Order child pages (#21)

* save ordering pages

* move to another collection

* requested changes. Code improvements

* add margin

* unit tests

* fix

* requested changes

* recursive method: create menu tree

* update comments

* fix bug

* requested changes

* move const

* fix error message on catch

* add migration

* rewrite to splices

* move methods

* testing put above method

* linter fix

src/models/pageOrder.js

@@ -0,0 +1,156 @@
+const {pagesOrder: db} = require('../utils/database/index');
+
+/**
+ * @typedef {Object} PageOrderData
+ * @property {string} _id - row unique id
+ * @property {string} page - page id
+ * @property {Array<string>} order - list of ordered pages
+ */
+
+/**
+ * @class PageOrder
+ * @classdesc PageOrder
+ *
+ * Creates order for Pages with children
+ */
+class PageOrder {
+  /**
+   * Returns current Page's children order
+   *
+   * @param {string} pageId - page's id
+   */
+  static async get(pageId) {
+    const order = await db.findOne({page: pageId});
+
+    let data = {};
+
+    if (!order) {
+      data.page = pageId;
+    } else {
+      data = order;
+    }
+
+    return new PageOrder(data);
+  }
+
+  /**
+   * @constructor
+   *
+   * @param {PageOrderData} data
+   */
+  constructor(data = {}) {
+    if (data === null) {
+      data = {};
+    }
+
+    if (data._id) {
+      this._id = data._id;
+    }
+
+    this.data = data;
+  }
+
+  /**
+   * constructor data setter
+   * @param {PageOrderData} pageOrderData
+   */
+  set data(pageOrderData) {
+    this._page = pageOrderData.page || 0;
+    this._order = pageOrderData.order || [];
+  }
+
+  /**
+   * Return Page Children order
+   * @returns {PageOrderData}
+   */
+  get data() {
+    return {
+      _id: this._id,
+      page: '' + this._page,
+      order: this._order
+    };
+  }
+
+  /**
+   * Pushes page id to the orders array
+   *
+   * @param {string} pageId - page's id
+   */
+  push(pageId) {
+    if (typeof pageId === 'string') {
+      this._order.push(pageId);
+    } else {
+      throw new Error('given id is not string');
+    }
+  }
+
+  /**
+   * Removes page id from orders array
+   *
+   * @param {string} pageId - page's id
+   */
+  remove(pageId) {
+    const found = this._order.indexOf(pageId);
+
+    if (found >= 0) {
+      this._order.splice(found, 1);
+    }
+  }
+
+  /**
+   * @param {string} currentPageId - page's id that changes the order
+   * @param {string} putAbovePageId - page's id above which we put the target page
+   *
+   * @returns void
+   */
+  putAbove(currentPageId, putAbovePageId) {
+    const found1 = this.order.indexOf(putAbovePageId);
+    const found2 = this.order.indexOf(currentPageId);
+
+    if (found1 === -1 || found2 === -1) {
+      return;
+    }
+
+    const margin = found1 < found2 ? 1 : 0;
+
+    this.order.splice(found1, 0, currentPageId);
+    this.order.splice(found2 + margin, 1);
+  }
+
+  /**
+   * Returns ordered list
+   *
+   * @return {string[]}
+   */
+  get order() {
+    return this._order;
+  }
+
+  /**
+   * Save or update page data in the database
+   */
+  async save() {
+    if (!this._id) {
+      const insertedRow = await db.insert(this.data);
+
+      this._id = insertedRow._id;
+    } else {
+      await db.update({_id: this._id}, this.data);
+    }
+
+    return this;
+  }
+
+  /**
+   * Remove page data from the database
+   */
+  async destroy() {
+    await db.remove({_id: this._id});
+
+    delete this._id;
+
+    return this;
+  }
+}
+
+module.exports = PageOrder;