revamped db schema and implemented some simple api

lib/models/model.js

@@ -0,0 +1,141 @@
+const Emitter = require('events');
+const uuidv4 = require('uuid/v4');
+const assert = require('assert');
+const {getMysqlConnection} = require('../db');
+const {DbErrorBadRequest} = require('../utils/errors');
+
+class Model extends Emitter {
+  constructor() {
+    super();
+  }
+
+  static getPrimaryKey() {
+    return this.fields.find((f) => f.primaryKey === true);
+  }
+
+  /**
+   * check validity of object to be inserted into db
+   */
+  static checkIsInsertable(obj) {
+    // check all required fields are present
+    const required = this.fields.filter((f) => f.required === true);
+    const missing = required.find((f) => !(f.name in obj));
+    if (missing) throw new DbErrorBadRequest(`missing field ${missing.name}`);
+    return true;
+  }
+
+  /**
+   * insert object into the database
+   */
+  static make(obj) {
+    return new Promise((resolve, reject) => {
+      const pk = this.getPrimaryKey();
+      const uuid = uuidv4();
+      obj[pk.name] = uuid;
+      this.checkIsInsertable(obj);
+      getMysqlConnection((err, conn) => {
+        if (err) return reject(err);
+        conn.query(`INSERT into ${this.table} SET ?`,
+          obj,
+          (err, results, fields) => {
+            conn.release();
+            if (err) return reject(err);
+            resolve(uuid);
+          });
+      });
+    });
+  }
+
+  /**
+   *  delete object from database
+   */
+  static remove(uuid) {
+    return new Promise((resolve, reject) => {
+      const pk = this.getPrimaryKey();
+      getMysqlConnection((err, conn) => {
+        if (err) return reject(err);
+        conn.query(`DELETE from ${this.table} WHERE ${pk.name} = ?`, uuid, (err, results) => {
+          conn.release();
+          if (err) return reject(err);
+          resolve(results.affectedRows);
+        });
+      });
+    });
+  }
+
+  /**
+   * retrieve all objects
+   */
+  static retrieveAll() {
+    return new Promise((resolve, reject) => {
+      getMysqlConnection((err, conn) => {
+        if (err) return reject(err);
+        conn.query(`SELECT * from ${this.table}`, (err, results, fields) => {
+          conn.release();
+          if (err) return reject(err);
+          resolve(results);
+        });
+      });
+    });
+  }
+
+  /**
+   * retrieve a specific object
+   */
+  static retrieve(sid) {
+    return new Promise((resolve, reject) => {
+      const pk = this.getPrimaryKey();
+      assert.ok(pk, 'field definitions must include the primary key');
+      getMysqlConnection((err, conn) => {
+        if (err) return reject(err);
+        conn.query(`SELECT * from ${this.table} WHERE ${pk.name} = ?`, sid, (err, results, fields) => {
+          conn.release();
+          if (err) return reject(err);
+          resolve(results);
+        });
+      });
+    });
+  }
+
+  /**
+   * update an object
+   */
+  static update(sid, obj) {
+    const pk = this.getPrimaryKey();
+    assert.ok(pk, 'field definitions must include the primary key');
+    return new Promise((resolve, reject) => {
+      if (pk.name in obj) throw new DbErrorBadRequest(`primary key ${pk.name} is immutable`);
+      getMysqlConnection((err, conn) => {
+        if (err) return reject(err);
+        conn.query(`UPDATE ${this.table} SET ? WHERE ${pk.name} = '${sid}'`, obj, (err, results, fields) => {
+          conn.release();
+          if (err) return reject(err);
+          resolve(results.affectedRows);
+        });
+      });
+    });
+  }
+
+  static getForeignKeyReferences(fk, sid) {
+    return new Promise((resolve, reject) => {
+      const arr = /(.*)\.(.*)/.exec(fk);
+      assert.ok(arr, `foreign key must be written as table.column: ${fk}`);
+      const table = arr[1];
+      const column = arr[2];
+      getMysqlConnection((err, conn) => {
+        if (err) return reject(err);
+        conn.query(`SELECT COUNT(*) as count from ${table} WHERE ${column} = ?`,
+          sid, (err, results, fields) => {
+            conn.release();
+            if (err) return reject(err);
+            resolve(results[0].count);
+          });
+      });
+    });
+  }
+}
+
+Model.table = 'subclassResponsibility';
+Model.fields = [];
+
+module.exports = Model;