Refactor GridManager with new DateColumnDataSource

Introduces DateColumnDataSource to centralize date column generation logic
Simplifies GridManager by delegating date calculations to dedicated data source
Enhances flexibility for different calendar views and date rendering strategies

Improves separation of concerns and makes calendar view management more modular

src/datasources/DateColumnDataSource.ts

@@ -0,0 +1,120 @@
+import { IColumnDataSource } from '../types/ColumnDataSource';
+import { DateService } from '../utils/DateService';
+import { Configuration } from '../configurations/CalendarConfig';
+import { CalendarView } from '../types/CalendarTypes';
+
+/**
+ * DateColumnDataSource - Provides date-based columns
+ *
+ * Calculates which dates to display based on:
+ * - Current date
+ * - Current view (day/week/month)
+ * - Workweek settings
+ */
+export class DateColumnDataSource implements IColumnDataSource {
+  private dateService: DateService;
+  private config: Configuration;
+  private currentDate: Date;
+  private currentView: CalendarView;
+
+  constructor(
+    dateService: DateService,
+    config: Configuration,
+    currentDate: Date,
+    currentView: CalendarView
+  ) {
+    this.dateService = dateService;
+    this.config = config;
+    this.currentDate = currentDate;
+    this.currentView = currentView;
+  }
+
+  /**
+   * Get columns (dates) to display
+   */
+  public getColumns(): Date[] {
+    switch (this.currentView) {
+      case 'week':
+        return this.getWeekDates();
+      case 'month':
+        return this.getMonthDates();
+      case 'day':
+        return [this.currentDate];
+      default:
+        return this.getWeekDates();
+    }
+  }
+
+  /**
+   * Get type of datasource
+   */
+  public getType(): 'date' | 'resource' {
+    return 'date';
+  }
+
+  /**
+   * Update current date
+   */
+  public setCurrentDate(date: Date): void {
+    this.currentDate = date;
+  }
+
+  /**
+   * Update current view
+   */
+  public setCurrentView(view: CalendarView): void {
+    this.currentView = view;
+  }
+
+  /**
+   * Get dates for week view based on workweek settings
+   */
+  private getWeekDates(): Date[] {
+    const weekStart = this.getISOWeekStart(this.currentDate);
+    const workWeekSettings = this.config.getWorkWeekSettings();
+    return this.dateService.getWorkWeekDates(weekStart, workWeekSettings.workDays);
+  }
+
+  /**
+   * Get all dates in current month
+   */
+  private getMonthDates(): Date[] {
+    const dates: Date[] = [];
+    const monthStart = this.getMonthStart(this.currentDate);
+    const monthEnd = this.getMonthEnd(this.currentDate);
+
+    const totalDays = Math.ceil((monthEnd.getTime() - monthStart.getTime()) / (1000 * 60 * 60 * 24)) + 1;
+
+    for (let i = 0; i < totalDays; i++) {
+      dates.push(this.dateService.addDays(monthStart, i));
+    }
+
+    return dates;
+  }
+
+  /**
+   * Get ISO week start (Monday)
+   */
+  private getISOWeekStart(date: Date): Date {
+    const weekBounds = this.dateService.getWeekBounds(date);
+    return this.dateService.startOfDay(weekBounds.start);
+  }
+
+  /**
+   * Get month start
+   */
+  private getMonthStart(date: Date): Date {
+    const year = date.getFullYear();
+    const month = date.getMonth();
+    return this.dateService.startOfDay(new Date(year, month, 1));
+  }
+
+  /**
+   * Get month end
+   */
+  private getMonthEnd(date: Date): Date {
+    const nextMonth = this.dateService.addMonths(date, 1);
+    const firstOfNextMonth = this.getMonthStart(nextMonth);
+    return this.dateService.endOfDay(this.dateService.addDays(firstOfNextMonth, -1));
+  }
+}