 1.0) {
  const s = new RiggingSession({ anchors: yard.anchors });
  for (const id of ids) if (!s.rig(id).ok) return null;
  for (let i = 0; i < ids.length; i++) if (!s.setHardware(ids[i], hw[i]).ok) return null;
  if (spares && !s.setSpares(spares).ok) return null;
  s.setTension(tension);
  return s;
}

/**
 * Fly a bought loadout through a storm and score it exactly as the game does.
 * @returns {{hp:number, lost:number, cover:number, spent:number, pond:number}}
 */
async function fly(yard, session, stormName, { repair = false, broom = false } = {}) {
  const def = await loadStorm(stormName);
  const wind = createWind(def);
  // main.js:369 does this at boot and this suite didn't — trees shelter the air
  // downwind of them, and a quad hanging off tree anchors sits right in it.
  // (Measured during gate 0: it doesn't change storm_02's verdict, but a harness
  // that claims to be the single source of truth doesn't get to skip a step the
  // game takes.)
  wind.setSheltersFromTrees(yard.anchors.filter((a) => a.type === 'tree'));
  const rig = session.commit(new SailRig({ anchors: yard.anchors, gridN: 10 }));
  const sky = createSkyFx({ wind, night: true });

  let hp = 100, pond = 0, used = 0;
  const steps = Math.round(def.duration / FIXED_DT);
  for (let i = 0; i < steps; i++) {
    const t = i * FIXED_DT;
    rig.step(FIXED_DT, wind, t);
    sky.step(FIXED_DT, t, { sail: rig });

    // main.js's exact drain: decision 13's hail term + a small rain term
    const exposure = sky.gardenHailExposure(yard.bed, t) * W_HAIL + sky.gardenExposure(yard.bed, t) * W_RAIN;
    if (exposure > 0) hp = Math.max(0, hp - GARDEN_DRAIN * exposure * FIXED_DT);

    const m = rig.pondMass();
    if (m > pond) pond = m;
    // a competent player: re-rig the first corner that goes (costs the spare),
    // and sweep the belly before it loads up
    if (repair && used < session.spares) {
      const k = rig.corners.findIndex((c) => c.broken);
      if (k >= 0) { rig.repair(k); used++; }
    }
    if (broom && m > 250) {
      const c = rig.pondCentroid();
      if (c) rig.drainPondAt(c.node, FIXED_DT, 3);
    }
  }
  sky.dispose?.();
  return {
    hp: Math.round(hp),
    lost: rig.corners.filter((c) => c.broken).length,
    spent: START_BUDGET - session.budget,
    pond: Math.round(pond),
  };
}

/**
 * @param {import('../testkit.js').Suite} t
 *
 * NOTE the shape: every storm is flown UP FRONT, then the asserts are plain
 * synchronous checks over the results. `Suite.test()` calls its fn without
 * awaiting it, so an `async` assert would hand it a Promise that never throws
 * synchronously and pass forever while proving nothing. `runAll` DOES await this
 * function, so the flying belongs here and the judging belongs in t.test().
 */
export default async function run(t) {
  const yard = await buildYard();

  // --- fly everything first -------------------------------------------------
  // 1 rated + 2 shackle + 1 carabiner + a spare = $80 EXACTLY. The spare is what
  // makes the repair legal, and it's the trap in this whole balance question: a
  // loadout that spends all $80 on hardware cannot repair anything.
  // A's measured line: four shackles + a spare = $75 (THREADS gate-1 entry).
  const lineShop = shop(yard, COVER_QUAD, [SHACKLE, SHACKLE, SHACKLE, SHACKLE], 1);
  const line = lineShop ? await fly(yard, lineShop, 'storm_02_wildnight', { repair: true, broom: true }) : null;

  const cheapShop = shop(yard, COVER_QUAD, [CARABINER, CARABINER, CARABINER, CARABINER], 0);
  const cheap = cheapShop ? await fly(yard, cheapShop, 'storm_02_wildnight') : null;

  const missShop = shop(yard, MISS_QUAD, [RATED, RATED, SHACKLE, CARABINER], 0);
  const miss = missShop ? await fly(yard, missShop, 'storm_02_wildnight', { broom: true }) : null;

  const gentleShop = shop(yard, COVER_QUAD, [CARABINER, CARABINER, CARABINER, CARABINER], 0);
  const gentle = gentleShop ? await fly(yard, gentleShop, 'storm_01_gentle') : null;

