@alliumlabs/panchanga-ts/src/calculations/time.ts

A TypeScript library for Hindu calendar (Panchanga) calculations including tithis, nakshatras, and other astronomical elements

import { AstroTime, Observer, Body, SearchRiseSet } from "astronomy-engine";
import { DayDurationResult, VaaraResult } from "../models/types";
import { formatTimeFromDate } from "../utils/helpers";

export function computeVaara(sunriseTime: AstroTime): VaaraResult {
  // Use local day of week instead of UTC to avoid timezone issues
  const weekdayIndex = sunriseTime.date.getDay();
  return {
    index: weekdayIndex,
    time: formatTimeFromDate(sunriseTime.date),
    description:
      "Vāra represents the weekday, each imbued with its own divine character and spiritual significance.",
  };
}

export function computeDayDuration(
  sunriseTime: AstroTime,
  sunsetTime: AstroTime
): DayDurationResult {
  const dtRise = sunriseTime.date.getTime();
  const dtSet = sunsetTime.date.getTime();
  const diffHours = (dtSet - dtRise) / 3600000;
  const totalSec = Math.round(diffHours * 3600);
  const hh = Math.floor(totalSec / 3600)
    .toString()
    .padStart(2, "0");
  const mm = Math.floor((totalSec % 3600) / 60)
    .toString()
    .padStart(2, "0");
  const ss = (totalSec % 60).toString().padStart(2, "0");
  return { duration: diffHours, formatted: `${hh}:${mm}:${ss}` };
}

export function calculateSunTimes(localDate: Date, observer: Observer) {
  const localMidnight = new Date(localDate);
  localMidnight.setHours(0, 0, 0, 0);
  const sunriseTime = SearchRiseSet(Body.Sun, observer, +1, localMidnight, 1);
  const sunsetTime = SearchRiseSet(Body.Sun, observer, -1, localMidnight, 1);

  if (!sunriseTime || !sunsetTime) {
    throw new Error("Failed to compute sunrise and sunset times.");
  }

  return { sunriseTime, sunsetTime };
}