/**
 * sail.selftest.js — assert suite for the sail sim.  [Lane B]
 *
 * Exports SAIL_TESTS as plain [name, fn] pairs so ONE set of asserts runs in
 * two harnesses: Lane A's selftest.html (via js/tests/b.test.js) and node
 * (`node web/world/js/sail.selftest.js`) for fast iteration without a browser.
 * Drives time with fixed-dt loops only — never rAF, never a clock.
 *
 * The headline assert is `hypar sheds load vs flat`: it is the game's thesis
 * stated as a test. If it ever goes red, the sail has stopped being a sail.
 */

import { SailRig } from './sail.js';
import { HARDWARE, FIXED_DT, createStubWind, rng } from './contracts.js';

const SIM_DT = FIXED_DT;

// ---------- deterministic stub wind ----------
// contracts.js ships createStubWind(), and the integration test below uses it.
// This local one exists only because the thesis needs the wind DIRECTION swept,
// which the shared stub does not expose. Lane C's weather.js replaces both.

function makeStubWind({ seed = 7, stormLen = 90, dir = { x: 0, y: 0, z: 1 }, calm = false } = {}) {
  const rand = rng(seed);
  const gusts = [];
  for (let t = 3; t < stormLen; t += 5 + rand() * 7) {
    gusts.push({ start: t, pow: 12 + rand() * 16 + 10 * (t / stormLen) });
  }
  const len = Math.hypot(dir.x, dir.y, dir.z) || 1;
  const dx = dir.x / len, dy = dir.y / len, dz = dir.z / len;
  const out = { x: 0, y: 0, z: 0 };

  return {
    speedAt(t) {
      if (calm) return 0;
      let speed = 8 + 26 * Math.min(1, (t / stormLen) * 1.6);
      for (const g of gusts) {
        const gt = t - g.start;
        if (gt < 0 || gt >= 5) continue;
        if (gt < 1.5) continue;                               // telegraph: seen, not felt
        else if (gt < 2.3) speed += g.pow * (gt - 1.5) / 0.8; // ramp
        else if (gt < 4.0) speed += g.pow;                    // hold
        else speed += g.pow * (5.0 - gt);                     // fade
      }
      return speed;
    },
    sample(pos, t) {
      const s = this.speedAt(t);
      out.x = dx * s; out.y = dy * s; out.z = dz * s;
      return out;
    },
    gustTelegraph: () => null,
  };
}

const constantWind = (v) => ({ sample: () => v, speedAt: () => Math.hypot(v.x, v.y, v.z), gustTelegraph: () => null });

// ---------- test rigs ----------
// Same 5x5 m footprint, same multiset of corner heights {4.0, 4.0, 2.5, 2.5}.
// Only the ARRANGEMENT differs: coplanar (flat, pitched) vs permuted (twisted
// hypar). Any load difference is therefore purely geometry, nothing else.

const FOOT = [
  { x: -2.5, z: -2.5 }, { x: 2.5, z: -2.5 }, { x: 2.5, z: 2.5 }, { x: -2.5, z: 2.5 },
];
export const HEIGHTS_FLAT = [4.0, 4.0, 2.5, 2.5];  // y linear in z -> one plane
export const HEIGHTS_HYPAR = [4.0, 2.5, 4.0, 2.5]; // opposite corners up/down -> saddle

/** Anchors shaped like contracts.js Anchor: sway(t) is the ABSOLUTE position. */
export const makeAnchors = (heights) =>
  FOOT.map((f, i) => {
    const pos = { x: f.x, y: heights[i], z: f.z };
    return { id: `a${i}`, type: 'post', pos, sway: () => pos };
  });

const ALL_IDS = ['a0', 'a1', 'a2', 'a3'];
const UNBREAKABLE = { name: 'test rig', cost: 0, rating: Infinity };

function rig(heights, { hw = UNBREAKABLE, tension = 1.0, porosity = 0 } = {}) {
  return new SailRig({ anchors: makeAnchors(heights), gridN: 10, porosity })
    .attach(ALL_IDS, [hw, hw, hw, hw], tension);
}

