import * as THREE from 'three';
import { createPhysicsWorld, initPhysics } from '../src/physics/world.js';
import { createMatch } from '../src/game/match.js';
import { closestLimbs, describeHit } from '../src/game/hits.js';
import { REGION } from '../src/character/skeleton.js';
import { segSegDistance } from '../src/core/math.js';
import { insideRink } from '../shared/rink.js';
import { done, near, ok, section } from './harness.mjs';

/**
 * Body checks, end to end and headless.
 *
 * The thing under test is the handoff: while upright the proxy capsule owns
 * position and the ragdoll is a kinematic passenger; a knockdown inverts that,
 * and getting up inverts it back. That round trip is the part of the design
 * with nowhere to hide, so most of this file is about proving it does not leak
 * a disabled proxy, a stranded sim position, or a skater who never gets up.
 */

const DT = 1 / 60;

await initPhysics();

/** A match with everyone parked, so only the skaters under test move. */
function arena(perTeam = 1) {
  const physics = createPhysicsWorld();
  const match = createMatch({ scene: new THREE.Group(), physics, perTeam, teams: 2 });
  return { physics, match };
}

/**
 * Drive skater 0 into skater 1 head on and run until something happens.
 * Returns the hits that landed.
 */
function collide({ closing = 'full', seconds = 6, gap = 16 } = {}) {
  const { physics, match } = arena(1);
  const [a, b] = match.states;
  const landed = [];
  const seen = new Set();

  a.x = -gap / 2; a.z = 0; a.yaw = Math.PI / 2; a.vx = 0; a.vz = 0;
  b.x = gap / 2; b.z = 0; b.yaw = -Math.PI / 2; b.vx = 0; b.vz = 0;
  match.skaters[0].proxy.teleport(a.x, a.z);
  match.skaters[1].proxy.teleport(b.x, b.z);

  // Drive both directly, so the AI's avoidance steering cannot politely
  // sidestep the collision this test exists to cause. With cameraYaw 0 the
  // stick's x maps straight to world +X.
  match.setControl(0, { x: 1, y: 0, sprint: true, brake: false, cameraYaw: 0 });
  match.setControl(1, closing === 'full'
    ? { x: -1, y: 0, sprint: true, brake: false, cameraYaw: 0 }
    : { x: 0, y: 0, sprint: false, brake: false, cameraYaw: 0 });

  const steps = Math.round(seconds / DT);
  for (let n = 0; n < steps; n++) {
    match.update(DT);
    for (const h of match.recentHits) {
      const id = `${h.at}|${h.attacker}|${h.victim}`;
      if (!seen.has(id)) {
        seen.add(id);
        landed.push(h);
      }
    }
  }
  return { physics, match, landed };
}

section('segment distance is correct');
{
  const A = new THREE.Vector3();
  const B = new THREE.Vector3();
  // Two parallel segments one metre apart.
  let d = segSegDistance(
    new THREE.Vector3(0, 0, 0), new THREE.Vector3(1, 0, 0),
    new THREE.Vector3(0, 1, 0), new THREE.Vector3(1, 1, 0), A, B,
  );
  near(d, 1, 1e-9, 'parallel segments');

  // Crossing segments touch.
  d = segSegDistance(
    new THREE.Vector3(-1, 0, 0), new THREE.Vector3(1, 0, 0),
    new THREE.Vector3(0, -1, 0), new THREE.Vector3(0, 1, 0), A, B,
  );
  near(d, 0, 1e-9, 'crossing segments');

  // Endpoint to endpoint, no overlap in parameter space.
  d = segSegDistance(
    new THREE.Vector3(0, 0, 0), new THREE.Vector3(1, 0, 0),
    new THREE.Vector3(3, 0, 0), new THREE.Vector3(4, 0, 0), A, B,
  );
  near(d, 2, 1e-9, 'collinear, disjoint');
  near(A.x, 1, 1e-9, 'closest point on the first segment is its end');
  near(B.x, 3, 1e-9, 'closest point on the second is its start');

