🚧 WIP

migration.ts

@@ -5,33 +5,33 @@ let v4Events: any[] = [];
 let v5Events: any[] = [];
 
 {
-    v4.enable('*');
-    const log = v4.diary("v0.4", event => {
-        v4Events.push(event);
-    });
+	v4.enable('*');
+	const log = v4.diary('v0.4', (event) => {
+		v4Events.push(event);
+	});
 
-    log.log("hello %s", "world", "extra", "props");
-    log.debug("hello %s", "world", "extra", "props");
-    log.info("hello %s", "world", "extra", "props");
-    log.warn("hello %s", "world", "extra", "props");
-    log.error("hello %s", "world", "extra", "props");
-    log.fatal("hello %s", "world", "extra", "props");
+	log.log('hello %s', 'world', 'extra', 'props');
+	log.debug('hello %s', 'world', 'extra', 'props');
+	log.info('hello %s', 'world', 'extra', 'props');
+	log.warn('hello %s', 'world', 'extra', 'props');
+	log.error('hello %s', 'world', 'extra', 'props');
+	log.fatal('hello %s', 'world', 'extra', 'props');
 }
 
 {
-    const log = v5.diary("v0.5", (...event: any[]) => {
-        v5Events.push(event);
-    });
+	const log = v5.diary('v0.5', (name, level, event, props) => {
+		v5Events.push({ name, level, messages: [event, props] });
+	});
 
-    log("log", "hello {phrase}", {phrase: "world", extra: ["extra", "props"]});
-    log("debug", "hello {phrase}", {phrase: "world", extra: ["extra", "props"]});
-    log("info", "hello {phrase}", {phrase: "world", extra: ["extra", "props"]});
-    log("warn", "hello {phrase}", {phrase: "world", extra: ["extra", "props"]});
-    log("error", "hello {phrase}", {phrase: "world", extra: ["extra", "props"]});
-    log("fatal", "hello {phrase}", {phrase: "world", extra: ["extra", "props"]});
+	log('log', 'hello {phrase}', { phrase: 'world', extra: ['extra', 'props'] });
+	log('debug', 'hello {phrase}', { phrase: 'world', extra: ['extra', 'props'] });
+	log('info', 'hello {phrase}', { phrase: 'world', extra: ['extra', 'props'] });
+	log('warn', 'hello {phrase}', { phrase: 'world', extra: ['extra', 'props'] });
+	log('error', 'hello {phrase}', { phrase: 'world', extra: ['extra', 'props'] });
+	log('fatal', 'hello {phrase}', { phrase: 'world', extra: ['extra', 'props'] });
 }
 
 console.log({
-    v4Events,
-    v5Events
-})
+	v4Events,
+	v5Events,
+});

src/mod.ts

@@ -7,6 +7,7 @@ export interface OnEmitFn {
 }
 
 export interface LogFn {
+	// TODO: how can we require props if there is a template in the event?
 	<const T extends string, P extends Props<T>>(level: Level, event: T, props: P): void;
 }
 

src/util.ts

@@ -1,18 +1,22 @@
-export type Props<T> = T extends `${string}{${infer U}}${infer Rest}`
-	? { [K in U]: unknown } & Props<Rest>
-	: Record<string, unknown>;
+type Evaluate<T> = T extends infer O ? { [K in keyof O]: O[K] } : never;
+
+export type Props<T> = Evaluate<
+	T extends `${string}{${infer U extends string}}${infer Rest extends string}`
+		? { [K in U]: unknown } & Props<Rest>
+		: unknown
+>;
 
 export function interpolate<const T extends string, O extends Props<T>>(
 	event: T,
 	props: O,
-	to_string: (v: keyof O) => string = String,
+	to_string: (v: O[keyof O], key: keyof O) => string = String,
 ): string {
 	return event.replaceAll(/\{([^}]+)\}/g, (_, key) => {
 		if (!hasOwn(props, key)) return `{${key}}`;
-		return to_string(props[key] as keyof O);
+		return to_string(props[key], key);
 	});
 }
 
-function hasOwn(obj: unknown, key: string) {
+function hasOwn<T extends Record<string, unknown>>(obj: T, key: PropertyKey): key is keyof T {
 	return Object.prototype.hasOwnProperty.call(obj, key);
 }