  // --- then judge -----------------------------------------------------------

  // SPRINT7 gate 0 — the skip is gone, and the dispute is settled by physics.
  //
  // Lane A measured this exact line (t2,p3,p4,t2b, 4×shackle + spare, $75) at
  // hp 58 / 1 lost. This suite says hp 36 / 2 lost. I went through every way the
  // two harnesses could differ and ruled each out by measurement:
  //
  //   tree wind-shelter (main.js:369 calls setSheltersFromTrees, this didn't)
  //                                     ... on vs off: hp 36 either way
  //   tension (this hardcoded 0.9, the game defaults 1.0)
  //                                     ... 0.6 / 0.75 / 0.9 / 1.0: hp 36, 2 lost, all four
  //   drain wiring (garden.step's signature changed to take hail+rain separately)
  //                                     ... same arithmetic: 5.0/0.25 × 0.9. Identical.
  //   yard geometry (the bug that bit this file once already)
  //                                     ... diffed all 12 anchors against the live game: zero drift
  //   frozen sway (tree anchors are shock absorbers — DESIGN.md)
  //                                     ... live sway is WORSE, not better: t2 4.4 → 4.6 kN
  //
  // What's left is not a harness difference, it's arithmetic. On this quad t2
  // peaks at 4.4-4.9 kN and a shackle is rated 3.2. t2 cannot hold, under any
  // variation above. Losing it spends the only spare; then p3 (3.7) or t2b (3.4)
  // — both also over 3.2 — goes too. Two corners down, the sail stops shadowing
  // the bed, and hp lands on 36, which is precisely the bare-bed score. That is
  // why every configuration returns the same number: 36 is not a coincidence,
  // it's "the rig contributed nothing".
  //
  // And the quad is not rescuable by shopping: putting the RATED shackle on t2
  // ($80 with a spare) still ends hp 36 / 2 lost, because p3 and t2b then break
  // instead. This quad needs THREE corners above shackle grade and $80 buys two.
  //
  // So: A's win does not reproduce, and I believe A's number is the artifact —
  // most likely the same phase-boundary contamination that produced my own
  // hp=99 last sprint (driving SHADES.rigSail and then advancing the phase
  // machine re-rigs from the game's own RiggingSession, so you score a rig you
  // didn't choose). A: the check is one line — assert rig.corners' anchorIds
  // and hw names immediately before your storm loop and confirm they're what you
  // bought. If they are, I'm wrong and the cause is still open.
  t.test('balance: storm_02 HAS a winnable line through the real $80 shop', () => {
    if (!line) throw new Error('the $80 shop cannot buy the candidate line at all');
    if (!WIN(line.hp, line.lost)) {
      throw new Error(
        `no winnable line: ${COVER_QUAD.join(',')} on 4×shackle+spare ($${line.spent}) ended ` +
        `hp=${line.hp}, lost=${line.lost}/4 (need hp>=50, lost<2). t2 peaks ~4.4 kN vs a 3.2 kN ` +
        `shackle and cannot hold; rating up t2 only moves the break to p3/t2b. Ruled out as causes: ` +
        `shelter, tension 0.6-1.0, drain wiring, yard drift, sway. See the comment above — ` +
        `this needs a LOAD lever (SPRINT7 gate 0), not a tuning one.`);
    }
    return `$${line.spent} on ${COVER_QUAD.join(',')} -> hp ${line.hp}, ${line.lost}/4 lost`;
  });

  t.test('balance: storm_02 punishes a cheap rig on the same quad', () => {
    if (!cheap) throw new Error('the shop could not buy four carabiners — the economy is broken');
    // The other half of fair: the SAME quad on four carabiners ($20) must lose,
    // or "winnable" just means "trivial".
    if (WIN(cheap.hp, cheap.lost)) {
      throw new Error(`four $5 carabiners won the wild night (hp=${cheap.hp}, lost=${cheap.lost}) — ` +
        `hardware choice has stopped mattering`);
    }
    return `$${cheap.spent} of carabiners -> hp ${cheap.hp}, ${cheap.lost}/4 lost — correctly punished`;
  });

  t.test('balance: a rig that misses the bed does not save the garden', () => {
    if (!miss) throw new Error('could not buy the miss-quad control');
    // decision 13's whole point. A rig up at the house is fine engineering and
    // useless gardening — if this wins, the garden score has stopped reading the
    // rig and we're back to Sprint 5's "a perfect rig ties with no rig at all".
    if (WIN(miss.hp, miss.lost)) {
      throw new Error(`a rig with no bed coverage won the night (hp=${miss.hp}) — the garden score ` +
        `is not reading the rig`);
    }
    return `${4 - miss.lost}/4 corners held but the bed was open -> hp ${miss.hp} — coverage is what scores`;
  });

  t.test('balance: storm_01 is a warm-up anyone wins', () => {
    if (!gentle) throw new Error('could not buy the gentle-day control');
    if (!WIN(gentle.hp, gentle.lost)) {
      throw new Error(`the gentle day beat a $${gentle.spent} rig (hp=${gentle.hp}, ` +
        `lost=${gentle.lost}) — storm_01 is the tutorial, it must not punish`);
    }
    return `$${gentle.spent} of carabiners survives the gentle day -> hp ${gentle.hp}`;
  });
}