Headers and Parameters

/**
 * HTTP headers management class
 * Polyfill for Fetch API Headers with full manipulation support
 */
class Headers {
  /**
   * Creates a new Headers instance
   * @param headers - Initial headers as Headers object, plain object, or null
   */
  constructor(headers?: Headers | {[name: string]: any} | null);
  
  /**
   * Creates Headers from response header string
   * @param headersString - Raw header string from HTTP response
   * @returns New Headers instance with parsed headers
   */
  static fromResponseHeaderString(headersString: string): Headers;
  
  /**
   * Appends a new value to existing header or creates new header
   * @param name - Header name
   * @param value - Header value to append
   */
  append(name: string, value: string): void;
  
  /**
   * Deletes a header
   * @param name - Header name to delete
   */
  delete(name: string): void;
  
  /**
   * Iterates over headers with callback function
   * @param fn - Callback function receiving values, name, and headers map
   */
  forEach(fn: (values: string[], name: string | undefined, headers: Map<string, string[]>) => void): void;
  
  /**
   * Gets first value of specified header
   * @param name - Header name
   * @returns First header value or null if not found
   */
  get(name: string): string | null;
  
  /**
   * Gets all values of specified header
   * @param name - Header name
   * @returns Array of header values or null if not found
   */
  getAll(name: string): string[] | null;
  
  /**
   * Checks if header exists
   * @param name - Header name
   * @returns True if header exists
   */
  has(name: string): boolean;
  
  /**
   * Gets all header names
   * @returns Array of header names
   */
  keys(): string[];
  
  /**
   * Sets header value, replacing any existing values
   * @param name - Header name
   * @param value - Header value or array of values
   */
  set(name: string, value: string | string[]): void;
  
  /**
   * Gets all header values as arrays
   * @returns Array of header value arrays
   */
  values(): string[][];
  
  /**
   * Converts headers to JSON object
   * @returns Plain object representation of headers
   */
  toJSON(): {[name: string]: any};
  
  /**
   * Gets header entries iterator
   * @throws Error - Not implemented
   */
  entries(): never;
}

import { Headers, Http, RequestOptions } from '@angular/http';

class HeaderService {
  constructor(private http: Http) {}
  
  // Basic header creation and manipulation
  createHeaders(): Headers {
    const headers = new Headers();
    headers.set('Content-Type', 'application/json');
    headers.set('Accept', 'application/json');
    headers.append('X-Custom-Header', 'value1');
    headers.append('X-Custom-Header', 'value2');
    
    console.log('Content-Type:', headers.get('Content-Type'));
    console.log('Custom headers:', headers.getAll('X-Custom-Header'));
    console.log('Has Authorization:', headers.has('Authorization'));
    
    return headers;
  }
  
  // Headers from object
  createFromObject(): Headers {
    const headerObj = {
      'Content-Type': 'application/json',
      'Authorization': 'Bearer token123',
      'X-API-Key': 'api-key-value'
    };
    
    return new Headers(headerObj);
  }
  
  // Authentication headers
  createAuthHeaders(token: string): Headers {
    const headers = new Headers();
    headers.set('Authorization', `Bearer ${token}`);
    headers.set('Content-Type', 'application/json');
    headers.set('Accept', 'application/json');
    
    return headers;
  }
  
  // Custom headers for API requests
  makeApiRequest(): Observable<any> {
    const headers = new Headers({
      'Content-Type': 'application/json',
      'X-API-Version': '2.0',
      'X-Client-Id': 'web-app',
      'Cache-Control': 'no-cache'
    });
    
    const options = new RequestOptions({ headers });
    
    return this.http.get('/api/data', options)
      .pipe(map(response => response.json()));
  }
  
  // Copy and modify headers
  modifyHeaders(originalHeaders: Headers): Headers {
    const newHeaders = new Headers(originalHeaders);
    newHeaders.delete('Cache-Control');
    newHeaders.set('X-Modified', 'true');
    
    return newHeaders;
  }
  
  // Iterate through headers
  logAllHeaders(headers: Headers): void {
    headers.forEach((values, name) => {
      console.log(`${name}:`, values.join(', '));
    });
    
    // Or iterate through keys
    headers.keys().forEach(key => {
      console.log(`${key}: ${headers.get(key)}`);
    });
  }
}

