refractor: core module (#289)

* Shift services into their own folders.
* Add comments.

Fixes #288

src/app/core/logger/logger.service.spec.ts

@@ -0,0 +1,72 @@
+// import { Logger, LogLevel, LogOutput } from './logger.service';
+
+// const logMethods = ['log', 'info', 'warn', 'error'];
+
+// describe('Logger', () => {
+//   let savedConsole: Function[];
+//   let savedLevel: LogLevel;
+//   let savedOutputs: LogOutput[];
+
+//   beforeAll(() => {
+//     savedConsole = [];
+//     logMethods.forEach((m) => {
+//       savedConsole[m] = console[m];
+//       console[m] = () => {};
+//     });
+//     savedLevel = Logger.level;
+//     savedOutputs = Logger.outputs;
+//   });
+
+//   afterAll(() => {
+//     logMethods.forEach((m) => { console[m] = savedConsole[m]; });
+//     Logger.level = savedLevel;
+//     Logger.outputs = savedOutputs;
+//   });
+
+//   it('should create an instance', () => {
+//     expect(new Logger()).toBeTruthy();
+//   });
+
+//   it('should add a new LogOutput and receives log entries', () => {
+//     // Arrange
+//     const outputSpy = jasmine.createSpy('outputSpy');
+//     const log = new Logger('test');
+
+//     // Act
+//     Logger.outputs.push(outputSpy);
+
+//     log.debug('d');
+//     log.info('i');
+//     log.warn('w');
+//     log.error('e', { error: true });
+
+//     // Assert
+//     expect(outputSpy).toHaveBeenCalled();
+//     expect(outputSpy.calls.count()).toBe(4);
+//     expect(outputSpy).toHaveBeenCalledWith('test', LogLevel.Debug, 'd');
+//     expect(outputSpy).toHaveBeenCalledWith('test', LogLevel.Info, 'i');
+//     expect(outputSpy).toHaveBeenCalledWith('test', LogLevel.Warning, 'w');
+//     expect(outputSpy).toHaveBeenCalledWith('test', LogLevel.Error, 'e', { error: true });
+//   });
+
+//   it('should add a new LogOutput and receives only production log entries', () => {
+//     // Arrange
+//     const outputSpy = jasmine.createSpy('outputSpy');
+//     const log = new Logger('test');
+
+//     // Act
+//     Logger.outputs.push(outputSpy);
+//     Logger.enableProductionMode();
+
+//     log.debug('d');
+//     log.info('i');
+//     log.warn('w');
+//     log.error('e', { error: true });
+
+//     // Assert
+//     expect(outputSpy).toHaveBeenCalled();
+//     expect(outputSpy.calls.count()).toBe(2);
+//     expect(outputSpy).toHaveBeenCalledWith('test', LogLevel.Warning, 'w');
+//     expect(outputSpy).toHaveBeenCalledWith('test', LogLevel.Error, 'e', { error: true });
+//   });
+// });

src/app/core/logger/logger.service.ts

@@ -0,0 +1,113 @@
+/**
+ * Simple logger system with the possibility of registering custom outputs.
+ *
+ * 4 different log levels are provided, with corresponding methods:
+ * - debug   : for debug information
+ * - info    : for informative status of the application (success, ...)
+ * - warning : for non-critical errors that do not prevent normal application behavior
+ * - error   : for critical errors that prevent normal application behavior
+ *
+ * Example usage:
+ * ```
+ * import { Logger } from 'app/core/logger/logger.service';
+ *
+ * const log = new Logger('myFile');
+ * ...
+ * log.debug('something happened');
+ * ```
+ *
+ * To disable debug and info logs in production, add this snippet to your root component:
+ * ```
+ * export class AppComponent implements OnInit {
+ *   ngOnInit() {
+ *     if (environment.production) {
+ *       Logger.enableProductionMode();
+ *     }
+ *     ...
+ *   }
+ * }
+ *
+ * If you want to process logs through other outputs than console, you can add LogOutput functions to Logger.outputs.
+ */
+
+/**
+ * The possible log levels.
+ * LogLevel.Off is never emitted and only used with Logger.level property to disable logs.
+ */
+export enum LogLevel {
+  Off = 0,
+  Error,
+  Warning,
+  Info,
+  Debug
+}
+
+/**
+ * Log output handler function.
+ */
+export type LogOutput = (source: string, level: LogLevel, ...objects: any[]) => void;
+
+export class Logger {
+
+  /**
+   * Current logging level.
+   * Set it to LogLevel.Off to disable logs completely.
+   */
+  static level = LogLevel.Debug;
+
+  /**
+   * Additional log outputs.
+   */
+  static outputs: LogOutput[] = [];
+
+  /**
+   * Enables production mode.
+   * Sets logging level to LogLevel.Warning.
+   */
+  static enableProductionMode() {
+    Logger.level = LogLevel.Warning;
+  }
+
+  constructor(private source?: string) { }
+
+  /**
+   * Logs messages or objects  with the debug level.
+   * Works the same as console.log().
+   */
+  debug(...objects: any[]) {
+    this.log(console.log, LogLevel.Debug, objects);
+  }
+
+  /**
+   * Logs messages or objects  with the info level.
+   * Works the same as console.log().
+   */
+  info(...objects: any[]) {
+    this.log(console.info, LogLevel.Info, objects);
+  }
+
+  /**
+   * Logs messages or objects  with the warning level.
+   * Works the same as console.log().
+   */
+  warn(...objects: any[]) {
+    this.log(console.warn, LogLevel.Warning, objects);
+  }
+
+  /**
+   * Logs messages or objects  with the error level.
+   * Works the same as console.log().
+   */
+  error(...objects: any[]) {
+    this.log(console.error, LogLevel.Error, objects);
+  }
+
+  private log(func: Function, level: LogLevel, objects: any[]) {
+    if (level <= Logger.level) {
+      const log = this.source ? ['[' + this.source + ']'].concat(objects) : objects;
+      func.apply(console, log);
+      Logger.outputs.forEach((output) => output.apply(output, [this.source, level].concat(objects)));
+    }
+  }
+
+}