feat: adding the option to handle polar night and midnight sun cases

.gitignore

@@ -1,2 +1,3 @@
 node_modules/
-coverage/
+coverage/
+.idea

src/Adhan.js

@@ -5,19 +5,21 @@ import { Madhab } from './Madhab';
 import HighLatitudeRule from './HighLatitudeRule';
 import CalculationMethod from './CalculationMethod';
 import CalculationParameters from './CalculationParameters';
-import qibla from './Qibla';
+import Qibla from './Qibla';
 import SunnahTimes from './SunnahTimes';
+import { PolarCircleResolution } from './PolarCircleResolution';
 
 const adhan = {
-    Prayer: Prayer,
-    Madhab: Madhab,
-    HighLatitudeRule: HighLatitudeRule,
-    Coordinates: Coordinates,
-    CalculationParameters: CalculationParameters,
-    CalculationMethod: CalculationMethod,
-    PrayerTimes: PrayerTimes,
-    SunnahTimes: SunnahTimes,
-    Qibla: qibla
+    Prayer,
+    Madhab,
+    HighLatitudeRule,
+    Coordinates,
+    CalculationParameters,
+    CalculationMethod,
+    PrayerTimes,
+    SunnahTimes,
+    Qibla,
+    PolarCircleResolution,
 };
 
 export default adhan;

src/CalculationParameters.js

@@ -1,5 +1,6 @@
 import { Madhab } from './Madhab';
 import HighLatitudeRule from './HighLatitudeRule';
+import { PolarCircleResolution } from './PolarCircleResolution';
 
 export default class CalculationParameters {
     constructor(methodName, fajrAngle, ishaAngle, ishaInterval, maghribAngle) {
@@ -12,6 +13,16 @@ export default class CalculationParameters {
         this.highLatitudeRule = HighLatitudeRule.MiddleOfTheNight;
         this.adjustments = { fajr: 0, sunrise: 0, dhuhr: 0, asr: 0, maghrib: 0, isha: 0 };
         this.methodAdjustments = { fajr: 0, sunrise: 0, dhuhr: 0, asr: 0, maghrib: 0, isha: 0 };
+        this.polarCircleResolution = PolarCircleResolution.unresolved;
+    }
+
+    clone() {
+        const {
+            methodName, fajrAngle, ishaAngle, ishaInterval, maghribAngle, polarCircleResolution,
+        } = this;
+        const parameters = new CalculationParameters(methodName, fajrAngle, ishaAngle, ishaInterval, maghribAngle);
+        parameters.polarCircleResolution = polarCircleResolution;
+        return parameters;
     }
 
     nightPortions() {

src/DateUtils.js

@@ -36,3 +36,7 @@ export function dayOfYear(date) {
 
     return returnedDayOfYear;
 }
+
+export function isValidDate(date) {
+    return date instanceof Date && !isNaN(date.valueOf());
+}

src/PolarCircleResolution.js

@@ -0,0 +1,74 @@
+import { dateByAddingSeconds, dayOfYear, isValidDate } from './DateUtils';
+import adhan from './Adhan';
+import SolarTime from './SolarTime';
+import Astronomical from './Astronomical';
+import TimeComponents from './TimeComponents';
+
+export const PolarCircleResolution = {
+  aqrabBalad: 'aqrab-balad',
+  aqrabYaum: 'aqrab-yaum',
+  unresolved: 'unresolved'
+};
+
+export const POLAR_CIRCLE_RESOLUTION_LATITUDE_VARIATION_STEP = 0.5; // Degrees to add/remove at each search step
+export const POLAR_CIRCLE_RESOLUTION_VALID_LATITUDE = 65; // Based on https://en.wikipedia.org/wiki/Midnight_sun
+
+const isValidSolarTime = (solarTime) => {
+  if (solarTime) {
+    return solarTime && !isNaN(solarTime.sunrise) && !isNaN(solarTime.sunset);
+  }
+  return false;
+}
+
+export const polarCircleResolvedValues = (resolver, date, coordinates) => {
+  let resolvedLatitude = coordinates.latitude;
+  let resolvedDate = new Date(date.getTime());
+  let resolvedSolarTime = null;
+  let daysAdded = 0;
+  let pastDate = ((date) => { const newDate = new Date(date.getTime()); newDate.setDate(date.getDate() - 1); return newDate; })(date);
+  let futureDate = ((date) => { const newDate = new Date(date.getTime()); newDate.setDate(date.getDate() + 1); return newDate; })(date);
+  let adjustedLatitude = coordinates.latitude;
+
+  switch (resolver) {
+    case PolarCircleResolution.aqrabYaum: {
+      while (!isValidSolarTime(resolvedSolarTime) && daysAdded <= Math.ceil(365 / 2)) { // Search within 6 months backward & forward
+        resolvedSolarTime = new SolarTime(pastDate, coordinates);
+        if (isValidSolarTime(resolvedSolarTime)) {
+          resolvedDate.setTime(pastDate.getTime());
+        } else {
+          resolvedSolarTime = new SolarTime(futureDate, coordinates);
+          if (isValidSolarTime(resolvedSolarTime)) {
+            resolvedDate.setTime(futureDate.getTime());
+          }
+        }
+        pastDate.setDate(pastDate.getDate() - 1);
+        futureDate.setDate(pastDate.getDate() + 1);
+        daysAdded++;
+      }
+      break;
+    }
+    default:
+    case PolarCircleResolution.aqrabBalad: {
+      while (!isValidSolarTime(resolvedSolarTime) && Math.abs(adjustedLatitude) >= POLAR_CIRCLE_RESOLUTION_VALID_LATITUDE) {
+        adjustedLatitude -= (Math.sign(adjustedLatitude) * POLAR_CIRCLE_RESOLUTION_LATITUDE_VARIATION_STEP);
+        resolvedSolarTime = new SolarTime(resolvedDate, {
+          ...coordinates,
+          latitude: adjustedLatitude,
+        });
+        if (isValidSolarTime(resolvedSolarTime)) {
+          resolvedLatitude = adjustedLatitude;
+        }
+      }
+      break;
+    }
+  }
+
+  return {
+    coordinates: {
+      ...coordinates,
+      latitude: resolvedLatitude,
+    },
+    date: resolvedDate,
+    solarTime: resolvedSolarTime,
+  };
+}