/** Fixed-dt fast-forward. Returns the peak corner load over the whole run, N. */
function runStorm(r, wind, secs, onStep) {
  const steps = Math.round(secs / SIM_DT);
  let peak = 0;
  for (let i = 0; i < steps; i++) {
    r.step(SIM_DT, wind, i * SIM_DT);
    const m = r.maxLoad();
    if (m > peak) peak = m;
    if (onStep) onStep(r, i);
  }
  return peak;
}

const TESTS = [];
const test = (name, fn) => TESTS.push([name, fn]);
const assert = (cond, msg) => { if (!cond) throw new Error(msg); };
const kN = (n) => `${(n / 1000).toFixed(2)} kN`;

// ---------- the suite ----------

test('sim stays finite through a full storm', () => {
  const r = rig(HEIGHTS_HYPAR);
  runStorm(r, makeStubWind({ stormLen: 90 }), 90);
  for (const v of r.pos) assert(Number.isFinite(v), 'node position went NaN/Infinity');
  for (const c of r.corners) assert(Number.isFinite(c.load), 'corner load went NaN');
  return `peak ${kN(r.corners.reduce((m, c) => Math.max(m, c.peakLoad), 0))}`;
});

test('sail sags under gravity when calm', () => {
  const r = rig(HEIGHTS_FLAT);
  runStorm(r, makeStubWind({ calm: true }), 6);
  const N = r.N, mid = (Math.floor(N / 2) * N + Math.floor(N / 2)) * 3;
  const midY = r.pos[mid + 1];
  const cornerMeanY = HEIGHTS_FLAT.reduce((a, b) => a + b) / 4;
  assert(midY < cornerMeanY, `belly (${midY.toFixed(2)}m) should hang below corner mean (${cornerMeanY}m)`);
  return `belly sags ${(cornerMeanY - midY).toFixed(2)} m below corner plane`;
});

// Newton's third law. This is what pins FABRIC_K to real newtons: if the corner
// reactions don't sum to the actual aerodynamic + weight force on the fabric,
// the load meter is lying and every kN rating on it is meaningless.
test('statics: corner reactions balance the applied force', () => {
  const w = constantWind({ x: 0, y: 0, z: 18 });
  const r = rig(HEIGHTS_FLAT);
  runStorm(r, w, 12); // settle
  // A membrane in steady wind never fully stops moving, so compare the
  // TIME-AVERAGED reaction against the time-averaged applied force. That is the
  // momentum balance that must hold; instant by instant it need not.
  let n = 0, ax = 0, ay = 0, az = 0, rx = 0, ry = 0, rz = 0;
  for (let i = 0; i < Math.round(4 / SIM_DT); i++) {
    const t = 12 + i * SIM_DT;
    r.step(SIM_DT, w, t);
    const f = r.netAppliedForce(w, t);
    ax += f.x; ay += f.y; az += f.z;
    for (const c of r.corners) { rx += c.loadVec.x; ry += c.loadVec.y; rz += c.loadVec.z; }
    n++;
  }
  ax /= n; ay /= n; az /= n; rx /= n; ry /= n; rz /= n;
  const appliedMag = Math.hypot(ax, ay, az);
  const err = Math.hypot(rx - ax, ry - ay, rz - az) / appliedMag;
  assert(err < 0.2, `reactions ${kN(Math.hypot(rx, ry, rz))} vs applied ${kN(appliedMag)} — ${(err * 100).toFixed(0)}% out of balance`);
  return `applied ${kN(appliedMag)}, reactions ${kN(Math.hypot(rx, ry, rz))}, residual ${(err * 100).toFixed(1)}%`;
});

