fix(meetings): resolve past meeting edit validation issue

When editing meetings with past start dates, form validation prevented
saving even when keeping the original date unchanged. This blocked
users from editing meeting details like description or attendees.

- Add editModeDateTimeValidator for conditional past date validation
- Allow past dates only if they match original meeting start time
- Maintain strict future date validation for new meetings
- Update meeting-manage component to use appropriate validator

Fixes LFXV2-532

Generated with [Claude Code](https://claude.ai/code)

Signed-off-by: Asitha de Silva <asithade@gmail.com>

Author: asithade

apps/lfx-one/src/app/modules/project/meetings/components/meeting-manage/meeting-manage.component.ts

@@ -38,7 +38,7 @@ import {
   getUserTimezone,
   mapRecurrenceToFormValue,
 } from '@lfx-one/shared/utils';
-import { futureDateTimeValidator } from '@lfx-one/shared/validators';
+import { editModeDateTimeValidator, futureDateTimeValidator } from '@lfx-one/shared/validators';
 import { MeetingService } from '@services/meeting.service';
 import { ProjectService } from '@services/project.service';
 import { ConfirmationService, MessageService } from 'primeng/api';
@@ -85,6 +85,7 @@ export class MeetingManageComponent {
   public mode = signal<'create' | 'edit'>('create');
   public meetingId = signal<string | null>(null);
   public isEditMode = computed(() => this.mode() === 'edit');
+  public originalStartTime = signal<string | null>(null);
   public registrantUpdates = signal<RegistrantPendingChanges>({
     toAdd: [],
     toUpdate: [],
@@ -508,6 +509,9 @@ export class MeetingManageComponent {
   }
 
   private populateFormWithMeetingData(meeting: Meeting): void {
+    // Store the original start time for validation
+    this.originalStartTime.set(meeting.start_time);
+
     // Parse start_time to separate date and time
     let startDate = null;
     let startTime = '';
@@ -593,6 +597,9 @@ export class MeetingManageComponent {
           endTypeUI: endTypeUI,
         });
     }
+
+    // Update the form validator to use edit mode validator with original start time
+    this.updateFormValidator();
   }
 
   private canNavigateToStep(step: number): boolean {
@@ -875,4 +882,18 @@ export class MeetingManageComponent {
 
     return false;
   }
+
+  private updateFormValidator(): void {
+    const currentForm = this.form();
+
+    // Apply appropriate validator based on mode
+    if (this.isEditMode() && this.originalStartTime()) {
+      currentForm.setValidators(editModeDateTimeValidator(this.originalStartTime()!));
+    } else {
+      currentForm.setValidators(futureDateTimeValidator());
+    }
+
+    // Update form validity
+    currentForm.updateValueAndValidity();
+  }
 }

packages/shared/src/validators/meeting.validators.ts

@@ -35,6 +35,52 @@ export function futureDateTimeValidator(): ValidatorFn {
   };
 }
 
+/**
+ * Validator for edit mode - allows past dates only if they match the original meeting start time
+ */
+export function editModeDateTimeValidator(originalStartTime?: string): ValidatorFn {
+  return (control: AbstractControl): ValidationErrors | null => {
+    const formGroup = control as any; // FormGroup
+    const startDate = formGroup.get?.('startDate')?.value;
+    const startTime = formGroup.get?.('startTime')?.value;
+    const timezone = formGroup.get?.('timezone')?.value;
+
+    if (!startDate || !startTime || !timezone) {
+      return null; // Don't validate if values are not set
+    }
+
+    // Combine the date and time with timezone awareness
+    const combinedDateTime = combineDateTime(startDate, startTime, timezone);
+    if (!combinedDateTime) {
+      return null; // Invalid time format
+    }
+
+    // Check if the datetime is in the future for the specified timezone
+    const isInFuture = isDateTimeInFutureForTimezone(combinedDateTime, timezone);
+
+    if (!isInFuture) {
+      // If in the past, check if it matches the original start time
+      if (originalStartTime) {
+        // Compare the combined datetime with the original start time
+        const originalDate = new Date(originalStartTime);
+        const newDate = new Date(combinedDateTime);
+
+        // Allow past date only if it matches the original (within 1 minute to account for formatting differences)
+        const timeDifferenceMs = Math.abs(originalDate.getTime() - newDate.getTime());
+        const oneMinuteMs = 60 * 1000;
+
+        if (timeDifferenceMs <= oneMinuteMs) {
+          return null; // Allow the original date/time even if in the past
+        }
+      }
+
+      return { futureDateTime: true };
+    }
+
+    return null;
+  };
+}
+
 /**
  * Validator to check if a time string is in valid 12-hour format
  */