Refactor: create DateCacheService to reduce date duplication

Co-authored-by: THoguet <61246905+THoguet@users.noreply.github.com>

src/app/components/calendar-month/calendar-month.ts

@@ -1,7 +1,8 @@
-import { Component, Input, OnInit } from '@angular/core';
+import { Component, Input, OnInit, inject } from '@angular/core';
 import { CalendarService, Month, monthNames, SelectedDates } from '../../services/calendar-service';
 import { MatTooltip } from '@angular/material/tooltip';
 import { CalendarSettingsService } from '../../services/calendar-settings-service';
+import { DateCacheService } from '../../services/date-cache.service';
 
 @Component({
 	selector: 'app-calendar-month',
@@ -10,7 +11,8 @@ import { CalendarSettingsService } from '../../services/calendar-settings-servic
 	styleUrl: './calendar-month.scss',
 })
 export class CalendarMonth implements OnInit {
-	constructor(protected calendarSettingsService: CalendarSettingsService) {}
+	protected calendarSettingsService = inject(CalendarSettingsService);
+	private dateCache = inject(DateCacheService);
 
 	@Input({ required: true })
 	monthIndex!: number;
@@ -18,18 +20,9 @@ export class CalendarMonth implements OnInit {
 	@Input({ required: true })
 	year!: number;
 
-	// Cache "now" as a class property to avoid recreating it on every call
-	// Note: This value is cached at component initialization and won't update if the day changes
-	// while the component is still mounted. This is acceptable for this use case since the app
-	// is primarily used within a single day session.
-	private readonly now: Date = (() => {
-		const date = new Date();
-		date.setHours(0, 0, 0, 0);
-		return date;
-	})();
-
+	// Use DateCacheService instead of creating Date objects
 	getNow(): Date {
-		return this.now;
+		return this.dateCache.getNow();
 	}
 
 	currentMonth: Date = new Date();

src/app/components/calendar-year/calendar-year.ts

@@ -1,4 +1,4 @@
-import { Component, effect, signal } from '@angular/core';
+import { Component, effect, signal, inject } from '@angular/core';
 import { UserInputService } from '../../services/user-input-service';
 import { MatCard, MatCardContent } from '@angular/material/card';
 import { CalendarMonth } from '../calendar-month/calendar-month';
@@ -6,6 +6,7 @@ import { CalendarService, SelectedDates } from '../../services/calendar-service'
 import { CommonModule } from '@angular/common';
 import { MatProgressSpinner } from '@angular/material/progress-spinner';
 import { CalendarSettingsService } from '../../services/calendar-settings-service';
+import { DateCacheService } from '../../services/date-cache.service';
 
 @Component({
 	selector: 'app-calendar-year',
@@ -14,17 +15,23 @@ import { CalendarSettingsService } from '../../services/calendar-settings-servic
 	styleUrl: './calendar-year.scss',
 })
 export class CalendarYear {
+	private dateCache = inject(DateCacheService);
+	private userInput = inject(UserInputService);
+	private calendarService = inject(CalendarService);
+	private calendarSettingsService = inject(CalendarSettingsService);
+
 	protected isLoading = signal(true);
 
-	// Cache current month and year to avoid repeated Date object creation
-	private readonly currentMonth = new Date().getMonth();
-	private readonly currentYear = new Date().getFullYear();
+	// Use DateCacheService instead of creating Date objects
+	private get currentMonth() {
+		return this.dateCache.getCurrentMonth();
+	}
 
-	constructor(
-		private userInput: UserInputService,
-		private calendarService: CalendarService,
-		private calendarSettingsService: CalendarSettingsService,
-	) {
+	private get currentYear() {
+		return this.dateCache.getCurrentYear();
+	}
+
+	constructor() {
 		effect(() => {
 			this.selectedDates = this.calendarService.getSelectedDatesForYear();
 			const vacationData = this.userInput.vacationNumberSignal();

src/app/services/calendar-service.ts

@@ -1,10 +1,11 @@
-import { Injectable } from '@angular/core';
+import { Injectable, inject } from '@angular/core';
 import { DateRange } from '@angular/material/datepicker';
 import Holidays, { HolidaysTypes } from 'date-holidays';
 import dayjs from 'dayjs';
 import weekOfYear from 'dayjs/plugin/weekOfYear';
 import isoWeek from 'dayjs/plugin/isoWeek';
 import { CalendarSettingsService } from './calendar-settings-service';
+import { DateCacheService } from './date-cache.service';
 
 dayjs.extend(weekOfYear);
 dayjs.extend(isoWeek);
@@ -19,6 +20,8 @@ const allTypesOptions: HolidaysTypes.Options = {
 	providedIn: 'root',
 })
 export class CalendarService {
+	private dateCache = inject(DateCacheService);
+
 	// Cache for holiday timestamps
 	private holidayTimestampsCache: Set<number> | null = null;
 	private holidayCacheYear: number | null = null;
@@ -36,11 +39,12 @@ export class CalendarService {
 		const monthInAYear = CalendarService.monthsInAYearFromNow();
 		let selectedDates: SelectedDates = new SelectedDates();
 
-		// Cache today's date components to avoid repeated new Date() calls
-		const today = new Date();
-		const todayDate = today.getDate();
-		const todayMonth = today.getMonth();
-		const todayYear = today.getFullYear();
+		// Use DateCacheService to get today's date components
+		const {
+			date: todayDate,
+			month: todayMonth,
+			year: todayYear,
+		} = this.dateCache.getTodayComponents();
 
