fix(calculation): refactor indian date calculation

src/__tests__/getDate.test.ts

@@ -36,4 +36,27 @@ describe('getDate', () => {
       );
     });
   });
+
+  const december162022 = new Date('2023-12-16');
+  describe(`Date: ${december162022}`, () => {
+    it(`(BD) should return 'শনিবার, ১ পৌষ, ১৪৩০'`, () => {
+      expect(getDate(december162022)).toEqual('শনিবার, ১ পৌষ, ১৪৩০');
+    });
+    it(`(IN) should return 'শনিবার, ২৯ অগ্রহায়ণ, ১৪৩০'`, () => {
+      expect(getDate(december162022, { calculationMethod: 'IN' })).toEqual(
+        'শনিবার, ২৯ অগ্রহায়ণ, ১৪৩০'
+      );
+    });
+  });
+  const june192023 = new Date('2023-06-19');
+  describe(`Date: ${june192023}`, () => {
+    it(`(BD) should return 'সোমবার, ৫ আষাঢ়, ১৪৩০'`, () => {
+      expect(getDate(june192023)).toEqual('সোমবার, ৫ আষাঢ়, ১৪৩০');
+    });
+    it(`(IN) should return 'সোমবার, ৩ আষাঢ়, ১৪৩০'`, () => {
+      expect(getDate(june192023, { calculationMethod: 'IN' })).toEqual(
+        'সোমবার, ৩ আষাঢ়, ১৪৩০'
+      );
+    });
+  });
 });

src/__tests__/getDay.test.ts

@@ -179,7 +179,8 @@ describe('getDay', () => {
       expect(getDay(august17, { calculationMethod: 'IN' })).toBe('৩১');
     });
   });
-  const august18 = new Date('August 18 2022 06:22:03');
+
+  const august18 = new Date('2022-08-18');
   describe(`Date: ${august18}`, () => {
     it(`(BD) should convert to '৩'`, () => {
       expect(getDay(august18)).toBe('৩');

src/__tests__/getMonth.test.ts

@@ -1,17 +1,5 @@
 import { getMonth } from '../getMonth';
 
-// const may14 = new Date('May 14 2021 06:22:03');
-// const may15 = new Date('May 15 2021 06:22:03');
-// const may16 = new Date('May 16 2021 06:22:03');
-
-// const june14 = new Date('June 14 2021 06:22:03');
-// const june15 = new Date('June 15 2021 06:22:03');
-// const june16 = new Date('June 16 2021 06:22:03');
-
-// const july15 = new Date('July 15 2021 06:22:03');
-// const july16 = new Date('July 16 2021 06:22:03');
-// const july18 = new Date('July 18 2021 06:22:03');
-
 describe('getMonth', () => {
   const april13 = new Date('April 13 2021 06:22:03');
   describe(`Date: ${april13}`, () => {
@@ -49,109 +37,23 @@ describe('getMonth', () => {
   const invalidDate = new Date('sdfasf');
   describe(`Date: ${invalidDate}`, () => {
     it(`(BD) should convert to 'Invalid Date'`, () => {
-      expect(getMonth(invalidDate)).toBe('Invalid Date');
+      let error: Error | undefined;
+      try {
+        getMonth(invalidDate);
+      } catch (err) {
+        error = err;
+      }
+      expect(error).toEqual(new Error('Invalid Date'));
     });
 