// THE THESIS. A twisted sail resists bellying into one coherent pocket, so its
// worst moment is gentler than a flat sail's worst moment.
//
// Scored on WORST CASE over wind direction, not per-direction. Lane C's storms
// veer, so the player never gets to choose the wind, and worst-case is what the
// hardware actually has to survive. Per-direction would be a false assert: a
// flat sail sitting edge-on to the wind genuinely does have low drag, and from
// that one angle it beats the hypar. Demanding otherwise would mean tuning the
// sim into a lie.
test('hypar sheds load vs flat, worst case over wind direction (the thesis)', () => {
  const DIRS = [
    { name: 'N', x: 0, z: 1 }, { name: 'NE', x: 0.707, z: 0.707 },
    { name: 'E', x: 1, z: 0 }, { name: 'SE', x: 0.707, z: -0.707 },
    { name: 'S', x: 0, z: -1 }, { name: 'SW', x: -0.707, z: -0.707 },
    { name: 'W', x: -1, z: 0 }, { name: 'NW', x: -0.707, z: 0.707 },
  ];
  const sweep = (heights) => {
    let worst = 0, at = '';
    for (const d of DIRS) {
      const storm = makeStubWind({ seed: 7, stormLen: 45, dir: { x: d.x, y: 0, z: d.z } });
      const p = runStorm(rig(heights), storm, 45);
      if (p > worst) { worst = p; at = d.name; }
    }
    return { worst, at };
  };
  const flat = sweep(HEIGHTS_FLAT);
  const hypar = sweep(HEIGHTS_HYPAR);
  assert(
    hypar.worst < flat.worst * 0.8,
    `hypar worst ${kN(hypar.worst)} (${hypar.at}) should be well under flat worst ${kN(flat.worst)} (${flat.at})`
  );
  return `flat worst ${kN(flat.worst)} from ${flat.at} -> hypar worst ${kN(hypar.worst)} from ${hypar.at} (sheds ${((1 - hypar.worst / flat.worst) * 100).toFixed(0)}%)`;
});

test('cascade: losing a corner spikes its neighbours', () => {
  const w = constantWind({ x: 0, y: 0, z: 22 });
  const r = rig(HEIGHTS_HYPAR);
  runStorm(r, w, 6); // settle
  const before = Math.max(r.corners[1].load, r.corners[3].load);
  r.corners[0].broken = true;
  r._repin(r.t);
  runStorm(r, w, 2.5); // let the load redistribute
  const after = Math.max(r.corners[1].load, r.corners[3].load);
  assert(after >= before * 2, `neighbour went ${kN(before)} -> ${kN(after)}, wanted >= 2x`);
  return `neighbour ${kN(before)} -> ${kN(after)} (${(after / before).toFixed(1)}x)`;
});

test('determinism: identical inputs give byte-equal load traces', () => {
  const trace = () => {
    const r = rig(HEIGHTS_HYPAR);
    const w = makeStubWind({ seed: 3, stormLen: 30 });
    const out = [];
    runStorm(r, w, 30, (rr) => { for (const c of rr.corners) out.push(c.load); });
    return out;
  };
  const a = trace(), b = trace();
  assert(a.length === b.length, 'traces differ in length');
  for (let i = 0; i < a.length; i++) assert(a[i] === b[i], `sample ${i} diverged: ${a[i]} vs ${b[i]}`);
  return `${a.length} load samples identical`;
});

test('determinism: variable frame dt matches fixed dt', () => {
  // Lane A's render loop delivers ragged dt. The internal accumulator has to
  // absorb that, or nothing the selftest proves applies to the real game.
  const w1 = makeStubWind({ seed: 5, stormLen: 20 });
  const fixed = rig(HEIGHTS_HYPAR);
  for (let i = 0; i < Math.round(20 / SIM_DT); i++) fixed.step(SIM_DT, w1, i * SIM_DT);

  const w2 = makeStubWind({ seed: 5, stormLen: 20 });
  const ragged = rig(HEIGHTS_HYPAR);
  const rand = rng(99);
  let acc = 0;
  while (acc < 20) {
    const dt = 0.004 + rand() * 0.02; // 4-24 ms frames
    ragged.step(dt, w2, acc);
    acc += dt;
  }
  for (let k = 0; k < 4; k++) {
    const d = Math.abs(fixed.corners[k].load - ragged.corners[k].load);
    assert(d < 1e-6, `corner ${k} drifted ${d.toFixed(6)} N between fixed and ragged dt`);
  }
  return 'ragged frame times converge on the fixed-dt trace';
});

test('tension dial changes load (drum tight shock-loads)', () => {
  const w = constantWind({ x: 0, y: 0, z: 20 });
  const loosePeak = runStorm(rig(HEIGHTS_HYPAR, { tension: 0.7 }), w, 8);
  const tightPeak = runStorm(rig(HEIGHTS_HYPAR, { tension: 1.35 }), w, 8);
  assert(tightPeak > loosePeak, `tight ${kN(tightPeak)} should exceed loose ${kN(loosePeak)}`);
  return `loose ${kN(loosePeak)} vs tight ${kN(tightPeak)}`;
});

