Answer:55

apps/angular/55-back-button-navigation/src/app/app.routes.ts

@@ -1,4 +1,5 @@
 import { Routes } from '@angular/router';
+import { canDeactivateGuard } from './can-deactivate.guard';
 import { HomeComponent } from './home/home.component';
 import { SensitiveActionComponent } from './sensitive-action/sensitive-action.component';
 import { SimpleActionComponent } from './simple-action/simple-action.component';
@@ -16,9 +17,11 @@ export const APP_ROUTES: Routes = [
   {
     path: 'simple-action',
     component: SimpleActionComponent,
+    canDeactivate: [canDeactivateGuard],
   },
   {
     path: 'sensitive-action',
     component: SensitiveActionComponent,
+    canDeactivate: [canDeactivateGuard],
   },
 ];

apps/angular/55-back-button-navigation/src/app/base-dialog.ts

@@ -0,0 +1,33 @@
+import {
+  AfterContentInit,
+  ChangeDetectionStrategy,
+  Component,
+  inject,
+} from '@angular/core';
+import { MAT_DIALOG_DATA } from '@angular/material/dialog';
+import { DialogData, DialogStrategyType } from './dialog-strategy';
+import { DialogService } from './dialog.service';
+
+@Component({
+  // eslint-disable-next-line @angular-eslint/component-selector
+  selector: '',
+  template: '',
+  standalone: true,
+  changeDetection: ChangeDetectionStrategy.OnPush,
+})
+export class BaseDialogComponent implements AfterContentInit {
+  readonly #data = inject<DialogData>(MAT_DIALOG_DATA);
+  protected readonly dialogService = inject(DialogService);
+
+  ngAfterContentInit(): void {
+    this.initStrategy();
+  }
+
+  private initStrategy() {
+    const strategyType: DialogStrategyType = this.#data?.strategy?.type
+      ? this.#data?.strategy?.type
+      : 'default';
+
+    this.dialogService.setStrategy(strategyType);
+  }
+}

apps/angular/55-back-button-navigation/src/app/can-deactivate.guard.ts

@@ -0,0 +1,18 @@
+import { CanDeactivateFn, UrlTree } from '@angular/router';
+import { Observable } from 'rxjs';
+
+export type CanDeactivateType =
+  | Observable<boolean | UrlTree>
+  | Promise<boolean | UrlTree>
+  | boolean
+  | UrlTree;
+
+export interface CanComponentDeactivate {
+  canDeactivate: () => CanDeactivateType;
+}
+
+export const canDeactivateGuard: CanDeactivateFn<CanComponentDeactivate> = (
+  component: CanComponentDeactivate,
+) => {
+  return component.canDeactivate ? component.canDeactivate() : true;
+};

apps/angular/55-back-button-navigation/src/app/confirm-dialog/confirm-dialog.component.html

@@ -0,0 +1,19 @@
+<h2 mat-dialog-title>Confirm Action</h2>
+<mat-dialog-content>
+  Are you sure you want to perform this action?
+</mat-dialog-content>
+<mat-dialog-actions>
+  <button
+    mat-button
+    mat-dialog-close
+    (click)="dialogService.closeActiveDialog()">
+    No
+  </button>
+  <button
+    mat-button
+    mat-dialog-close
+    cdkFocusInitial
+    (click)="dialogService.closeAll()">
+    Yes
+  </button>
+</mat-dialog-actions>

apps/angular/55-back-button-navigation/src/app/confirm-dialog/confirm-dialog.component.ts

@@ -0,0 +1,28 @@
+import { ChangeDetectionStrategy, Component } from '@angular/core';
+import { MatButtonModule } from '@angular/material/button';
+import {
+  MatDialogActions,
+  MatDialogClose,
+  MatDialogContent,
+  MatDialogTitle,
+} from '@angular/material/dialog';
+import { BaseDialogComponent } from '../base-dialog';
+
+@Component({
+  selector: 'app-confirm-dialog',
+  templateUrl: './confirm-dialog.component.html',
+  standalone: true,
+  imports: [
+    MatButtonModule,
+    MatDialogActions,
+    MatDialogClose,
+    MatDialogTitle,
+    MatDialogContent,
+  ],
+  changeDetection: ChangeDetectionStrategy.OnPush,
+})
+export class ConfirmDialogComponent extends BaseDialogComponent {
+  constructor() {
+    super();
+  }
+}

