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# Angular Guidelines Use this guidelines when working with Angular related code. ## 1. Core Architecture - **Standalone Components:** Components, directives, and pipes are standalone by default. The `standalone: true` flag is no longer required and should be omitted in new code (Angular v17+ and above). - **Strong Typing:** TypeScript types, interfaces, and models provide type safety throughout the codebase - **Single Responsibility:** Each component and service has a single, well-defined responsibility - **Rule of One:** Files focus on a single concept or functionality - **Reactive State:** Signals provide reactive and efficient state management - **Dependency Injection:** Angular's DI system manages service instances - **Function-Based DI:** Use function-based dependency injection with the `inject()` function instead of constructor-based injection in all new code. Example: ```typescript import { inject } from "@angular/core"; import { HttpClient } from "@angular/common/http"; export class MyService { private readonly http = inject(HttpClient); // ... } ``` - **Lazy Loading:** Deferrable Views and route-level lazy loading with `loadComponent` improve performance - **Directive Composition:** The Directive Composition API enables reusable component behavior - **Standalone APIs Only:** Do not use NgModules, CommonModule, or RouterModule. Import only required standalone features/components. - **No Legacy Modules:** Do not use or generate NgModules for new features. Migrate existing modules to standalone APIs when possible. ## 2. Angular Style Guide Patterns - **Code Size:** Files are limited to 400 lines of code - **Single Purpose Files:** Each file defines one entity (component, service, etc.) - **Naming Conventions:** Symbols have consistent, descriptive names - **Folder Structure:** Code is organized by feature-based folders - **File Separation:** Templates and styles exist in their own files for components - **Property Decoration:** Input and output properties have proper decoration - **Component Selectors:** Component selectors use custom prefixes and kebab-case (e.g., `app-feature-name`) - **No CommonModule or RouterModule Imports:** Do not import CommonModule or RouterModule in standalone components. Import only the required standalone components, directives, or pipes. ## 3. Input Signal Patterns - **Signal-Based Inputs:** The `input()` function creates InputSignals: ```typescript // Current pattern readonly value = input(0); // Creates InputSignal // Legacy pattern @Input() value = 0; ``` - **Required Inputs:** The `input.required()` function marks inputs as mandatory: ```typescript readonly value = input.required<number>(); ``` - **Input Transformations:** Transformations convert input values: ```typescript readonly disabled = input(false, { transform: booleanAttribute }); readonly value = input(0, { transform: numberAttribute }); ``` - **Two-Way Binding:** Model inputs enable two-way binding: ```typescript readonly value = model(0); // Creates a model input with change propagation // Model values update with .set() or .update() increment(): void { this.value.update(v => v + 1); } ``` - **Input Aliases:** Aliases provide alternative input names: ```typescript readonly value = input(0, { alias: "sliderValue" }); ``` ## 3a. Typed Reactive Forms - **Typed Forms:** Always use strictly typed reactive forms by defining an interface for the form values and using `FormGroup<MyFormType>`, `FormBuilder.group<MyFormType>()`, and `FormControl<T>()`. - **Non-Nullable Controls:** Prefer `nonNullable: true` for controls to avoid null issues and improve type safety. - **Patch and Get Values:** Use `patchValue` and `getRawValue()` to work with typed form values. - **Reference:** See the [Angular Typed Forms documentation](https://angular.dev/guide/forms/typed-forms) for details and examples. ## 4. Component Patterns - **Naming Pattern:** Components follow consistent naming - `feature.type.ts` (e.g., `hero-list.component.ts`) - **Template Extraction:** Non-trivial templates exist in separate `.html` files - **Style Extraction:** Styles exist in separate `.css/.scss` files - **Signal-Based Inputs:** Components use the `input()` function for inputs - **Two-Way Binding:** Components use the `model()` function for two-way binding - **Lifecycle Hooks:** Components implement appropriate lifecycle hook interfaces (OnInit, OnDestroy, etc.) - **Element Selectors:** Components use element selectors (`selector: 'app-hero-detail'`) - **Logic Delegation:** Services contain complex logic - **Input Initialization:** Inputs have default values or are marked as required - **Lazy Loading:** The `@defer` directive loads heavy components or features - **Error Handling:** Try-catch blocks handle errors - **Modern Control Flow:** Templates use `@if`, `@for`, `@switch` instead of structural directives - **State Representation:** Components implement loading and error states - **Derived State:** The `computed()` function calculates derived state - **No NgModules:** Do not use or reference NgModules in new code. ## 5. Styling Patterns - **Component Encapsulation:** Components use scoped styles with proper encapsulation - **CSS Methodology:** BEM methodology guides CSS class naming when not using Angular Material - **Component Libraries:** Angular Material or other component libraries provide consistent UI elements - **Theming:** Color systems and theming enable consistent visual design - **Accessibility:** Components follow a11y standards - **Dark Mode:** Components support dark mode where appropriate ## 5a. Angular Material and Angular CDK Usage - **Standard UI Library:** Use Angular Material v3 for all standard UI components (buttons, forms, navigation, dialogs, etc.) to ensure consistency, accessibility, and alignment with Angular best practices. - **Component Development:** Build new UI components and features using Angular Material components as the foundation. Only create custom components when Material does not provide a suitable solution. - **Behavioral Primitives:** Use Angular CDK for advanced behaviors (drag-and-drop, overlays, accessibility, virtual scrolling, etc.) and for building custom components that require low-level primitives. - **Theming:** Leverage Angular Material's theming system for consistent color schemes, dark mode support, and branding. Define and use custom themes in `styles.scss` or feature-level styles as needed. - **Accessibility:** All UI components must meet accessibility (a11y) standards. Prefer Material components for built-in a11y support. When using CDK or custom components, follow WCAG and ARIA guidelines. - **Best Practices:** - Prefer Material's layout and typography utilities for spacing and text. - Use Material icons and fonts for visual consistency. - Avoid mixing multiple UI libraries in the same project. - Reference the [Angular Material documentation](https://material.angular.io) for usage patterns and updates. - **CDK Utilities:** Use Angular CDK utilities for custom behaviors, overlays, accessibility, and testing harnesses. - **Migration:** For legacy or custom components, migrate to Angular Material/CDK where feasible. ## 5b. Template Patterns - **Modern Control Flow:** Use the new Angular control flow syntax: `@if`, `@for`, `@switch` in templates. Do not use legacy structural directives such as `*ngIf`, `*ngFor`, or `*ngSwitch`. - **No Legacy Structural Directives:** Remove or migrate any usage of `*ngIf`, `*ngFor`, or `*ngSwitch` to the new control flow syntax in all new code. Legacy code should be migrated when touched. - **Referencing Conditional Results:** When using `@if`, reference the result using the `as` keyword, e.g. `@if (user(); as u) { ... }`. This is the recommended pattern for