arcana-angular-developer-skill

name	arcana-angular-developer-skill
description	Angular development guide based on Arcana Angular enterprise architecture. Provides comprehensive support for Clean Architecture, Offline-First design with 4-layer caching, Angular Signals, MVVM Input/Output/Effect pattern, and enterprise security. Suitable for Angular project development, architecture design, code review, and debugging.
allowed-tools	["Read","Grep","Glob","Bash","Write","Edit"]

Angular Developer Skill

Professional Angular development skill based on Arcana Angular enterprise architecture.

---

⚡ Workflow — Always Start From the Reference Project

Every task starts by cloning the complete reference project — NEVER scaffold from scratch (no ng new):

git clone https://github.com/jrjohn/arcana-angular.git [new-project-directory]

1. Clone the reference project (command above).
2. Build + test the UNTOUCHED clone first — npm install && npm run build && npm run test -- --watch=false --browsers=ChromeHeadless must be green before any modification (known-good baseline).
3. Follow 0. Project Setup to rename the project and strip demo code — KEEP the infrastructure: auth (guards/interceptors), 4-layer caching, offline/sync, security layers, DI/core, router skeleton.
4. Add features by copying the nearest working feature, then adapting (see 🔁 Adding a feature) — the File-by-File Feature Recipe below is the completeness checklist.

🔁 Adding a feature = copy the nearest working feature (NOT from scratch)

When you add a new feature, do NOT re-create it from memory by walking the File-by-File Recipe on a blank slate. Copy the nearest already-working feature in the cloned reference, then adapt it.

1. Find the closest conformant feature already in the reference — e.g. the example users feature (user-list / user-detail / user-form) — it already has the full Model → Repository → Service → ViewModel (Input/Output/Effect) → Component → specs chain wired through DI.
2. Duplicate its ENTIRE file set (model, validator, service interface + impl, repository interface + impl, DTO, mapper, mock repository, provider binding, ViewModel, component, NavGraph methods, route, specs) 1:1, keeping every layer.
3. Rename + adapt to the new domain (types, routes, endpoints, DI bindings/providers).
4. Diff against the original to confirm nothing was dropped — same layer split, same ViewModel/service/repository boundary, same error model, same tests.

Why this is mandatory: the File-by-File Recipe is a checklist of what must exist, not a from-scratch build order. Re-deriving the pattern each time makes every step a chance to skip a layer (the ViewModel, the repository), wire a shortcut (component → data/API directly), or drop the tests — the "vibe-coding" deviations that pass local build + coverage but fail architecture review (e.g. arch-qube). Copying a known-good feature carries conformance in by construction; the recipe is then only your verification that nothing is missing.

Supporting files — load on demand

File	When to read
patterns.md	Detailed design patterns beyond the core examples in this file
patterns/mvvm-input-output.md	Deep-dive on the MVVM Input/Output/Effect ViewModel pattern
examples.md	Full working code examples for complete features
checklists/production-ready.md	Pre-release production & code review checklists
verification/commands.md	Complete catalog of verification bash commands
reference.md	Technical reference (versions, APIs, configuration details)

---

Quick Reference Card

New Screen Checklist:

1. Add route → app.routes.ts (path + component)
2. Create Component with ChangeDetectionStrategy.OnPush
3. Create ViewModel (Input/Output/Effect with Signals)
4. Create template with Loading/Error/Empty states
5. Wire @Output events in parent template
6. Verify mock data returns non-empty values

New Repository Checklist:

1. Interface → domain/repositories/xxx.repository.ts
2. Implementation → data/repositories/xxx.repository.impl.ts
3. Mock → data/repositories/mock/mock-xxx.repository.ts
4. Provider binding → core/providers/repository.providers.ts
5. Mock data (NEVER return [] or null!)
6. Verify ID consistency across repositories

Quick Diagnosis:

Symptom	Check Command
Blank screen	`grep "\[\]\
Navigation crash	Compare app.routes.ts paths vs component imports
Button does nothing	grep "(click)=\"\"" src/app/**/*.html
Data not loading	`grep "throw.*NotImplemented\

---

File-by-File Feature Recipe

Create files in this order when adding a new feature (example: project):

1. Model              -> src/app/domain/models/project.model.ts
2. Validator          -> src/app/domain/validators/project.validator.ts
3. Service Interface  -> src/app/domain/services/project.service.ts
4. Service Impl       -> src/app/domain/services/project.service.impl.ts
5. Repository Interface -> src/app/domain/repositories/project.repository.ts
6. Repository Impl    -> src/app/data/repositories/project.repository.impl.ts
7. DTO                -> src/app/data/remote/dtos/project.dto.ts
8. Mapper             -> src/app/data/remote/mappers/project.mapper.ts
9. Mock Repository    -> src/app/data/repositories/mock/mock-project.repository.ts
10. Provider Binding  -> src/app/core/providers/repository.providers.ts
11. ViewModel         -> src/app/presentation/projects/project.viewmodel.ts
12. Component         -> src/app/presentation/projects/project.component.ts
13. NavGraph Methods  -> src/app/core/services/nav-graph.service.ts (toProjectList, toProjectDetail)
14. Route             -> src/app/app.routes.ts (path + component)
15. Tests             -> project.viewmodel.spec.ts + service/repository specs

Step notes:

• 1-2: Model is a plain TypeScript interface; validator is pure logic (no Angular imports beyond signals if needed).
• 3-6: Service depends on the repository INTERFACE (abstract class, step 5), never the impl. Repository impl wraps the 4-layer cache + offline sync (Dexie).
• 7-8: DTO mirrors the API payload exactly; mapper converts DTO <-> domain model. Never leak DTOs above the data layer.
• 9: Mock data must be realistic and non-empty (see Mock Data Rules — NEVER return [] / of([])).
• 10: Bind impl vs mock in repository.providers.ts via environment.production switch.
• 11: @Injectable() ViewModel with Input/Output/Effect pattern — Signals for output, Subject for effects, single onInput() entry point.
• 12: Standalone component with ChangeDetectionStrategy.OnPush, providers: [ProjectViewModel], Loading/Error/Empty/Content states, subscribe to effect$.
• 13-14: Every route added in app.routes.ts MUST get a matching NavGraphService method, and every @Output() navigation event must be bound in the parent template.
• 15: ViewModel specs first (90%+ target), then service (85%+) and repository (80%+) specs.

Verify after wiring: npm run build && npm run test -- --watch=false --browsers=ChromeHeadless.

