// src/layers/awareness/rangeRing.test.mjs — the 250 km Global Context range
// ring is a haloed polyline that stays legible on light and dark ground,
// sits where the old ellipse outline did, and follows the subject.
// Dim sonar pulses grow slowly from the subject to the ring, each with an
// inward-fading gradient behind it; the ring flashes as each one arrives and
// the overlay's echo field follows the subject. Under reduced motion the ring
// simply stays on screen.
import '../../testSupport/registerDom.mjs';
import test from 'node:test';
import assert from 'node:assert/strict';
import * as Cesium from 'cesium';
import { AWARENESS_RADIUS_M } from '../../data/militaryAwarenessEngine.js';
import {
  AWARENESS_RANGE_ECHO,
  AWARENESS_RANGE_PULSE,
  AWARENESS_RANGE_RING_STYLE,
  CONTEXT_RIM_HEIGHT_M,
} from './policy.js';
import { CYBER_SONAR_RENDER_INTERVAL_MS } from '../../cyberSonar.js';
import {
  AWARENESS_PULSE_GRADIENT_MAX,
  awarenessPulseLevel,
  awarenessPulseState,
  awarenessRangeRingPositions,
  awarenessRingFlash,
  createRendering,
  wakeAwarenessPulses,
} from './rendering.js';
import { getAwarenessEchoField } from '../../awarenessEcho.js';
import { createLifecycle } from './lifecycle.js';
import { createState } from './state.js';

/** WCAG relative luminance of a Cesium colour, ignoring alpha. */
function luminance(color) {
  const channel = (c) =>
    c <= 0.03928 ? c / 12.92 : ((c + 0.055) / 1.055) ** 2.4;
  return (
    0.2126 * channel(color.red) +
    0.7152 * channel(color.green) +
    0.0722 * channel(color.blue)
  );
}

/**
 * The rendering part over a bare entity collection, counting render asks and
 * by reason. `reducedMotion` stubs the media query for the length of the
 * test; `motion.set(on)` flips it later and tells its listeners, as the
 * browser does.
 */
function ringRendering(t, { reducedMotion = false } = {}) {
  const previous = globalThis.matchMedia;
  const listeners = new Set();
  const query = {
    get matches() {
      return reducedMotion;
    },
    addEventListener(type, listener) {
      if (type === 'change') listeners.add(listener);
    },
    removeEventListener(type, listener) {
      if (type === 'change') listeners.delete(listener);
    },
  };
  globalThis.matchMedia = (media) =>
    media === '(prefers-reduced-motion: reduce)'
      ? query
      : { matches: false, addEventListener() {}, removeEventListener() {} };
  t.after(() => {
    globalThis.matchMedia = previous;
  });
  const motion = {
    set(on) {
      reducedMotion = on;
      for (const listener of [...listeners]) listener({ matches: on });
    },
    /** Change the preference without a change event, as old browsers do. */
    setQuietly(on) {
      reducedMotion = on;
    },
    listeners: () => listeners.size,
  };
  const state = createState({ services: {} });
  const entities = new Cesium.EntityCollection();
  const scene = {
    primitives: new Cesium.PrimitiveCollection(),
    preRender: new Cesium.Event(),
    postRender: new Cesium.Event(),
  };
  state.viewer = { entities, scene };
  const reasons = [];
  const rendering = createRendering({
    state,
    services: {
      geometry: {},
      render: {
        governorRequestRender(reason) {
          reasons.push(reason);
        },
      },
    },
    parts: {},
  });
  // A shown ring keeps a pulse timer; never leave one running past a test.
  t.after(() => rendering.clearVisual());
  return {
    state,
    entities,
    scene,
    rendering,
    motion,
    reasons,
    renders: () => reasons.filter((r) => r === 'awareness-visual').length,
    pulseFrames: () => reasons.filter((r) => r === 'awareness-pulse').length,
  };
}

