kliedz/src/logger/level_priority.ts

Dead-simple, stateless logging utility for JavaScript and TypeScript. Pure functions. No dependencies. Just log.

import type { LogLevel } from "../types/log_level.js";
import { type LogThreshold, logThresholds } from "../types/log_threshold.js";

function fromEntriesStrict<K extends PropertyKey, V>(
	entries: readonly (readonly [K, V])[],
): Record<K, V> {
	return Object.fromEntries(entries) as Record<K, V>;
}

/**
 * Assigns a numeric priority to each log threshold level.
 * Lower numbers mean more verbose; higher means more critical.
 * "silent" is given a very high value to suppress all output.
 */
export const levelPriority = fromEntriesStrict(
	logThresholds.map(
		(level, index) =>
			[level, level === "silent" ? Number.POSITIVE_INFINITY : index] as const,
	),
) satisfies Record<LogThreshold, number>;

/**
 * Returns the numeric priority for a given log level or threshold.
 * Throws if the level is unknown or not registered.
 *
 * @param level - Log level or threshold
 * @returns Priority number
 */
export function getPriorityFor(level: LogLevel | LogThreshold): number {
	const p = levelPriority[level];
	if (p === undefined)
		throw new Error(`Unknown log level/threshold: "${level}"`);
	return p;
}

/**
 * Determines whether a message with the given `level` should be logged
 * based on the user-defined `threshold`.
 *
 * @param threshold - The minimum log level required to allow output
 * @param level - The log level of the current message
 * @returns `true` if the message should be printed, `false` otherwise
 */
export function shouldLog(threshold: LogThreshold, level: LogLevel): boolean {
	return getPriorityFor(level) >= getPriorityFor(threshold);
}