---

Rules Priority

🔴 CRITICAL (Must Fix Immediately)

Rule	Description	Verification
Zero-Empty Policy	Repository stubs NEVER return empty arrays	`grep "\[\]\
Navigation Wiring	ALL routes MUST have component imports	Count paths vs components
@Output Binding	ALL @Output events MUST be bound in parent	Check template bindings
ID Consistency	Cross-repository IDs must match	Check mock data IDs

🟡 IMPORTANT (Should Fix Before PR)

Rule	Description	Verification
UI States	Loading/Error/Empty for all screens	grep -L "isLoading" *.component.ts
Mock Data Quality	Realistic, varied values (not all same)	Review mock data arrays
Error Messages	User-friendly, not technical errors	Check error handling
OnPush Detection	All components use OnPush	Check changeDetection

🟢 RECOMMENDED (Nice to Have)

Rule	Description
Animations	Smooth route transitions
Accessibility	ARIA labels for interactive elements
Dark Mode	Support system theme preference
PWA	Service worker for offline

---

Error Handling Pattern

AppError - Unified Error Model

// domain/models/app-error.ts
export type AppError =
  | { type: 'NETWORK_UNAVAILABLE' }
  | { type: 'TIMEOUT' }
  | { type: 'SERVER_ERROR'; statusCode: number }
  | { type: 'UNAUTHORIZED' }
  | { type: 'TOKEN_EXPIRED' }
  | { type: 'INVALID_CREDENTIALS' }
  | { type: 'NOT_FOUND' }
  | { type: 'VALIDATION_FAILED'; message: string }
  | { type: 'DATA_CORRUPTED' }
  | { type: 'UNKNOWN'; underlying: Error };

export function getErrorMessage(error: AppError): string {
  switch (error.type) {
    case 'NETWORK_UNAVAILABLE':
      return 'No internet connection. Please check your network.';
    case 'TIMEOUT':
      return 'Request timed out. Please try again.';
    case 'SERVER_ERROR':
      return `Server error (${error.statusCode}). Please try again later.`;
    case 'UNAUTHORIZED':
    case 'TOKEN_EXPIRED':
      return 'Session expired. Please login again.';
    case 'INVALID_CREDENTIALS':
      return 'Invalid email or password.';
    case 'NOT_FOUND':
      return 'The requested item was not found.';
    case 'VALIDATION_FAILED':
      return error.message;
    case 'DATA_CORRUPTED':
      return 'Data error. Please contact support.';
    case 'UNKNOWN':
      return 'An unexpected error occurred.';
  }
}

export function requiresReauth(error: AppError): boolean {
  return error.type === 'UNAUTHORIZED' || error.type === 'TOKEN_EXPIRED';
}

Error Handling Flow

┌─────────────────────────────────────────────────────────────────┐
│                        Error Flow                                │
├─────────────────────────────────────────────────────────────────┤
│  Repository Layer:                                               │
│    - Catch HTTP errors                                           │
│    - Map to AppError                                             │
│    - Throw AppError                                              │
├─────────────────────────────────────────────────────────────────┤
│  Service Layer:                                                  │
│    - Catch repository errors                                     │
│    - Add business context if needed                              │
│    - Re-throw as AppError                                        │
├─────────────────────────────────────────────────────────────────┤
│  ViewModel Layer:                                                │
│    - Catch all errors                                            │
│    - Update _error signal with getErrorMessage()                 │
│    - Check requiresReauth() for auth redirect                    │
├─────────────────────────────────────────────────────────────────┤
│  Component Layer:                                                │
│    - Display error from output().error                           │
│    - Show retry button                                           │
│    - Handle auth redirect via effect                             │
└─────────────────────────────────────────────────────────────────┘

Error Handling by Layer

HTTP Interceptor (functional HttpInterceptorFn — the modern primary pattern; see 9. HTTP Interceptors for the legacy class-based alternative):

// core/interceptors/error.interceptor.ts
import { HttpInterceptorFn, HttpErrorResponse } from '@angular/common/http';
import { catchError, throwError } from 'rxjs';

export const errorInterceptor: HttpInterceptorFn = (req, next) =>
  next(req).pipe(
    catchError((error: HttpErrorResponse) => {
      let appError: AppError;

      if (error.status === 0) {
        appError = { type: 'NETWORK_UNAVAILABLE' };
      } else if (error.status === 401) {
        appError = { type: 'UNAUTHORIZED' };
      } else if (error.status === 404) {
        appError = { type: 'NOT_FOUND' };
      } else if (error.status >= 500) {
        appError = { type: 'SERVER_ERROR', statusCode: error.status };
      } else {
        appError = { type: 'UNKNOWN', underlying: error };
      }

      return throwError(() => appError);
    })
  );

ViewModel Layer:

private async loadData(): Promise<void> {
  this._isLoading.set(true);
  this._error.set(null);

  try {
    const items = await this.repository.getItems();
    this._items.set(items);
  } catch (error) {
    const appError = error as AppError;
    this._error.set(getErrorMessage(appError));
    if (requiresReauth(appError)) {
      this._effect.next({ type: 'NAVIGATE_TO_LOGIN' });
    }
  } finally {
    this._isLoading.set(false);
  }
}

---

Test Coverage Targets

Coverage by Layer

Layer	Target	Focus Areas
ViewModel	90%+	All Input handlers, state transitions, effects
Service	85%+	Business logic, edge cases
Repository	80%+	Data mapping, error handling
Component	60%+	Template binding, user interactions

What to Test

ViewModel Tests (Highest Priority):

describe('FeatureViewModel', () => {
  // Test each Input type
  it('should load items on LOAD input', async () => { });
  it('should set error on LOAD failure', async () => { });
  it('should emit toast on REFRESH success', async () => { });
  it('should navigate on ITEM_CLICKED', () => { });

  // Test state transitions
  it('should set isLoading true then false', async () => { });

  // Test edge cases
  it('should show empty state when no items', async () => { });
});

Service Tests:

describe('UserService', () => {
  // Test business rules
  it('should validate email format', () => { });
  it('should calculate score correctly', () => { });
});

Repository Tests:

describe('UserRepository', () => {
  // Test data mapping
  it('should map DTO to domain model', async () => { });

  // Test offline behavior
  it('should return cached data when offline', async () => { });
});

Test Commands

# Run all tests with coverage
npm run test -- --code-coverage --watch=false --browsers=ChromeHeadless

# View coverage report
open coverage/[app-name]/index.html

---

Core Architecture Principles

Clean Architecture - Three Layers

┌─────────────────────────────────────────────────────┐
│                  Presentation Layer                  │
│      Components + MVVM + Input/Output/Effect        │
├─────────────────────────────────────────────────────┤
│                    Domain Layer                      │
│          Business Logic + Services + Models         │
├─────────────────────────────────────────────────────┤
│                     Data Layer                       │
│   Offline-First Repository + IndexedDB + 4L Cache   │
└─────────────────────────────────────────────────────┘

Dependency Rules

• Unidirectional Dependencies: Presentation → Domain → Data
• Interface Segregation: Decouple layers through interfaces
• Dependency Inversion: Data layer implements Domain layer interfaces

Instructions

When handling Angular development tasks, follow these principles:

Quick Verification Commands

Use these commands to quickly check for common issues:

# 1. Check for unimplemented services (MUST be empty)
grep -rn "throw.*NotImplemented\|TODO.*implement" src/app/

# 2. Check for empty click handlers (MUST be empty)
grep -rn "(click)=\"\"\|(click)=\"undefined\"" src/app/

# 3. Check for missing route components (compare routes vs components)
echo "Routes defined:" && grep -c "path:" src/app/app.routes.ts 2>/dev/null || echo 0
echo "Components imported:" && grep -c "component:" src/app/app.routes.ts 2>/dev/null || echo 0

# 4. Check NavGraphService has all navigation methods
grep -c "to\|navigate" src/app/core/services/nav-graph.service.ts 2>/dev/null || echo 0

# 5. Verify build compiles
npm run build

# 6. 🚨 Check for Output events with no parent binding (CRITICAL!)
echo "=== Component @Output Events ===" && \
grep -rh "@Output()" src/app/presentation/ | grep -oE "[a-zA-Z]+\s*=" | sed 's/\s*=//' | sort -u
echo "=== Bound Events in Templates ===" && \
grep -rh "([a-zA-Z]*Navigate[a-zA-Z]*)=" src/app/**/*.html 2>/dev/null | grep -oE "\([a-zA-Z]+\)" | tr -d '()' | sort -u

# 7. 🚨 Verify ALL routes have NavGraphService navigation methods
echo "=== Routes Defined ===" && \
grep -rh "path:" src/app/app.routes.ts | grep -oE "'[^']+'" | sort -u
echo "=== NavGraphService Methods ===" && \
grep -rh "to[A-Z][a-zA-Z]*\(" src/app/core/services/nav-graph.service.ts | grep -oE "to[A-Z][a-zA-Z]*" | sort -u

# 8. 🚨 Check for navigation callbacks in Components not wired in parent
grep -rn "onNavigate.*:\s*EventEmitter" src/app/presentation/

# 9. 🚨 Check Service→Repository wiring (CRITICAL!)
echo "=== Repository Methods Called in Services ===" && \
grep -roh "this\.[a-zA-Z]*Repository\.[a-zA-Z]*(" src/app/domain/services/*.ts | sort -u
echo "=== Repository Interface Methods ===" && \
grep -rh "[a-zA-Z]*\(" src/app/domain/repositories/*.repository.ts | grep -oE "[a-zA-Z]+\(" | sort -u

# 10. 🚨 Verify ALL Repository interface methods have implementations
echo "=== Repository Interface Methods ===" && \
grep -rh "abstract\|[a-zA-Z]*\(" src/app/domain/repositories/*.repository.ts | grep -oE "[a-zA-Z]+\(" | sort -u
echo "=== Repository Implementation Methods ===" && \
grep -rh "[a-zA-Z]*\(" src/app/data/repositories/*.repository.impl.ts | grep -oE "[a-zA-Z]+\(" | sort -u

⚠️ CRITICAL: All routes in app.routes.ts MUST have corresponding component imports. Missing components cause runtime errors.

⚠️ NAVIGATION WIRING CRITICAL: Commands #6-#8 detect navigation @Output events that exist in Components but aren't bound in parent templates. A Component can declare @Output() onNavigateToSettings = new EventEmitter() but if the parent template doesn't bind (onNavigateToSettings)="handler()", the event does nothing!

If any of these return results or counts don't match, FIX THEM before completing the task.

---

📊 Mock Data Requirements for Repository Stubs

The Chart Data Problem

When implementing Repository stubs, NEVER return empty arrays for data that powers UI charts or visualizations. This causes:

• Charts that render but show nothing (blank ng2-charts/D3 canvas)
• Line charts that skip rendering (e.g., if (data.length < 2) return;)
• Empty state components even when data structure exists

Mock Data Rules

Rule 1: Array data for charts MUST have at least 7 items

// ❌ BAD - Chart will be blank
getCurrentWeekSummary(): Observable<WeeklySummary> {
    return of({
        dailyReports: []  // ← Chart has no data to render!
    });
}

// ✅ GOOD - Chart has data to display
getCurrentWeekSummary(): Observable<WeeklySummary> {
    const mockDailyReports = Array.from({ length: 7 }, (_, i) =>
        this.createMockDailyReport(
            [72, 78, 85, 80, 76, 88, 82][i],
            [390, 420, 450, 410, 380, 460, 435][i]
        )
    );
    return of({ dailyReports: mockDailyReports });
}

Rule 2: Use realistic, varied sample values

// ❌ BAD - Monotonous test data
const scores = Array(7).fill(80);

// ✅ GOOD - Realistic variation
const scores = [72, 78, 85, 80, 76, 88, 82];  // Shows trend

Rule 3: Data must match interface exactly

# Before creating mock data, ALWAYS verify the interface definition:
grep -A 20 "interface TherapyData" src/app/domain/models/*.ts

Rule 4: Create helper functions for complex mock data

// ✅ Create reusable mock factory
private createMockDailyReport(score: number, duration: number): DailySleepReport {
    return {
        id: `mock_${Date.now()}`,
        sleepScore: score,
        sleepDuration: { totalMinutes: duration, ... },
        // ... all required fields
    };
}

Quick Verification Commands for Mock Data

# 11. 🚨 Check for empty array returns in Repository stubs (MUST FIX)
grep -rn "\[\]" src/app/data/repositories/*.repository.impl.ts

# 12. 🚨 Verify chart-related data has mock values
grep -rn "dailyReports\|weeklyData\|chartData" src/app/data/repositories/ | grep -E "= \[\]|of\(\[\]\)"

---

0. Project Setup - CRITICAL

⚠️ IMPORTANT: This reference project has been validated with tested npm/Angular settings and library versions. NEVER reconfigure project structure or modify package.json / angular.json, or it will cause compilation errors.

Step 1: Clone the reference project

git clone https://github.com/jrjohn/arcana-angular.git [new-project-directory]
cd [new-project-directory]

Step 2: Reinitialize Git (remove original repo history)

rm -rf .git
git init
git add .
git commit -m "Initial commit from arcana-angular template"

Step 3: Modify project name Only modify the following required items:

• name field in package.json
• Project name in angular.json
• <title> in src/index.html
• Update related settings in environment configuration files

Step 4: Clean up example code The cloned project contains example UI (e.g., Arcana User Management). Clean up and replace with new project screens:

Core architecture files to KEEP (do not delete):

• src/app/core/ - Common utilities (Guards, Interceptors, Services)
• src/app/shared/ - Shared components and Pipes
• src/app/data/local/ - IndexedDB (Dexie) base configuration
• src/app/data/repositories/ - Repository base classes
• src/app/app.component.ts - App entry point
• src/app/app.routes.ts - Route configuration (modify routes)

Example files to REPLACE:

• src/app/presentation/ - Delete all example screens, create new project Components
• src/app/domain/models/ - Delete example Models, create new Domain Models
• src/app/data/remote/ - Modify API endpoints
• src/assets/ - Update resource files

Step 5: Install dependencies and verify build

npm install
npm run build

❌ Prohibited Actions

• DO NOT create new Angular project from scratch (ng new)
• DO NOT modify version numbers in package.json
• DO NOT add or remove npm dependencies (unless explicitly required)
• DO NOT modify build settings in angular.json
• DO NOT reconfigure Bootstrap, Dexie, ng-bootstrap, or other library settings

✅ Allowed Modifications

• Add business-related TypeScript code (following existing architecture)
• Add Components, Services, ViewModels
• Add Domain Models, Repository
• Modify resources in src/assets/
• Add routing modules

1. TDD & Spec-Driven Development Workflow - MANDATORY

⚠️ CRITICAL: All development MUST follow this TDD workflow. Every Spec requirement must have corresponding tests BEFORE implementation.