  // Degenerate: both segments are points.
  d = segSegDistance(
    new THREE.Vector3(0, 0, 0), new THREE.Vector3(0, 0, 0),
    new THREE.Vector3(3, 4, 0), new THREE.Vector3(3, 4, 0), A, B,
  );
  near(d, 5, 1e-9, 'two points');
}

section('the closest limb pair is found between two posed rigs');
{
  const { physics, match } = arena(1);
  const [a, b] = match.skaters;
  // Stand them shoulder to shoulder.
  match.states[0].x = 0; match.states[0].z = 0;
  match.states[1].x = 0.75; match.states[1].z = 0;
  a.applyState(match.states[0], 0);
  b.applyState(match.states[1], 0);
  a.update(DT);
  b.update(DT);

  const pair = closestLimbs(a.ragdoll, b.ragdoll);
  ok(pair, 'a pair was found');
  ok(pair.attackerPart && pair.victimPart, 'both sides identified');
  ok(pair.distance < 0.6, `and they are genuinely close (${pair.distance.toFixed(3)}m)`);
  // Side by side, the nearest parts must be on the facing sides, i.e. arms or
  // torso — never a foot to a head.
  ok(
    pair.attackerPart.name !== 'footL' && pair.attackerPart.name !== 'footR',
    `a shoulder-to-shoulder stance does not resolve to a foot (${pair.attackerPart.name})`,
  );
  physics.destroy();
}

section('a full-speed head-on check lands and knocks someone down');
{
  const { physics, match, landed } = collide({ closing: 'full' });
  ok(landed.length > 0, `a hit was registered (${landed.length})`);
  const hit = landed[0];
  ok(hit.speed > 4, `with real closing speed (${hit.speed.toFixed(1)} m/s)`);
  ok(hit.outcome !== 'bump', `and it was more than a bump (${hit.outcome})`);
  ok(hit.attacker !== hit.victim, 'attacker and victim are different skaters');
  ok(typeof hit.by === 'string' && hit.by.length > 0, `it was delivered by something (${hit.by})`);
  ok(typeof describeHit(hit) === 'string', `and describes itself: "${describeHit(hit)}"`);
  physics.destroy();
}

section('a skater who is run over goes down, then gets back up');
{
  const { physics, match } = collide({ closing: 'stationary', seconds: 5 });
  const downed = match.skaters.filter((s) => s.limp);
  // Either someone is still down, or they already got up — both mean the path
  // ran. Keep simulating until nobody is down, and check it terminates.
  let steps = 0;
  while (match.skaters.some((s) => s.limp) && steps < 60 / DT) {
    match.update(DT);
    steps++;
  }
  ok(steps < 60 / DT, `everyone got back up (took ${(steps * DT).toFixed(1)}s)`);
  for (let i = 0; i < match.skaters.length; i++) {
    const sk = match.skaters[i];
    ok(!sk.limp, `skater ${i} is upright`);
    ok(sk.proxy.enabled, `skater ${i}'s proxy is switched back on`);
    ok(sk.ragdoll.mode === 'driven', `skater ${i}'s rig is back under animation`);
    ok(insideRink(match.states[i].x, match.states[i].z, 0.3), `skater ${i} is on the ice`);
    ok(Number.isFinite(match.states[i].x), `skater ${i}'s position is finite`);
  }
  physics.destroy();
}

section('a knockdown puts a skater on the ice, not in the air');
{
  // The failure this catches is specific and very visible: applying the whole
  // impulse at the contact point, which sits well above the centre of mass,
  // cartwheels the victim up over the hitter's head instead of driving them
  // down and back.
  const { physics, match } = collide({ closing: 'full', gap: 24, seconds: 3 });
  const victim = match.skaters.find((s) => s.limp);
  ok(victim, 'somebody went down');