test('porous shade cloth carries less load than solid membrane', () => {
  const w = constantWind({ x: 0, y: 0, z: 20 });
  const solid = runStorm(rig(HEIGHTS_HYPAR, { porosity: 0 }), w, 8);
  const porous = runStorm(rig(HEIGHTS_HYPAR, { porosity: 0.35 }), w, 8);
  assert(porous < solid, `porous ${kN(porous)} should be under solid ${kN(solid)}`);
  return `solid ${kN(solid)} vs porous ${kN(porous)}`;
});

test('coverage: sail shades the ground under it, not beside it', () => {
  const r = rig(HEIGHTS_FLAT);
  runStorm(r, makeStubWind({ calm: true }), 4);
  // world.gardenBed rects are CENTRE + size, so this bed straddles the origin.
  const under = r.coverageOver({ x: 0, z: 0, w: 4, d: 4 });
  const beside = r.coverageOver({ x: 14, z: 14, w: 4, d: 4 });
  assert(under > 0.9, `ground under the sail only ${(under * 100).toFixed(0)}% shaded`);
  assert(beside === 0, `ground 14 m away reported ${(beside * 100).toFixed(0)}% shaded`);
  return `under sail ${(under * 100).toFixed(0)}%, off to the side ${(beside * 100).toFixed(0)}%`;
});

test('coverage tracks a low sun off to the side', () => {
  const r = rig(HEIGHTS_FLAT);
  runStorm(r, makeStubWind({ calm: true }), 4);
  const noon = r.coverageOver({ x: 0, z: 0, w: 4, d: 4 }, { x: 0, y: 1, z: 0 });
  const lowSun = r.coverageOver({ x: 0, z: 0, w: 4, d: 4 }, { x: 0.9, y: 0.25, z: 0 });
  assert(noon > lowSun, `shadow should slide off the bed as the sun drops (noon ${noon}, low ${lowSun})`);
  return `noon ${(noon * 100).toFixed(0)}% -> low sun ${(lowSun * 100).toFixed(0)}%`;
});

// PLAN3D §7 definition of done, in miniature.
test('cheap flat rig cascades; twisted mixed rig survives', () => {
  const storm = () => makeStubWind({ seed: 11, stormLen: 90 });
  const cheap = rig(HEIGHTS_FLAT, { hw: HARDWARE[0], tension: 1.35 });
  runStorm(cheap, storm(), 90);
  const cheapBroken = cheap.corners.filter((c) => c.broken).length;

  const good = rig(HEIGHTS_HYPAR, { hw: HARDWARE[2], tension: 0.95 });
  runStorm(good, storm(), 90);
  const goodBroken = good.corners.filter((c) => c.broken).length;

  assert(cheapBroken >= 2, `flat drum-tight carabiner rig only lost ${cheapBroken} corners — should cascade`);
  assert(goodBroken === 0, `twisted rated-shackle rig lost ${goodBroken} corners — should survive`);
  return `cheap flat lost ${cheapBroken}/4, good hypar lost ${goodBroken}/4`;
});

// PLAN3D §5-B: "broken corner frees the node -> flogging is emergent". This
// drives a REAL overload failure rather than setting broken by hand, because
// hand-setting it was exactly what hid the bug where _checkFailure marked a
// corner broken but never gave its node its mass back — so a blown corner
// stayed welded in mid-air and the sail never flogged.
test('a blown corner is freed and flies (flogging is emergent)', () => {
  const w = makeStubWind({ seed: 11, stormLen: 90 });
  const r = rig(HEIGHTS_FLAT, { hw: HARDWARE[0], tension: 1.3 }); // cheap and tight: this one lets go
  const broke = [];
  r.events.on('break', (e) => broke.push(e));