🚨 ABSOLUTE RULE: TDD = Tests + Implementation. Writing tests without implementation is INCOMPLETE. Every test file MUST have corresponding production code that passes the tests.

┌─────────────────────────────────────────────────────────────────┐
│                    TDD Development Workflow                      │
├─────────────────────────────────────────────────────────────────┤
│  Step 1: Analyze Spec → Extract all SRS & SDD requirements      │
│  Step 2: Create Tests → Write tests for EACH Spec item          │
│  Step 3: Verify Coverage → Ensure 100% Spec coverage in tests   │
│  Step 4: Implement → Build features to pass tests  ⚠️ MANDATORY │
│  Step 5: Mock APIs → Use mock data for unfinished Cloud APIs    │
│  Step 6: Run All Tests → ALL tests must pass before completion  │
│  Step 7: Verify 100% → Tests written = Features implemented     │
└─────────────────────────────────────────────────────────────────┘

⛔ FORBIDDEN: Tests Without Implementation

// ❌ WRONG - Test exists but no implementation
// Test file exists: login.viewmodel.spec.ts (32 tests)
// Production file: login.viewmodel.ts → MISSING or throws NotImplementedError
// This is INCOMPLETE TDD!

// ✅ CORRECT - Test AND Implementation both exist
// Test file: login.viewmodel.spec.ts (32 tests)
// Production file: login.viewmodel.ts (fully implemented)
// All 32 tests PASS

⛔ Placeholder Component Policy

Placeholder components are ONLY allowed as a temporary route during active development. They are FORBIDDEN as a final state.

// ❌ WRONG - Placeholder component left in production
{ path: 'training', component: PlaceholderComponent } // FORBIDDEN!

// ✅ CORRECT - Real component implementation
{ path: 'training', component: TrainingComponent }

Placeholder Check Command:

# This command MUST return empty for production-ready code
grep -rn "PlaceholderComponent\|throw.*NotImplemented\|TODO.*implement\|即將推出\|Coming Soon" src/app/

Step 1: Analyze Spec Documents (SRS & SDD)

Before writing any code, extract ALL requirements from both SRS and SDD:

/**
 * Requirements extracted from specification documents:
 *
 * SRS (Software Requirements Specification):
 * - SRS-001: User must be able to login with email/password
 * - SRS-002: App must show splash screen for 2 seconds
 * - SRS-003: Dashboard must display user's stars and coins
 *
 * SDD (Software Design Document):
 * - SDD-001: Use Angular Signals for state management
 * - SDD-002: Implement MVVM Input/Output/Effect pattern
 * - SDD-003: Use IndexedDB (Dexie) for offline storage
 */

Step 2: Create Test Cases for Each Spec Item

// src/app/presentation/auth/login.viewmodel.spec.ts
import { TestBed } from '@angular/core/testing';
import { LoginViewModel } from './login.viewmodel';
import { AuthRepository } from '../../domain/repositories/auth.repository';

describe('LoginViewModel', () => {
  let viewModel: LoginViewModel;
  let mockAuthRepository: jasmine.SpyObj<AuthRepository>;

  beforeEach(() => {
    mockAuthRepository = jasmine.createSpyObj('AuthRepository', ['login', 'isLoggedIn']);

    TestBed.configureTestingModule({
      providers: [
        LoginViewModel,
        { provide: AuthRepository, useValue: mockAuthRepository }
      ]
    });

    viewModel = TestBed.inject(LoginViewModel);
  });

  // SRS-001: User must be able to login with email/password
  it('should login successfully with valid credentials', async () => {
    // Given
    mockAuthRepository.login.and.returnValue(Promise.resolve());

    // When
    viewModel.onInput({ type: 'updateEmail', value: '[e-mail]' });
    viewModel.onInput({ type: 'updatePassword', value: 'password123' });
    await viewModel.onInput({ type: 'submit' });

    // Then
    expect(viewModel.output().isLoginSuccess).toBeTrue();
    expect(viewModel.output().error).toBeNull();
  });

  // SRS-001: Invalid credentials should show error
  it('should show error with invalid credentials', async () => {
    // Given
    mockAuthRepository.login.and.returnValue(Promise.reject(new Error('Invalid credentials')));

    // When
    await viewModel.onInput({ type: 'submit' });

    // Then
    expect(viewModel.output().isLoginSuccess).toBeFalse();
    expect(viewModel.output().error).toBeTruthy();
  });
});

Step 3: Spec Coverage Verification Checklist

Before implementation, verify ALL SRS and SDD items have tests:

/**
 * Spec Coverage Checklist - [Project Name]
 *
 * SRS Requirements:
 * [x] SRS-001: Login with email/password - login.viewmodel.spec.ts
 * [x] SRS-002: Splash screen display - splash.component.spec.ts
 * [x] SRS-003: Register new account - register.viewmodel.spec.ts
 * [x] SRS-010: Display user stars - dashboard.viewmodel.spec.ts
 * [x] SRS-011: Display S-coins - dashboard.viewmodel.spec.ts
 * [ ] SRS-020: List training items - TODO
 *
 * SDD Design Requirements:
 * [x] SDD-001: Angular Signals state - viewmodel.spec.ts
 * [x] SDD-002: MVVM Input/Output/Effect - viewmodel.spec.ts
 * [x] SDD-003: IndexedDB offline storage - repository.spec.ts
 * [ ] SDD-004: 4-layer caching - TODO
 */

Step 4: Mock API Implementation - MANDATORY

⚠️ CRITICAL: Every Service/Repository method MUST return valid mock data. NEVER leave methods throwing NotImplementedError.