/**
 * URL search parameters management class
 * Similar to native URLSearchParams with custom encoding support
 */
class URLSearchParams {
  /** Internal parameters map */
  paramsMap: Map<string, string[]>;
  
  /** Raw parameters string */
  rawParams: string;
  
  /**
   * Creates a new URLSearchParams instance
   * @param rawParams - Raw query string (without leading ?)
   * @param queryEncoder - Custom query encoder (defaults to QueryEncoder)
   */
  constructor(rawParams?: string, queryEncoder?: QueryEncoder);
  
  /**
   * Creates a clone of the URLSearchParams
   * @returns New URLSearchParams instance with same parameters
   */
  clone(): URLSearchParams;
  
  /**
   * Checks if parameter exists
   * @param param - Parameter name
   * @returns True if parameter exists
   */
  has(param: string): boolean;
  
  /**
   * Gets first value of specified parameter
   * @param param - Parameter name
   * @returns First parameter value or null if not found
   */
  get(param: string): string | null;
  
  /**
   * Gets all values of specified parameter
   * @param param - Parameter name
   * @returns Array of parameter values
   */
  getAll(param: string): string[];
  
  /**
   * Sets parameter value, replacing any existing values
   * @param param - Parameter name
   * @param val - Parameter value
   */
  set(param: string, val: string): void;
  
  /**
   * Sets all parameters from another URLSearchParams instance
   * @param searchParams - Source URLSearchParams instance
   */
  setAll(searchParams: URLSearchParams): void;
  
  /**
   * Appends a new value to existing parameter or creates new parameter
   * @param param - Parameter name
   * @param val - Parameter value to append
   */
  append(param: string, val: string): void;
  
  /**
   * Appends all parameters from another URLSearchParams instance
   * @param searchParams - Source URLSearchParams instance
   */
  appendAll(searchParams: URLSearchParams): void;
  
  /**
   * Replaces all parameters with those from another URLSearchParams instance
   * @param searchParams - Source URLSearchParams instance
   */
  replaceAll(searchParams: URLSearchParams): void;
  
  /**
   * Converts parameters to query string
   * @returns Encoded query string without leading ?
   */
  toString(): string;
  
  /**
   * Deletes a parameter
   * @param param - Parameter name to delete
   */
  delete(param: string): void;
}

import { URLSearchParams, Http, RequestOptions } from '@angular/http';

class ParameterService {
  constructor(private http: Http) {}
  
  // Basic parameter creation and manipulation
  createParams(): URLSearchParams {
    const params = new URLSearchParams();
    params.set('page', '1');
    params.set('limit', '10');
    params.set('sort', 'name');
    params.append('filter', 'active');
    params.append('filter', 'verified');
    
    console.log('Page:', params.get('page'));
    console.log('Filters:', params.getAll('filter'));
    console.log('Query string:', params.toString());
    
    return params;
  }
  
  // Parameters from string
  parseQueryString(): URLSearchParams {
    const queryString = 'q=angular&category=framework&version=6';
    const params = new URLSearchParams(queryString);
    
    console.log('Search query:', params.get('q'));
    console.log('Category:', params.get('category'));
    
    return params;
  }
  
  // Search API with parameters
  searchUsers(query: string, page: number, filters: string[]): Observable<any> {
    const params = new URLSearchParams();
    params.set('q', query);
    params.set('page', page.toString());
    params.set('limit', '20');
    
    // Add multiple filter values
    filters.forEach(filter => {
      params.append('filter', filter);
    });
    
    const options = new RequestOptions({ search: params });
    
    return this.http.get('/api/users/search', options)
      .pipe(map(response => response.json()));
  }
  
  // Complex parameter manipulation
  buildAdvancedQuery(): URLSearchParams {
    const params = new URLSearchParams();
    
    // Basic parameters
    params.set('include', 'profile,settings');
    params.set('expand', 'true');
    
    // Array parameters
    const categories = ['tech', 'science', 'business'];
    categories.forEach(cat => params.append('category', cat));
    
    // Date range
    params.set('start_date', '2023-01-01');
    params.set('end_date', '2023-12-31');
    