  // step until the first corner lets go
  let i = 0;
  for (const end = Math.round(90 / SIM_DT); i < end && !broke.length; i++) r.step(SIM_DT, w, i * SIM_DT);
  assert(broke.length > 0, 'a carabiner rig should have blown a corner somewhere in a 90 s storm');

  const k = r.corners.indexOf(broke[0].corner);
  const node = r.cornerIdx[k], ci = node * 3;
  const anchor = r.corners[k].anchor.pos;
  const before = [r.pos[ci], r.pos[ci + 1], r.pos[ci + 2]];
  for (let j = 0; j < Math.round(3 / SIM_DT); j++) r.step(SIM_DT, w, (i + j) * SIM_DT);

  const moved = Math.hypot(r.pos[ci] - before[0], r.pos[ci + 1] - before[1], r.pos[ci + 2] - before[2]);
  const fromAnchor = Math.hypot(r.pos[ci] - anchor.x, r.pos[ci + 1] - anchor.y, r.pos[ci + 2] - anchor.z);

  assert(r.invMass[node] > 0, 'blown corner still has infinite mass — it is welded in mid-air, not flogging');
  assert(moved > 0.05, `blown corner only drifted ${moved.toFixed(3)} m in 3 s — it is not flogging`);
  assert(fromAnchor > 0.2, `blown corner is still ${fromAnchor.toFixed(2)} m from its anchor — it never let go`);
  return `corner ${broke[0].anchorId} blew at t=${broke[0].t.toFixed(1)}s, tore ${fromAnchor.toFixed(2)} m off its anchor and is flying`;
});

test('break and repair emit on the events Emitter', () => {
  const w = constantWind({ x: 0, y: 0, z: 20 });
  const r = rig(HEIGHTS_HYPAR, { hw: UNBREAKABLE });
  const seen = [];
  r.events.on('break', (e) => seen.push(e));
  r.events.on('repair', (e) => seen.push(e));

  runStorm(r, w, 4);
  r.corners[0].broken = true;
  r._repin(r.t);
  runStorm(r, w, 1);
  assert(r.corners[0].load === 0, 'broken corner should carry no load');

  assert(r.repairCorner(0, UNBREAKABLE), 'repairCorner should report success');
  runStorm(r, w, 3);
  assert(r.corners[0].load > 100, `repaired corner only pulling ${kN(r.corners[0].load)}`);
  assert(seen.some((e) => e.type === 'repair' && e.corner === r.corners[0]), 'no repair event with {type, corner}');
  return `repaired corner back to ${kN(r.corners[0].load)}, ${seen.length} event(s) emitted`;
});

// --- SPRINT2 decision 4: the seam Lane D already calls ---------------------

test('decision 4: repair(i) re-rigs a blown corner with the spare', () => {
  const w = constantWind({ x: 0, y: 0, z: 20 });
  const r = rig(HEIGHTS_HYPAR, { hw: HARDWARE[0] });
  runStorm(r, w, 4);
  r.corners[0].broken = true;
  r._repin(r.t);

  // exactly Lane D's interact.js call: no hardware argument, return ignored
  r.repair(0);
  assert(!r.corners[0].broken, 'repair(0) should have re-rigged the corner');
  assert(r.corners[0].hw === HARDWARE[1], `spare should re-rig at shackle grade, got ${r.corners[0].hw.name}`);
  assert(r.invMass[r.cornerIdx[0]] === 0, 'repaired corner should be pinned again');
  runStorm(r, w, 3);
  assert(r.corners[0].load > 100, `repaired corner only pulling ${kN(r.corners[0].load)}`);
  return `repair(0) -> ${r.corners[0].hw.name}, back to ${kN(r.corners[0].load)}`;
});

test('decision 4: repair(i) on an intact corner is a no-op', () => {
  const r = rig(HEIGHTS_HYPAR, { hw: HARDWARE[2] });
  runStorm(r, constantWind({ x: 0, y: 0, z: 12 }), 2);
  const hw = r.corners[1].hw;
  r.repair(1); // D gates on corner.broken, but the rig must not trust that
  assert(r.corners[1].hw === hw, 'repairing an intact corner downgraded its hardware');
  return 'intact corner untouched';
});

