Structure change

classes/delete.class.js

-const Query = require('./query.class');
-const { Pool } = require('pg');
-const { WhereMixin } = require('../mixins');
-
-/**
- * Class for execution of DELETE queries
- *
- * @class Insert
- */
-class Delete extends WhereMixin(Query) {
-  /**
-   * Creates an instance of Delete.
-   *
-   * @param {Pool} db
-   * @param {string} table
-   */
-  constructor(db, table) {
-    super(db);
-    this.table = table;
-  }
-
-  get query() {
-    return `DELETE FROM ${this.table} ${this.whereSQL}`;
-  }
-}
-
-module.exports = Delete;

classes/index.js

-module.exports = {
-  Query: require('./query.class'),
-  Select: require('./select.class'),
-  Insert: require('./insert.class'),
-  Delete: require('./delete.class')
-};

index.js

-const { Pool } = require('pg');
-const { Query, Select, Insert, Delete } = require('./classes');
-
-/**
- * Class for communication with PostgreSQL database
- *
- * @class DB
- */
-class DB {
-  /**
-   *
-   * @param {Object} params
-   * @param {string} params.host - Connection Host
-   * @param {number} params.port - Connection Port
-   * @param {string} params.database - DB Name
-   * @param {string} params.user - DB User
-   * @param {string} params.password - DB Password
-   */
-  constructor({ host, port, database, user, password }) {
-    this._db = new Pool({ host, port, database, user, password });
-  }
-
-  /**
-   * Creates a Query object
-   *
-   * @param {string} query
-   * @param {Array.<any>} data
-   * @returns {Query} query
-   */
-  query(query, data = []) {
-    return new Query(this._db, query, data);
-  }
-
-  /**
-   * Creates a Select object
-   *
-   * @param {string} table
-   * @returns {Select} select
-   */
-  select(table) {
-    return new Select(this._db, table);
-  }
-
-  /**
-   * Creates an Insert object
-   *
-   * @param {string} table
-   * @returns {Insert} insert
-   */
-  insert(table) {
-    return new Insert(this._db, table);
-  }
-
-  /**
-   * Creates a Delete object
-   *
-   * @param {string} table
-   * @returns {Delete} delete
-   */
-  delete(table) {
-    return new Delete(this._db, table);
-  }
-}
-
-module.exports = DB;
+module.exports = require('./src/database.class');

src/classes/delete.class.js

+const SpecificQuery = require('./query.specific.class');
+const { WhereMixin } = require('../mixins');
+
+class Delete extends WhereMixin(SpecificQuery) {
+  get query() {
+    return `DELETE FROM ${this.table} ${this.whereSQL}`;
+  }
+}
+
+module.exports = Delete;

classes/insert.class.js → src/classes/insert.class.js

-const Query = require('./query.class');
-const { Pool } = require('pg');
+const SpecificQuery = require('./query.specific.class');
 const { ValuesMixin } = require('../mixins');
 
-/**
- * Class for execution of INSERT queries
- *
- * @class Insert
- */
-class Insert extends ValuesMixin(Query) {
-  /**
-   * Creates an instance of Insert.
-   *
-   * @param {Pool} db
-   * @param {string} table
-   */
-  constructor(db, table) {
-    super(db);
-    this.table = table;
-  }
-
+class Insert extends ValuesMixin(SpecificQuery) {
   get canExecute() {
     return this._values != null;
   }

classes/query.class.js → src/classes/query.class.js

-const { Pool } = require('pg');
+/** @typedef {import('../database.class.js') Database} */
 
 class Query {
   /**
    * Creates an instance of Query.
    *
-   * @param {Pool} db
-   * @param {string} [query='']
-   * @param {array} [data=[]]
+   * @param {Database} db
    */
-  constructor(db, query = '', data = []) {
-    this._db = db;
-    this._query = query;
-    this.data = data;
+  constructor(db) {
+    this._db = db._db;
+
+    this.data = [];
 
     this.executed = false;
     this.success = null;
@@ -20,12 +18,13 @@ class Query {
   }
 
   /**
-   * Getter for query; can be overridden
+   * Returns the PostgreSQL query
    *
+   * @type String
    * @readonly
    */
   get query() {
-    return this._query;
+    return null;
   }
 