Rules for Mock Services:

1. ALL service methods must return valid mock data (Promise.resolve or Observable.of)
2. Use setTimeout() or delay() to simulate network latency (500-1000ms)
3. Mock data must match the interface structure exactly
4. Check TypeScript enums exist before using them
5. Include all required properties for interfaces

For APIs not yet available from Cloud team, implement mock services:

// src/app/data/repositories/mock/mock-auth.repository.ts
import { Injectable } from '@angular/core';
import { AuthRepository } from '../../../domain/repositories/auth.repository';

interface MockUser {
  email: string;
  password: string;
  name: string;
}

@Injectable()
export class MockAuthRepository implements AuthRepository {

  // Mock user data for testing
  private static readonly MOCK_USERS: MockUser[] = [
    { email: '[e-mail]', password: 'password123', name: 'Test User' },
    { email: '[e-mail]', password: 'demo123', name: 'Demo User' }
  ];

  async login(email: string, password: string): Promise<void> {
    // Simulate network delay
    await new Promise(resolve => setTimeout(resolve, 1000));

    const user = MockAuthRepository.MOCK_USERS.find(
      u => u.email === email && u.password === password
    );

    if (user) {
      // Save mock token
      localStorage.setItem('access_token', `mock_token_${Date.now()}`);
      localStorage.setItem('user_name', user.name);
    } else {
      throw new Error('Invalid email or password');
    }
  }

  isLoggedIn(): boolean {
    return !!localStorage.getItem('access_token');
  }
}

// src/app/core/providers/repository.providers.ts - Switch between Mock and Real
import { environment } from '../../../environments/environment';

export const repositoryProviders = [
  {
    provide: AuthRepository,
    useClass: environment.production
      ? AuthRepositoryImpl  // Production
      : MockAuthRepository  // Development/Testing
  }
];

Step 5: Run All Tests Before Completion

# Run all unit tests
npm run test

# Run tests with coverage report
npm run test -- --code-coverage

# Run tests in CI mode (single run)
npm run test -- --watch=false --browsers=ChromeHeadless

# Run e2e tests
npm run e2e

# Verify all tests pass
npm run test -- --watch=false && npm run e2e

Test Directory Structure

src/app/
├── presentation/
│   ├── auth/
│   │   ├── login.viewmodel.ts
│   │   ├── login.viewmodel.spec.ts      # Unit test
│   │   ├── login.component.ts
│   │   └── login.component.spec.ts      # Component test
│   └── dashboard/
│       ├── dashboard.viewmodel.spec.ts
│       └── dashboard.component.spec.ts
├── domain/
│   └── services/
│       ├── user.service.ts
│       └── user.service.spec.ts
├── data/
│   └── repositories/
│       ├── auth.repository.impl.ts
│       ├── auth.repository.spec.ts
│       └── mock/
│           └── mock-auth.repository.ts
e2e/
├── login.e2e-spec.ts
└── dashboard.e2e-spec.ts

2. Project Structure

src/
├── app/
│   ├── presentation/     # UI Layer
│   │   ├── components/   # Smart & Dumb Components
│   │   ├── layouts/      # Page Layouts
│   │   └── forms/        # Form Components
│   ├── domain/           # Domain Layer
│   │   ├── models/       # Domain Models
│   │   ├── services/     # Business Services
│   │   └── repositories/ # Repository Interfaces
│   └── data/             # Data Layer
│       ├── repositories/ # Repository Implementations
│       ├── local/        # IndexedDB (Dexie)
│       └── remote/       # API Client
├── assets/
└── styles/               # SCSS with Bootstrap

3. ViewModel Input/Output/Effect Pattern with Signals

import { Injectable, signal, computed } from '@angular/core';
import { Subject } from 'rxjs';

// Input: Sealed type defining all events
export type UserInput =
  | { type: 'UPDATE_NAME'; name: string }
  | { type: 'UPDATE_EMAIL'; email: string }
  | { type: 'SUBMIT' };

// Output: State container
export interface UserOutput {
  name: string;
  email: string;
  isLoading: boolean;
  error: string | null;
}

// Effect: One-time events
export type UserEffect =
  | { type: 'NAVIGATE_BACK' }
  | { type: 'SHOW_SNACKBAR'; message: string };

@Injectable()
export class UserViewModel {
  // Output: Read-only signals
  private readonly _name = signal('');
  private readonly _email = signal('');
  private readonly _isLoading = signal(false);
  private readonly _error = signal<string | null>(null);

  readonly output = computed<UserOutput>(() => ({
    name: this._name(),
    email: this._email(),
    isLoading: this._isLoading(),
    error: this._error(),
  }));

  // Effect: One-time events stream
  private readonly _effect = new Subject<UserEffect>();
  readonly effect$ = this._effect.asObservable();

  constructor(private readonly userService: UserService) {}

  // Input: Single entry point
  onInput(input: UserInput): void {
    switch (input.type) {
      case 'UPDATE_NAME':
        this._name.set(input.name);
        break;
      case 'UPDATE_EMAIL':
        this._email.set(input.email);
        break;
      case 'SUBMIT':
        this.submit();
        break;
    }
  }

  private async submit(): Promise<void> {
    this._isLoading.set(true);
    this._error.set(null);

    try {
      await this.userService.updateUser({
        name: this._name(),
        email: this._email(),
      });
      this._effect.next({ type: 'NAVIGATE_BACK' });
    } catch (error) {
      this._error.set(error instanceof Error ? error.message : 'Unknown error');
    } finally {
      this._isLoading.set(false);
    }
  }
}

4. Four-Layer Offline-First Caching

import { Injectable } from '@angular/core';
import Dexie from 'dexie';

interface CacheEntry<T> {
  value: T;
  timestamp: number;
}

@Injectable({ providedIn: 'root' })
export class CacheManager<T> {
  // L1: Memory cache (<1ms)
  private memoryCache = new Map<string, CacheEntry<T>>();

  // L2: LRU + TTL cache (~2ms)
  private lruCache = new Map<string, CacheEntry<T>>();
  private readonly maxLruSize = 100;
  private readonly ttlMs = 5 * 60 * 1000; // 5 minutes

  // L3: IndexedDB persistence (~10ms)
  private db: Dexie;

  // L4: Remote API fallback (~200ms)
  constructor(private readonly apiClient: ApiClient) {
    this.db = new Dexie('AppCache');
    this.db.version(1).stores({
      cache: 'key, value, timestamp',
    });
  }

  async get(key: string, loader: () => Promise<T>): Promise<T> {
    const now = Date.now();

    // Check L1: Memory cache
    const memEntry = this.memoryCache.get(key);
    if (memEntry && now - memEntry.timestamp < this.ttlMs) {
      return memEntry.value;
    }

    // Check L2: LRU cache
    const lruEntry = this.lruCache.get(key);
    if (lruEntry && now - lruEntry.timestamp < this.ttlMs) {
      this.memoryCache.set(key, lruEntry);
      return lruEntry.value;
    }

    // Check L3: IndexedDB
    const dbEntry = await this.db.table('cache').get(key);
    if (dbEntry && now - dbEntry.timestamp < this.ttlMs) {
      const entry = { value: dbEntry.value, timestamp: dbEntry.timestamp };
      this.memoryCache.set(key, entry);
      this.addToLru(key, entry);
      return dbEntry.value;
    }