apps/angular/55-back-button-navigation/src/app/dialog-strategy.ts

@@ -0,0 +1,47 @@
+import { Injectable, inject } from '@angular/core';
+import { ConfirmDialogComponent } from './confirm-dialog/confirm-dialog.component';
+import { DialogService } from './dialog.service';
+
+export type DialogStrategyType = 'default' | 'confirm';
+
+export type DialogData = {
+  strategy: {
+    type: DialogStrategyType;
+  };
+};
+
+export abstract class DialogStrategy {
+  protected readonly dialogService = inject(DialogService);
+
+  abstract onBackBrowserNavigation(): boolean;
+}
+
+@Injectable({
+  providedIn: 'root',
+})
+export class DefaultDialogStrategy extends DialogStrategy {
+  override onBackBrowserNavigation(): boolean {
+    this.dialogService.closeActiveDialog();
+
+    return false;
+  }
+}
+
+@Injectable({
+  providedIn: 'root',
+})
+export class ConfirmDialogStrategy extends DialogStrategy {
+  override onBackBrowserNavigation(): boolean {
+    this.dialogService.openDialog(ConfirmDialogComponent, {
+      width: '250px',
+      closeOnNavigation: false,
+    });
+
+    return false;
+  }
+}
+
+export const DialogStrategyMap = new Map<DialogStrategyType, any>([
+  ['default', DefaultDialogStrategy],
+  ['confirm', ConfirmDialogStrategy],
+]);

apps/angular/55-back-button-navigation/src/app/dialog.service.ts

@@ -0,0 +1,109 @@
+import { ComponentType } from '@angular/cdk/portal';
+import { Injectable, Injector, inject } from '@angular/core';
+import { MatDialog, MatDialogConfig } from '@angular/material/dialog';
+import { take, tap } from 'rxjs';
+import {
+  DialogStrategy,
+  DialogStrategyMap,
+  DialogStrategyType,
+} from './dialog-strategy';
+
+@Injectable({
+  providedIn: 'root',
+})
+export class DialogService {
+  readonly #dialog = inject(MatDialog);
+  readonly #dialogsStrategyState: {
+    id: string;
+    type: DialogStrategy;
+    active: boolean;
+  }[] = [];
+
+  readonly #injector = inject(Injector);
+
+  openDialog<T extends ComponentType<any>, Z extends MatDialogConfig<any>>(
+    component: T,
+    config: Z,
+  ) {
+    const dialogRef = this.#dialog.open<T, Z>(component, config);
+
+    dialogRef
+      .afterClosed()
+      .pipe(
+        take(1),
+        tap(() => this.removeDialogStrategyStateById(dialogRef.id)),
+      )
+      .subscribe();
+  }
+
+  setStrategy(type: DialogStrategyType) {
+    this.#dialog.openDialogs.forEach((d) => {
+      const state = this.getDialogStrategyStateById(d.id);
+
+      if (!state) {
+        this.addDialogStrategyState(d.id, type);
+      }
+    });
+  }
+
+  getStrategyType() {
+    const active = this.getActiveDialog();
+
+    if (!active) {
+      return null;
+    }
+
+    return this.getDialogStrategyStateById(active.id)?.type;
+  }
+
+  closeActiveDialog() {
+    const activeDialog = this.#dialogsStrategyState.find((d) => d.active);
+
+    if (!activeDialog) {
+      return;
+    }
+
+    this.#dialog.getDialogById(activeDialog.id)?.close();
+  }
+
+  closeAll() {
+    this.#dialogsStrategyState.splice(0, this.#dialogsStrategyState.length);
+
+    this.#dialog.closeAll();
+  }
+
+  getActiveDialog() {
+    return this.#dialogsStrategyState.find((d) => d.active);
+  }
+
+  addDialogStrategyState(id: string, type: DialogStrategyType) {
+    const t = this.#injector.get<DialogStrategy>(DialogStrategyMap.get(type));
+
+    this.#dialogsStrategyState.map((x) => (x.active = false));
+
+    this.#dialogsStrategyState.push({ id, type: t, active: true });
+  }
+
+  getDialogStrategyStateById(id: string) {
+    return this.#dialogsStrategyState.find((s) => s.id === id);
+  }
+
+  removeDialogStrategyStateById(id: string) {
+    const indexToRemove = this.#dialogsStrategyState.findIndex(
+      (d) => d.id === id,
+    );
+
+    if (indexToRemove > 0) {
+      this.#dialogsStrategyState[indexToRemove - 1] = {
+        ...this.#dialogsStrategyState[indexToRemove - 1],
+        active: true,
+      };
+    }
+
+    this.#dialogsStrategyState.splice(indexToRemove, 1);
+  }
+
+  getDialogsStrategyState() {
+    return this.#dialogsStrategyState;
+  }
+}

apps/angular/55-back-button-navigation/src/app/dialog/dialog.component.ts

@@ -1,15 +1,15 @@
-import { ChangeDetectionStrategy, Component, inject } from '@angular/core';
+import { ChangeDetectionStrategy, Component } from '@angular/core';
 import { MatButtonModule } from '@angular/material/button';
 import {
   MatDialogActions,
   MatDialogClose,
   MatDialogContent,
-  MatDialogRef,
   MatDialogTitle,
 } from '@angular/material/dialog';
+import { BaseDialogComponent } from '../base-dialog';
 
