astrology-insights/panchang/src/birthchart/core/houses.ts

Comprehensive Vedic astrology engine for Node.js — Panchang, birth charts (Kundli), Vimshottari Dasha, divisional charts, dosha analysis, and planetary remedies. Swiss Ephemeris precision, validated against Drik Panchang.

/**
 * House Calculation
 * Assign signs to houses and planets to houses.
 */

import { GrahaName, GrahaPosition, HouseInfo, HouseSystemType } from '../types';
import { SIGN_NAMES } from './constants';

/**
 * Calculate the 12 houses given the lagna sign and house system.
 *
 * @param lagnaSignNumber - The sign number of the ascendant (1-12)
 * @param houseSystem - House system type
 * @param cusps - Optional sidereal cusp longitudes (index 1-12)
 * @returns Array of 12 HouseInfo
 */
export function calculateHouses(
  lagnaSignNumber: number,
  houseSystem: HouseSystemType,
  cusps?: number[],
): HouseInfo[] {
  const houses: HouseInfo[] = [];

  for (let h = 1; h <= 12; h++) {
    // Whole sign: house N has sign = (lagnaSign - 1 + N - 1) % 12 + 1
    const signNumber = ((lagnaSignNumber - 1 + h - 1) % 12) + 1;
    const cuspDegree = cusps && cusps[h] !== undefined ? cusps[h] : (signNumber - 1) * 30;

    houses.push({
      number: h,
      signName: SIGN_NAMES[signNumber] || 'Unknown',
      signNumber,
      cuspDegree: Math.round(cuspDegree * 100) / 100,
      planets: [],
    });
  }

  return houses;
}

/**
 * Assign planets to houses based on their sign positions.
 * For whole-sign: house = (planetSign - lagnaSign + 12) % 12 + 1
 *
 * @returns Record mapping planet name to house number (1-12)
 */
export function assignPlanetsToHouses(
  planets: GrahaPosition[],
  lagnaSignNumber: number,
  houseSystem: HouseSystemType,
): Record<string, number> {
  const assignment: Record<string, number> = {};

  for (const planet of planets) {
    if (houseSystem === 'whole_sign' || houseSystem === 'equal') {
      // Whole-sign logic: planet's sign determines the house
      const houseNum = ((planet.signNumber - lagnaSignNumber + 12) % 12) + 1;
      assignment[planet.name] = houseNum;
    } else {
      // Placidus: determine house by cusp ranges (simplified — use whole-sign fallback)
      const houseNum = ((planet.signNumber - lagnaSignNumber + 12) % 12) + 1;
      assignment[planet.name] = houseNum;
    }
  }

  return assignment;
}

/**
 * Populate the houses' planet arrays using the assignment map.
 */
export function populateHousePlanets(
  houses: HouseInfo[],
  planets: GrahaPosition[],
  assignment: Record<string, number>,
): HouseInfo[] {
  // Clear existing planet arrays
  for (const h of houses) {
    h.planets = [];
  }

  for (const planet of planets) {
    const houseNum = assignment[planet.name];
    if (houseNum >= 1 && houseNum <= 12) {
      const house = houses.find(h => h.number === houseNum);
      if (house) {
        house.planets.push(planet.name as GrahaName);
      }
    }
  }

  return houses;
}