import type { Location } from "@deadhead/content";
import { bodyPosition, type GameTime, type Position } from "@deadhead/sim";

/**
 * Map coordinates: the Sun at (0, 0), the edge of the map at radius 1, y down.
 * Real distances are compressed so the inner planets and Jupiter fit together.
 */
export interface MapPoint {
  x: number;
  y: number;
}

/** Heliocentric radius (million km) shown at the edge of the map. */
export const MAP_EDGE_MILLION_KM = 1000;

/** Moons are drawn this far from their planet (map units), whatever the real distance. */
export const MOON_MAP_OFFSET = 0.04;

/**
 * Compressed radial scale: real distance from the Sun (million km) to map
 * radius. Square root keeps the order (farther stays farther) while bringing
 * Jupiter (~780M km) within a few times Earth's (~150M km) distance.
 */
export function radialScale(millionKm: number): number {
  return Math.sqrt(Math.max(0, millionKm) / MAP_EDGE_MILLION_KM);
}

/** A heliocentric position on the map: same angle, compressed radius. */
export function toMapPoint(position: Position): MapPoint {
  const r = Math.hypot(position.x, position.y);
  if (r === 0) return { x: 0, y: 0 };
  const k = radialScale(r) / r;
  // Screens grow downwards; flip y so orbits run counter-clockwise as seen from above.
  return { x: position.x * k, y: -position.y * k };
}

/**
 * Where a location is drawn. The Moon sits a fixed small distance from Earth
 * in its true direction, since at map scale it would overlap Earth.
 */
export function locationMapPoint(location: Location, gameTime: GameTime): MapPoint {
  if (location.body !== "moon") return toMapPoint(bodyPosition(location.body, gameTime));
  const earth = bodyPosition("earth", gameTime);
  const moon = bodyPosition("moon", gameTime);
  const dx = moon.x - earth.x;
  const dy = -(moon.y - earth.y);
  const length = Math.hypot(dx, dy) || 1;
  const base = toMapPoint(earth);
  return {
    x: base.x + (dx / length) * MOON_MAP_OFFSET,
    y: base.y + (dy / length) * MOON_MAP_OFFSET,
  };
}