feat: add transformations

Fixes #9

src/common.ts

@@ -12,14 +12,13 @@
  * You should have received a copy of the GNU General Public License along with
  * this program. If not, see <https://www.gnu.org/licenses/>.
  */
+import {Transport, VerifiableTransport} from './transport';
 
 /**
  * A recursive partial object
  *
  * Copied from https://stackoverflow.com/a/51365037
  */
-import {Transport, VerifiableTransport} from './transport';
-
 export type RecursivePartial<T> = {
   [P in keyof T]?: T[P] extends Array<infer U> ?
     Array<RecursivePartial<U>> :

src/logger.ts

@@ -12,9 +12,10 @@
  * You should have received a copy of the GNU General Public License along with
  * this program. If not, see <https://www.gnu.org/licenses/>.
  */
-import chalk from 'chalk';
 import {stringify} from 'flatted';
 import {isNodeEnvironment, isProductiveNodeEnvironment} from './common';
+import {Transformation} from './transformation';
+import {AddLogLevel} from './transformations/add-log-level';
 import {Transport} from './transport';
 
 /**
@@ -28,7 +29,12 @@ function hasStAppsLogLevel(something: object): something is { STAPPS_LOG_LEVEL:
 }
 
 /**
- * Logger with colors, loglevel and transport
+ * A log level
+ */
+export type LogLevel = 'INFO' | 'LOG' | 'WARN' | 'ERROR' | 'OK';
+
+/**
+ * A logger with transports and transformations
  *
  * Log level can be defined by setting the environment variable STAPPS_LOG_LEVEL to a valid log level. Log levels are
  * set in a binary way. For example STAPPS_LOG_LEVEL=12 does result in logs only for `Logger.warn` and `Logger.error`.
@@ -51,7 +57,7 @@ export class Logger {
   /**
    * Log levels
    */
-  private static readonly logLevels = [
+  private static readonly logLevels: LogLevel[] = [
     'INFO',
     'LOG',
     'WARN',
@@ -64,17 +70,43 @@ export class Logger {
    */
   private static readonly logLevelSum = Math.pow(Logger.binaryBase, Logger.logLevels.length) - 1;
 
+  /**
+   * Transformers for log output
+   */
+  private static transformations?: Transformation[] = [
+    new AddLogLevel(),
+  ];
+
   /**
    * Transport for errors
    */
   private static transport?: Transport;
 
+  /**
+   * Apply transformations to an output
+   *
+   * @param logLevel Log level of the output
+   * @param output Output to apply transformations to
+   */
+  private static applyTransformers(logLevel: LogLevel, output: string): string {
+    if (!Array.isArray(Logger.transformations) || Logger.transformations.length === 0) {
+      return output;
+    }
+
+    let transformedOutput = output;
+    for (const transformation of Logger.transformations) {
+      transformedOutput = transformation.transform(logLevel, transformedOutput);
+    }
+
+    return transformedOutput;
+  }
+
   /**
    * Check if intended log level is allowed in environment log level
    *
    * @param logLevel Log level to check
    */
-  private static checkLogLevel(logLevel: string): boolean {
+  private static checkLogLevel(logLevel: LogLevel): boolean {
     const logLevelNumber = Math.pow(Logger.binaryBase, Logger.logLevels.indexOf(logLevel) + 1) - 1;
 
     // tslint:disable-next-line:no-bitwise
@@ -110,7 +142,7 @@ export class Logger {
     }
 
     /* tslint:disable-next-line:no-console */
-    console.error(chalk.bold.red(`[ERROR] ${Logger.stringifyArguments(...args)}`));
+    console.error(Logger.applyTransformers('ERROR', Logger.stringifyArguments(...args)));
 
     if (isProductiveNodeEnvironment()) {
       if (typeof Logger.transport !== 'undefined') {
@@ -134,7 +166,7 @@ export class Logger {
     }
 
     /* tslint:disable-next-line:no-console */
-    console.info(chalk.cyan(`[INFO] ${Logger.stringifyArguments(...args)}`));
+    console.info(Logger.applyTransformers('INFO', Logger.stringifyArguments(...args)));
   }
 
   /**
@@ -146,8 +178,7 @@ export class Logger {
         throw new Error(`Productive environment doesn't set a transport for error notifications.`);
       }
 
-      /* tslint:disable-next-line:no-console */
-      console.warn(chalk.yellow(`Productive environment doesn't set a transport for error notifications.`));
+      Logger.warn(`Productive environment doesn't set a transport for error notifications.`);
     }
   }
 