     it(`(IN) should convert to 'Invalid Date'`, () => {
-      expect(getMonth(invalidDate, { calculationMethod: 'IN' })).toBe(
-        'Invalid Date'
-      );
+      let error: Error | undefined;
+      try {
+        getMonth(invalidDate, { calculationMethod: 'IN' });
+      } catch (err) {
+        error = err;
+      }
+      expect(error).toEqual(new Error('Invalid Date'));
     });
   });
 });
-
-// test(`converts ${may14} to 'বৈশাখ'`, () => {
-//   expect(getMonth(may14)).toBe('বৈশাখ');
-// });
-
-// test(`converts ${may14} to 'বৈশাখ'`, () => {
-//   expect(getMonth(may14, { calculationMethod: 'IN' })).toBe('বৈশাখ');
-// });
-
-// test(`converts ${may15} to 'জ্যৈষ্ঠ'`, () => {
-//   expect(getMonth(may15)).toBe('জ্যৈষ্ঠ');
-// });
-
-// test(`converts ${may15} to 'বৈশাখ'`, () => {
-//   expect(getMonth(may15, { calculationMethod: 'IN' })).toBe('বৈশাখ');
-// });
-
-// test(`converts ${may16} to 'জ্যৈষ্ঠ'`, () => {
-//   expect(getMonth(may16)).toBe('জ্যৈষ্ঠ');
-// });
-
-// test(`converts ${may16} to 'জ্যৈষ্ঠ'`, () => {
-//   expect(getMonth(may16, { calculationMethod: 'IN' })).toBe('জ্যৈষ্ঠ');
-// });
-
-// test(`converts ${may14} to 'বৈশাখ'`, () => {
-//   expect(getMonth(may14)).toBe('বৈশাখ');
-// });
-
-// test(`converts ${may14} to 'বৈশাখ'`, () => {
-//   expect(getMonth(may14, { calculationMethod: 'IN' })).toBe('বৈশাখ');
-// });
-
-// test(`converts ${may15} to 'জ্যৈষ্ঠ'`, () => {
-//   expect(getMonth(may15)).toBe('জ্যৈষ্ঠ');
-// });
-
-// test(`converts ${may15} to 'বৈশাখ'`, () => {
-//   expect(getMonth(may15, { calculationMethod: 'IN' })).toBe('বৈশাখ');
-// });
-
-// test(`converts ${may16} to 'জ্যৈষ্ঠ'`, () => {
-//   expect(getMonth(may16)).toBe('জ্যৈষ্ঠ');
-// });
-
-// test(`converts ${may16} to 'জ্যৈষ্ঠ'`, () => {
-//   expect(getMonth(may16, { calculationMethod: 'IN' })).toBe('জ্যৈষ্ঠ');
-// });
-
-// test(`converts ${june14} to 'জ্যৈষ্ঠ'`, () => {
-//   expect(getMonth(june14)).toBe('জ্যৈষ্ঠ');
-// });
-
-// test(`converts ${june14} to 'জ্যৈষ্ঠ'`, () => {
-//   expect(getMonth(june14, { calculationMethod: 'IN' })).toBe('জ্যৈষ্ঠ');
-// });
-
-// test(`converts ${june15} to 'আষাঢ়'`, () => {
-//   expect(getMonth(june15)).toBe('আষাঢ়');
-// });
-
-// test(`converts ${june15} to 'জ্যৈষ্ঠ'`, () => {
-//   expect(getMonth(june15, { calculationMethod: 'IN' })).toBe('জ্যৈষ্ঠ');
-// });
-
-// test(`converts ${june16} to 'আষাঢ়'`, () => {
-//   expect(getMonth(june16)).toBe('আষাঢ়');
-// });
-
-// test(`converts ${june16} to 'আষাঢ়'`, () => {
-//   expect(getMonth(june16, { calculationMethod: 'IN' })).toBe('আষাঢ়');
-// });
-
-// test(`converts ${july15} to 'আষাঢ়'`, () => {
-//   expect(getMonth(july15)).toBe('আষাঢ়');
-// });
-
-// test(`converts ${july15} to 'আষাঢ়'`, () => {
-//   expect(getMonth(july15, { calculationMethod: 'IN' })).toBe('আষাঢ়');
-// });
-
-// test(`converts ${july16} to 'শ্রাবণ'`, () => {
-//   expect(getMonth(july16)).toBe('শ্রাবণ');
-// });
-
-// test(`converts ${july16} to 'আষাঢ়'`, () => {
-//   expect(getMonth(july16, { calculationMethod: 'IN' })).toBe('আষাঢ়');
-// });
-
-// test(`converts ${july18} to 'শ্রাবণ'`, () => {
-//   expect(getMonth(july18)).toBe('শ্রাবণ');
-// });
-
-// test(`converts ${july18} to 'শ্রাবণ'`, () => {
-//   expect(getMonth(july18, { calculationMethod: 'IN' })).toBe('শ্রাবণ');
-// });

src/__tests__/getYear.test.ts

@@ -48,13 +48,49 @@ describe('getYear', () => {
   const invalidDate = new Date('xyzdate');
   describe(`Date: ${invalidDate}`, () => {
     it(`(BD) should convert to 'Invalid Date'`, () => {
-      expect(getYear(invalidDate, { format: 'YY' })).toBe('Invalid Date');
+      let error: Error | undefined;
+      try {
+        getYear(invalidDate, { format: 'YY' });
+      } catch (err) {
+        error = err;
+      }
+      expect(error).toEqual(new Error('Invalid Date'));
     });
 
     it(`(IN) should convert to 'Invalid Date'`, () => {
-      expect(
-        getYear(invalidDate, { format: 'YY', calculationMethod: 'IN' })
-      ).toBe('Invalid Date');
+      let error: Error | undefined;
+      try {
+        getYear(invalidDate, { format: 'YY', calculationMethod: 'IN' });
+      } catch (err) {
+        error = err;
+      }
+      expect(error).toEqual(new Error('Invalid Date'));
+    });
+  });
+
+  const beforeBanglaDate = new Date('593-04-13');
+  describe(`Date: ${beforeBanglaDate}`, () => {
+    it(`(BD) should convert to 'Invalid Date'`, () => {
+      let error: Error | undefined;
+      try {
+        getYear(beforeBanglaDate, { format: 'YY' });
+      } catch (err) {
+        error = err;
+      }
+      expect(error).toEqual(new Error('Invalid Date'));
+    });
+
+    it(`(IN) should convert to 'Invalid Date'`, () => {
+      let error: Error | undefined;
+      try {
+        getYear(beforeBanglaDate, {
+          format: 'YY',
+          calculationMethod: 'IN',
+        });
+      } catch (err) {
+        error = err;
+      }
+      expect(error).toEqual(new Error('Invalid Date'));
     });
   });
 });

