refactor(std/log): support enum log level (#4859)

1 files changed, 52 insertions, 19 deletions

diff --git a/std/log/levels.ts b/std/log/levels.ts
index be960dd57..ed6010ba2 100644
--- a/std/log/levels.ts
+++ b/std/log/levels.ts
@@ -1,26 +1,59 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
-export const LogLevel: Record<string, number> = {
-  NOTSET: 0,
-  DEBUG: 10,
-  INFO: 20,
-  WARNING: 30,
-  ERROR: 40,
-  CRITICAL: 50,
-};
+/** Get log level numeric values through enum constants
+ */
+export enum LogLevels {
+  NOTSET = 0,
+  DEBUG = 10,
+  INFO = 20,
+  WARNING = 30,
+  ERROR = 40,
+  CRITICAL = 50,
+}
+
+/** Permitted log level names */
+export const LogLevelNames = Object.keys(LogLevels).filter((key) =>
+  isNaN(Number(key))
+);
+
+/** Union of valid log level strings */
+export type LevelName = keyof typeof LogLevels;
 
-const byLevel = {
-  [LogLevel.NOTSET]: "NOTSET",
-  [LogLevel.DEBUG]: "DEBUG",
-  [LogLevel.INFO]: "INFO",
-  [LogLevel.WARNING]: "WARNING",
-  [LogLevel.ERROR]: "ERROR",
-  [LogLevel.CRITICAL]: "CRITICAL",
+const byLevel: Record<string, LevelName> = {
+  [String(LogLevels.NOTSET)]: "NOTSET",
+  [String(LogLevels.DEBUG)]: "DEBUG",
+  [String(LogLevels.INFO)]: "INFO",
+  [String(LogLevels.WARNING)]: "WARNING",
+  [String(LogLevels.ERROR)]: "ERROR",
+  [String(LogLevels.CRITICAL)]: "CRITICAL",
 };
 
-export function getLevelByName(name: string): number {
-  return LogLevel[name];
+/** Returns the numeric log level associated with the passed,
+ * stringy log level name.
+ */
+export function getLevelByName(name: LevelName): number {
+  switch (name) {
+    case "NOTSET":
+      return LogLevels.NOTSET;
+    case "DEBUG":
+      return LogLevels.DEBUG;
+    case "INFO":
+      return LogLevels.INFO;
+    case "WARNING":
+      return LogLevels.WARNING;
+    case "ERROR":
+      return LogLevels.ERROR;
+    case "CRITICAL":
+      return LogLevels.CRITICAL;
+    default:
+      throw new Error(`no log level found for "${name}"`);
+  }
 }
 
-export function getLevelName(level: number): string {
-  return byLevel[level];
+/** Returns the stringy log level name provided the numeric log level */
+export function getLevelName(level: number): LevelName {
+  const levelName = byLevel[level];
+  if (levelName) {
+    return levelName;
+  }
+  throw new Error(`no level name found for level: ${level}`);
 }