cosmo/frontend/src/utils/renderPosition.ts

/**
 * Position calculator for celestial bodies
 * Returns the scaled rendering position without artificial offsets
 */

import { scalePosition } from './scaleDistance';
import type { CelestialBody } from '../types';

/**
 * Calculate rendering position using true scaled coordinates
 * For satellites, add a radial offset relative to PARENT PLANET
 */
export function calculateRenderPosition(
  body: CelestialBody,
  allBodies: CelestialBody[]
): { x: number; y: number; z: number; hasOffset: boolean } {
  const pos = body.positions[0];
  if (!pos) {
    return { x: 0, y: 0, z: 0, hasOffset: false };
  }

  // 1. Calculate base scaled position (fallback)
  const scaled = scalePosition(pos.x, pos.y, pos.z);

  // 2. Special handling for satellites (like Moon)
  if (body.type === 'satellite') {
    const parent = findParentPlanet(body, allBodies);
    if (parent) {
      const parentPos = parent.positions[0];
      // Calculate parent's scaled position (where it is rendered)
      // Note: Recursion is possible if parent is also a satellite, but unlikely for planets
      const parentScaled = scalePosition(parentPos.x, parentPos.y, parentPos.z);
      
      // Calculate vector from Parent to Satellite (in True AU coordinates)
      const dx = pos.x - parentPos.x;
      const dy = pos.y - parentPos.y;
      const dz = pos.z - parentPos.z;
      
      const dist = Math.sqrt(dx*dx + dy*dy + dz*dz);
      
      if (dist > 0) {
        // Normalize the direction vector
        const nx = dx / dist;
        const ny = dy / dist;
        const nz = dz / dist;

        // Set a fixed visual offset distance
        // Earth radius is 0.6, Moon is 0.15. 
        // A distance of 1.5 units ensures they are close but distinct and don't overlap.
        // This simulates a "mini-system" view at the planet's location.
        const visualOffset = 1.5;

        return {
          x: parentScaled.x + nx * visualOffset,
          y: parentScaled.y + ny * visualOffset,
          z: parentScaled.z + nz * visualOffset,
          hasOffset: true
        };
      }
    }
  }

  return { x: scaled.x, y: scaled.y, z: scaled.z, hasOffset: false };
}

/**
 * Find the parent planet for a celestial body (e.g., Moon orbits Earth)
 * Returns the planet that this body is closest to
 */
export function findParentPlanet(
  body: CelestialBody,
  allBodies: CelestialBody[]
): CelestialBody | null {
  const pos = body.positions[0];
  if (!pos) return null;

  // Look for planets or dwarf planets
  const planets = allBodies.filter(b => b.type === 'planet' || b.type === 'dwarf_planet');

  let closestPlanet: CelestialBody | null = null;
  let minDistance = Infinity;

  for (const planet of planets) {
    const planetPos = planet.positions[0];
    if (!planetPos) continue;

    const distance = Math.sqrt(
      Math.pow(pos.x - planetPos.x, 2) +
      Math.pow(pos.y - planetPos.y, 2) +
      Math.pow(pos.z - planetPos.z, 2)
    );

    // Consider as "parent" if within 0.1 AU
    // Moon is ~0.0026 AU from Earth
    // Io is ~0.0028 AU from Jupiter
    if (distance < 0.1 && distance < minDistance) {
      closestPlanet = planet;
      minDistance = distance;
    }
  }

  return closestPlanet;
}

/**
 * Get description for bodies that are close to planets
 */
export function getOffsetDescription(body: CelestialBody, allBodies: CelestialBody[]): string | null {
  // This function is kept for compatibility but no longer calculates offsets
  // Could be used to show proximity information in the future
  return null;
}