/**
 * One-click camera transfer for layer-owned world targets.
 */
import * as Cesium from 'cesium';

export const WORLD_FOCUS_REQUEST_EVENT = 'gev:world-request-focus';
export const WORLD_CLICK_FOCUS_DURATION_SEC = 1.9;

export const WORLD_FOCUS_FRAMING = Object.freeze({
  vessel: Object.freeze({ radiusM: 150, rangeM: 1200, pitchDeg: -30 }),
  fire: Object.freeze({ radiusM: 400, rangeM: 3000, pitchDeg: -35 }),
});

/** Validate a layer-owned focus target before camera policy can release tracking. */
export function isValidWorldFocusTarget(detail) {
  if (!detail || !WORLD_FOCUS_FRAMING[detail.kind]) return false;
  if (!String(detail.id || '').trim()) return false;
  const { position } = detail;
  if (
    !position ||
    !Number.isFinite(position.x) ||
    !Number.isFinite(position.y) ||
    !Number.isFinite(position.z)
  )
    return false;
  // Vessel and fire targets are surface-anchored Earth positions. Merely
  // finite coordinates near the ECEF origin cannot be flown to, and must be
  // rejected before the camera policy releases a current follow owner.
  const magnitude = Cesium.Cartesian3.magnitude(position);
  return (
    Number.isFinite(magnitude) &&
    magnitude >= Cesium.Ellipsoid.WGS84.minimumRadius * 0.95
  );
}

/** Announce a valid user-click focus request. */
export function requestWorldFocus(detail, eventTarget = globalThis.window) {
  if (!isValidWorldFocusTarget(detail)) return false;
  if (typeof eventTarget?.dispatchEvent !== 'function') return false;
  eventTarget.dispatchEvent(
    new CustomEvent(WORLD_FOCUS_REQUEST_EVENT, { detail }),
  );
  return true;
}

/** Register one listener and return an idempotent disposer. */
export function registerWorldFocusRequestListener(eventTarget, listener) {
  if (
    !eventTarget?.addEventListener ||
    !eventTarget?.removeEventListener ||
    typeof listener !== 'function'
  )
    return () => {};
  eventTarget.addEventListener(WORLD_FOCUS_REQUEST_EVENT, listener);
  let disposed = false;
  return () => {
    if (disposed) return;
    disposed = true;
    eventTarget.removeEventListener(WORLD_FOCUS_REQUEST_EVENT, listener);
  };
}

/** Route a valid request through the UI-owned camera policy. */
export function routeWorldFocusRequest(event, runExplicitFocus, fly) {
  const detail = event?.detail;
  if (!isValidWorldFocusTarget(detail)) return false;
  if (typeof runExplicitFocus !== 'function' || typeof fly !== 'function')
    return false;
  return runExplicitFocus(detail, () => fly(detail));
}

/** Fly to a world target after ownership has been released. */
export function flyToWorldTarget(viewer, target = {}) {
  const camera = viewer?.camera;
  const framing = WORLD_FOCUS_FRAMING[target.kind];
  if (!camera || !framing || !isValidWorldFocusTarget(target)) return false;
  const heading = Number.isFinite(camera.heading) ? camera.heading : 0;
  const duration =
    target.durationSec > 0
      ? target.durationSec
      : WORLD_CLICK_FOCUS_DURATION_SEC;
  camera.cancelFlight?.();
  camera.flyToBoundingSphere(
    new Cesium.BoundingSphere(target.position, framing.radiusM),
    {
      offset: new Cesium.HeadingPitchRange(
        heading,
        Cesium.Math.toRadians(framing.pitchDeg),
        framing.rangeM,
      ),
      duration,
      easingFunction: Cesium.EasingFunction.CUBIC_IN_OUT,
    },
  );
  return true;
}