  const pelvis = new THREE.Vector3();
  const head = new THREE.Vector3();
  let peakPelvis = 0;
  let peakHead = 0;
  for (let n = 0; n < 2.5 / DT; n++) {
    match.update(DT);
    victim.ragdoll.parts.pelvis.bone.getWorldPosition(pelvis);
    victim.ragdoll.parts.head.bone.getWorldPosition(head);
    peakPelvis = Math.max(peakPelvis, pelvis.y);
    peakHead = Math.max(peakHead, head.y);
  }
  // Standing hip height is ~1.0m and standing head height ~1.6m. Going above
  // those while being knocked over means they were launched.
  ok(peakPelvis < 1.35, `the hips never went above standing height (peak ${peakPelvis.toFixed(2)}m)`);
  ok(peakHead < 2.0, `and neither did the head (peak ${peakHead.toFixed(2)}m)`);
  physics.destroy();
}

section('a knockdown drives the victim away from the hit, not back into it');
{
  // Run until contact rather than for a fixed time: how long the run-up takes
  // depends on the acceleration curve, and a test that silently ends before
  // the collision proves nothing.
  const { physics, match } = collide({ closing: 'stationary', gap: 22, seconds: 3 });
  let waited = 0;
  while (!match.skaters.some((s) => s.limp) && waited < 6) {
    match.update(DT);
    waited += DT;
  }
  const victimIndex = match.skaters.findIndex((s) => s.limp);
  ok(victimIndex >= 0, `somebody went down (after ${waited.toFixed(1)}s of extra run-up)`);
  const pelvis = new THREE.Vector3();
  match.skaters[victimIndex].ragdoll.parts.pelvis.bone.getWorldPosition(pelvis);
  const startX = pelvis.x;
  for (let n = 0; n < 1.2 / DT; n++) match.update(DT);
  match.skaters[victimIndex].ragdoll.parts.pelvis.bone.getWorldPosition(pelvis);
  // The attacker was travelling +X, so the victim has to end up further +X.
  ok(pelvis.x > startX, `the body carried on down the ice (${startX.toFixed(2)} → ${pelvis.x.toFixed(2)})`);
  physics.destroy();
}

section('getting up does not teleport the body');
{
  // The bug this pins down: while limp the ragdoll writes the body's
  // displacement into the *root bone*, because the mover stays parked where
  // they fell. Moving the mover onto the pelvis without re-expressing that
  // offset applies the displacement twice — the skater visibly flies out by
  // however far they slid and the crossfade then drags them back.
  //
  // Measured on the rendered bones, not on the sim state, because the sim
  // state was always right; it was the drawn pose that jumped.
  const { physics, match } = arena(1);
  const sk = match.skaters[0];
  const st = match.states[0];
  st.x = -4;
  st.z = 3;
  sk.proxy.teleport(st.x, st.z);
  for (let n = 0; n < 20; n++) match.update(DT);

  sk.goDown({ severity: 9, direction: new THREE.Vector3(1, 0, 0), victimPart: 'spine2' });
  // Send them sliding so the fall position and the resting position differ by
  // a long way — with them equal the bug cannot show.
  sk.ragdoll.applyImpulse('spine2', new THREE.Vector3(300, 30, 90), null);

  const sample = new THREE.Vector3();
  const bones = ['pelvis', 'head', 'footL', 'handR'];
  const before = new Map();
  let slid = 0;

  while (sk.limp) {
    // Remember the last frame before the handoff.
    for (const b of bones) {
      sk.ragdoll.parts[b].bone.getWorldPosition(sample);
      before.set(b, sample.clone());
    }
    sk.ragdoll.parts.pelvis.bone.getWorldPosition(sample);
    slid = Math.hypot(sample.x - st.x, sample.z - st.z);
    match.update(DT);
  }

  ok(slid > 0.5, `the body really did slide away from where it fell (${slid.toFixed(2)}m)`);

  // First frame back under animation: every bone must be where it just was.
  let worst = 0;
  let worstBone = '';
  for (const b of bones) {
    sk.ragdoll.parts[b].bone.getWorldPosition(sample);
    const moved = sample.distanceTo(before.get(b));
    if (moved > worst) {
      worst = moved;
      worstBone = b;
    }
  }
  ok(worst < 0.12, `no bone jumped across the handoff (worst ${worstBone} ${worst.toFixed(3)}m)`);