/**
 * A request-render scene on a fake clock: `performance.now()` and the
 * timers advance together, and any render ask is drawn (preRender, then
 * postRender) on the next millisecond, as Cesium's request-render mode does.
 * `draw()` draws a frame someone else asked for.
 */
function frameLoop(t, ring) {
  let clock = 1_000_000;
  t.mock.method(performance, 'now', () => clock);
  t.mock.timers.enable({ apis: ['setTimeout', 'setInterval'] });
  let drawn = 0;
  const draw = () => {
    drawn = ring.reasons.length;
    ring.scene.preRender.raiseEvent(ring.scene);
    ring.scene.postRender.raiseEvent(ring.scene);
  };
  return {
    now: () => clock,
    draw,
    advance(ms) {
      for (let step = 0; step < ms; step++) {
        clock++;
        t.mock.timers.tick(1);
        if (ring.reasons.length > drawn) draw();
      }
    },
  };
}

/** The pulse gradient disc and the echo collection among scene primitives. */
function pulsePrimitives(scene) {
  const all = Array.from({ length: scene.primitives.length }, (_, i) =>
    scene.primitives.get(i),
  );
  return {
    disc: all.find((p) => p instanceof Cesium.Primitive),
    count: all.length,
  };
}

const flight = (lon) => ({
  layerId: 'flights',
  id: 'abc123',
  position: Cesium.Cartesian3.fromDegrees(lon, 27, 9000),
});

/** Surface distance from `center` to each ring position. */
function surfaceDistances(center, positions) {
  const from = Cesium.Cartographic.fromCartesian(center);
  return positions.map((position) => {
    const to = Cesium.Cartographic.fromCartesian(position);
    return new Cesium.EllipsoidGeodesic(from, to).surfaceDistance;
  });
}

for (const [place, lat, lon] of [
  ['equator', 0, 0],
  ['Sahara', 27, 3],
  ['Greenland', 72, -40],
  ['antimeridian', 10, 179.9],
]) {
  test(`ring positions stay 250 km from the subject at ${place}`, () => {
    const center = Cesium.Cartesian3.fromDegrees(lon, lat, 0);
    const positions = awarenessRangeRingPositions(
      center,
      AWARENESS_RADIUS_M,
      CONTEXT_RIM_HEIGHT_M,
    );
    assert.equal(positions.length, AWARENESS_RANGE_RING_STYLE.segments + 1);
    assert.ok(
      Cesium.Cartesian3.equalsEpsilon(positions[0], positions.at(-1), 0, 1e-6),
      'the ring closes on itself',
    );
    // Within 100 m of 250 km on the WGS84 ellipsoid.
    for (const distance of surfaceDistances(center, positions))
      assert.ok(Math.abs(distance - AWARENESS_RADIUS_M) < 100, `${distance} m`);
    for (const position of positions)
      assert.ok(
        Math.abs(
          Cesium.Cartographic.fromCartesian(position).height -
            CONTEXT_RIM_HEIGHT_M,
        ) < 1e-3,
      );
  });
}

test('the ring core and halo contrast on light and dark ground', () => {
  const core = Cesium.Color.fromCssColorString(
    AWARENESS_RANGE_RING_STYLE.color,
  );
  const halo = Cesium.Color.fromCssColorString(
    AWARENESS_RANGE_RING_STYLE.outlineColor,
  );
  // Core against halo is the edge that survives bright desert and snow, and
  // the monochrome styles that map everything to luminance.
  const ratio = (luminance(core) + 0.05) / (luminance(halo) + 0.05);
  assert.ok(ratio >= 4.5, `core:halo contrast ${ratio.toFixed(2)}`);
  assert.ok(core.alpha >= 0.9 && halo.alpha >= 0.7);
  // A visible halo on each side of a core at least 2 px wide.
  const { width, outlineWidth } = AWARENESS_RANGE_RING_STYLE;
  assert.ok(outlineWidth >= 1);
  assert.ok(width - 2 * outlineWidth >= 2);
});