accessing the value inside the block. See the [Angular documentation](https://angular.dev/guide/templates/control-flow#referencing-the-conditional-expressions-result) for details. ## 6. Service and DI Patterns - **Service Declaration:** Services use the `@Injectable()` decorator with `providedIn: 'root'` for singletons - **Data Services:** Data services handle API calls and data operations - **Error Handling:** Services include error handling - **DI Hierarchy:** Services follow the Angular DI hierarchy - **Service Contracts:** Interfaces define service contracts - **Focused Responsibilities:** Services focus on specific tasks - **Function-Based DI:** Use function-based dependency injection with the `inject()` function instead of constructor-based injection in all new code. Example: ```typescript import { inject } from "@angular/core"; import { HttpClient } from "@angular/common/http"; export class MyService { private readonly http = inject(HttpClient); // ... } ``` ## 7. Directive and Pipe Patterns - **Attribute Directives:** Directives handle presentation logic without templates - **Host Property:** The `host` property manages bindings and listeners: ```typescript @Directive({ selector: '[appHighlight]', host: { // Host bindings '[class.highlighted]': 'isHighlighted', '[style.color]': 'highlightColor', // Host listeners '(click)': 'onClick($event)', '(mouseenter)': 'onMouseEnter()', '(mouseleave)': 'onMouseLeave()', // Static properties 'role': 'button', '[attr.aria-label]': 'ariaLabel' } }) ``` - **Selector Prefixes:** Directive selectors use custom prefixes - **Pure Pipes:** Pipes are pure when possible for better performance - **Pipe Naming:** Pipes follow camelCase naming conventions ## 8. State Management Patterns - **Signals:** Signals serve as the primary state management solution - **Component Inputs:** Signal inputs with `input()` handle component inputs - **Two-Way Binding:** Model inputs with `model()` enable two-way binding - **Local State:** Writable signals with `signal()` manage local component state - **Derived State:** Computed signals with `computed()` calculate derived state - **Side Effects:** The `effect()` function handles side effects - **Error Handling:** Signal computations include error handling - **Signal Conversion:** The `toSignal()` and `toObservable()` functions enable interoperability with RxJS ## 9. Testing Patterns - **Test Coverage:** Tests cover components and services - **Unit Tests:** Focused unit tests verify services, pipes, and components - **Component Testing:** TestBed and component harnesses test components - **Mocking:** Tests use mocking techniques for dependencies - **Test Organization:** Tests follow the AAA pattern (Arrange, Act, Assert) - **Test Naming:** Tests have descriptive names that explain the expected behavior - **Playwright Usage:** Playwright handles E2E testing with fixtures and test isolation - **Test Environment:** Test environments match production as closely as possible ## 10. Performance Patterns - **Change Detection:** Components use OnPush change detection strategy - **Lazy Loading:** Routes and components load lazily - **Virtual Scrolling:** Virtual scrolling renders long lists efficiently - **Memoization:** Memoization optimizes expensive computations - **Bundle Size:** Bundle size monitoring and optimization reduce load times - **Server-Side Rendering:** SSR improves initial load performance - **Web Workers:** Web workers handle intensive operations ## 11. Security Patterns - **XSS Prevention:** User input undergoes sanitization - **CSRF Protection:** CSRF tokens secure forms - **Content Security Policy:** CSP headers restrict content sources - **Authentication:** Secure authentication protects user accounts - **Authorization:** Authorization checks control access - **Sensitive Data:** Client-side code excludes sensitive data ## 12. Accessibility Patterns - **ARIA Attributes:** ARIA attributes enhance accessibility - **Keyboard Navigation:** Interactive elements support keyboard access - **Color Contrast:** UI elements maintain proper color contrast ratios - **Screen Readers:** Components work with screen readers - **Focus Management:** Focus management guides user interaction - **Alternative Text:** Images include alt text

Add as custom prompt to Roocode you can completely replace the system prompt for this mode (aside from the role definition and custom instructions) by creating a file at .roo/system-prompt-codershortrules in your workspace. You are Roo, a highly skilled software engineer with extensive knowledge in many programming languages, frameworks, design patterns, and best practices. Use tools one at a time to complete tasks step-by-step. Wait for user confirmation after each tool use. Tools read_file: Read file contents. Use for analyzing code, text files, or configs. Output includes line numbers. Extracts text from PDFs and DOCX. Not for other binary files. Parameters: path (required) search_files: Search files in a directory using regex. Shows matches with context. Useful for finding code patterns or specific content. Parameters: path (required), regex (required), file_pattern (optional) list_files: List files and directories. Can be recursive. Don’t use to check if files you created exist; user will confirm. Parameters: path (required), recursive (optional) list_code_definition_names: List top-level code definitions (classes, functions, etc.) in a directory. Helps understand codebase structure. Parameters: path (required) apply_diff: Replace code in a file using a search and replace block. Must match existing content exactly. Use read_file first if unsure. Parameters: path (required), diff (required), start_line (required), end_line (required) Diff Format: text Wrap Copy &lt;&lt;&lt;&lt;&lt;&lt;&lt; SEARCH [exact content] ======= [new content] &gt;&gt;&gt;&gt;&gt;&gt;&gt; REPLACE write_to_file: Write full content to a file. Overwrites if exists, creates if not. MUST provide COMPLETE file content, not partial updates. MUST include app 3 parameters, path, content, and line_count Parameters: path (required), content (required), line_count (required) execute_command: Run CLI commands. Explain what the command does. Prefer complex commands over scripts. Commands run in the current directory. To run in a different directory, use cd path &amp;&amp; command. Parameters: command (required) ask_followup_question: Ask the user a question to get more information. Use when you need clarification or details. Parameters: question (required) attempt_completion: Present the task result to the user. Optionally provide a CLI command to demo the result. Don’t use it until previous tool uses are confirmed successful. Parameters: result (required), command (optional) Tool Use Formatting IMPORTANT REPLACE tool_name with the tool you want to use, for example read_file. IMPORTANT REPLACE parameter_name with the parameter name, for example path. Format tool use with XML tags, e.g.: text Wrap Copy value1 value2 Guidelines Choose the right tool for the task. Use one tool at a time. Format tool use correctly. Wait for user confirmation after each tool use. Don’t assume tool success; wait for user feedback. Rules pass correct paths to tools. Don’t use ~ or $HOME. Tailor commands to the user's system. Prefer other editing tools over write_to_file for changes. Provide complete file content when using write_to_file. Don’t ask unnecessary questions; use tools to get information. Don’t be conversational; be direct and technical. Consider environment_details for context. ALWAYS replace tool_name, parameter_name, and parameter_value with actual values. Objective Break task into steps. Use tools to accomplish each step. Wait for user confirmation after each tool use. Use attempt_completion when task is complete.