    // L4: Load from remote
    const value = await loader();
    const entry = { value, timestamp: now };

    this.memoryCache.set(key, entry);
    this.addToLru(key, entry);
    await this.db.table('cache').put({ key, ...entry });

    return value;
  }

  private addToLru(key: string, entry: CacheEntry<T>): void {
    if (this.lruCache.size >= this.maxLruSize) {
      const oldestKey = this.lruCache.keys().next().value;
      if (oldestKey) this.lruCache.delete(oldestKey);
    }
    this.lruCache.set(key, entry);
  }
}

5. Offline-First Repository

import { Injectable } from '@angular/core';
import { BehaviorSubject, Observable } from 'rxjs';
import Dexie from 'dexie';

enum SyncStatus {
  SYNCED = 'synced',
  PENDING = 'pending',
  FAILED = 'failed',
}

@Injectable({ providedIn: 'root' })
export class UserRepository {
  private db: Dexie;
  private usersSubject = new BehaviorSubject<User[]>([]);

  constructor(
    private readonly apiClient: ApiClient,
    private readonly syncManager: SyncManager
  ) {
    this.db = new Dexie('UsersDB');
    this.db.version(1).stores({
      users: 'id, name, email, syncStatus, updatedAt',
    });
    this.loadFromLocal();
  }

  // IndexedDB as single source of truth
  getUsers(): Observable<User[]> {
    return this.usersSubject.asObservable();
  }

  // Local-first updates
  async updateUser(user: User): Promise<void> {
    // 1. Immediately update local database
    const entity = {
      ...user,
      syncStatus: SyncStatus.PENDING,
      updatedAt: Date.now(),
    };
    await this.db.table('users').put(entity);
    this.loadFromLocal();

    // 2. Schedule background sync
    this.syncManager.scheduleSync();
  }

  // Background sync processing
  async syncPendingChanges(): Promise<void> {
    const pendingUsers = await this.db
      .table('users')
      .where('syncStatus')
      .equals(SyncStatus.PENDING)
      .toArray();

    for (const user of pendingUsers) {
      try {
        await this.apiClient.updateUser(user);
        await this.db.table('users').update(user.id, {
          syncStatus: SyncStatus.SYNCED,
        });
      } catch {
        // Keep pending status for retry
      }
    }

    this.loadFromLocal();
  }

  private async loadFromLocal(): Promise<void> {
    const users = await this.db.table('users').toArray();
    this.usersSubject.next(users);
  }
}

6. Component with OnPush Change Detection

import { Component, ChangeDetectionStrategy, inject } from '@angular/core';
import { CommonModule } from '@angular/common';
import { ReactiveFormsModule } from '@angular/forms';
import { UserViewModel, UserInput } from './user.viewmodel';

@Component({
  selector: 'app-user',
  standalone: true,
  imports: [CommonModule, ReactiveFormsModule],
  changeDetection: ChangeDetectionStrategy.OnPush,
  template: `
    <form (ngSubmit)="onSubmit()">
      <div class="form-group">
        <label for="name">Name</label>
        <input
          id="name"
          type="text"
          [value]="vm.output().name"
          (input)="onNameChange($event)"
        />
      </div>

      <div class="form-group">
        <label for="email">Email</label>
        <input
          id="email"
          type="email"
          [value]="vm.output().email"
          (input)="onEmailChange($event)"
        />
      </div>

      @if (vm.output().error) {
        <div class="error">{{ vm.output().error }}</div>
      }

      <button type="submit" [disabled]="vm.output().isLoading">
        @if (vm.output().isLoading) {
          Loading...
        } @else {
          Submit
        }
      </button>
    </form>
  `,
  providers: [UserViewModel],
})
export class UserComponent {
  protected readonly vm = inject(UserViewModel);

  constructor() {
    // Handle effects
    this.vm.effect$.subscribe((effect) => {
      switch (effect.type) {
        case 'NAVIGATE_BACK':
          // Navigate back
          break;
        case 'SHOW_SNACKBAR':
          // Show snackbar
          break;
      }
    });
  }

  onNameChange(event: Event): void {
    const input = event.target as HTMLInputElement;
    this.vm.onInput({ type: 'UPDATE_NAME', name: input.value });
  }

  onEmailChange(event: Event): void {
    const input = event.target as HTMLInputElement;
    this.vm.onInput({ type: 'UPDATE_EMAIL', email: input.value });
  }

  onSubmit(): void {
    this.vm.onInput({ type: 'SUBMIT' });
  }
}

7. Type-Safe Navigation (NavGraphService)

import { Injectable, inject } from '@angular/core';
import { Router } from '@angular/router';

@Injectable({ providedIn: 'root' })
export class NavGraphService {
  private readonly router = inject(Router);

  // Type-safe navigation methods
  toHome(): Promise<boolean> {
    return this.router.navigate(['/']);
  }

  toUserList(): Promise<boolean> {
    return this.router.navigate(['/users']);
  }

  toUserDetail(userId: string): Promise<boolean> {
    return this.router.navigate(['/users', userId]);
  }

  toUserEdit(userId: string): Promise<boolean> {
    return this.router.navigate(['/users', userId, 'edit']);
  }

  toProjectList(): Promise<boolean> {
    return this.router.navigate(['/projects']);
  }

  toProjectDetail(projectId: string): Promise<boolean> {
    return this.router.navigate(['/projects', projectId]);
  }

  back(): void {
    window.history.back();
  }
}

8. Security - Input Sanitization

import { Injectable } from '@angular/core';
import { DomSanitizer, SafeHtml } from '@angular/platform-browser';

@Injectable({ providedIn: 'root' })
export class SanitizationService {
  constructor(private readonly sanitizer: DomSanitizer) {}

  // Sanitize HTML to prevent XSS
  sanitizeHtml(html: string): SafeHtml {
    return this.sanitizer.bypassSecurityTrustHtml(this.stripDangerousTags(html));
  }

  // Strip dangerous tags
  private stripDangerousTags(html: string): string {
    const dangerousTags = ['script', 'iframe', 'object', 'embed', 'form'];
    let result = html;

    for (const tag of dangerousTags) {
      const regex = new RegExp(`<${tag}[^>]*>.*?</${tag}>`, 'gi');
      result = result.replace(regex, '');
    }

    // Remove event handlers
    result = result.replace(/\s*on\w+="[^"]*"/gi, '');
    result = result.replace(/\s*on\w+='[^']*'/gi, '');

    return result;
  }

  // Sanitize user input
  sanitizeInput(input: string): string {
    return input
      .replace(/&/g, '&amp;')
      .replace(/</g, '&lt;')
      .replace(/>/g, '&gt;')
      .replace(/"/g, '&quot;')
      .replace(/'/g, '&#x27;');
  }
}

9. HTTP Interceptors

Modern (primary): functional interceptors with HttpInterceptorFn + withInterceptors. Match what the reference repo uses; modern Angular prefers functional.