test('renderVisual draws one haloed polyline ring, not an ellipse outline', (t) => {
  const { entities, rendering } = ringRendering(t);
  rendering.renderVisual(flight(3));
  assert.equal(entities.values.length, 1 + AWARENESS_RANGE_PULSE.count);
  assert.ok(entities.values.every((entity) => entity.ellipse === undefined));
  const [entity] = entities.values;
  assert.equal(entity.ellipse, undefined);
  const now = Cesium.JulianDate.now();
  assert.equal(entity.polyline.width.getValue(now), 4);
  assert.equal(entity.polyline.arcType.getValue(now), Cesium.ArcType.NONE);
  const material = entity.polyline.material;
  assert.ok(material instanceof Cesium.PolylineOutlineMaterialProperty);
  // The ring's hue is fixed; its opacity flashes with arriving pulses.
  const core = Cesium.Color.fromCssColorString(
    AWARENESS_RANGE_RING_STYLE.color,
  );
  const color = material.color.getValue(now);
  assert.equal(color.red, core.red);
  assert.equal(color.blue, core.blue);
  assert.ok(color.alpha >= 0 && color.alpha <= core.alpha + 1e-9);
  assert.equal(
    material.outlineWidth.getValue(now),
    AWARENESS_RANGE_RING_STYLE.outlineWidth,
  );
  const ground = Cesium.Cartesian3.fromDegrees(3, 27, 0);
  for (const distance of surfaceDistances(
    ground,
    entity.polyline.positions.getValue(now),
  ))
    assert.ok(Math.abs(distance - AWARENESS_RADIUS_M) < 100);
});

test('the ring and pulses follow the subject past 250 m and ignore smaller drift', (t) => {
  const { entities, rendering, renders } = ringRendering(t);
  const subject = flight;
  rendering.renderVisual(subject(3));
  const [entity] = entities.values;
  const now = Cesium.JulianDate.now();
  const first = entity.polyline.positions.getValue(now);
  const rendersAfterAdd = renders();

  // ~100 m east: under the threshold, nothing is rebuilt or rendered.
  rendering.renderVisual(subject(3.001));
  assert.equal(entity.polyline.positions.getValue(now), first);
  assert.equal(renders(), rendersAfterAdd);

  // ~1 km east: the same entity moves to the new centre.
  rendering.renderVisual(subject(3.01));
  assert.equal(entities.values.length, 1 + AWARENESS_RANGE_PULSE.count);
  assert.equal(entities.values[0], entity);
  const moved = entity.polyline.positions.getValue(now);
  assert.notEqual(moved, first);
  for (const distance of surfaceDistances(
    Cesium.Cartesian3.fromDegrees(3.01, 27, 0),
    moved,
  ))
    assert.ok(Math.abs(distance - AWARENESS_RADIUS_M) < 100);
  assert.equal(renders(), rendersAfterAdd + 1);
  // Each pulse is a circle around the NEW centre: one radius all the way round.
  for (const pulse of entities.values.slice(1)) {
    const radii = surfaceDistances(
      Cesium.Cartesian3.fromDegrees(3.01, 27, 0),
      pulse.polyline.positions.getValue(now),
    );
    assert.ok(Math.max(...radii) - Math.min(...radii) < 100);
  }

  rendering.clearVisual();
  assert.equal(entities.values.length, 0);
});

test('a pulse grows slowly from the subject and arrives dim at the ring', () => {
  const {
    periodMs,
    count,
    startFraction,
    fadeInFraction,
    peakOpacity,
    endOpacityFraction,
  } = AWARENESS_RANGE_PULSE;
  const at = (phase) => awarenessPulseState(phase * periodMs, 0);
  // Starts small and invisible, so nothing pops in at the centre.
  assert.equal(at(0).radiusM, AWARENESS_RADIUS_M * startFraction);
  assert.equal(at(0).alpha, 0);
  // Dim: never brighter than `peakOpacity`, which sits well under the ring.
  let brightest = 0;
  for (let phase = 0; phase < 1; phase += 0.005) {
    const { alpha } = at(phase);
    assert.ok(alpha >= 0 && alpha <= peakOpacity, `alpha ${alpha} at ${phase}`);
    brightest = Math.max(brightest, alpha);
  }
  assert.ok(Math.abs(brightest - at(fadeInFraction).alpha) < 0.01);
  assert.ok(peakOpacity <= 0.6);
  // Fading as it travels, but still visible when it reaches the ring, where
  // the ring takes over with its flash.
  assert.ok(at(0.5).alpha < at(0.25).alpha);
  assert.ok(at(0.9).alpha < at(0.5).alpha);
  assert.ok(
    Math.abs(at(0.999).alpha - peakOpacity * endOpacityFraction) < 0.01,
  );
  assert.ok(at(0.999).alpha >= 0.15, 'the arriving pulse is still visible');
  assert.ok(Math.abs(at(0.999).radiusM - AWARENESS_RADIUS_M) < 300);
  // Constant speed: equal time steps add equal radius.
  const step = at(0.4).radiusM - at(0.3).radiusM;
  assert.ok(Math.abs(at(0.7).radiusM - at(0.6).radiusM - step) < 1e-6);
  // Calm: a new pulse at most every 2.5 s, crossing 250 km in 8 s or more.
  assert.ok(periodMs / count >= 2500);
  assert.ok(periodMs >= 8000);
  // Pulses are evenly staggered across one period, and the cycle repeats.
  const near = (a, b) =>
    Math.abs(a.radiusM - b.radiusM) < 1e-6 &&
    Math.abs(a.alpha - b.alpha) < 1e-9;
  for (let index = 1; index < count; index++)
    assert.ok(
      near(
        awarenessPulseState(0, index),
        awarenessPulseState((index / count) * periodMs, 0),
      ),
    );
  assert.ok(
    near(
      awarenessPulseState(periodMs * 7 + 123, 1),
      awarenessPulseState(123, 1),
    ),
  );
});

