Improve Logging (#1519)

Improve Logging

Signed-off-by: Tilman Vatteroth <git@tilmanvatteroth.de>

src/utils/logger.ts

@@ -0,0 +1,83 @@
+/*
+ * SPDX-FileCopyrightText: 2021 The HedgeDoc developers (see AUTHORS file)
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { DateTime } from 'luxon'
+
+export enum LogLevel {
+  DEBUG = 'debug',
+  INFO = 'info',
+  WARN = 'warn',
+  ERROR = 'error'
+}
+
+type OutputFunction = (...data: unknown[]) => void
+
+/**
+ * Simple logger that prefixes messages with a timestamp and a name
+ */
+export class Logger {
+  private readonly scope: string
+
+  constructor(scope: string) {
+    this.scope = scope
+  }
+
+  /**
+   * Logs a debug message
+   * @param data data to log
+   */
+  debug(...data: unknown[]): void {
+    this.log(LogLevel.DEBUG, ...data)
+  }
+
+  /**
+   * Logs a normal informative message
+   * @param data data to log
+   */
+  info(...data: unknown[]): void {
+    this.log(LogLevel.INFO, ...data)
+  }
+
+  /**
+   * Logs a warning
+   * @param data data to log
+   */
+  warn(...data: unknown[]): void {
+    this.log(LogLevel.WARN, ...data)
+  }
+
+  /**
+   * Logs an error
+   * @param data data to log
+   */
+  error(...data: unknown[]): void {
+    this.log(LogLevel.ERROR, ...data)
+  }
+
+  private log(loglevel: LogLevel, ...data: unknown[]) {
+    const preparedData = [...this.prefix(), ...data]
+    const logOutput = Logger.getLogOutput(loglevel)
+    logOutput(...preparedData)
+  }
+
+  private static getLogOutput(logLevel: LogLevel): OutputFunction {
+    switch (logLevel) {
+      case LogLevel.INFO:
+        return console.info
+      case LogLevel.DEBUG:
+        return console.debug
+      case LogLevel.ERROR:
+        return console.error
+      case LogLevel.WARN:
+        return console.warn
+    }
+  }
+
+  private prefix(): string[] {
+    const timestamp = DateTime.now().toFormat('yyyy-MM-dd HH:mm:ss')
+    return [`%c[${timestamp}] %c(${this.scope})`, 'color: yellow', 'color: orange']
+  }
+}