# TypeScript Performance Optimization Standards: Best Practices for Efficient Applications This document outlines coding standards and best practices specifically for performance optimization in TypeScript projects. Adhering to these guidelines will improve the speed, responsiveness, efficient use of resources, and overall user experience of your applications. ## Table of Contents - [1. Architectural Considerations for Performance](#1-architectural-considerations-for-performance) - [1.1. Code Splitting](#11-code-splitting) - [1.2. Lazy Loading Modules](#12-lazy-loading-modules) - [1.3. Server-Side Rendering (SSR) or Static Site Generation (SSG)](#13-server-side-rendering-ssr-or-static-site-generation-ssg) - [1.4. Data Structure Selection](#14-data-structure-selection) ## 1. Architectural Considerations for Performance ### 1.1. Code Splitting **Standard:** Implement code splitting to reduce the initial load time of your application. **Why:** Loading only the necessary code on initial page load significantly improves the user experience. **Do This:** * Utilize dynamic imports (`import()`) to load modules on demand. * Configure your bundler (Webpack, Parcel, Rollup) to create separate chunks for different parts of your application. **Don't Do This:** * Load the entire application code in a single bundle. * Use `require()` statements (CommonJS) in modern TypeScript projects where ES Modules are supported. **Example:** ```typescript // Before: Loading everything upfront import { featureA } from './featureA'; import { featureB } from './featureB'; // After: Code splitting with dynamic imports async function loadFeatureA() { const { featureA } = await import('./featureA'); featureA.init(); } async function loadFeatureB() { const { featureB } = await import('./featureB'); featureB.init(); } // Use loadFeatureA or loadFeatureB based on user interaction or route ``` **Bundler Configuration (Webpack example):** ```javascript // webpack.config.js module.exports = { entry: './src/index.ts', output: { filename: '[name].bundle.js', path: path.resolve(__dirname, 'dist'), }, module: { rules: [ { test: /\.tsx?$/, use: 'ts-loader', exclude: /node_modules/, }, ], }, resolve: { extensions: ['.tsx', '.ts', '.js'], }, optimization: { splitChunks: { chunks: 'all', // Split all chunks of code }, }, }; ``` ### 1.2. Lazy Loading Modules **Standard:** Employ lazy loading for non-critical modules or components. **Why:** Reduce the amount of code that needs to be parsed and compiled on initial load. **Do This:** * Load components or modules only when they are needed. * Utilize Intersection Observer API to load components when they become visible in the viewport. **Don't Do This:** * Load modules that are not immediately required for the current user interaction. **Example (Intersection Observer Lazy Loading):** ```typescript function lazyLoadComponent(element: HTMLElement, importPath: string) { const observer = new IntersectionObserver((entries) => { entries.forEach(async (entry) => { if (entry.isIntersecting) { const { default: Component } = await import(importPath); const componentInstance = new Component(); // Instantiate the component. element.appendChild(componentInstance.render()); // Append to the DOM (adjust according to your framework). observer.unobserve(element); } }); }); observer.observe(element); } // Usage: const lazyComponentElement = document.getElementById('lazy-component'); if (lazyComponentElement) { lazyLoadComponent(lazyComponentElement, './MyHeavyComponent'); } ``` ### 1.3. Server-Side Rendering (SSR) or Static Site Generation (SSG) **Standard:** Consider using SSR or SSG for content-heavy, SEO-sensitive, or performance-critical applications. **Why:** Reduces the time to first paint (TTFP) and improves SEO by providing crawlers with pre-rendered content. **Do This:** * Evaluate the trade-offs between SSR, SSG, and client-side rendering (CSR) based on your application's needs. * Use frameworks like Next.js (React), Nuxt.js (Vue), or Angular Universal. * Implement appropriate caching strategies for SSR. **Don't Do This:** * Default to CSR when SSR or SSG could provide significant performance benefits. **Example (Next.js):** ```typescript // pages/index.tsx (Next.js example) import React from 'react'; interface Props { data: { title: string; description: string; }; } const HomePage: React.FC<Props> = ({ data }) => { return ( <div> <h1>{data.title}</h1> <p>{data.description}</p> </div> ); }; export async function getServerSideProps() { // Fetch data from an API, database, or file system. const data = { title: 'My Awesome Website', description: 'Welcome to my extremely performant website!', }; return { props: { data, }, }; } export default HomePage; ``` ### 1.4. Data Structure Selection **Standard:** Select the most appropriate data structure for each specific use case. **Why:** Using appropriate data structures will reduce the complexity and improve the execution speed of algorithms. **Do This:** * Use `Map` when you need to associate keys with values, especially when the keys are not strings or numbers. * Use `Set` when you need to store a collection of unique values. * Use `Record<K, V>` type for type-safe object mapping. * Consider specialized data structures for specific performance needs (e.g., priority queues, linked lists). **Don't Do This:** * Use generic arrays or objects when more specialized data structures would be more efficient. * Perform frequent lookups in arrays when using a Map or Set would be more performant. **Example:** ```typescript // Before: Using an array for lookups const users = [ { id: 1, name: 'Alice' }, { id: 2, name: 'Bob' }, { id: 3, name: 'Charlie' } ]; // O(n) lookup operation const findUser = (id: number) => users.find(user => user.id === id); // After: Using Map for efficient lookups const userMap = new Map<number, {id: number, name: string}>(); userMap.set(1, { id: 1, name: 'Alice' }); userMap.set(2, { id: 2, name: 'Bob' }); userMap.set(3, { id: 3, name: 'Charlie' }); // O(1) lookup operation const getUser = (id: number) => userMap.get(id); ```

# NgRx Signals Patterns This document outlines the state management patterns used in our Angular applications with NgRx Signals Store. ## 1. NgRx Signals Architecture - **Component-Centric Design:** Stores are designed around component requirements - **Hierarchical State:** State is organized in hierarchical structures - **Computed State:** Derived state uses computed values - **Declarative Updates:** State updates use patchState for immutability - **Store Composition:** Stores compose using features and providers - **Reactivity:** UIs build on automatic change detection - **Signal Interoperability:** Signals integrate with existing RxJS-based systems - **SignalMethod & RxMethod:** Use `signalMethod` for lightweight, signal-driven side effects; use `rxMethod` for Observable-based side effects and RxJS integration. When a service returns an Observable, always use `rxMethod` for side effects instead of converting to Promise or using async/await. ## 2. Signal Store Structure - **Store Creation:** The `signalStore` function creates stores - **Protected State:** Signal Store state is protected by default (`{ protectedState: true }`) - **State Definition:** Initial state shape is defined with `withState<StateType>({...