test('pulses ask for a frame 80 ms after each drawn frame instead of holding continuous rendering', (t) => {
  const ring = ringRendering(t);
  const { entities, rendering, pulseFrames } = ring;
  const loop = frameLoop(t, ring);
  rendering.renderVisual(flight(3));
  // A Contacts view repaints at the Cyber sonar cadence, ~12.5 fps, while
  // the pulses run, never every display frame.
  assert.equal(pulseFrames(), 0);
  loop.advance(1); // the frame the new ring asked for arms the first request
  loop.advance(CYBER_SONAR_RENDER_INTERVAL_MS * 10);
  assert.ok(Math.abs(pulseFrames() - 10) <= 1, `${pulseFrames()} frames`);
  const now = Cesium.JulianDate.now();
  const core = Cesium.Color.fromCssColorString(
    AWARENESS_RANGE_RING_STYLE.color,
  );
  for (const pulse of entities.values.slice(1)) {
    assert.equal(pulse.polyline.positions.isConstant, false);
    assert.equal(
      pulse.polyline.width.getValue(now),
      AWARENESS_RANGE_PULSE.width,
    );
    const color = pulse.polyline.material.color.getValue(now);
    assert.ok(color.alpha >= 0 && color.alpha <= core.alpha);
    assert.equal(color.red, core.red);
    const radii = surfaceDistances(
      Cesium.Cartesian3.fromDegrees(3, 27, 0),
      pulse.polyline.positions.getValue(now),
    );
    assert.ok(
      Math.min(...radii) >=
        AWARENESS_RADIUS_M * AWARENESS_RANGE_PULSE.startFraction - 100,
    );
    assert.ok(Math.max(...radii) <= AWARENESS_RADIUS_M + 100);
  }
  const frames = pulseFrames();
  rendering.clearVisual();
  assert.equal(entities.values.length, 0);
  assert.equal(ring.scene.postRender.numberOfListeners, 0);
  loop.advance(CYBER_SONAR_RENDER_INTERVAL_MS * 10);
  assert.equal(pulseFrames(), frames, 'no frames once the ring is gone');
});

test('a parked view stops asking for frames once the pulses rest', (t) => {
  const ring = ringRendering(t);
  const { entities, scene, rendering, pulseFrames } = ring;
  const loop = frameLoop(t, ring);
  const { activeMs, count, periodMs } = AWARENESS_RANGE_PULSE;
  // Long enough for three ring flashes, then quiet.
  assert.ok(activeMs >= 3 * (periodMs / count));
  rendering.renderVisual(flight(3));
  loop.advance(activeMs + 500);
  const frames = pulseFrames();
  assert.ok(frames >= activeMs / CYBER_SONAR_RENDER_INTERVAL_MS - 2);
  // Parked: a minute later not one more request.
  loop.advance(60_000);
  assert.equal(pulseFrames(), frames, 'render requests stop after the bound');
  // At rest the ring stands on screen at full, as without pulses, and the
  // pulses, gradient and echoes are hidden.
  const now = Cesium.JulianDate.now();
  const core = Cesium.Color.fromCssColorString(
    AWARENESS_RANGE_RING_STYLE.color,
  );
  const [ringEntity, ...pulses] = entities.values;
  assert.ok(
    Math.abs(
      ringEntity.polyline.material.color.getValue(now).alpha - core.alpha,
    ) < 1e-9,
  );
  for (const pulse of pulses)
    assert.equal(pulse.polyline.show.getValue(now), false);
  assert.equal(pulsePrimitives(scene).disc.show, false);
  assert.equal(getAwarenessEchoField().level(loop.now()), 0);
});