test('decision 4: trim(i, delta) tightens one corner only', () => {
  const r = rig(HEIGHTS_HYPAR);
  r.trim(0, +0.1);
  assert(Math.abs(r.corners[0].trim - 1.1) < 1e-9, `corner 0 trim ${r.corners[0].trim}`);
  assert(r.corners[1].trim === 1.0, 'trim leaked onto a neighbour');
  for (let i = 0; i < 40; i++) r.trim(0, +0.1); // Lane D can hold the key down
  assert(r.corners[0].trim <= 1.15 + 1e-9, `trim ran past its clamp: ${r.corners[0].trim}`);
  return `trim clamps at ${r.corners[0].trim.toFixed(2)}, neighbours unmoved`;
});

test('decision 4: cornerPos(i) is live, fresh, and chases a flogging corner', () => {
  const w = makeStubWind({ seed: 11, stormLen: 90 });
  const r = rig(HEIGHTS_FLAT, { hw: HARDWARE[0], tension: 1.3 });
  const anchor = r.corners[0].anchor.pos;
  const p0 = r.cornerPos(0);
  assert(Math.hypot(p0.x - anchor.x, p0.y - anchor.y, p0.z - anchor.z) < 1e-6,
    'an intact corner should report its anchor position');
  assert(r.cornerPos(0) !== r.cornerPos(0), 'cornerPos must return a FRESH vector, not shared scratch');

  // blow it, then confirm the prompt would follow the flying corner
  r.corners[0].broken = true;
  r._repin(r.t);
  runStorm(r, w, 6);
  const p1 = r.cornerPos(0);
  const drift = Math.hypot(p1.x - anchor.x, p1.y - anchor.y, p1.z - anchor.z);
  assert(drift > 0.3, `blown corner's prompt only moved ${drift.toFixed(2)} m off the anchor`);
  assert(new SailRig({ anchors: makeAnchors(HEIGHTS_FLAT) }).cornerPos(0) === null,
    'cornerPos on an unrigged rig should be null, not a throw');
  return `prompt tracks the blown corner ${drift.toFixed(2)} m off its anchor`;
});

// --- SPRINT2 decision 5: debris -------------------------------------------

const crate = (over) => ({ x: 0, y: 3.25, z: 0, vx: 0, vy: 0, vz: 14, r: 0.3, mass: 9, alive: true, ...over });

test('decision 5: a crate hitting the sail conserves momentum', () => {
  const r = rig(HEIGHTS_FLAT);
  runStorm(r, makeStubWind({ calm: true }), 4); // settle, so the cloth isn't ringing
  // aimed at the belly, not a corner: a pinned corner would (correctly) dump
  // momentum into the house and there'd be nothing to conserve
  const mid = r.N * Math.floor(r.N / 2) + Math.floor(r.N / 2);
  const p = crate({ x: r.pos[mid * 3], y: r.pos[mid * 3 + 1] - 0.25, z: r.pos[mid * 3 + 2], vy: 6, vz: 0 });

  const clothP = () => {
    let x = 0, y = 0, z = 0;
    for (let n = 0; n < r.invMass.length; n++) {
      if (r.invMass[n] === 0) continue; // pinned: its momentum belongs to the house
      const i = n * 3;
      x += (r.pos[i] - r.prev[i]) / SIM_DT * r.nodeMass;
      y += (r.pos[i + 1] - r.prev[i + 1]) / SIM_DT * r.nodeMass;
      z += (r.pos[i + 2] - r.prev[i + 2]) / SIM_DT * r.nodeMass;
    }
    return { x, y, z };
  };
  const total = () => {
    const c = clothP();
    return { x: c.x + p.vx * p.mass, y: c.y + p.vy * p.mass, z: c.z + p.vz * p.mass };
  };

  const before = total();
  r._applyDebris([p], SIM_DT);
  const after = total();

  const drift = Math.hypot(after.x - before.x, after.y - before.y, after.z - before.z);
  const scale = Math.hypot(before.x, before.y, before.z);
  assert(scale > 1, 'test crate carries no momentum to conserve');
  assert(drift / scale < 0.01, `momentum drifted ${drift.toFixed(3)} of ${scale.toFixed(1)} kg·m/s (${(drift / scale * 100).toFixed(1)}%)`);
  assert(p.vy < 6, `the crate should have LOST speed to the cloth, still at ${p.vy.toFixed(2)} m/s`);
  return `crate ${scale.toFixed(0)} kg·m/s, exchange conserves to ${(drift / scale * 100).toFixed(3)}%`;
});