})` - Root level state is always an object: `withState({ users: [], count: 0 })` - Arrays are contained within objects: `withState({ items: [] })` - **Dependency Injection:** Stores are injectable with `{ providedIn: 'root' }` or feature/component providers - **Store Features:** Built-in features (`withEntities`, `withHooks`, `signalStoreFeature`) handle cross-cutting concerns and enable store composition - **State Interface:** State interfaces provide strong typing - **Private Members:** Prefix all internal state, computed signals, and methods with an underscore (`_`). Ensure unique member names across state, computed, and methods. ```typescript withState({ count: 0, _internalCount: 0 }); withComputed(({ count, _internalCount }) => ({ doubleCount: computed(() => count() * 2), _doubleInternal: computed(() => _internalCount() * 2), })); ``` - **Member Integrity:** Store members have unique names across state, computed, and methods - **Initialization:** State initializes with meaningful defaults - **Collection Management:** The `withEntities` feature manages collections. Prefer atomic entity operations (`addEntity`, `updateEntity`, `removeEntity`, `setAllEntities`) over bulk state updates. Use `entityConfig` and `selectId` for entity identification. - **Entity Adapter Configuration:** Use `entityConfig` to configure the entity adapter for each store. Always specify the `entity` type, `collection` name, and a `selectId` function for unique entity identification. Pass the config to `withEntities<T>(entityConfig)` for strong typing and consistent entity management. ```typescript const userEntityConfig = entityConfig({ entity: type<User>(), collection: "users", selectId: (user: User) => user.id, }); export const UserStore = signalStore( { providedIn: "root" }, withState(initialState), withEntities(userEntityConfig), // ... ); ``` - **Custom Store Properties:** Use `withProps` to add static properties, observables, and dependencies. Expose observables with `toObservable`. ```typescript // Signal store structure example import { signalStore, withState, withComputed, withMethods, patchState, type, } from "@ngrx/signals"; import { withEntities, entityConfig } from "@ngrx/signals/entities"; import { computed, inject } from "@angular/core"; import { UserService } from "./user.service"; import { User } from "./user.model"; import { setAllEntities } from "@ngrx/signals/entities"; export interface UserState { selectedUserId: string | null; loading: boolean; error: string | null; } const initialState: UserState = { selectedUserId: null, loading: false, error: null, }; const userEntityConfig = entityConfig({ entity: type<User>(), collection: "users", selectId: (user: User) => user.id, }); export const UserStore = signalStore( { providedIn: "root" }, withState(initialState), withEntities(userEntityConfig), withComputed(({ usersEntities, usersEntityMap, selectedUserId }) => ({ selectedUser: computed(() => { const id = selectedUserId(); return id ? usersEntityMap()[id] : undefined; }), totalUserCount: computed(() => usersEntities().length), })), withMethods((store, userService = inject(UserService)) => ({ loadUsers: rxMethod<void>( pipe( switchMap(() => { patchState(store, { loading: true, error: null }); return userService.getUsers().pipe( tapResponse({ next: (users) => patchState(store, setAllEntities(users, userEntityConfig), { loading: false, }), error: () => patchState(store, { loading: false, error: "Failed to load users", }), }), ); }), ), ), selectUser(userId: string | null): void { patchState(store, { selectedUserId: userId }); }, })), ); ``` ## 3. Signal Store Methods - **Method Definition:** Methods are defined within `withMethods` - **Dependency Injection:** The `inject()` function accesses services within `withMethods` - **Method Organization:** Methods are grouped by domain functionality - **Method Naming:** Methods have clear, action-oriented names - **State Updates:** `patchState(store, newStateSlice)` or `patchState(store, (currentState) => newStateSlice)` updates state immutably - **Async Operations:** Methods handle async operations and update loading/error states - **Computed Properties:** `withComputed` defines derived state - **RxJS Integration:** `rxMethod` integrates RxJS streams. Use `rxMethod` for all store methods that interact with Observable-based APIs or services. Avoid using async/await with Observables in store methods. ```typescript // Signal store method patterns import { signalStore, withState, withMethods, patchState } from "@ngrx/signals"; import { inject } from "@angular/core"; import { TodoService } from "./todo.service"; import { Todo } from "./todo.model"; export interface TodoState { todos: Todo[]; loading: boolean; } export const TodoStore = signalStore( { providedIn: "root" }, withState<TodoState>({ todos: [], loading: false }), withMethods((store, todoService = inject(TodoService)) => ({ addTodo(todo: Todo): void { patchState(store, (state) => ({ todos: [...state.todos, todo], })); }, loadTodosSimple: rxMethod<void>( pipe( switchMap(() => { patchState(store, { loading: true }); return todoService.getTodos().pipe( tapResponse({ next: (todos) => patchState(store, { todos, loading: false }), error: () => patchState(store, { loading: false }), }), ); }), ), ), })), ); ``` ## 4. Entity Management - **Entity Configuration:** Entity configurations include ID selectors - **Collection Operations:** Entity operations handle CRUD operations - **Entity Relationships:** Computed properties manage entity relationships - **Entity Updates:** Prefer atomic entity operations (`addEntity`, `updateEntity`, `removeEntity`, `setAllEntities`) over bulk state updates. Use `entityConfig` and `selectId` for entity identification. ```typescript // Entity management patterns const userEntityConfig = entityConfig({ entity: type<User>(), collection: "users", selectId: (user: User) => user.id, }); export const UserStore = signalStore( withEntities(userEntityConfig), withMethods((store) => ({ addUser: signalMethod<User>((user) => { patchState(store, addEntity(user, userEntityConfig)); }), updateUser: signalMethod<{ id: string; changes: Partial<User> }>( ({ id, changes }) => { patchState(store, updateEntity({ id, changes }, userEntityConfig)); }, ), removeUser: signalMethod<string>((id) => { patchState(store, removeEntity(id, userEntityConfig)); }), setUsers: signalMethod<User[]>((users) => { patchState(store, setAllEntities(users, userEntityConfig)); }), })), ); ``` ## 5. Component Integration ### Component State Access - **Signal Properties:** Components access signals directly in templates - **OnPush Strategy:** Signal-based components use OnPush change detection - **Store Injection:** Components inject store services with the `inject` function - **Default Values:** Signals have default values - **Computed Values:** Components derive computed values from signals - **Signal Effects:** Component effects handle side effects ```typescript // Component integration patterns @Component({ standalone: true, imports: [UserListComponent], template: ` @if (userStore.users().length > 0) { <app-user-list [users]="userStore.users()"></app-user-list> } @else { <p>No users loaded yet.