// core/interceptors/auth.interceptor.ts
import { HttpInterceptorFn, HttpErrorResponse } from '@angular/common/http';
import { inject } from '@angular/core';
import { throwError } from 'rxjs';
import { catchError, retry } from 'rxjs/operators';

// Auth Interceptor (functional)
export const authInterceptor: HttpInterceptorFn = (req, next) => {
  const token = inject(AuthService).getToken();

  if (token) {
    req = req.clone({
      setHeaders: { Authorization: `Bearer ${token}` },
    });
  }

  return next(req);
};

// Error Interceptor (functional)
export const errorInterceptor: HttpInterceptorFn = (req, next) =>
  next(req).pipe(
    retry(1),
    catchError((error: HttpErrorResponse) => {
      const errorMessage =
        error.error instanceof ErrorEvent
          ? error.error.message // Client-side error
          : `Error Code: ${error.status}\nMessage: ${error.message}`; // Server-side error

      console.error(errorMessage);
      return throwError(() => new Error(errorMessage));
    })
  );

// app.config.ts - Registration
import { provideHttpClient, withInterceptors } from '@angular/common/http';

export const appConfig: ApplicationConfig = {
  providers: [
    provideHttpClient(withInterceptors([authInterceptor, errorInterceptor])),
  ],
};

Legacy alternative: class-based HttpInterceptor (only if the reference repo still uses it — registered via HTTP_INTERCEPTORS multi-provider):

import { Injectable } from '@angular/core';
import {
  HttpInterceptor,
  HttpRequest,
  HttpHandler,
  HttpEvent,
  HttpErrorResponse,
} from '@angular/common/http';
import { Observable, throwError } from 'rxjs';
import { catchError, retry } from 'rxjs/operators';

// Auth Interceptor
@Injectable()
export class AuthInterceptor implements HttpInterceptor {
  constructor(private readonly authService: AuthService) {}

  intercept(req: HttpRequest<unknown>, next: HttpHandler): Observable<HttpEvent<unknown>> {
    const token = this.authService.getToken();

    if (token) {
      req = req.clone({
        setHeaders: {
          Authorization: `Bearer ${token}`,
        },
      });
    }

    return next.handle(req);
  }
}

// Error Interceptor
@Injectable()
export class ErrorInterceptor implements HttpInterceptor {
  intercept(req: HttpRequest<unknown>, next: HttpHandler): Observable<HttpEvent<unknown>> {
    return next.handle(req).pipe(
      retry(1),
      catchError((error: HttpErrorResponse) => {
        let errorMessage = 'An unknown error occurred';

        if (error.error instanceof ErrorEvent) {
          // Client-side error
          errorMessage = error.error.message;
        } else {
          // Server-side error
          errorMessage = `Error Code: ${error.status}\nMessage: ${error.message}`;
        }

        console.error(errorMessage);
        return throwError(() => new Error(errorMessage));
      })
    );
  }
}

10. Form Validation

import { signal, computed } from '@angular/core';

export class FormState {
  private readonly _email = signal('');
  private readonly _emailTouched = signal(false);

  readonly email = this._email.asReadonly();

  readonly emailError = computed(() => {
    if (!this._emailTouched()) return null;

    const email = this._email();
    if (!email) return 'Email is required';
    if (!this.isValidEmail(email)) return 'Invalid email format';

    return null;
  });

  readonly isValid = computed(() => {
    const email = this._email();
    return !!email && this.isValidEmail(email);
  });

  setEmail(value: string): void {
    this._email.set(value);
  }

  markEmailTouched(): void {
    this._emailTouched.set(true);
  }

  private isValidEmail(email: string): boolean {
    const emailRegex = /^[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,}$/;
    return emailRegex.test(email);
  }
}

Navigation Wiring Verification Guide

🚨 The Navigation Wiring Blind Spot

Angular Components often declare @Output navigation events that need parent binding:

// settings.component.ts
@Component({...})
export class SettingsComponent {
  @Output() onNavigateToAccountInfo = new EventEmitter<void>();  // ⚠️ Needs parent binding!
  @Output() onNavigateToChangePassword = new EventEmitter<void>();  // ⚠️ Needs parent binding!
  @Output() onNavigateToUserList = new EventEmitter<void>();  // ⚠️ Needs parent binding!

  goToAccountInfo(): void {
    this.onNavigateToAccountInfo.emit();  // Does nothing if not bound in parent!
  }
}

Problem: If the parent Component's template doesn't bind these @Output events, the buttons appear functional but do nothing when clicked!

Detection Patterns

# Find Components with @Output navigation events
grep -rn "@Output().*Navigate" src/app/presentation/

# Find bound events in templates
grep -rn "(onNavigate" src/app/**/*.html

# Find routes defined
grep -rn "path:" src/app/app.routes.ts

# Compare: Every @Output navigation event MUST have corresponding parent binding

Verification Checklist

1. Count @Output navigation events in each Component:

   grep -c "@Output().*Navigate" src/app/presentation/settings/settings.component.ts
   

2. Count bound events where Component is used:

   grep -c "(onNavigate" src/app/presentation/home/home.component.html
   

3. Counts MUST match! Any mismatch = unwired navigation

Correct Wiring Example

// settings.component.ts (Child)
@Component({ selector: 'app-settings', ... })
export class SettingsComponent {
  @Output() onNavigateToAccountInfo = new EventEmitter<void>();
  @Output() onNavigateToChangePassword = new EventEmitter<void>();
  @Output() onNavigateToUserList = new EventEmitter<void>();
}

// home.component.html (Parent - correctly wired)
<app-settings
  (onNavigateToAccountInfo)="navGraph.toAccountInfo()"
  (onNavigateToChangePassword)="navGraph.toChangePassword()"
  (onNavigateToUserList)="navGraph.toUserList()">
</app-settings>

// app.routes.ts (routes exist)
export const routes: Routes = [
  { path: 'account-info', component: AccountInfoComponent },  // ✅ Route exists
  { path: 'change-password', component: ChangePasswordComponent },  // ✅ Route exists
  { path: 'user-list', component: UserListComponent },  // ✅ Route exists
];

// nav-graph.service.ts (methods exist)
toAccountInfo(): Promise<boolean> { return this.router.navigate(['/account-info']); }  // ✅
toChangePassword(): Promise<boolean> { return this.router.navigate(['/change-password']); }  // ✅
toUserList(): Promise<boolean> { return this.router.navigate(['/user-list']); }  // ✅

Code Review Checklist

Required Items

• Follow Clean Architecture layering
• ViewModel uses Input/Output/Effect pattern with Signals
• Repository implements offline-first with IndexedDB
• Components use OnPush change detection
• Type-safe navigation via NavGraphService
• No implicit any types (strict mode)
• 🚨 ALL @Output navigation events are bound in parent templates
• 🚨 ALL routes have corresponding NavGraphService methods
• 🚨 ALL Service→Repository method calls exist in Repository interfaces
• 🚨 ALL Repository interface methods have implementations

Performance Checks

• Use OnPush change detection across components
• Implement virtual scrolling for large datasets
• Use lazy loading and code splitting
• Leverage Angular Signals (99+ instances recommended)

Security Checks

• Content Security Policy headers configured
• Input sanitization service used
• HTTP interceptors for auth and error handling
• XSS/CSRF protection enabled
• No hardcoded API keys

Common Issues

Signal Update Issues

1. Ensure signals are updated within the Angular zone
2. Use computed() for derived state
3. Avoid mutating signal values directly

IndexedDB Issues

1. Handle version upgrades properly with Dexie
2. Use transactions for batch operations
3. Implement proper error handling

Build Optimization

1. Enable production mode
2. Configure tree shaking
3. Use lazy loading for feature modules

---

Spec Gap Prediction System

When Spec is incomplete, use these universal rules to predict and supplement missing UI/UX elements.