 		// Create a Set of holiday timestamps for O(1) lookup instead of O(n)
 		const holidayTimestamps = new Set(holidays.map((h) => h.getTime()));
@@ -99,7 +103,7 @@ export class CalendarService {
 
 	getHolidays(): Date[] {
 		// Cache holidays to avoid recalculation
-		const currentYear = new Date().getFullYear();
+		const currentYear = this.dateCache.getCurrentYear();
 		if (this.holidayCacheYear === currentYear && this.holidayTimestampsCache) {
 			// Return timestamps directly for efficient lookup
 			return Array.from(this.holidayTimestampsCache).map((ts) => new Date(ts));
@@ -164,9 +168,10 @@ export class CalendarService {
 	}
 
 	static monthsInAYearFromNow(): Year {
+		const dateCache = inject(DateCacheService);
 		const months: Year = [];
-		const currentMonthIndex = new Date().getMonth();
-		const currentYear = new Date().getFullYear();
+		const currentMonthIndex = dateCache.getCurrentMonth();
+		const currentYear = dateCache.getCurrentYear();
 		for (let i = 0; i < 12; i++) {
 			const monthIndex = (currentMonthIndex + i) % 12;
 			const year = currentYear + Math.floor((currentMonthIndex + i) / 12);

src/app/services/date-cache.service.spec.ts

@@ -0,0 +1,46 @@
+import { TestBed } from '@angular/core/testing';
+import { DateCacheService } from './date-cache.service';
+
+describe('DateCacheService', () => {
+	let service: DateCacheService;
+
+	beforeEach(() => {
+		TestBed.configureTestingModule({});
+		service = TestBed.inject(DateCacheService);
+	});
+
+	it('should be created', () => {
+		expect(service).toBeTruthy();
+	});
+
+	it('should cache today date', () => {
+		const today1 = service.getToday();
+		const today2 = service.getToday();
+		expect(today1).toBe(today2); // Same reference
+	});
+
+	it('should cache today components', () => {
+		const components1 = service.getTodayComponents();
+		const components2 = service.getTodayComponents();
+		expect(components1).toBe(components2); // Same reference
+	});
+
+	it('should cache current month', () => {
+		const month1 = service.getCurrentMonth();
+		const month2 = service.getCurrentMonth();
+		expect(month1).toBe(month2);
+	});
+
+	it('should cache current year', () => {
+		const year1 = service.getCurrentYear();
+		const year2 = service.getCurrentYear();
+		expect(year1).toBe(year2);
+	});
+
+	it('should clear cache', () => {
+		const year1 = service.getCurrentYear();
+		service.clearCache();
+		const year2 = service.getCurrentYear();
+		expect(year1).toBe(year2); // Values should be the same even after clearing
+	});
+});

src/app/services/date-cache.service.ts

@@ -0,0 +1,105 @@
+import { Injectable } from '@angular/core';
+
+/**
+ * Service to cache and provide commonly used date values.
+ * This reduces redundant Date object creation across the application.
+ */
+@Injectable({
+	providedIn: 'root',
+})
+export class DateCacheService {
+	private _today: Date | null = null;
+	private _todayComponents: { date: number; month: number; year: number } | null = null;
+	private _currentMonth: number | null = null;
+	private _currentYear: number | null = null;
+
+	/**
+	 * Get today's date (time set to 00:00:00.000)
+	 */
+	getToday(): Date {
+		if (!this._today || this.isNewDay(this._today)) {
+			this._today = new Date();
+			this._today.setHours(0, 0, 0, 0);
+			this._todayComponents = null; // Invalidate components cache
+		}
+		return this._today;
+	}
+
+	/**
+	 * Get today's date components (date, month, year) for efficient comparison
+	 */
+	getTodayComponents(): { date: number; month: number; year: number } {
+		if (!this._todayComponents || (this._today && this.isNewDay(this._today))) {
+			const today = this.getToday();
+			this._todayComponents = {
+				date: today.getDate(),
+				month: today.getMonth(),
+				year: today.getFullYear(),
+			};
+		}
+		return this._todayComponents;
+	}
+
+	/**
+	 * Get current month (0-11)
+	 */
+	getCurrentMonth(): number {
+		if (this._currentMonth === null || this.isNewMonth()) {
+			this._currentMonth = new Date().getMonth();
+		}
+		return this._currentMonth;
+	}
+
+	/**
+	 * Get current year
+	 */
+	getCurrentYear(): number {
+		if (this._currentYear === null || this.isNewYear()) {
+			this._currentYear = new Date().getFullYear();
+		}
+		return this._currentYear;
+	}
+
+	/**
+	 * Get current date with time set to 00:00:00.000 (alias for getToday)
+	 */
+	getNow(): Date {
+		return this.getToday();
+	}
+
+	/**
+	 * Check if a cached date is from a previous day
+	 */
+	private isNewDay(cachedDate: Date): boolean {
+		const now = new Date();
+		return (
+			cachedDate.getDate() !== now.getDate() ||
+			cachedDate.getMonth() !== now.getMonth() ||
+			cachedDate.getFullYear() !== now.getFullYear()
+		);
+	}
+
+	/**
+	 * Check if we're in a new month
+	 */
+	private isNewMonth(): boolean {
+		return this._currentMonth !== null && this._currentMonth !== new Date().getMonth();
+	}
+
+	/**
+	 * Check if we're in a new year
+	 */
+	private isNewYear(): boolean {
+		return this._currentYear !== null && this._currentYear !== new Date().getFullYear();
+	}
+
+	/**
+	 * Clear all caches (useful for testing)
+	 */
+	clearCache(): void {
+		this._today = null;
+		this._todayComponents = null;
+		this._currentMonth = null;
+		this._currentYear = null;
+	}
+}