  // And the whole get-up should be a pose change, not a journey.
  sk.ragdoll.parts.pelvis.bone.getWorldPosition(sample);
  const riseStart = sample.clone();
  let drift = 0;
  while (sk.rising > 0) {
    match.update(DT);
    sk.ragdoll.parts.pelvis.bone.getWorldPosition(sample);
    drift = Math.max(drift, Math.hypot(sample.x - riseStart.x, sample.z - riseStart.z));
  }
  ok(drift < 0.6, `they stood up roughly where they lay (drifted ${drift.toFixed(2)}m)`);
  physics.destroy();
}

section('a skater who gets up faces the way they were lying');
{
  const { physics, match } = arena(1);
  const sk = match.skaters[0];
  const st = match.states[0];
  st.x = 0;
  st.z = 0;
  st.yaw = 0;
  sk.proxy.teleport(0, 0);
  for (let n = 0; n < 20; n++) match.update(DT);
  sk.goDown(null);
  sk.ragdoll.applyImpulse('spine2', new THREE.Vector3(0, 20, 260), null);
  while (sk.limp) match.update(DT);

  const pelvis = new THREE.Vector3();
  const chest = new THREE.Vector3();
  sk.ragdoll.parts.pelvis.bone.getWorldPosition(pelvis);
  sk.ragdoll.parts.spine3.bone.getWorldPosition(chest);
  const bodyYaw = Math.atan2(chest.x - pelvis.x, chest.z - pelvis.z);
  const off = Math.abs(Math.atan2(Math.sin(st.yaw - bodyYaw), Math.cos(st.yaw - bodyYaw)));
  ok(off < 0.9, `facing follows the sprawled body rather than a stale yaw (${off.toFixed(2)} rad off)`);
  ok(Number.isFinite(st.yaw), 'and is a real number');
  physics.destroy();
}

section('the sim follows the body across a knockdown');
{
  const { physics, match } = arena(1);
  const sk = match.skaters[0];
  const st = match.states[0];
  st.x = -5; st.z = 2; st.vx = 0; st.vz = 0;
  sk.proxy.teleport(st.x, st.z);
  for (let n = 0; n < 20; n++) match.update(DT);

  sk.goDown({ severity: 9, direction: new THREE.Vector3(1, 0, 0), victimPart: 'spine2' });
  ok(sk.limp, 'they are down');
  ok(!sk.proxy.enabled, 'the proxy switched off — no invisible bollard left behind');

  // Shove the rig so it ends up somewhere other than where it fell.
  sk.ragdoll.applyImpulse('spine2', new THREE.Vector3(260, 40, 0), null);
  for (let n = 0; n < 90; n++) match.update(DT);

  const pelvis = new THREE.Vector3();
  sk.ragdoll.parts.pelvis.bone.getWorldPosition(pelvis);
  while (sk.limp) match.update(DT);

  ok(sk.proxy.enabled, 'the proxy came back');
  const gap = Math.hypot(st.x - pelvis.x, st.z - pelvis.z);
  ok(gap < 1.2, `the sim was moved to where the body actually ended up (${gap.toFixed(2)}m off)`);
  ok(Math.hypot(st.vx, st.vz) < 2, 'and starts from rest rather than inheriting the slide');
  physics.destroy();
}

section('a downed skater is not driven around by the sim');
{
  const { physics, match } = arena(1);
  const sk = match.skaters[0];
  const st = match.states[0];
  st.x = 0; st.z = 0;
  sk.proxy.teleport(0, 0);
  for (let n = 0; n < 10; n++) match.update(DT);
  sk.goDown(null);
  const at = { x: st.x, z: st.z };
  // Hold full sprint intent for a second while down.
  for (let n = 0; n < 60; n++) {
    st.ix = 1;
    st.iz = 0;
    st.sprint = true;
    match.update(DT);
  }
  const moved = Math.hypot(st.x - at.x, st.z - at.z);
  near(moved, 0, 1e-6, 'the frozen sim position did not skate off without the body');
  physics.destroy();
}