test('a camera move wakes resting pulses for another bounded run', (t) => {
  const ring = ringRendering(t);
  const { rendering, pulseFrames } = ring;
  const loop = frameLoop(t, ring);
  const { activeMs } = AWARENESS_RANGE_PULSE;
  rendering.renderVisual(flight(3));
  loop.advance(activeMs + 500);
  const rested = pulseFrames();
  // The camera moves: lifecycle wakes the pulses inside the frame it draws,
  // and that frame arms the next request. Waking asks for none of its own.
  rendering.wakePulses();
  assert.equal(pulseFrames(), rested);
  loop.draw();
  loop.advance(activeMs + 500);
  const woke = pulseFrames() - rested;
  assert.ok(woke >= activeMs / CYBER_SONAR_RENDER_INTERVAL_MS - 2, `${woke}`);
  loop.advance(60_000);
  assert.equal(pulseFrames(), rested + woke, 'and rest again');
  // The subject moving does not wake them: a flying subject moves on every
  // refresh, which would bring the endless repaint back.
  rendering.renderVisual(flight(3.01));
  loop.advance(10_000);
  assert.equal(pulseFrames(), rested + woke);
});

test('a camera move seen by the lifecycle wakes resting pulses; a parked camera does not', (t) => {
  const ring = ringRendering(t);
  const { state, rendering, pulseFrames } = ring;
  const loop = frameLoop(t, ring);
  const { activeMs } = AWARENESS_RANGE_PULSE;
  state.enabled = true;
  state.viewer.camera = {
    positionWC: Cesium.Cartesian3.fromDegrees(3, 20, 800_000),
    heading: 0,
    pitch: -1,
    roll: 0,
  };
  const lifecycle = createLifecycle({
    state,
    services: {
      render: { holdContinuousRender() {}, releaseContinuousRender() {} },
    },
    parts: {
      rendering,
      model: {
        awarenessRefreshDecision: () => ({ moving: false, refresh: false }),
        awarenessNeedsContinuousRender: () => false,
      },
    },
  });
  lifecycle.attachRuntimeListeners();
  t.after(() => lifecycle.detachRuntimeListeners());
  rendering.renderVisual(flight(3));
  loop.advance(activeMs + 500);
  const rested = pulseFrames();
  // Parked: frames other owners draw do not wake the pulses.
  loop.draw();
  loop.advance(activeMs);
  assert.equal(pulseFrames(), rested);
  // The camera pans 50 km: the next frame wakes them for another run.
  state.viewer.camera.positionWC = Cesium.Cartesian3.fromDegrees(
    3.5,
    20,
    800_000,
  );
  loop.draw();
  loop.advance(activeMs + 500);
  assert.ok(
    pulseFrames() - rested >= activeMs / CYBER_SONAR_RENDER_INTERVAL_MS - 2,
  );
  const woke = pulseFrames();
  loop.advance(60_000);
  assert.equal(pulseFrames(), woke, 'and rest again once it parks');
});

test('pulse requests wait 80 ms after any frame, so they cannot beat the Cyber sonar', (t) => {
  const ring = ringRendering(t);
  const { rendering, pulseFrames } = ring;
  const loop = frameLoop(t, ring);
  rendering.renderVisual(flight(3));
  loop.advance(1);
  const frames = pulseFrames();
  // Another owner (the Cyber sonar, a data update) draws 67 ms after ours.
  loop.advance(67);
  loop.draw();
  loop.advance(CYBER_SONAR_RENDER_INTERVAL_MS - 1);
  assert.equal(pulseFrames(), frames, 'no request 13 ms after that frame');
  loop.advance(1);
  assert.equal(pulseFrames(), frames + 1, 'one request 80 ms after it');
});

