svelte-kit-vice/src/arts/storage/defaults-registry.ts

import { STORAGE_OP_READ } from './consts';
import { StorageEntryDefaultsMismatchError } from './errors';
import type { StorageErrorContext } from './types';

export interface RegisterStorageDefaultInput {
	readonly registryKey: string;
	readonly key: string;
	readonly fullKey: string;
	readonly initialDefault: unknown;
	readonly adapterName: string;
	report(ctx: Omit<StorageErrorContext, 'adapter'>, adapterName: string): void;
}

export interface StorageDefaultsRegistry {
	register(input: RegisterStorageDefaultInput): () => void;
}

export function createStorageDefaultsRegistry(): StorageDefaultsRegistry {
	const defaults = new Map<string, { value: unknown; refs: number }>();

	function register(input: RegisterStorageDefaultInput): () => void {
		const previous = defaults.get(input.registryKey);
		if (previous !== undefined) {
			try {
				if (JSON.stringify(previous.value) !== JSON.stringify(input.initialDefault)) {
					input.report(
						{
							key: input.key,
							fullKey: input.fullKey,
							op: STORAGE_OP_READ,
							error: new StorageEntryDefaultsMismatchError(input.key)
						},
						input.adapterName
					);
				}
			} catch {
				/* circular default — skip the diagnostic */
			}
			previous.refs += 1;
		} else {
			defaults.set(input.registryKey, { value: input.initialDefault, refs: 1 });
		}

		return () => {
			const slot = defaults.get(input.registryKey);
			if (slot === undefined) return;
			slot.refs -= 1;
			if (slot.refs <= 0) defaults.delete(input.registryKey);
		};
	}

	return { register };
}