Add log function

src/index.ts

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+import { log } from './logger'

src/logger.ts

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+type LogLevel = 'DEBUG' | 'INFO' | 'WARN' | 'ERROR';
+const colours: Record<LogLevel, string> = {
+    DEBUG: '\x1b[36m', // Cyan
+    INFO:  '\x1b[32m', // Green
+    WARN:  '\x1b[33m', // Yellow
+    ERROR: '\x1b[31m', // Red
+};
+
+const levelWeight: Record<LogLevel, number> = {
+    DEBUG: 0,
+    INFO: 1,
+    WARN: 2,
+    ERROR: 3,
+};
+
+const RESET = '\x1b[0m';
+
+const CURRENT_LOG_LEVEL = (process.env.LOG_LEVEL as LogLevel) || 'INFO';
+const MIN_WEIGHT = levelWeight[CURRENT_LOG_LEVEL] ?? 1;
+
+export function log(level: LogLevel, msg: string, ...args: any[]): void {
+    // Drop log if below LOG_LEVEL
+    if (levelWeight[level] < MIN_WEIGHT) return;
+
+    const timestamp = new Date().toISOString();
+    const colour = colours[level] || RESET;
+
+    const header = `[${timestamp}] [${colour}${level.padEnd(5)}${RESET}]: ${msg}`;
+
+    if (args.length > 0) {
+        if (level === 'ERROR') {
+            console.error(header, ...args);
+        } else {
+            console.log(header, ...args);
+        }
+    } else {
+        level === 'ERROR' ? console.error(header) : console.log(header);
+    }
+}