test('the pulse level fades in, holds, fades out and keeps its level when woken', () => {
  const { activeMs, settleMs } = AWARENESS_RANGE_PULSE;
  const wake = wakeAwarenessPulses(
    { startMs: -Infinity, untilMs: -Infinity },
    0,
  );
  assert.equal(awarenessPulseLevel(0, wake), 0);
  assert.ok(Math.abs(awarenessPulseLevel(settleMs / 2, wake) - 0.5) < 1e-9);
  assert.equal(awarenessPulseLevel(activeMs / 2, wake), 1);
  assert.ok(
    Math.abs(awarenessPulseLevel(activeMs - settleMs / 4, wake) - 0.25) < 1e-9,
  );
  assert.equal(awarenessPulseLevel(activeMs, wake), 0);
  assert.equal(awarenessPulseLevel(activeMs * 10, wake), 0);
  // Woken mid-fade-out: no jump back to full, then a fresh run.
  const at = activeMs - settleMs / 4;
  wakeAwarenessPulses(wake, at);
  assert.ok(Math.abs(awarenessPulseLevel(at, wake) - 0.25) < 1e-9);
  assert.equal(awarenessPulseLevel(at + settleMs, wake), 1);
  assert.equal(awarenessPulseLevel(at + activeMs, wake), 0);
});

test('a scene without primitives or preRender gets the static ring only', (t) => {
  const { state, entities, rendering, pulseFrames } = ringRendering(t);
  for (const scene of [
    {},
    { primitives: { add() {} } },
    { primitives: { add() {} }, preRender: new Cesium.Event() },
    undefined,
  ]) {
    state.viewer = { entities, scene };
    rendering.clearVisual();
    rendering.renderVisual(flight(3));
    assert.equal(entities.values.length, 1);
    assert.equal(entities.values[0].polyline.positions.isConstant, true);
  }
  rendering.clearVisual();
  assert.equal(pulseFrames(), 0);
});

test('a gradient disc behind the pulses fades inward and follows the subject', (t) => {
  const ring = ringRendering(t);
  const { scene, rendering } = ring;
  const loop = frameLoop(t, ring);
  rendering.renderVisual(flight(3));
  assert.ok(AWARENESS_RANGE_PULSE.count <= AWARENESS_PULSE_GRADIENT_MAX);
  const { disc, count } = pulsePrimitives(scene);
  assert.equal(count, 1, 'the gradient disc');
  assert.ok(disc);
  // Never a click or tap target, and see-through.
  assert.equal(disc.allowPicking, false);
  assert.equal(disc.appearance.translucent, true);
  const { material } = disc.appearance;
  assert.ok(
    Math.abs(
      material.uniforms.depth - AWARENESS_RANGE_PULSE.gradientDepthFraction,
    ) < 1e-9,
  );
  assert.ok(
    Math.abs(
      material.uniforms.color.alpha - AWARENESS_RANGE_PULSE.gradientOpacity,
    ) < 1e-6,
  );
  // Each frame writes the pulses' radius (as a fraction of the range) and
  // opacity into the shader, from the same curve the lines use, once the
  // pulses have faded in.
  assert.equal(scene.preRender.numberOfListeners, 1);
  loop.advance(AWARENESS_RANGE_PULSE.settleMs + 500);
  scene.preRender.raiseEvent(scene);
  assert.equal(disc.show, true);
  const { radii, alphas } = material.uniforms;
  for (let index = 0; index < AWARENESS_RANGE_PULSE.count; index++) {
    const radius = Cesium.Cartesian4.pack(radii, [])[index];
    const alpha = Cesium.Cartesian4.pack(alphas, [])[index];
    const expected = awarenessPulseState(loop.now(), index);
    assert.ok(Math.abs(radius - expected.radiusM / AWARENESS_RADIUS_M) < 1e-6);
    assert.ok(alpha >= 0 && alpha <= AWARENESS_RANGE_PULSE.peakOpacity);
    assert.ok(Math.abs(alpha - expected.alpha) < 1e-6);
  }
  // Unused shader slots stay empty.
  assert.equal(
    Cesium.Cartesian4.pack(alphas, [])[AWARENESS_PULSE_GRADIENT_MAX - 1],
    0,
  );