@@ -162,7 +193,7 @@ export class Logger {
     }
 
     /* tslint:disable-next-line:no-console */
-    console.log(chalk.white(`[LOG] ${Logger.stringifyArguments(...args)}`));
+    console.log(Logger.applyTransformers('LOG', Logger.stringifyArguments(...args)));
   }
 
   /**
@@ -176,7 +207,16 @@ export class Logger {
     }
 
     /* tslint:disable-next-line:no-console */
-    console.log(chalk.bold.green(`[OK] ${Logger.stringifyArguments(...args)}`));
+    console.log(Logger.applyTransformers('OK', Logger.stringifyArguments(...args)));
+  }
+
+  /**
+   * Set transformations for log output
+   *
+   * @param transformations List of transformations
+   */
+  public static setTransformations(transformations: Transformation[]) {
+    Logger.transformations = transformations;
   }
 
   /**
@@ -224,6 +264,6 @@ export class Logger {
     }
 
     /* tslint:disable-next-line:no-console */
-    console.warn(chalk.yellow(`[WARN] ${Logger.stringifyArguments(...args)}`));
+    console.warn(Logger.applyTransformers('WARN', Logger.stringifyArguments(...args)));
   }
 }

src/transformation.ts

@@ -0,0 +1,28 @@
+/*
+ * Copyright (C) 2019 StApps
+ * This program is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation, version 3.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program. If not, see <https://www.gnu.org/licenses/>.
+ */
+import {LogLevel} from './logger';
+
+/**
+ * A transformer for log output
+ */
+export interface Transformation {
+  /**
+   * Transform an output
+   *
+   * @param logLevel Log level to transform output for
+   * @param output Output to transform
+   */
+  transform(logLevel: LogLevel, output: string): string;
+}

src/transformations/add-log-level.ts

@@ -0,0 +1,32 @@
+/*
+ * Copyright (C) 2019 StApps
+ * This program is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation, version 3.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program. If not, see <https://www.gnu.org/licenses/>.
+ */
+import {LogLevel} from '../logger';
+import {Transformation} from '../transformation';
+
+/**
+ * Transformation that adds the log level to output
+ */
+export class AddLogLevel implements Transformation {
+  /**
+   * Add log level to output
+   *
+   * @param logLevel Log level to add to output
+   * @param output Output to colorize
+   */
+  // tslint:disable-next-line:prefer-function-over-method
+  transform(logLevel: LogLevel, output: string): string {
+    return `[${logLevel}] ${output}`;
+  }
+}

src/transformations/colorize.ts

@@ -0,0 +1,47 @@
+/*
+ * Copyright (C) 2019 StApps
+ * This program is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation, version 3.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program. If not, see <https://www.gnu.org/licenses/>.
+ */
+import chalk, {Chalk} from 'chalk';
+import {LogLevel} from '../logger';
+import {Transformation} from '../transformation';
+
+/**
+ * Transformation that colorizes log output
+ */
+export class Colorize implements Transformation {
+  /**
+   * Instantiate a new colorize transformation
+   *
+   * @param logLevelToColor Map from log level to color transformation to apply
+   */
+  constructor(private readonly logLevelToColor: { [k in LogLevel]: Chalk; } = {
+    ERROR: chalk.bold.red,
+    INFO: chalk.cyan,
+    LOG: chalk.white,
+    OK: chalk.bold.green,
+    WARN: chalk.yellow,
+  }) {
+    // noop
+  }
+
+  /**
+   * Colorize log output
+   *
+   * @param logLevel Log level to choose color for
+   * @param output Output to colorize
+   */
+  transform(logLevel: LogLevel, output: string): string {
+    return this.logLevelToColor[logLevel](output);
+  }
+}

src/transformations/timestamp.ts

@@ -0,0 +1,45 @@
+/*
+ * Copyright (C) 2019 StApps
+ * This program is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation, version 3.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program. If not, see <https://www.gnu.org/licenses/>.
+ */
+import * as moment from 'moment';
+import {LogLevel} from '../logger';
+import {Transformation} from '../transformation';
+
+/**
+ * Transformation that adds a timestamp to output
+ */
+export class Timestamp implements Transformation {
+  /**
+   * Instantiate a new timestamp transformation
+   *
+   * @see https://momentjs.com/docs/#/displaying/format/
+   *
+   * @param format Format for timestamps
+   */
+  constructor(private readonly format = 'LLLL') {
+    // noop
+  }
+
+  /**
+   * Add timestamp to output
+   *
+   * @param _logLevel Log level to add timestamp to output for
+   * @param output Output to add timestamp to
+   */
+  transform(_logLevel: LogLevel, output: string): string {
+    const now = moment();
+
+    return `[${now.format(this.format)}] ${output}`;
+  }
+}