@curveball/kernel/src/headers.ts

Curveball is a framework writting in Typescript for Node.js

/**
 * This interface represents a set of HTTP headers.
 */
export interface HeadersInterface {

  /**
   * Sets a HTTP header name and value
   */
  set(name: string, value: string | string[] | number): void;

  /**
   * Gets a HTTP header's value.
   *
   * This function will return null if the header did not exist. If it did
   * exist, it will return a string.
   *
   * If there were multiple headers with the same value, it will join the
   * headers with a comma.
   */
  get(name: string): string|null;

  /**
   * Gets all values of a HTTP header
   *
   * This function will return an array with 0 or more values of a header.
   *
   */
  getMany(name: string): string[];

  /**
   * Returns true or false depending on if a HTTP header exists.
   */
  has(name: string): boolean;

  /**
   * Removes a HTTP header
   */
  delete(name: string): void;

  /**
   * Returns all HTTP headers.
   *
   * Headernames are lowercased. Values may be either strings or arrays of
   * strings or numbers.
   */
  getAll(): HeadersObject;

  /**
   * Appends a new header, without removing an old one with the same name.
   */
  append(name: string, value: string | string[] | number): void;

}

/**
 * This type is a simple key-value object that can be used to instantiate a
 * Headers class.
 */
export type HeadersObject = {
  [headerName: string]: string | string[] | number;
};

export class Headers implements HeadersInterface {

  private store: {
    [name: string]: [string, string | string[] | number];
  };

  constructor(headersObj: HeadersObject = {}) {

    this.store = {};
    for (const key of Object.keys(headersObj)) {
      this.set(key, headersObj[key]);
    }

  }

  /**
   * Sets a HTTP header name and value.
   */
  set(name: string, value: string | string[] | number): void {

    // Storing the header name case-insenstive, but we retain the original
    // case as well.
    this.store[name.toLowerCase()] = [name, value];

  }

  /**
   * Gets a HTTP header's value.
   *
   * This function will return null if the header did not exist. If it did
   * exist, it will return a string.
   *
   * If there were multiple headers with the same value, it will join the
   * headers with a comma.
   */
  get(name: string): string|null {

    const tuple = this.store[name.toLowerCase()];
    if (tuple === undefined) {
      return null;
    }
    const value = tuple[1];
    if (typeof(value) === 'string') {
      return value;
    } else if (Array.isArray(value)) {
      return value.join(', ');
    } else {
      return value.toString();
    }

  }

  /**
   * Gets all values of a HTTP header
   *
   * This function will return an array with 0 or more values of a header.
   *
   */
  getMany(name: string): string[] {

    const tuple = this.store[name.toLowerCase()];
    if (tuple === undefined) {
      return [];
    }
    const value = tuple[1];

    if (Array.isArray(value)) {
      return value;
    } else {
      return [value.toString()];
    }
  }

  /**
   * Returns true or false depending on if a HTTP header exists.
   */
  has(name: string): boolean {

    return this.store[name.toLowerCase()] !== undefined;

  }

  /**
   * Returns all HTTP headers.
   *
   * Headernames are lowercased. Values may be either strings or arrays of
   * strings or numbers.
   */
  getAll(): HeadersObject {

    const result: HeadersObject = {};
    for (const headerName of Object.keys(this.store)) {

      result[headerName] = this.store[headerName][1];

    }
    return result;

  }

  /**
   * Appends a new header, without removing an old one with the same name.
   */
  append(name: string, value: string | string[] | number): void {

    const lowerName = name.toLowerCase();
    if (this.store[lowerName] === undefined) {
      this.store[lowerName] = [name, value];
      return;
    }

    const oldArray: string[] = Array.isArray(this.store[lowerName][1]) ? this.store[lowerName][1] as string[] : [this.store[lowerName][1].toString()];
    this.store[lowerName][1] = oldArray.concat(value as string[]|string);

  }

  /**
   * Removes a HTTP header
   */
  delete(name: string): void {

    delete this.store[name.toLowerCase()];

  }

}


export default Headers;