   /**

src/classes/query.generic.class.js

+/** @typedef {import('../database.class') Database}*/
+
+const Query = require('./query.class');
+
+/**
+ * Generic query is not bound to any table
+ *
+ * @class GenericQuery
+ * @extends {Query}
+ */
+class GenericQuery extends Query {
+  /**
+   * Creates an instance of GenericQuery.
+   *
+   * @param {Database} db
+   * @param {String} query
+   * @param {Object[]} [data=[]]
+   */
+  constructor(db, query, data = []) {
+    super(db);
+
+    this._query = query;
+    this.data = data;
+  }
+
+  /**
+   * Getter for query; can be overridden
+   *
+   * @readonly
+   */
+  get query() {
+    return this._query;
+  }
+}
+
+module.exports = GenericQuery;

src/classes/query.specific.class.js

+/** @typedef {import('../database.class') Database}*/
+
+const Query = require('./query.class');
+
+/**
+ * Specific query is bound to a table.
+ * This class is used as a parent class for other queries:
+ * - SELECT
+ * - INSERT
+ * - DELETE
+ * - UPDATE
+ *
+ * @class SpecificQuery
+ * @extends {Query}
+ */
+class SpecificQuery extends Query {
+  /**
+   * Creates an instance of SpecificQuery.
+   *
+   * @param {Database} db
+   * @param {String} table
+   * @memberof SpecificQuery
+   */
+  constructor(db, table) {
+    super(db);
+
+    this.table = table;
+  }
+}
+
+module.exports = SpecificQuery;

classes/select.class.js → src/classes/select.class.js

-const Query = require('./query.class');
-const { Pool } = require('pg');
+const SpecificQuery = require('./query.specific.class');
 const {
   ColumnsMixin,
   LimitMixin,
@@ -7,23 +6,9 @@ const {
   WhereMixin
 } = require('../mixins');
 
-/**
- * Class for execution of SELECT queries
- *
- * @class Select
- */
-class Select extends WhereMixin(OffsetMixin(LimitMixin(ColumnsMixin(Query)))) {
-  /**
-   * Creates an instance of Select.
-   *
-   * @param {Pool} db
-   * @param {string} table
-   */
-  constructor(db, table) {
-    super(db);
-    this.table = table;
-  }
-
+class Select extends WhereMixin(
+  OffsetMixin(LimitMixin(ColumnsMixin(SpecificQuery)))
+) {
   get canExecute() {
     return this._columns != null;
   }

src/database.class.js

+const { Pool } = require('pg');
+const GenericQuery = require('./classes/query.specific.class');
+const Select = require('./classes/select.class');
+const Insert = require('./classes/insert.class');
+const Delete = require('./classes/delete.class');
+
+/**
+ * Class for communication with PostgreSQL database
+ *
+ * @class Database
+ */
+class Database {
+  /**
+   *
+   * @param {Object} params
+   * @param {String} params.host - Connection Host
+   * @param {number} params.port - Connection Port
+   * @param {String} params.database - DB Name
+   * @param {String} params.user - DB User
+   * @param {String} params.password - DB Password
+   */
+  constructor({ host, port, database, user, password }) {
+    this._db = new Pool({ host, port, database, user, password });
+  }
+
+  /**
+   * Creates a Query object
+   *
+   * @param {String} query
+   * @param {Array.<any>} data
+   * @returns {Query} query
+   */
+  query(query, data = []) {
+    return new GenericQuery(this, query, data);
+  }
+
+  /**
+   * Creates a Select object
+   *
+   * @param {String} table
+   * @returns {Select} select
+   */
+  select(table) {
+    return new Select(this, table);
+  }
+
+  /**
+   * Creates an Insert object
+   *
+   * @param {String} table
+   * @returns {Insert} insert
+   */
+  insert(table) {
+    return new Insert(this, table);
+  }
+
+  /**
+   * Creates a Delete object
+   *
+   * @param {String} table
+   * @returns {Delete} delete
+   */
+  delete(table) {
+    return new Delete(this, table);
+  }
+}
+
+module.exports = Database;