</p> } <div>Selected user: {{ selectedUserName() }}</div> `, changeDetection: ChangeDetectionStrategy.OnPush, }) export class UsersContainerComponent implements OnInit { readonly userStore = inject(UserStore); selectedUserName = computed(() => { const user = this.userStore.selectedUser(); return user ? user.name : "None"; }); constructor() { effect(() => { const userId = this.userStore.selectedUserId(); if (userId) { console.log(`User selected: ${userId}`); } }); } ngOnInit() { this.userStore.loadUsers(); } } ``` ### Signal Store Hooks - **Lifecycle Hooks:** The `withHooks` feature adds lifecycle hooks to stores - **Initialization:** The `onInit` hook initializes stores - **Cleanup:** The `onDestroy` hook cleans up resources - **State Synchronization:** Hooks synchronize state between stores ```typescript // Signal store hooks patterns export const UserStore = signalStore( withState<UserState>({ /* initial state */ }), withMethods(/* store methods */), withHooks({ onInit: (store) => { // Initialize the store store.loadUsers(); // Return cleanup function if needed return () => { // Cleanup code }; }, }), ); ``` ## 6. Advanced Signal Patterns ### Signal Store Features - **Feature Creation:** The `signalStoreFeature` function creates reusable features - **Generic Feature Types:** Generic type parameters enhance feature reusability ```typescript function withMyFeature<T>(config: Config<T>) { return signalStoreFeature(/*...*/); } ``` - **Feature Composition:** Multiple features compose together - **Cross-Cutting Concerns:** Features handle logging, undo/redo, and other concerns - **State Slices:** Features define and manage specific state slices ```typescript // Signal store feature patterns export function withUserFeature() { return signalStoreFeature( withState<UserFeatureState>({ /* feature state */ }), withComputed((state) => ({ /* computed properties */ })), withMethods((store) => ({ /* methods */ })), ); } // Using the feature export const AppStore = signalStore( withUserFeature(), withOtherFeature(), withMethods((store) => ({ /* app-level methods */ })), ); ``` ### Signals and RxJS Integration - **Signal Conversion:** `toSignal()` and `toObservable()` convert between Signals and Observables - **Effects:** Angular's `effect()` function reacts to signal changes - **RxJS Method:** `rxMethod<T>(pipeline)` handles Observable-based side effects. Always prefer `rxMethod` for Observable-based service calls in stores. Do not convert Observables to Promises for store logic. - Accepts input values, Observables, or Signals - Manages subscription lifecycle automatically - **Reactive Patterns:** Signals combine with RxJS for complex asynchronous operations ```typescript // Signal and RxJS integration patterns import { signalStore, withState, withMethods, patchState } from "@ngrx/signals"; import { rxMethod } from "@ngrx/signals/rxjs-interop"; import { tapResponse } from "@ngrx/operators"; import { pipe, switchMap } from "rxjs"; import { inject } from "@angular/core"; import { HttpClient } from "@angular/common/http"; import { User } from "./user.model"; export interface UserState { users: User[]; loading: boolean; error: string | null; } export const UserStore = signalStore( { providedIn: "root" }, withState({ users: [], loading: false, error: null }), withMethods((store, http = inject(HttpClient)) => ({ loadUsers: rxMethod<void>( pipe( switchMap(() => { patchState(store, { loading: true, error: null }); return http.get<User[]>("/api/users").pipe( tapResponse({ next: (users) => patchState(store, { users, loading: false }), error: () => patchState(store, { loading: false, error: "Failed to load users", }), }), ); }), ), ), })), ); ``` ### Signal Method for Side Effects The `signalMethod` function manages side effects driven by Angular Signals within Signal Store: - **Input Flexibility:** The processor function accepts static values or Signals - **Automatic Cleanup:** The underlying effect cleans up when the store is destroyed - **Explicit Tracking:** Only the input signal passed to the processor function is tracked - **Lightweight:** Smaller bundle size compared to `rxMethod` ```typescript // Signal method patterns import { signalStore, withState, withMethods, patchState } from '@ngrx/signals'; import { signalMethod } from '@ngrx/signals'; import { inject } from '@angular/core'; import { Logger } from './logger'; interface UserPreferencesState { theme: 'light' | 'dark'; sendNotifications: boolean; const initialState: UserPreferencesState = { theme: 'light', sendNotifications: true, }; export const PreferencesStore = signalStore( { providedIn: 'root' }, withState(initialState), withProps(() => ({ logger: inject(Logger), })); withMethods((store) => ({ setSendNotifications(enabled: boolean): void { patchState(store, { sendNotifications: enabled }); }, // Signal method reacts to theme changes logThemeChange: signalMethod<'light' | 'dark'>((theme) => { store.logger.log(`Theme changed to: ${theme}`); }), setTheme(newTheme: 'light' | 'dark'): void { patchState(store, { theme: newTheme }); }, })), ); ``` ## 7. Custom Store Properties - **Custom Properties:** The `withProps` feature adds static properties, observables, and dependencies - **Observable Exposure:** `toObservable` within `withProps` exposes state as observables ```typescript withProps(({ isLoading }) => ({ isLoading$: toObservable(isLoading), })); ``` - **Dependency Grouping:** `withProps` groups dependencies for use across store features ```typescript withProps(() => ({ booksService: inject(BooksService), logger: inject(Logger), })); ``` ## 8. Project Organization ### Store Organization - **File Location:** Store definitions (`*.store.ts`) exist in dedicated files - **Naming Convention:** Stores follow the naming pattern `FeatureNameStore` - **Model Co-location:** State interfaces and models exist near store definitions - **Provider Functions:** Provider functions (`provideFeatureNameStore()`) encapsulate store providers ```typescript // Provider function pattern import { Provider } from "@angular/core"; import { UserStore } from "./user.store"; export function provideUserSignalStore(): Provider { return UserStore; } ``` ### Store Hierarchy - **Parent-Child Relationships:** Stores have clear relationships - **State Sharing:** Related components share state - **State Ownership:** Each state slice has a clear owner - **Store Composition:** Complex UIs compose multiple stores

# State Management Standards for Clean Code This document outlines coding standards for state management within Clean Code principles. It provides specific guidelines and examples to ensure code related to state is maintainable, readable, performant, and secure. These standards are designed to work with the latest recommended practices and features within the Clean Code ecosystem. ## 1. Principles of Clean State Management Clean state management is about structuring your application's data in a way that's predictable, manageable, and testable. It involves making state changes explicit, limiting side effects, and ensuring data consistency. Applying clean code principles to state enhances maintainability, reduces bugs, and improves collaborative development. * **Single Source of Truth:** Ensure each piece of data has one authoritative source. This prevents inconsistencies and simplifies debugging. * **Immutability:** Favor immutable data structures. Immutable data makes state changes more predictable and helps prevent unintended side effects. * **Explicit State Transitions:** State transitions should be clear and well-defined, making it easier to understand how the application evolves over time. * **Separation of Concerns:** Keep state management logic separate from UI components or business logic. This enhances modularity and testability. * **Minimal Global State:** Limit the use of global state. Widespread global state can make it difficult to track dependencies and lead to unexpected behavior. ## 2. Architectural Patterns for State Management Choosing the right architecture for state management depends on the complexity of the application. Here are a few common patterns and guidelines: ### 2.1 Local State Managing state within a single component should be a default option. You typically use local state for isolated functionalities that don't necessitate sharing state or reactivity beyond the component’s scope. * **Do This:** Use local state for isolated component features. * **Don't Do This:** Share local state directly between unrelated components. """javascript // Example React local state using useState import React, { useState } from 'react'; function Counter() { const [count, setCount] = useState(0); return ( <div> <p>Count: {count}</p> <button onClick={() => setCount(count + 1)}>Increment</button> </div> ); } """ ### 2.2 Redux Pattern (Centralized State) The Redux pattern emphasizes a single store for application state, using reducers to handle actions and state transitions immutably. * **Do This:** * Use Redux or similar libraries for complex, application-wide state. * Define actions as plain objects with a "type" field. * Use pure functions as reducers to ensure predictable state transitions. * Selectors should cache results to prevent unnecessary re-renders. * **Don't Do This:** * Mutate the state directly in reducers. * Perform asynchronous operations directly in reducers. * Overuse Redux for simple components with minimal state. """javascript // Example Redux setup // Action const INCREMENT = 'INCREMENT'; const DECREMENT = 'DECREMENT'; const increment = () => ({ type: INCREMENT }); const decrement = () => ({ type: DECREMENT }); // Reducer const initialState = { count: 0 }; const counterReducer = (state = initialState, action) => { switch (action.type) { case INCREMENT: return { ...state, count: state.count + 1 }; case DECREMENT: return { ...state, count: state.count - 1 }; default: return state; } }; // Store creation import { createStore } from 'redux'; const store = createStore(counterReducer); // Component integration (React example) import { useSelector, useDispatch } from 'react-redux'; function CounterComponent() { const count = useSelector(state => state.count); const dispatch = useDispatch(); return ( <div> <p>Count: {count}</p> <button onClick={() => dispatch(increment())}>Increment</button> <button onClick={() => dispatch(decrement())}>Decrement</button> </div> ); } """ ### 2.3 Context API (Scoped State) Context API provides a way to pass data through the component tree without having to pass props manually at every level. While it is simpler than Redux it is still intended for scenarios that benefit from shared state. * **Do This:** * Use Context API for theming, user authentication, or other application-wide configurations. * Use "useContext" hook to consume context values. * Combine Context API with "useReducer" for complex state logic. * **Don't Do This:** * Use Context API as a general replacement for prop drilling in scenarios where component composition is better suited. * Overuse Context API resulting in unnecessary re-renders. """javascript // Example Context API setup import React, { createContext, useContext, useState } from 'react'; // Create Context const ThemeContext = createContext(); // Context Provider function ThemeProvider({ children }) { const [theme, setTheme] = useState('light'); const toggleTheme = () => { setTheme(prevTheme => (prevTheme === 'light' ? 'dark' : 'light')); }; return ( <ThemeContext.Provider value={{ theme, toggleTheme }}> {children} </ThemeContext.Provider> ); } // Custom Hook to consume Context function useTheme() { return useContext(ThemeContext); } // Component using Context function ThemeToggler() { const { theme, toggleTheme } = useTheme(); return ( <button onClick={toggleTheme}> Toggle Theme (Current: {theme}) </button> ); } // Usage in App function App() { return ( <ThemeProvider> <div> <ThemeToggler /> </div> </ThemeProvider> ); } """ ### 2.4 Observable Pattern (Reactive State) The observable pattern, often implemented with libraries like RxJS, is used for handling asynchronous data streams and complex event-driven applications. * **Do This:** * Use RxJS or similar libraries for handling asynchronous data streams. * Structure application logic as a pipeline of observable transformations. * Use subjects to bridge different parts of the application. * **Don't Do This:** * Overuse RxJS for simple event handling. * Introduce memory leaks by not unsubscribing from observables. * Create overly complex observable chains that are hard to understand. """javascript // Example RxJS setup import { fromEvent, interval } from 'rxjs'; import { map, filter, scan, takeUntil } from 'rxjs/operators'; // Example: Click