From 7db177d1814985485bb8262940e43f24a240f221 Mon Sep 17 00:00:00 2001
From: Joey Perrott <josephperrott@gmail.com>
Date: Mon, 18 May 2020 15:37:18 -0700
Subject: [PATCH] feat(dev-infra): create logging utils with support for
 defined logging levels (#37192)

Creates common logging functions at different levels. Allows for providing
logging statements which are actually printed to the console based on the
LOG_LEVEL environment variable.

PR Close #37192
---
 dev-infra/utils/BUILD.bazel |  1 +
 dev-infra/utils/console.ts  | 92 +++++++++++++++++++++++++++++++++++++
 2 files changed, 93 insertions(+)

diff --git a/dev-infra/utils/BUILD.bazel b/dev-infra/utils/BUILD.bazel
index 48b015feeb..062f2080af 100644
--- a/dev-infra/utils/BUILD.bazel
+++ b/dev-infra/utils/BUILD.bazel
@@ -10,6 +10,7 @@ ts_library(
         "@npm//@types/inquirer",
         "@npm//@types/node",
         "@npm//@types/shelljs",
+        "@npm//chalk",
         "@npm//shelljs",
         "@npm//tslib",
         "@npm//typed-graphqlify",
diff --git a/dev-infra/utils/console.ts b/dev-infra/utils/console.ts
index f6ca0c9d9e..78bfb6dc81 100644
--- a/dev-infra/utils/console.ts
+++ b/dev-infra/utils/console.ts
@@ -6,8 +6,15 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
+import chalk from 'chalk';
 import {prompt} from 'inquirer';
 
+
+/** Reexport of chalk colors for convenient access. */
+export const red: typeof chalk = chalk.red;
+export const green: typeof chalk = chalk.green;
+export const yellow: typeof chalk = chalk.yellow;
+
 /** Prompts the user with a confirmation question and a specified message. */
 export async function promptConfirm(message: string, defaultValue = false): Promise<boolean> {
   return (await prompt<{result: boolean}>({
@@ -18,3 +25,88 @@ export async function promptConfirm(message: string, defaultValue = false): Prom
          }))
       .result;
 }
+
+/**
+ * Supported levels for logging functions.
+ *
+ * Levels are mapped to numbers to represent a hierarchy of logging levels.
+ */
+export enum LOG_LEVELS {
+  SILENT = 0,
+  ERROR = 1,
+  WARN = 2,
+  LOG = 3,
+  INFO = 4,
+  DEBUG = 5,
+}
+
+/** Default log level for the tool. */
+export const DEFAULT_LOG_LEVEL = LOG_LEVELS.INFO;
+
+/** Write to the console for at INFO logging level */
+export function info(...text: string[]): void;
+export function info(color: typeof chalk, ...text: string[]): void;
+export function info(color: typeof chalk|string, ...text: string[]) {
+  runConsoleCommand(console.info, LOG_LEVELS.INFO, color, ...text);
+}
+
+/** Write to the console for at ERROR logging level */
+export function error(...text: string[]): void;
+export function error(color: typeof chalk, ...text: string[]): void;
+export function error(color: typeof chalk|string, ...text: string[]) {
+  runConsoleCommand(console.error, LOG_LEVELS.ERROR, color, ...text);
+}
+
+/** Write to the console for at DEBUG logging level */
+export function debug(...text: string[]): void;
+export function debug(color: typeof chalk, ...text: string[]): void;
+export function debug(color: typeof chalk|string, ...text: string[]) {
+  runConsoleCommand(console.debug, LOG_LEVELS.DEBUG, color, ...text);
+}
+
+/** Write to the console for at LOG logging level */
+export function log(...text: string[]): void;
+export function log(color: typeof chalk, ...text: string[]): void;
+export function log(color: typeof chalk|string, ...text: string[]) {
+  // tslint:disable-next-line: no-console
+  runConsoleCommand(console.log, LOG_LEVELS.LOG, color, ...text);
+}
+
+/** Write to the console for at WARN logging level */
+export function warn(...text: string[]): void;
+export function warn(color: typeof chalk, ...text: string[]): void;
+export function warn(color: typeof chalk|string, ...text: string[]) {
+  runConsoleCommand(console.warn, LOG_LEVELS.WARN, color, ...text);
+}
+
+/**
+ * Run the console command provided, if the environments logging level greater than the
+ * provided logging level.
+ */
+function runConsoleCommand(
+    command: Function, logLevel: LOG_LEVELS, color: typeof chalk|string, ...text: string[]) {
+  if (getLogLevel() >= logLevel) {
+    if (typeof color === 'function') {
+      text = text.map(entry => color(entry));
+    } else {
+      text = [color as string, ...text];
+    }
+    for (const textEntry of text) {
+      command(textEntry);
+    }
+  }
+}
+
+/**
+ * Retrieve the log level from environment variables, if the value found
+ * based on the LOG_LEVEL environment variable is undefined, return the default
+ * logging level.
+ */
+function getLogLevel() {
+  const logLevelEnvValue: any = (process.env[`LOG_LEVEL`] || '').toUpperCase();
+  const logLevel = LOG_LEVELS[logLevelEnvValue];
+  if (logLevel === undefined) {
+    return DEFAULT_LOG_LEVEL;
+  }
+  return logLevel;
+}