  // The disc is rebuilt only past `gradientRebuildM` (2 km), not on every
  // 250 m step the lines take, and keeps its material.
  rendering.renderVisual(flight(3.001));
  assert.equal(pulsePrimitives(scene).disc, disc);
  rendering.renderVisual(flight(3.01)); // ~1 km: the lines move, the disc stays
  assert.equal(pulsePrimitives(scene).disc, disc);
  assert.ok(!disc.isDestroyed());
  rendering.renderVisual(flight(3.03)); // ~3 km from the disc's centre
  assert.equal(pulsePrimitives(scene).count, 1);
  const moved = pulsePrimitives(scene).disc;
  assert.notEqual(moved, disc);
  assert.ok(disc.isDestroyed());
  assert.equal(moved.appearance.material, material);
  assert.equal(moved.allowPicking, false);

  rendering.clearVisual();
  assert.equal(scene.primitives.length, 0);
  assert.equal(scene.preRender.numberOfListeners, 0);
});

test('pulses evaluate every frame without breaking, reusing their positions', (t) => {
  const { entities, rendering } = ringRendering(t);
  rendering.renderVisual(flight(3));
  const center = Cesium.Cartesian3.fromDegrees(3, 27, 0);
  for (const pulse of entities.values.slice(1)) {
    const property = pulse.polyline.positions;
    const first = property.getValue(Cesium.JulianDate.now());
    // Cesium calls this on every rendered frame; the second call is where a
    // reused Cartesian once landed in the ellipsoid argument and threw.
    for (let frame = 0; frame < 5; frame++) {
      const positions = property.getValue(Cesium.JulianDate.now());
      assert.equal(positions, first, 'the same array is reused');
      assert.equal(positions.length, AWARENESS_RANGE_PULSE.segments + 1);
      const radii = surfaceDistances(center, positions);
      assert.ok(radii.every(Number.isFinite));
      assert.ok(Math.max(...radii) - Math.min(...radii) < 100);
    }
  }
});

test('reduced motion keeps the static ring and drops the pulses', (t) => {
  t.mock.timers.enable({ apis: ['setTimeout', 'setInterval'] });
  const { entities, scene, rendering, pulseFrames } = ringRendering(t, {
    reducedMotion: true,
  });
  rendering.renderVisual(flight(3));
  assert.equal(entities.values.length, 1);
  assert.equal(entities.values[0].polyline.positions.isConstant, true);
  t.mock.timers.tick(1000);
  assert.equal(pulseFrames(), 0);
  assert.equal(scene.primitives.length, 0);
  assert.equal(scene.preRender.numberOfListeners, 0);
  assert.equal(scene.postRender.numberOfListeners, 0);
});

test('turning reduced motion on mid-session stops the pulses, and off restarts them', (t) => {
  const ring = ringRendering(t);
  const { entities, scene, rendering, motion, state } = ring;
  const loop = frameLoop(t, ring);
  state.subject = flight(3);
  rendering.renderVisual(state.subject);
  assert.equal(entities.values.length, 1 + AWARENESS_RANGE_PULSE.count);
  loop.advance(1000);
  // The OS setting changes while the same aircraft stays tracked.
  motion.set(true);
  assert.equal(entities.values.length, 1);
  assert.equal(entities.values[0].polyline.material.color.isConstant, true);
  assert.equal(scene.primitives.length, 0);
  assert.equal(scene.preRender.numberOfListeners, 0);
  assert.equal(scene.postRender.numberOfListeners, 0);
  assert.equal(getAwarenessEchoField(), null);
  const frames = ring.pulseFrames();
  loop.advance(5000);
  assert.equal(ring.pulseFrames(), frames);
  motion.set(false);
  assert.equal(entities.values.length, 1 + AWARENESS_RANGE_PULSE.count);
  assert.ok(getAwarenessEchoField());
  // One media-query listener per visual; none once the ring is gone.
  assert.equal(motion.listeners(), 1);
  rendering.clearVisual();
  assert.equal(motion.listeners(), 0);
});

