webrequest/readme.md

# @push.rocks/webrequest

Modern, fetch-compatible web request library with intelligent HTTP caching, retry strategies, and advanced fault tolerance.

## Features

- 🌐 **Fetch-Compatible API** - Drop-in replacement for native `fetch()` with enhanced features
- 💾 **Intelligent HTTP Caching** - Respects `Cache-Control`, `ETag`, `Last-Modified`, and `Expires` headers (RFC 7234)
- 🔄 **Multiple Cache Strategies** - network-first, cache-first, stale-while-revalidate, network-only, cache-only
- 🔁 **Advanced Retry System** - Configurable retry with exponential/linear/constant backoff
- 🎯 **Request/Response Interceptors** - Middleware pattern for transforming requests and responses
- 🚫 **Request Deduplication** - Automatically deduplicate simultaneous identical requests
- 📘 **TypeScript Generics** - Type-safe response parsing with `webrequest.getJson<T>()`
- 🛡️ **Better Fault Tolerance** - Multi-endpoint fallback with retry strategies
- ⏱️ **Timeout Support** - Configurable request timeouts with AbortController

## Installation

```bash
pnpm install @push.rocks/webrequest
# or
npm install @push.rocks/webrequest
```

This package requires a modern JavaScript environment with ESM and TypeScript support.

## Quick Start

### Basic Fetch-Compatible Usage

```typescript
import { webrequest } from '@push.rocks/webrequest';

// Use exactly like fetch()
const response = await webrequest('https://api.example.com/data');
const data = await response.json();

// With options (fetch-compatible + enhanced)
const response = await webrequest('https://api.example.com/data', {
  method: 'POST',
  headers: { 'Content-Type': 'application/json' },
  body: JSON.stringify({ key: 'value' }),
  timeout: 30000,
  retry: true
});
```

### JSON Convenience Methods

```typescript
import { webrequest } from '@push.rocks/webrequest';

// GET JSON with type safety
interface User {
  id: number;
  name: string;
  email: string;
}

const user = await webrequest.getJson<User>('https://api.example.com/user/1');
// user is typed as User

// POST JSON
const result = await webrequest.postJson('https://api.example.com/users', {
  name: 'John Doe',
  email: 'john@example.com'
});

// Other convenience methods
await webrequest.putJson(url, data);
await webrequest.patchJson(url, data);
await webrequest.deleteJson(url);
```

## Cache Strategies

### Network-First (Default)

Always fetch from network, fall back to cache on failure. Respects HTTP caching headers.

```typescript
const data = await webrequest.getJson('https://api.example.com/data', {
  cacheStrategy: 'network-first'
});
```

### Cache-First

Check cache first, only fetch from network if not cached or stale.

```typescript
const data = await webrequest.getJson('https://api.example.com/data', {
  cacheStrategy: 'cache-first',
  cacheMaxAge: 60000 // 60 seconds
});
```

### Stale-While-Revalidate

Return cached data immediately, update in background.

```typescript
const data = await webrequest.getJson('https://api.example.com/data', {
  cacheStrategy: 'stale-while-revalidate'
});
```

### Network-Only and Cache-Only

```typescript
// Always fetch from network, never cache
const data = await webrequest.getJson(url, {
  cacheStrategy: 'network-only'
});

// Only use cache, never fetch from network
const data = await webrequest.getJson(url, {
  cacheStrategy: 'cache-only'
});
```

### HTTP Header-Based Caching

The library automatically respects HTTP caching headers:

```typescript
// Server returns: Cache-Control: max-age=3600, ETag: "abc123"
const response = await webrequest('https://api.example.com/data', {
  cacheStrategy: 'network-first'
});

// Subsequent requests automatically send:
// If-None-Match: "abc123"
// Server returns 304 Not Modified - cache is used
```

### Custom Cache Keys

```typescript
const response = await webrequest('https://api.example.com/search?q=test', {
  cacheStrategy: 'cache-first',
  cacheKey: (request) => {
    const url = new URL(request.url);
    return `search:${url.searchParams.get('q')}`;
  }
});
```

## Retry Strategies

### Basic Retry

```typescript
const response = await webrequest('https://api.example.com/data', {
  retry: true // Uses defaults: 3 attempts, exponential backoff
});
```