src/getDate.ts

@@ -12,9 +12,14 @@ export function getDate(
     calculationMethod: 'BD',
   }
 ) {
-  if (!isValidDate(date)) return errorMessage;
+  if (!isValidDate(date)) {
+    throw new Error(errorMessage);
+  }
 
   const inputDate = new Date(date);
+  inputDate.setTime(
+    inputDate.getTime() + (inputDate.getTimezoneOffset() + 360) * 60 * 1000
+  );
   const { format = 'eeee, D MMMM, YYYY', calculationMethod = 'BD' } = options;
 
   let formattedDate = format.replace(/eeee|eee/gi, (fmt) => {

src/getDay.ts

@@ -1,5 +1,14 @@
 import { DayOptions } from './types';
-import { errorMessage, formatDay, isLeapYear, isValidDate } from './utils';
+import {
+  errorMessage,
+  formatDay,
+  getJulianDate,
+  isLeapYear,
+  isValidDate,
+  monthLengthIN,
+  startJulianDate,
+  yearLength,
+} from './utils';
 
 function getDayBD(day: number, month: number, year: number): number {
   let banglaDay: number;
@@ -49,71 +58,47 @@ function getDayBD(day: number, month: number, year: number): number {
 }
 
 function getDayIN(day: number, month: number, year: number): number {
+  const julianDate = getJulianDate(year, month + 1, day);
+
+  if (julianDate < startJulianDate) {
+    throw new Error(errorMessage);
+  }
+
+  const banglaYear = Math.floor((julianDate - startJulianDate) / yearLength);
+  const calculatedJulianDate = startJulianDate + banglaYear * yearLength;
+  let ps: number;
+  let ns: number;
   let banglaDay: number;
-  switch (month) {
-    case 0:
-      banglaDay = day < 16 ? day + 15 : day - 15;
-      break;
-    case 1:
-      banglaDay = day < 14 ? day + 16 : day - 13;
-      break;
-    case 2:
-      if (isLeapYear(year)) {
-        banglaDay = day < 15 ? day + 16 : day - 14;
-      } else {
-        banglaDay = day < 16 ? day + 15 : day - 15;
-      }
-      break;
-    case 3:
-      if (isLeapYear(year)) {
-        banglaDay = day < 14 ? day + 17 : day - 13;
-      } else {
-        banglaDay = day < 15 ? day + 16 : day - 14;
-      }
-      break;
-    case 4:
-      banglaDay = day < 16 ? day + 16 : day - 15;
-      break;
-    case 5:
-      banglaDay = day < 16 ? day + 16 : day - 15;
-      break;
-    case 6:
-      banglaDay = day < 18 ? day + 15 : day - 17;
-      break;
-    case 7:
-      banglaDay = day < 18 ? day + 14 : day - 17;
-      break;
-    case 8:
-      banglaDay = day < 18 ? day + 14 : day - 17;
-      break;
-    case 9:
-      banglaDay = day < 19 ? day + 13 : day - 18;
-      break;
-    case 10:
-      banglaDay = day < 18 ? day + 13 : day - 17;
-      break;
-    case 11:
-      banglaDay = day < 17 ? day + 13 : day - 16;
-      break;
-    default:
-      banglaDay = day < 15 ? day + 16 : day - 14;
-      break;
+  for (let i = 0; i < 12; i += 1) {
+    ps = calculatedJulianDate + monthLengthIN[i];
+    ns = calculatedJulianDate + monthLengthIN[i + 1];
+
+    if (julianDate >= ps && julianDate <= Math.floor(ns) + 1.75) {
+      banglaDay = Math.floor(julianDate - ps) + 1;
+    }
   }
+
   return banglaDay;
 }
 
 export function getDay(
   date: Date = new Date(),
   options: DayOptions = { format: 'D', calculationMethod: 'BD' }
 ): string {
-  if (!isValidDate(date)) return errorMessage;
+  if (!isValidDate(date)) {
+    throw new Error(errorMessage);
+  }
 
   const inputDate = new Date(date);
+  inputDate.setTime(
+    inputDate.getTime() + (inputDate.getTimezoneOffset() + 360) * 60 * 1000
+  );
 
   const day = inputDate.getUTCDate();
   const month = inputDate.getMonth();
   const year = inputDate.getFullYear();
   const { format, calculationMethod = 'BD' } = options;
+
   const banglaDay =
     calculationMethod === 'BD'
       ? getDayBD(day, month, year)