Screen Type → Required States (Universal)

Screen Type	Required States	Auto-Predict
List Screen	Loading, Error, Empty, Content	Virtual scroll, Search/Filter
Detail Screen	Loading, Error, Content	Back navigation, Edit action
Form Screen	Validation, Submit Loading, Success, Error	Input validation, Cancel action
Dashboard	Loading, Error, Content	Refresh, Section navigation
Settings	Content	Back navigation, Section headers
Auth Screen	Loading, Error, Success	Forgot password link, Terms link

Flow Completion Prediction

┌─────────────────────────────────────────────────────────────────┐
│                    Flow Completion Rules                         │
├─────────────────────────────────────────────────────────────────┤
│  IF Spec has Login:                                              │
│    → PREDICT: Register, Forgot Password, Logout                  │
│                                                                  │
│  IF Spec has Register:                                           │
│    → PREDICT: Onboarding flow after registration                 │
│    → PREDICT: Email verification (if email-based)                │
│                                                                  │
│  IF Spec has List:                                               │
│    → PREDICT: Detail view for list items                         │
│    → PREDICT: Search/Filter functionality                        │
│    → PREDICT: Empty state when no items                          │
│                                                                  │
│  IF Spec has Settings:                                           │
│    → PREDICT: Account info edit                                  │
│    → PREDICT: Change password                                    │
│    → PREDICT: Notification preferences                           │
│    → PREDICT: Logout confirmation                                │
│                                                                  │
│  IF Spec has any data display:                                   │
│    → PREDICT: Offline cached view                                │
│    → PREDICT: Sync status indicator                              │
└─────────────────────────────────────────────────────────────────┘

Data Operation Prediction (CRUD)

Spec Mentions	Auto-Predict Operations
"Display items"	Read + Loading + Error + Empty states
"Add item"	Create + Validation + Success feedback
"Edit item"	Update + Validation + Optimistic UI
"Delete item"	Delete + Confirmation dialog + Undo option
"Search"	Debounced input + No results state
"Filter"	Filter UI + Clear filter + Active filter indicator

Navigation Completeness Prediction

// If app.routes.ts has these paths:
export const routes: Routes = [
  { path: 'login', ... },      // → Predict: register, forgot-password
  { path: 'dashboard', ... },  // → Predict: settings, profile
  { path: 'items', ... },      // → Predict: items/:id (detail)
  { path: 'settings', ... },   // → Predict: account, change-password, about
];

// Auto-check: Every @Output navigation event must be bound in parent

UI State Prediction Matrix

Data Source	Success	Empty	Error	Loading
API Call	Content	Empty view + CTA	Error view + Retry	Spinner
IndexedDB	Content	Empty view + CTA	Error view + Retry	Spinner
User Input	Show result	Prompt input	Validation error	Submit loading

Spec Gap Detection Commands

# 1. Detect components missing loading state
grep -L "isLoading\|loading" src/app/presentation/**/*.viewmodel.ts

# 2. Detect components missing error state
grep -L "error\|Error" src/app/presentation/**/*.viewmodel.ts

# 3. Detect lists missing empty state
grep -l "ngFor\|*ngFor" src/app/presentation/**/*.html | \
xargs grep -L "empty\|Empty\|length === 0"

# 4. Detect forms missing validation
grep -l "formControl\|ngModel" src/app/presentation/**/*.html | \
xargs grep -L "invalid\|error\|valid"

# 5. Detect missing navigation flows
echo "=== Auth Flow Check ===" && \
grep -q "login" src/app/app.routes.ts && \
(grep -q "register" src/app/app.routes.ts || echo "⚠️ Missing: Register route") && \
(grep -q "forgot-password" src/app/app.routes.ts || echo "⚠️ Missing: Forgot Password route")

# 6. Detect missing CRUD operations
echo "=== CRUD Completeness ===" && \
grep -rh "get.*\|fetch.*\|load.*" src/app/domain/repositories/*.ts | head -5 && \
grep -rh "create.*\|add.*\|save.*" src/app/domain/repositories/*.ts | head -5 && \
grep -rh "update.*\|edit.*" src/app/domain/repositories/*.ts | head -5 && \
grep -rh "delete.*\|remove.*" src/app/domain/repositories/*.ts | head -5

Prediction Implementation Example

When implementing a List screen from Spec:

// Spec says: "Display user's items"
// Auto-predict required implementation:

@Component({
  selector: 'app-item-list',
  changeDetection: ChangeDetectionStrategy.OnPush,
  template: `
    <!-- 1. LOADING - Always needed for API/DB calls -->
    @if (vm.output().isLoading) {
      <div class="spinner-border" role="status">
        <span class="visually-hidden">Loading...</span>
      </div>
    }

    <!-- 2. ERROR - Always needed for API/DB calls -->
    @else if (vm.output().error) {
      <div class="alert alert-danger">
        {{ vm.output().error }}
        <button class="btn btn-primary" (click)="onInput({ type: 'RETRY' })">
          Retry
        </button>
      </div>
    }

    <!-- 3. EMPTY - Always needed for list screens -->
    @else if (vm.output().items.length === 0) {
      <div class="empty-state text-center">
        <h3>No Items</h3>
        <p>Add your first item to get started</p>
        <button class="btn btn-primary" (click)="onInput({ type: 'ADD_CLICKED' })">
          Add Item
        </button>
      </div>
    }

    <!-- 4. CONTENT - The actual list -->
    @else {
      <ul class="list-group">
        @for (item of vm.output().items; track item.id) {
          <li class="list-group-item" (click)="onInput({ type: 'ITEM_CLICKED', id: item.id })">
            {{ item.name }}
          </li>
        }
      </ul>
    }
  `,
  providers: [ItemListViewModel],
})
export class ItemListComponent {
  protected readonly vm = inject(ItemListViewModel);

  protected onInput(input: ItemListInput): void {
    this.vm.onInput(input);
  }
}

---

Tech Stack Reference

Technology	Recommended Version
Angular	20.3+
TypeScript	5.7+
RxJS	7.8+
Bootstrap	5.0+
ng-bootstrap	19.0+
Dexie	4.0+
@ngx-translate	Latest