test('decision 5: a crate through the sail shoves the cloth and emits', () => {
  const r = rig(HEIGHTS_FLAT);
  runStorm(r, makeStubWind({ calm: true }), 4);
  const hits = [];
  r.events.on('debrisHit', (e) => hits.push(e));

  const mid = r.N * Math.floor(r.N / 2) + Math.floor(r.N / 2);
  const before = r.pos[mid * 3 + 1];
  const p = crate({ x: r.pos[mid * 3], y: r.pos[mid * 3 + 1] - 0.6, z: r.pos[mid * 3 + 2], vy: 12, vz: 0 });
  const v0 = p.vy;

  // Peak, not final: the crate crosses the cloth in about three frames and the
  // membrane springs back well inside the run, so sampling the end measures the
  // recovery rather than the punch.
  const wind = makeStubWind({ calm: true });
  let peak = before;
  for (let i = 0; i < 30; i++) {
    r.step(SIM_DT, wind, i * SIM_DT, { pieces: [p] });
    p.y += p.vy * SIM_DT; p.z += p.vz * SIM_DT;
    peak = Math.max(peak, r.pos[mid * 3 + 1]);
  }
  assert(hits.length > 0, 'crate passed through the cloth without a single contact');
  assert(peak > before + 0.05, `belly only lifted ${(peak - before).toFixed(3)} m — the crate went straight through`);
  assert(p.vy < v0, `crate left at ${p.vy.toFixed(2)} m/s, never paid for the punch (entered at ${v0})`);
  return `${hits.length} contacts, belly punched ${(peak - before).toFixed(2)} m, crate ${v0} -> ${p.vy.toFixed(1)} m/s`;
});

test('decision 5: no debris and empty debris are both fine', () => {
  const w = makeStubWind({ seed: 2, stormLen: 20 });
  const a = rig(HEIGHTS_HYPAR), b = rig(HEIGHTS_HYPAR);
  for (let i = 0; i < 600; i++) {
    a.step(SIM_DT, w, i * SIM_DT);                    // Lane A's 3-arg call still works
    b.step(SIM_DT, makeStubWind({ seed: 2, stormLen: 20 }), i * SIM_DT, { pieces: [] });
  }
  for (let k = 0; k < 4; k++) {
    assert(Math.abs(a.corners[k].load - b.corners[k].load) < 1e-9,
      'an empty debris list changed the sim');
  }
  return 'empty and absent debris both no-op';
});

test('runs against the shared contracts.js stub wind', () => {
  // Proves the rig eats the sanctioned Wind implementation, not just my local
  // stub — so nothing surprises us when Lane C's weather.js drops in.
  const r = rig(HEIGHTS_HYPAR, { hw: HARDWARE[1] });
  const wind = createStubWind({ seed: 1, stormLen: 90 });
  const peak = runStorm(r, wind, 90);
  for (const v of r.pos) assert(Number.isFinite(v), 'went NaN on the shared stub wind');
  assert(peak > 0, 'shared stub wind produced no load at all');
  return `90 s on contracts.js stub wind, peak ${kN(peak)}, ${r.corners.filter((c) => c.broken).length}/4 corners lost`;
});

export const SAIL_TESTS = TESTS;

export function runSailSelftest() {
  const results = TESTS.map(([name, fn]) => {
    try { return { name, pass: true, detail: fn() || '' }; }
    catch (e) { return { name, pass: false, detail: e.message }; }
  });
  return { pass: results.every((r) => r.pass), results };
}

export function report(out) {
  const lines = out.results.map(
    (r) => `${r.pass ? 'PASS' : 'FAIL'}  ${r.name}${r.detail ? `\n        ${r.detail}` : ''}`
  );
  return `${lines.join('\n')}\n\n${out.pass ? 'ALL GREEN' : 'FAILURES'} — ${out.results.filter((r) => r.pass).length}/${out.results.length}`;
}

// Run only when invoked directly; importing this module must not run the suite.
if (typeof process !== 'undefined' && process.versions?.node && import.meta.filename === process.argv[1]) {
  const out = runSailSelftest();
  console.log(report(out));
  process.exit(out.pass ? 0 : 1);
}

export { makeStubWind };