 @Component({
-  selector: 'app-dialog-dialog',
+  selector: 'app-dialog',
   templateUrl: './dialog.component.html',
   standalone: true,
   imports: [
@@ -21,6 +21,8 @@ import {
   ],
   changeDetection: ChangeDetectionStrategy.OnPush,
 })
-export class DialogComponent {
-  readonly dialogRef = inject(MatDialogRef<DialogComponent>);
+export class DialogComponent extends BaseDialogComponent {
+  constructor() {
+    super();
+  }
 }

apps/angular/55-back-button-navigation/src/app/home/home.component.html

@@ -1,7 +1,7 @@
-<a mat-raised-button routerLink="/simple-action" routerLinkActive="active">
+<a mat-raised-button routerLink="/simple-action">
   Go to simple dialog action page
 </a>
 
-<a mat-raised-button routerLink="/sensitive-action" routerLinkActive="active">
+<a mat-raised-button routerLink="/sensitive-action">
   Go to sensitive dialog action page
 </a>

apps/angular/55-back-button-navigation/src/app/sensitive-action/sensitive-action.component.html

@@ -1,3 +1,5 @@
 <button mat-raised-button (click)="openDialog()">
   Open dialog with confirmation dialog on browser back button click
 </button>
+
+<a mat-raised-button routerLink="/">Home</a>

apps/angular/55-back-button-navigation/src/app/sensitive-action/sensitive-action.component.ts

@@ -1,20 +1,30 @@
 import { Component, inject } from '@angular/core';
 import { MatButtonModule } from '@angular/material/button';
-import { MatDialog } from '@angular/material/dialog';
-import { DialogComponent } from '../dialog/dialog.component';
+import { RouterLink } from '@angular/router';
+import { CanComponentDeactivate } from '../can-deactivate.guard';
+import { DialogService } from '../dialog.service';
+import { SensitiveDialogComponent } from '../sensitive-dialog/sensitive-dialog.component';
 
 @Component({
   standalone: true,
-  imports: [MatButtonModule],
+  imports: [MatButtonModule, RouterLink],
   selector: 'app-sensitive-action',
   templateUrl: './sensitive-action.component.html',
 })
-export class SensitiveActionComponent {
-  readonly #dialog = inject(MatDialog);
+export class SensitiveActionComponent implements CanComponentDeactivate {
+  readonly #dialogService = inject(DialogService);
 
   openDialog(): void {
-    this.#dialog.open(DialogComponent, {
-      width: '250px',
+    this.#dialogService.openDialog(SensitiveDialogComponent, {
+      width: '450px',
+      data: { strategy: { type: 'confirm' } },
+      closeOnNavigation: false,
     });
   }
+
+  canDeactivate() {
+    return (
+      this.#dialogService.getStrategyType()?.onBackBrowserNavigation() ?? true
+    );
+  }
 }

apps/angular/55-back-button-navigation/src/app/sensitive-dialog/sensitive-dialog.component.html

@@ -0,0 +1,6 @@
+<h2 mat-dialog-title>Sensitive File Deletion</h2>
+<mat-dialog-content>Would you like to delete cat.jpeg?</mat-dialog-content>
+<mat-dialog-actions>
+  <button mat-button mat-dialog-close>No</button>
+  <button mat-button mat-dialog-close cdkFocusInitial>Ok</button>
+</mat-dialog-actions>

apps/angular/55-back-button-navigation/src/app/sensitive-dialog/sensitive-dialog.component.ts

@@ -0,0 +1,28 @@
+import { ChangeDetectionStrategy, Component } from '@angular/core';
+import { MatButtonModule } from '@angular/material/button';
+import {
+  MatDialogActions,
+  MatDialogClose,
+  MatDialogContent,
+  MatDialogTitle,
+} from '@angular/material/dialog';
+import { BaseDialogComponent } from '../base-dialog';
+
+@Component({
+  selector: 'app-sensitive-dialog',
+  templateUrl: './sensitive-dialog.component.html',
+  standalone: true,
+  imports: [
+    MatButtonModule,
+    MatDialogActions,
+    MatDialogClose,
+    MatDialogTitle,
+    MatDialogContent,
+  ],
+  changeDetection: ChangeDetectionStrategy.OnPush,
+})
+export class SensitiveDialogComponent extends BaseDialogComponent {
+  constructor() {
+    super();
+  }
+}