mirror of
https://github.com/acamarata/pray-calc.git
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6f165b79ad
- Add @typescript-eslint/parser and @typescript-eslint/eslint-plugin as direct devDependencies (were only transitive, not linked in node_modules) - Add files pattern and parserOptions.project to eslint.config.mjs so ESLint finds and type-checks src/**/*.ts files correctly - Run prettier --write to fix formatting across all src files
104 lines
4.1 KiB
TypeScript
104 lines
4.1 KiB
TypeScript
/**
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* Core prayer times computation using the PrayCalc Dynamic Method.
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*
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* Returns all prayer times as fractional hours using the dynamic twilight
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* angle algorithm. Times are in local time as determined by the timezone
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* offset (tz parameter).
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*/
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import { getSpa } from "nrel-spa";
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import { computeAngles } from "./getAngles.js";
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import { getAsr } from "./getAsr.js";
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import { getQiyam } from "./getQiyam.js";
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import { getMidnight } from "./getMidnight.js";
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import { validateInputs } from "./validate.js";
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import { DHUHR_OFFSET_MINUTES } from "./constants.js";
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import type { PrayerTimes } from "./types.js";
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/**
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* Compute prayer times for a given date and location.
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*
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* Uses the dynamic twilight angle algorithm to determine Fajr and Isha
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* depression angles, then solves for all prayer events via SPA.
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*
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* @param date - Observer's local date (time-of-day is ignored)
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* @param lat - Latitude in decimal degrees (-90 to 90, south = negative)
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* @param lng - Longitude in decimal degrees (-180 to 180, west = negative)
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* @param tz - UTC offset in hours (e.g. -5 for EST). Defaults to the
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* system timezone derived from the Date object.
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* @param elevation - Observer elevation in meters (default: 0)
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* @param temperature - Ambient temperature in °C (default: 15)
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* @param pressure - Atmospheric pressure in mbar/hPa (default: 1013.25)
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* @param hanafi - Asr convention: false = Shafi'i/Maliki/Hanbali (default),
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* true = Hanafi
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* @returns Prayer times as fractional hours and the dynamic angles used.
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* Any time that cannot be computed (e.g. polar night/day, or the
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* sun never reaching the required depression) is returned as `NaN`.
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* @throws {RangeError} if lat, lng, tz, or elevation are out of valid range
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*/
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export function getTimes(
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date: Date,
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lat: number,
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lng: number,
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tz: number = -date.getTimezoneOffset() / 60,
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elevation = 0,
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temperature = 15,
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pressure = 1013.25,
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hanafi = false,
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): PrayerTimes {
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validateInputs(lat, lng, tz, elevation);
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// 1. Compute dynamic twilight angles and reuse solar declination.
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const { fajrAngle, ishaAngle, decl } = computeAngles(
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date,
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lat,
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lng,
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elevation,
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temperature,
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pressure,
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);
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// 2. Convert depression angles to SPA zenith angles.
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// SPA uses zenith angle (90° + depression) for custom altitude events.
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const fajrZenith = 90 + fajrAngle;
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const ishaZenith = 90 + ishaAngle;
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// 3. Run SPA for solar position + custom twilight times.
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const spaOpts = { elevation, temperature, pressure };
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const spaData = getSpa(date, lat, lng, tz, spaOpts, [fajrZenith, ishaZenith]);
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// Non-null assertions: getSpa was called with exactly [fajrZenith, ishaZenith], so
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// index 0 and 1 are always defined.
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// eslint-disable-next-line @typescript-eslint/no-non-null-assertion
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const fajrTime = spaData.angles[0]!.sunrise;
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const sunriseTime = spaData.sunrise;
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const noonTime = spaData.solarNoon;
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const maghribTime = spaData.sunset;
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// eslint-disable-next-line @typescript-eslint/no-non-null-assertion
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const ishaTime = spaData.angles[1]!.sunset;
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// Dhuhr: offset after solar noon (standard practice to confirm transit).
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const dhuhrTime = noonTime + DHUHR_OFFSET_MINUTES / 60;
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// 4. Asr time (reuses declination from computeAngles — no extra ephemeris call).
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const asrTime = getAsr(noonTime, lat, decl, hanafi);
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// 5. Qiyam al-Layl (last third of the night).
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const qiyamTime = getQiyam(fajrTime, ishaTime);
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// 6. Midnight: midpoint between Maghrib and Fajr (standard definition).
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const midnightTime = getMidnight(maghribTime, fajrTime);
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return {
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Qiyam: isFinite(qiyamTime) ? qiyamTime : NaN,
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Fajr: isFinite(fajrTime) ? fajrTime : NaN,
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Sunrise: isFinite(sunriseTime) ? sunriseTime : NaN,
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Noon: isFinite(noonTime) ? noonTime : NaN,
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Dhuhr: isFinite(dhuhrTime) ? dhuhrTime : NaN,
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Asr: isFinite(asrTime) ? asrTime : NaN,
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Maghrib: isFinite(maghribTime) ? maghribTime : NaN,
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Isha: isFinite(ishaTime) ? ishaTime : NaN,
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Midnight: isFinite(midnightTime) ? midnightTime : NaN,
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angles: { fajrAngle, ishaAngle },
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};
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}
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