test('a refresh after reduced motion changed rebuilds the visual too', (t) => {
  const { entities, rendering, motion } = ringRendering(t);
  rendering.renderVisual(flight(3));
  assert.equal(entities.values.length, 1 + AWARENESS_RANGE_PULSE.count);
  // No change event: the next same-subject refresh notices on its own.
  motion.setQuietly(true);
  rendering.renderVisual(flight(3));
  assert.equal(entities.values.length, 1);
  assert.equal(entities.values[0].polyline.positions.isConstant, true);
});

test('while pulses run the ring flashes as each one arrives, then rests', (t) => {
  const ring = ringRendering(t);
  const { entities, rendering } = ring;
  const loop = frameLoop(t, ring);
  rendering.renderVisual(flight(3));
  const ringEntity = entities.values[0];
  const core = Cesium.Color.fromCssColorString(
    AWARENESS_RANGE_RING_STYLE.color,
  );
  assert.equal(ringEntity.polyline.material.color.isConstant, false);
  const { periodMs, count } = AWARENESS_RANGE_PULSE;
  const { flashMs, restOpacity } = AWARENESS_RANGE_RING_STYLE;
  // Full the moment a front reaches 250 km, gone `flashMs` later.
  const arrival = periodMs * 6; // pulse 0 wraps here
  assert.ok(Math.abs(awarenessRingFlash(arrival) - 1) < 1e-6);
  assert.ok(awarenessRingFlash(arrival + flashMs / 2) > 0.2);
  assert.equal(awarenessRingFlash(arrival + flashMs + 1), 0);
  // Between flashes the 250 km edge stays readable, dimmed, not gone.
  assert.ok(restOpacity >= 0.35 && restOpacity <= 0.5, `${restOpacity}`);
  // Once per arriving pulse: `count` flashes in any one-period window that
  // starts after a flash has faded.
  let flashes = 0;
  let wasLit = false;
  const from = arrival + flashMs + 1;
  for (let ms = 0; ms < periodMs; ms += 10) {
    const lit = awarenessRingFlash(from + ms) > 0.5;
    if (lit && !wasLit) flashes++;
    wasLit = lit;
  }
  assert.equal(flashes, count);
  // Once the pulses have faded in, the live colour tracks the flash, and
  // never drops below `restOpacity`.
  loop.advance(AWARENESS_RANGE_PULSE.settleMs);
  for (let step = 0; step < 40; step++) {
    loop.advance(100);
    const alpha = ringEntity.polyline.material.color.getValue(
      Cesium.JulianDate.now(),
    ).alpha;
    const expected =
      core.alpha * Math.max(restOpacity, awarenessRingFlash(loop.now()));
    assert.ok(Math.abs(alpha - expected) < 1e-9, `${alpha} vs ${expected}`);
  }
});

test('without pulses the ring stays on screen at full strength', (t) => {
  const { entities, rendering } = ringRendering(t, { reducedMotion: true });
  rendering.renderVisual(flight(3));
  const color = entities.values[0].polyline.material.color;
  assert.equal(color.isConstant, true);
  assert.equal(
    color.getValue(Cesium.JulianDate.now()).toCssColorString(),
    Cesium.Color.fromCssColorString(
      AWARENESS_RANGE_RING_STYLE.color,
    ).toCssColorString(),
  );
  assert.equal(getAwarenessEchoField(), null);
});

test('the echo field follows the subject while pulses run and clears with the ring', (t) => {
  const { rendering } = ringRendering(t);
  rendering.renderVisual(flight(3));
  const field = getAwarenessEchoField();
  assert.ok(field);
  assert.equal(field.radiusM, AWARENESS_RADIUS_M);
  assert.equal(field.pulse, AWARENESS_RANGE_PULSE);
  assert.equal(field.echo, AWARENESS_RANGE_ECHO);
  assert.ok(
    Cesium.Cartesian3.equalsEpsilon(
      field.center,
      Cesium.Cartesian3.fromDegrees(3, 27, 0),
      0,
      1e-3,
    ),
  );
  // ~1 km later the same field has moved with the subject.
  rendering.renderVisual(flight(3.01));
  assert.equal(getAwarenessEchoField(), field);
  assert.ok(
    Cesium.Cartesian3.equalsEpsilon(
      field.center,
      Cesium.Cartesian3.fromDegrees(3.01, 27, 0),
      0,
      1e-3,
    ),
  );
  rendering.clearVisual();
  assert.equal(getAwarenessEchoField(), null);
});