counter observable const button = document.getElementById('myButton'); const click$ = fromEvent(button, 'click'); const counter$ = click$.pipe( map(() => 1), scan((acc, value) => acc + value, 0) ); counter$.subscribe(count => { console.log("Button clicked ${count} times"); }); // Example: Auto-incrementing counter that stops after 5 seconds const interval$ = interval(1000); const stop$ = fromEvent(document.getElementById('stopButton'), 'click'); interval$.pipe( takeUntil(stop$) // Stop the interval when the stop button is clicked ).subscribe(val => console.log("Interval value: ${val}")); """ ### 2.5 State Machines State machines are useful for managing complex state transitions with clearly defined states and transitions. * **Do This:** * Use state machines for scenarios with clearly defined states and transitions. * Model state transitions explicitly, reducing possible unexpected states. * Ensure state machines are well-documented, especially for complex systems. * **Don't Do This:** * Overuse state machines for simple state management. * Create monolithic state machines that are difficult to understand. """javascript // Example: JavaScript state machine using XState import { createMachine, interpret } from 'xstate'; // Define the state machine const trafficLightMachine = createMachine({ id: 'trafficLight', initial: 'green', states: { green: { after: { 5000: 'yellow' // After 5 seconds, transition to yellow } }, yellow: { after: { 1000: 'red' // After 1 second, transition to red } }, red: { after: { 6000: 'green' // After 6 seconds, transition to green } } } }); // Interpret the state machine const trafficService = interpret(trafficLightMachine).start(); trafficService.onTransition(state => { console.log("Traffic light is now ${state.value}"); }); // Example usage (simulating events or external triggers) // trafficService.send('TIMER'); """ ## 3. Implementing Immutability Immutability ensures that once an object is created, its state cannot be changed. This helps prevent accidental state mutations, making it easier to track and manage state changes, which aids in debugging and improves performance in certain scenarios. * **Do This:** * Use immutable data structures and operations. * Make copies of objects or arrays before modifying them. * Employ libraries like Immutable.js for more complex scenarios. * **Don't Do This:** * Directly modify object properties or array elements. * Assume that passing an object or array creates a new copy. ### 3.1 JavaScript Immutability Techniques """javascript // Immutable Object Update const originalObject = { name: 'John', age: 30 }; const updatedObject = { ...originalObject, age: 31 }; // Create a new object // Immutable Array Update const originalArray = [1, 2, 3]; const updatedArray = [...originalArray, 4]; // Create a new array const removedArray = originalArray.filter(item => item !== 2); // Create new array without '2' console.log(originalObject); // { name: 'John', age: 30 } console.log(updatedObject); // { name: 'John', age: 31 } console.log(originalArray); // [1, 2, 3] console.log(updatedArray); // [1, 2, 3, 4] console.log(removedArray); // [1, 3] """ ### 3.2 Immutable.js Immutable.js provides persistent immutable data structures, improving performance and simplifying state management for complex applications. """javascript import { Map, List } from 'immutable'; // Immutable Map const originalMap = Map({ name: 'John', age: 30 }); const updatedMap = originalMap.set('age', 31); // Immutable List const originalList = List([1, 2, 3]); const updatedList = originalList.push(4); console.log(originalMap.toJS()); // { name: 'John', age: 30 } console.log(updatedMap.toJS()); // { name: 'John', age: 31 } console.log(originalList.toJS()); // [1, 2, 3] console.log(updatedList.toJS()); // [1, 2, 3, 4] """ ## 4. Handling Side Effects Side effects are operations that affect the state of the application outside of the current function or component. Properly managing side effects is crucial for maintaining predictable and testable code. * **Do This:** * Isolate side effects in dedicated functions or modules. * Use effect hooks (e.g., "useEffect" in React) to manage side effects in components. * Handle errors gracefully when performing side effects. * **Don't Do This:** * Perform side effects directly within reducers or pure functions. * Ignore potential errors in side effect operations. ### 4.1 Managing Effects with "useEffect" """javascript import React, { useState, useEffect } from 'react'; function DataFetcher({ url }) { const [data, setData] = useState(null); const [loading, setLoading] = useState(true); const [error, setError] = useState(null); useEffect(() => { const fetchData = async () => { try { const response = await fetch(url); if (!response.ok) { throw new Error("HTTP error! status: ${response.status}"); } const result = await response.json(); setData(result); } catch (e) { setError(e); } finally { setLoading(false); } }; fetchData(); // Cleanup function (optional) return () => { // Cancel any pending requests or subscriptions }; }, [url]); // Dependency array: effect runs only when 'url' changes if (loading) return <p>Loading...</p>; if (error) return <p>Error: {error.message}</p>; if (!data) return <p>No data available.</p>; return ( <pre>{JSON.stringify(data, null, 2)}</pre> ); } """ ### 4.2 Using Thunks with Redux Thunks allow you to perform asynchronous operations in Redux actions. """javascript // Example Redux Thunk Action const fetchDataRequest = () => ({ type: 'FETCH_DATA_REQUEST' }); const fetchDataSuccess = (data) => ({ type: 'FETCH_DATA_SUCCESS', payload: data }); const fetchDataFailure = (error) => ({ type: 'FETCH_DATA_FAILURE', payload: error }); // Async action using Redux Thunk const fetchData = (url) => { return async (dispatch) => { dispatch(fetchDataRequest()); try { const response = await fetch(url); if (!response.ok) { throw new Error("HTTP error! status: ${response.status}"); } const data = await response.json(); dispatch(fetchDataSuccess(data)); } catch (error) { dispatch(fetchDataFailure(error.message)); } }; }; // Usage in Component import { useDispatch } from 'react-redux'; function DataFetchButton({ url }) { const dispatch = useDispatch(); return ( <button onClick={() => dispatch(fetchData(url))}> Fetch Data </button> ); } """ ## 5. Testing State Management Testing state management involves verifying that state transitions occur correctly and that side effects are handled properly. * **Do This:** * Write unit tests for reducers to verify state transitions. * Use mock stores and actions to test components connected to Redux. * Test side effects by mocking external dependencies. * **Don't Do This:** * Omit testing for state management logic. * Write integration tests without proper unit testing. ### 5.1 Testing Reducers """javascript // Reducer Test Example (Jest) import counterReducer from './counterReducer'; // Assuming counterReducer.js import { INCREMENT, DECREMENT } from './actions'; describe('counterReducer', () => { it('should return the initial state', () => { expect(counterReducer(undefined, {})).toEqual({ count: 0 }); }); it('should handle INCREMENT', () => { expect(counterReducer({ count: 0 }, { type: INCREMENT })).toEqual({ count: 1 }); }); it('should handle DECREMENT', () => { expect(counterReducer({ count: 1 }, { type: DECREMENT })).toEqual({ count: 0 }); }); }); """ ### 5.2 Testing React Components with Redux """javascript // Component Test Example (React Testing Library and Redux Mock Store) import React from 'react'; import { render, fireEvent } from '@testing-library/react'; import { Provider } from 'react-redux'; import configureStore from 'redux-mock-store'; import CounterComponent from './CounterComponent'; // Assuming CounterComponent.js const mockStore = configureStore([]); describe('CounterComponent', () => { let store; let component; beforeEach(() => { store = mockStore({ count: 0 }); store.dispatch = jest.fn(); // Mock dispatch function component = render( <Provider store={store}> <CounterComponent /> </Provider> ); }); it('should display the initial count', () => { expect(component.getByText('Count: 0')).toBeInTheDocument(); }); it('should dispatch increment action when increment button is clicked', () => { fireEvent.click(component.getByText('Increment')); expect(store.dispatch).toHaveBeenCalledWith({ type: 'INCREMENT' }); }); }); """ ## 6. Security Considerations for State Management Security is a critical aspect of state management. Properly securing the state ensures that sensitive data is protected from unauthorized access and tampering. * **Do This:** * Protect sensitive data in the state with encryption. * Validate data received from external sources before storing it in the state. * Sanitize user input to prevent XSS. * **Don't Do This:** * Store sensitive data in plain text in the state. * Trust data received from external sources without validation. * Expose sensitive data in logs or error messages. ### 6.1 Data Validation """javascript // Example Data Validation const validateData = (data) => { if (typeof data.email !== 'string' || !data.email.includes('@')) { throw new Error('Invalid email format'); } if (typeof data.age !== 'number' || data.age < 0 || data.age > 120) { throw new Error('Invalid age'); } return data; }; // Usage in Reducer const userReducer = (state = {}, action) => { switch (action.type) { case 'UPDATE_USER': try { const validatedData = validateData(action.payload); return { ...state, ...validatedData }; } catch (error) { console.error('Data validation failed:', error.message); return state; } default: return state; } }; """ ### 6.2 Encryption Encrypting sensitive data ensures that even if the state is compromised, the data remains unreadable without the decryption key. """javascript // Example Encryption (using CryptoJS) import CryptoJS from 'crypto-js'; const encryptData = (data, key) => { const encrypted = CryptoJS.AES.encrypt(JSON.stringify(data), key).toString(); return encrypted; }; const decryptData = (encryptedData, key) => { const bytes = CryptoJS.AES.decrypt(encryptedData, key); try { const decrypted = JSON.parse(bytes.toString(CryptoJS.enc.Utf8)); return decrypted; } catch (e) { console.error("Decryption error", e); return null; // Or handle the error as appropriate } }; // Example usage const sensitiveData = { creditCardNumber: '1234-5678-9012-3456' }; const encryptionKey = 'my-secret-key'; const encryptedData = encryptData(sensitiveData, encryptionKey); console.log('Encrypted:', encryptedData); const decryptedData = decryptData(encryptedData, encryptionKey); console.log('Decrypted:', decryptedData); """ ## 7. Optimizing Performance Efficient state management is crucial for optimizing application performance, especially in complex applications with frequent state updates. * **Do This:** * Use memoization techniques to prevent unnecessary re-renders. * Implement lazy loading for components that rely on large state objects. * Batch state updates to minimize the number of renders. * **Don't Do This:** * Update the state unnecessarily. * Cause components to re-render frequently with negligible impact. ### 7.1 Memoization Memoization prevents re-renders by caching the results of expensive calculations or component renders. """javascript import React, { useState, useMemo } from 'react'; function ExpensiveComponent({ data }) { // Simulate an expensive computation const computedValue = useMemo(() => { console.log('Computing expensive value...'); // Complex calculation based on data return data.map(item => item * 2).reduce((acc, val) => acc + val, 0); }, [data]); // Only recompute if 'data' changes return ( <div> <p>Computed Value: {computedValue}</p> </div> ); } function ParentComponent() { const [count, setCount] = useState(0); const data = [1, 2, 3, 4, 5]; // Static data return ( <div> <button onClick={() => setCount(count + 1)}>Increment Count</button> <p>Count: {count}</p> {/*ExpensiveComponent only re-renders if "data" changes, not on count changes*/} <ExpensiveComponent data={data} /> </div> ); } function MemoizedComponent({ data }) { // Simulate a render-heavy component console.log('Rendering MemoizedComponent...'); return <p>Data: {data.join(', ')}</p>; } // Memoize MemoizedComponent to prevent unnecessary re-renders const OptimizedMemoizedComponent = React.memo(MemoizedComponent); function ParentMemoComponent() { const [count, setCount] = useState(0); const data = [1, 2, 3, 4, 5]; return ( <div> <button onClick={() => setCount(count + 1)}>Increment Count</button> <p>Count: {count}</p> {/* MemoizedComponent only re-renders if its props change, not on count changes */} <OptimizedMemoizedComponent data={data} /> </div> ); } """ ### 7.2 Batching Updates Batching updates ensures that multiple state updates are grouped into a single render cycle. """javascript import React, { useState } from 'react'; import { unstable_batchedUpdates } from 'react-dom'; // Available only in some React versions function BatchUpdatesComponent() { const [count1, setCount1] = useState(0); const [count2, setCount2] = useState(0); const updateBothCounts = () => { unstable_batchedUpdates(() => { // Both state updates are batched into a single render setCount1(prevCount => prevCount + 1); setCount2(prevCount => prevCount + 1); }); }; return ( <div> <p>Count 1: {count1}</p> <p>Count 2: {count2}</p> <button onClick={updateBothCounts}>Update Both Counts</button> </div> ); } """ These standards provide a comprehensive guide to managing state in a clean and maintainable way. By following these guidelines, developers can build robust, performant, and secure applications.