const Model = require('../models/page');

/**
 * @class Pages
 * @classdesc Pages controller
 */
class Pages {
  /**
   * @static
   * Fields required for page model creation
   *
   * @returns {['title', 'body']}
   */
  static get REQUIRED_FIELDS() {
    return ['title', 'body'];
  }

  /**
   * @static
   * Find and return page model with passed id
   *
   * @param {string} id - page id
   * @returns {Promise<Page>}
   */
  static async get(id) {
    const page = await Model.get(id);

    if (!page._id) {
      throw new Error('Page with given id does not exist');
    }

    return page;
  }

  /**
   * Return all pages
   *
   * @returns {Promise<Page[]>}
   */
  static async getAll() {
    return Model.getAll();
  }

  /**
   * Create new page model and save it in the database
   *
   * @param {PageData} data
   * @returns {Promise<Page>}
   */
  static async insert(data) {
    if (!Pages.validate(data)) {
      throw new Error('Invalid request format');
    }

    const page = new Model(data);

    return page.save();
  }

  /**
   * Check PageData object for required fields
   *
   * @param {PageData} data
   * @returns {boolean}
   */
  static validate(data) {
    return Pages.REQUIRED_FIELDS.every(field => typeof data[field] !== 'undefined');
  }

  /**
   * Update page with given id in the database
   *
   * @param {string} id - page id
   * @param {PageData} data
   * @returns {Promise<Page>}
   */
  static async update(id, data) {
    const page = await Model.get(id);

    if (!page._id) {
      throw new Error('Page with given id does not exist');
    }

    page.data = data;

    return page.save();
  }

  /**
   * Remove page with given id from the database
   *
   * @param {string} id - page id
   * @returns {Promise<Page>}
   */
  static async remove(id) {
    const page = await Model.get(id);

    if (!page._id) {
      throw new Error('Page with given id does not exist');
    }

    return page.destroy();
  }
}

module.exports = Pages;