import type { components } from '$lib/generated/api';

type TimelineEntryDTO = components['schemas']['TimelineEntryDTO'];

/**
 * Stable `{#each}` key for a timeline entry. Prefers the entry's own identity
 * (`eventId` for curated events, `documentId` for letters); derived life-events
 * carry neither, so they key on `derivedType` + their linked person ids — which
 * keeps two derived births in the same year distinct. The `kind` prefix keeps an
 * event and a letter that happen to share an id from colliding.
 *
 * Used by both `YearBand` (per-band rows) and `TimelineView` (the undated
 * bucket), where entries can be events without a `documentId`.
 */
export function entryKey(entry: TimelineEntryDTO): string {
	return (
		entry.kind +
		':' +
		(entry.eventId ??
			entry.documentId ??
			`${entry.derivedType}:${(entry.linkedPersonIds ?? []).join('-')}`)
	);
}