### Advanced Retry Configuration

```typescript
const response = await webrequest('https://api.example.com/data', {
  retry: {
    maxAttempts: 5,
    backoff: 'exponential', // or 'linear', 'constant'
    initialDelay: 1000,      // 1 second
    maxDelay: 30000,         // 30 seconds
    retryOn: [408, 429, 500, 502, 503, 504], // Status codes to retry
    onRetry: (attempt, error, nextDelay) => {
      console.log(`Retry attempt ${attempt}, waiting ${nextDelay}ms`);
    }
  }
});
```

### Multi-Endpoint Fallback

```typescript
const response = await webrequest('https://api1.example.com/data', {
  fallbackUrls: [
    'https://api2.example.com/data',
    'https://api3.example.com/data'
  ],
  retry: {
    maxAttempts: 3,
    backoff: 'exponential'
  }
});
```

## Request/Response Interceptors

### Global Interceptors

```typescript
import { webrequest } from '@push.rocks/webrequest';

// Add authentication to all requests
webrequest.addRequestInterceptor((request) => {
  const headers = new Headers(request.headers);
  headers.set('Authorization', `Bearer ${getToken()}`);
  return new Request(request, { headers });
});

// Log all responses
webrequest.addResponseInterceptor((response) => {
  console.log(`${response.status} ${response.url}`);
  return response;
});

// Handle errors globally
webrequest.addErrorInterceptor((error) => {
  console.error('Request failed:', error);
  throw error;
});
```

### Per-Request Interceptors

```typescript
const response = await webrequest('https://api.example.com/data', {
  interceptors: {
    request: [(req) => {
      console.log('Sending:', req.url);
      return req;
    }],
    response: [(res) => {
      console.log('Received:', res.status);
      return res;
    }],
    error: [(err) => {
      console.error('Error:', err);
      throw err;
    }]
  }
});
```

## Request Deduplication

Automatically prevent duplicate simultaneous requests:

```typescript
// Only one actual network request is made
const [res1, res2, res3] = await Promise.all([
  webrequest('https://api.example.com/data', { deduplicate: true }),
  webrequest('https://api.example.com/data', { deduplicate: true }),
  webrequest('https://api.example.com/data', { deduplicate: true }),
]);

// All three get the same response
```

## Client API with Default Options

For more control, use `WebrequestClient` to set default options:

```typescript
import { WebrequestClient } from '@push.rocks/webrequest';

const apiClient = new WebrequestClient({
  logging: true,
  timeout: 30000,
  cacheStrategy: 'network-first',
  retry: {
    maxAttempts: 3,
    backoff: 'exponential'
  }
});

// Add global interceptors to this client
apiClient.addRequestInterceptor((request) => {
  const headers = new Headers(request.headers);
  headers.set('X-API-Key', process.env.API_KEY);
  return new Request(request, { headers });
});

// All requests through this client use the configured defaults
const data = await apiClient.getJson('https://api.example.com/data');

// Standard fetch-compatible API also available
const response = await apiClient.request('https://api.example.com/data');
```

## Advanced Features

### Timeout

```typescript
const response = await webrequest('https://api.example.com/data', {
  timeout: 5000 // 5 seconds
});
```

### Custom Headers

```typescript
const response = await webrequest('https://api.example.com/data', {
  headers: {
    'Authorization': 'Bearer token123',
    'X-Custom-Header': 'value'
  }
});
```

### Cache Management

```typescript
// Clear all cached responses
await webrequest.clearCache();

// Clear specific cache entry
await webrequest.clearCache('https://api.example.com/data');
```

## TypeScript Support

Full TypeScript support with generics for type-safe responses:

```typescript
interface ApiResponse<T> {
  data: T;
  status: 'success' | 'error';
  message?: string;
}

interface User {
  id: number;
  name: string;
  email: string;
}

// Fully typed response
const response = await webrequest.getJson<ApiResponse<User>>(
  'https://api.example.com/user/1'
);

// response.data.id, response.data.name, response.data.email are all typed
```

## API Reference

### Main Function

```typescript
webrequest(input: string | Request | URL, options?: IWebrequestOptions): Promise<Response>
```