    // Special characters (will be URL encoded)
    params.set('search', 'hello world!');
    params.set('tags', 'C++,TypeScript');
    
    return params;
  }
  
  // Merge parameters from different sources
  mergeParams(base: URLSearchParams, additional: URLSearchParams): URLSearchParams {
    const merged = base.clone();
    merged.appendAll(additional);
    
    return merged;
  }
  
  // Convert object to URLSearchParams
  fromObject(obj: {[key: string]: any}): URLSearchParams {
    const params = new URLSearchParams();
    
    Object.keys(obj).forEach(key => {
      const value = obj[key];
      if (Array.isArray(value)) {
        value.forEach(v => params.append(key, v.toString()));
      } else if (value !== null && value !== undefined) {
        params.set(key, value.toString());
      }
    });
    
    return params;
  }
}

/**
 * Query string encoder for URL parameters
 * Handles special character encoding for query parameters
 */
class QueryEncoder {
  /**
   * Encodes parameter key
   * @param key - Parameter key to encode
   * @returns URL-encoded key
   */
  encodeKey(key: string): string;
  
  /**
   * Encodes parameter value
   * @param value - Parameter value to encode
   * @returns URL-encoded value
   */
  encodeValue(value: string): string;
}

import { URLSearchParams, QueryEncoder } from '@angular/http';

// Custom encoder for special requirements
class CustomQueryEncoder extends QueryEncoder {
  encodeKey(key: string): string {
    // Custom key encoding logic
    return encodeURIComponent(key).replace(/%20/g, '+');
  }
  
  encodeValue(value: string): string {
    // Custom value encoding logic
    return encodeURIComponent(value).replace(/%20/g, '+');
  }
}

class EncodingService {
  
  // Use custom encoder
  createCustomParams(): URLSearchParams {
    const encoder = new CustomQueryEncoder();
    const params = new URLSearchParams('', encoder);
    
    params.set('search term', 'hello world');
    params.set('special chars', 'a+b=c&d');
    
    console.log('Encoded:', params.toString());
    // Output might be: search+term=hello+world&special+chars=a%2Bb%3Dc%26d
    
    return params;
  }
  
  // Default encoding behavior
  testDefaultEncoding(): void {
    const params = new URLSearchParams();
    params.set('spaces here', 'value with spaces');
    params.set('symbols', '!@#$%^&*()');
    params.set('unicode', 'café naïve');
    
    console.log('Default encoding:', params.toString());
  }
}

import { Http, Headers, URLSearchParams, RequestOptions } from '@angular/http';

class CompleteRequestService {
  constructor(private http: Http) {}
  
  makeCompleteRequest(): Observable<any> {
    // Create headers
    const headers = new Headers({
      'Content-Type': 'application/json',
      'Authorization': 'Bearer token123',
      'Accept': 'application/json',
      'X-API-Version': '2.0'
    });
    
    // Create parameters
    const params = new URLSearchParams();
    params.set('page', '1');
    params.set('limit', '10');
    params.set('sort', 'created_date');
    params.set('order', 'desc');
    params.append('include', 'author');
    params.append('include', 'comments');
    
    // Combine in request options
    const options = new RequestOptions({
      headers: headers,
      search: params
    });
    
    return this.http.get('/api/posts', options)
      .pipe(map(response => response.json()));
  }
  
  // POST with both headers and body
  createResource(data: any): Observable<any> {
    const headers = new Headers({
      'Content-Type': 'application/json',
      'Authorization': this.getAuthToken()
    });
    
    const options = new RequestOptions({ headers });
    
    return this.http.post('/api/resources', JSON.stringify(data), options)
      .pipe(map(response => response.json()));
  }
  
  // Dynamic header and parameter building
  buildDynamicRequest(config: any): Observable<any> {
    const headers = new Headers();
    const params = new URLSearchParams();
    
    // Build headers based on config
    if (config.auth) {
      headers.set('Authorization', `Bearer ${config.auth}`);
    }
    if (config.contentType) {
      headers.set('Content-Type', config.contentType);
    }
    
    // Build parameters based on config
    if (config.filters) {
      Object.keys(config.filters).forEach(key => {
        params.set(key, config.filters[key]);
      });
    }
    
    const options = new RequestOptions({ headers, search: params });
    
    return this.http.get(config.url, options)
      .pipe(map(response => response.json()));
  }
  
  private getAuthToken(): string {
    return localStorage.getItem('authToken') || '';
  }
}