section('ragdoll limbs join the collision world only while dynamic');
{
  const { physics, match } = arena(1);
  const sk = match.skaters[0];
  const api = physics.api;
  const shape = sk.ragdoll.parts.spine2.shape;

  const drivenMask = api.b3Shape_GetFilter(shape).maskBits;
  sk.goDown(null);
  const limpMask = api.b3Shape_GetFilter(shape).maskBits;
  ok(limpMask !== drivenMask, 'the filter changed when the rig went dynamic');
  ok(limpMask > drivenMask, 'and it got wider, not narrower');

  while (sk.limp) match.update(DT);
  const backMask = api.b3Shape_GetFilter(shape).maskBits;
  near(Number(backMask), Number(drivenMask), 0, 'and went back on standing up');
  physics.destroy();
}

section('a 3-on-3 with hits enabled stays sane');
{
  const { physics, match } = arena(3);
  for (let n = 0; n < 90 / DT; n++) match.update(DT);
  for (let i = 0; i < match.states.length; i++) {
    const s = match.states[i];
    ok(Number.isFinite(s.x) && Number.isFinite(s.z), `skater ${i} finite after 90s`);
    ok(insideRink(s.x, s.z, 0.3), `skater ${i} still on the ice`);
  }
  ok(match.recentHits.length >= 0, 'the hit list did not blow up');
  physics.destroy();
}

section('hit severity is graded, not binary');
{
  // Different run-ups must produce different outcomes, or "varied hits" is a
  // lie. A short approach is a shove; a long one puts someone on the ice.
  const outcomes = new Set();
  const byShortRun = [];
  const byLongRun = [];
  for (const [gap, into] of [[2.5, byShortRun], [22, byLongRun]]) {
    const { physics, landed } = collide({ closing: 'stationary', gap, seconds: 6 });
    for (const h of landed) {
      outcomes.add(h.outcome);
      into.push(h);
    }
    physics.destroy();
  }
  ok(outcomes.size >= 2, `run-up length changes the outcome (${[...outcomes].join(', ')})`);
  ok(byShortRun.length > 0 && byLongRun.length > 0, 'both approaches landed something');
  ok(
    byLongRun[0].severity > byShortRun[0].severity,
    `a longer run-up hits harder (${byLongRun[0].severity.toFixed(1)} vs ${byShortRun[0].severity.toFixed(1)})`,
  );
}

section('the kind of hit follows the pose, not a coin flip');
{
  // Two geometries that should produce genuinely different checks: running
  // down a stationary skater leads with the shoulder, while a head-on between
  // two skaters both crouched low at speed is a hip check.
  const kinds = new Set();
  const seen = [];
  for (const closing of ['stationary', 'full']) {
    const { physics, landed } = collide({ closing, gap: 22, seconds: 6 });
    for (const h of landed) {
      kinds.add(h.by);
      seen.push(`${closing}: ${describeHit(h)}`);
    }
    physics.destroy();
  }
  ok(kinds.size >= 2, `more than one kind of hit is reachable (${[...kinds].join(', ')})`);
  ok(kinds.has('shoulder') || kinds.has('hip'), `and they are real checks (${seen.join(' | ')})`);
}

section('nobody delivers a check with their head');
{
  // A skater at speed is pitched forward, which makes the head the leading
  // part of the body geometrically. Without the delivering-part restriction
  // almost every hit resolves to a headbutt.
  const delivered = new Set();
  for (const closing of ['stationary', 'full']) {
    for (const gap of [5, 14, 22]) {
      const { physics, landed } = collide({ closing, gap, seconds: 6 });
      for (const h of landed) delivered.add(h.attackerPart);
      physics.destroy();
    }
  }
  ok(!delivered.has('head'), `no hit was credited to a head (${[...delivered].join(', ')})`);
  ok(!delivered.has('neck'), 'nor to a neck');
  ok(delivered.size > 0, 'and hits did land');
}

done('hits');