### Convenience Methods

```typescript
webrequest.getJson<T>(url: string, options?: IWebrequestOptions): Promise<T>
webrequest.postJson<T>(url: string, body: any, options?: IWebrequestOptions): Promise<T>
webrequest.putJson<T>(url: string, body: any, options?: IWebrequestOptions): Promise<T>
webrequest.patchJson<T>(url: string, body: any, options?: IWebrequestOptions): Promise<T>
webrequest.deleteJson<T>(url: string, options?: IWebrequestOptions): Promise<T>
```

### Global Methods

```typescript
webrequest.addRequestInterceptor(interceptor: TRequestInterceptor): void
webrequest.addResponseInterceptor(interceptor: TResponseInterceptor): void
webrequest.addErrorInterceptor(interceptor: TErrorInterceptor): void
webrequest.clearCache(url?: string): Promise<void>
```

### Options Interface

```typescript
interface IWebrequestOptions extends Omit<RequestInit, 'cache'> {
  // Standard fetch options
  method?: string;
  headers?: HeadersInit;
  body?: BodyInit;

  // Enhanced options
  cache?: 'default' | 'no-store' | 'reload' | 'no-cache' | 'force-cache' | 'only-if-cached';
  cacheStrategy?: 'network-first' | 'cache-first' | 'stale-while-revalidate' | 'network-only' | 'cache-only';
  cacheMaxAge?: number; // milliseconds
  cacheKey?: (request: Request) => string;

  retry?: boolean | IRetryOptions;
  fallbackUrls?: string[];
  timeout?: number; // milliseconds

  interceptors?: {
    request?: TRequestInterceptor[];
    response?: TResponseInterceptor[];
    error?: TErrorInterceptor[];
  };

  deduplicate?: boolean;
  logging?: boolean;
}
```

## Migration from v3

Version 4.0 is a **complete rewrite** of `@push.rocks/webrequest` with breaking changes. **The v3 API has been completely removed** - all v3 code must be migrated to v4.

### What's New in v4

- **Fetch-Compatible API**: Drop-in replacement for native `fetch()` with enhanced features
- **Intelligent HTTP Caching**: Respects `Cache-Control`, `ETag`, `Last-Modified`, and `Expires` headers (RFC 7234)
- **Multiple Cache Strategies**: network-first, cache-first, stale-while-revalidate, network-only, cache-only
- **Advanced Retry System**: Configurable retry with exponential/linear/constant backoff
- **Request/Response Interceptors**: Middleware pattern for transforming requests and responses
- **Request Deduplication**: Automatically deduplicate simultaneous identical requests
- **TypeScript Generics**: Type-safe response parsing with `webrequest.getJson<T>()`
- **Better Fault Tolerance**: Enhanced multi-endpoint fallback with retry strategies

### Breaking Changes

1. **Removed `WebRequest` class** - Use `webrequest` function or `WebrequestClient` class instead
2. **Cache API changed** - Boolean `useCache` replaced with explicit `cacheStrategy` options
3. **Multi-endpoint API changed** - `requestMultiEndpoint()` replaced with `fallbackUrls` option

### Migration Examples

#### Basic Fetch-Compatible Usage

```typescript
// v3
import { WebRequest } from '@push.rocks/webrequest';
const client = new WebRequest();
const response = await client.request('https://api.example.com/data', {
  method: 'GET'
});
const data = await response.json();

// v4 - Fetch-compatible
import { webrequest } from '@push.rocks/webrequest';
const response = await webrequest('https://api.example.com/data');
const data = await response.json();
```

#### JSON Convenience Methods

```typescript
// v3
const client = new WebRequest();
const data = await client.getJson('https://api.example.com/data', true);

// v4 - Function API
import { webrequest } from '@push.rocks/webrequest';
const data = await webrequest.getJson('https://api.example.com/data', {
  cacheStrategy: 'cache-first'
});

// v4 - Client API (similar to v3)
import { WebrequestClient } from '@push.rocks/webrequest';
const client = new WebrequestClient({ logging: true });
const data = await client.getJson('https://api.example.com/data', {
  cacheStrategy: 'cache-first'
});
```

#### Caching

```typescript
// v3 - Boolean flag
const data = await client.getJson(url, true); // useCache = true

// v4 - Explicit strategies
const data = await webrequest.getJson(url, {
  cacheStrategy: 'cache-first',
  cacheMaxAge: 60000 // 60 seconds
});

// v4 - HTTP header-based caching (automatic)
const data = await webrequest.getJson(url, {
  cacheStrategy: 'network-first' // Respects Cache-Control headers
});
```

