Extract Format interface from the console sink

Author: Yamgirly

format.ts

@@ -0,0 +1,26 @@
+/** A parsed format */
+export interface Format {
+  /** The original format string */
+  format: string;
+  /** The parsed string */
+  output: string;
+  /** A map of raw variables from the string */
+  variables: Map<string, unknown>;
+}
+
+/** Parse a string format with variables */
+export const parseFormat = (format: string, ...args: unknown[]): Format => {
+  const variables = new Map<string, unknown>();
+
+  const output = format.replace(/\{(.*?)\}/g, (_, p1: string) => {
+    const arg = args.shift();
+    variables.set(p1, arg);
+    return `${arg}` || "";
+  });
+
+  return {
+    format,
+    output,
+    variables,
+  };
+};

logger.ts

@@ -1,5 +1,6 @@
 // Copyright 2020 Yamboy1. All rights reserved. MIT license.
 
+import { parseFormat } from "./format.ts";
 import { LogLevel } from "./levels.ts";
 import { Sink, consoleSink } from "./sinks.ts";
 
@@ -13,6 +14,8 @@ export function createLogger(
   });
 }
 
+type LogFunction = (format: string, ...args: unknown[]) => void;
+
 export interface LoggerOptions {
   minimumLevel: LogLevel;
   sinks: Sink[];
@@ -22,11 +25,11 @@ export interface Logger {
   /** Add a sink at runtime, in most cases, the sinks parameter from createLogger should be used instead. */
   addSink(sink: Sink): this;
 
-  debug(format: string, ...args: unknown[]): void;
-  info(format: string, ...args: unknown[]): void;
-  warning(format: string, ...args: unknown[]): void;
-  error(format: string, ...args: unknown[]): void;
-  critical(format: string, ...args: unknown[]): void;
+  debug: LogFunction;
+  info: LogFunction;
+  warning: LogFunction;
+  error: LogFunction;
+  critical: LogFunction;
 }
 
 class LoggerImpl {
@@ -43,17 +46,19 @@ class LoggerImpl {
     return this;
   }
 
-  private log(level: LogLevel, format: string, ...args: unknown[]): void {
+  private log(level: LogLevel, formatString: string, ...args: unknown[]): void {
     if (level < this.minimumLevel) return;
 
+    const format = parseFormat(formatString, ...args);
+
     if (this.sinks.length === 0) {
       console.error(
         "[Deno Structured Logging] Warning: No sinks are provided.",
       );
     }
 
     for (let sink of this.sinks) {
-      sink(level, format, ...args);
+      sink(level, format);
     }
   }
 

sinks.ts

@@ -7,45 +7,31 @@ import {
   red,
   bold,
 } from "https://deno.land/std@0.51.0/fmt/colors.ts";
+import { Format } from "./format.ts";
 import { LogLevel } from "./levels.ts";
 
 /** An output for the logger, sometimes known as a handler */
 export type Sink = (
   level: LogLevel,
-  format: string,
-  ...args: unknown[]
+  format: Format,
 ) => void;
 
 /** The default console sink */
 export const consoleSink: Sink = (
   level: LogLevel,
-  format: string,
-  ...args: unknown[]
+  format: Format,
 ) => {
-  const message = format.replace(/\{.*?\}/g, () => `${args.shift()}` || "");
-  const timestamp = `[${new Date().toISOString()} ${LogLevel[level]}]`;
+  const message = `[${new Date().toISOString()} ${
+    LogLevel[level]
+  }] ${format.output}`;
 
-  let color;
-  switch (level) {
-    case LogLevel.DEBUG:
-      color = gray;
-      break;
-    case LogLevel.INFO:
-      color = white;
-      break;
-    case LogLevel.WARNING:
-      color = yellow;
-      break;
-    case LogLevel.ERROR:
-      color = red;
-      break;
-    case LogLevel.CRITICAL:
-      color = (str: string) => bold(red(str));
-      break;
-    default:
-      color = white;
-      break;
-  }
+  const color = ({
+    [LogLevel.DEBUG]: gray,
+    [LogLevel.INFO]: white,
+    [LogLevel.WARNING]: yellow,
+    [LogLevel.ERROR]: red,
+    [LogLevel.CRITICAL]: (str: string) => bold(red(str)),
+  })[level] ?? white;
 
-  console.log(color(`${timestamp} ${message}`));
+  console.log(color(message));
 };