#### Multi-Endpoint Fallback

```typescript
// v3
const client = new WebRequest();
const response = await client.requestMultiEndpoint(
  ['https://api1.example.com/data', 'https://api2.example.com/data'],
  { method: 'GET' }
);

// v4
import { webrequest } from '@push.rocks/webrequest';
const response = await webrequest('https://api1.example.com/data', {
  fallbackUrls: ['https://api2.example.com/data'],
  retry: {
    maxAttempts: 3,
    backoff: 'exponential'
  }
});
```

#### Timeout

```typescript
// v3
const response = await client.request(url, {
  method: 'GET',
  timeoutMs: 30000
});

// v4
const response = await webrequest(url, {
  timeout: 30000 // milliseconds
});
```

## Examples

### Complete Example with All Features

```typescript
import { webrequest } from '@push.rocks/webrequest';

async function fetchUserData(userId: string) {
  interface User {
    id: string;
    name: string;
    email: string;
  }

  const user = await webrequest.getJson<User>(
    `https://api.example.com/users/${userId}`,
    {
      // Caching
      cacheStrategy: 'stale-while-revalidate',
      cacheMaxAge: 300000, // 5 minutes

      // Retry
      retry: {
        maxAttempts: 3,
        backoff: 'exponential',
        retryOn: [500, 502, 503, 504]
      },

      // Fallback
      fallbackUrls: [
        'https://api-backup.example.com/users/${userId}'
      ],

      // Timeout
      timeout: 10000, // 10 seconds

      // Deduplication
      deduplicate: true,

      // Per-request interceptor
      interceptors: {
        request: [(req) => {
          console.log(`Fetching user ${userId}`);
          return req;
        }]
      }
    }
  );

  return user;
}
```

### Building a Typed API Client

```typescript
import { WebrequestClient } from '@push.rocks/webrequest';

class ApiClient {
  private client: WebrequestClient;

  constructor(private baseUrl: string, private apiKey: string) {
    this.client = new WebrequestClient({
      timeout: 30000,
      cacheStrategy: 'network-first',
      retry: {
        maxAttempts: 3,
        backoff: 'exponential'
      }
    });

    // Add auth interceptor
    this.client.addRequestInterceptor((request) => {
      const headers = new Headers(request.headers);
      headers.set('Authorization', `Bearer ${this.apiKey}`);
      headers.set('Content-Type', 'application/json');
      return new Request(request, { headers });
    });
  }

  async getUser(id: string): Promise<User> {
    return this.client.getJson<User>(`${this.baseUrl}/users/${id}`);
  }

  async createUser(data: CreateUserData): Promise<User> {
    return this.client.postJson<User>(`${this.baseUrl}/users`, data);
  }

  async updateUser(id: string, data: UpdateUserData): Promise<User> {
    return this.client.putJson<User>(`${this.baseUrl}/users/${id}`, data);
  }

  async deleteUser(id: string): Promise<void> {
    await this.client.deleteJson(`${this.baseUrl}/users/${id}`);
  }
}

// Usage
const api = new ApiClient('https://api.example.com', process.env.API_KEY);
const user = await api.getUser('123');
```

## License and Legal Information

This repository contains open-source code that is licensed under the MIT License. A copy of the MIT License can be found in the [license](license) file within this repository.

**Please note:** The MIT License does not grant permission to use the trade names, trademarks, service marks, or product names of the project, except as required for reasonable and customary use in describing the origin of the work and reproducing the content of the NOTICE file.

### Trademarks

This project is owned and maintained by Task Venture Capital GmbH. The names and logos associated with Task Venture Capital GmbH and any related products or services are trademarks of Task Venture Capital GmbH and are not included within the scope of the MIT license granted herein. Use of these trademarks must comply with Task Venture Capital GmbH's Trademark Guidelines, and any usage must be approved in writing by Task Venture Capital GmbH.

### Company Information

Task Venture Capital GmbH
Registered at District court Bremen HRB 35230 HB, Germany

For any legal inquiries or if you require further information, please contact us via email at hello@task.vc.

By using this repository, you acknowledge that you have read this section, agree to comply with its terms, and understand that the licensing of the code does not imply endorsement by Task Venture Capital GmbH of any derivative works.