Recipe Manager

Ownership and transitions

A revision is immutable historical content. Rollback appends a historical copy as a new latest version and never discards the audit trail. Current-name uniqueness changes when a recipe is renamed; historical names remain in older revisions but do not reserve a name. Explicit read/write permissions are independent. Copy input lists and every nested result list. A simple current-name/ingredient scan costs O(recipes); history snapshots cost returned content size.

JavaScript boundaries

Use native classes with per-instance state and plain object/array snapshots. Object assignment shares a reference; copy retained inputs and every outward mutable container, including nested arrays. null means absence. Map handles arbitrary string keys safely, including "__proto__"; do not confuse a missing key with zero or an empty string. Domain validation uses RangeError. Numeric inputs must satisfy Number.isSafeInteger, so booleans, fractions, infinities, and NaN are invalid where an integer is required. All documented aggregate results and timestamp-plus-duration sums fit the safe-integer range. Strings use exact case-sensitive equality; lexical order compares JavaScript UTF-16 code units. Calls are serialized and synchronous.

const internal = ["initial"];
const snapshot = [...internal];
snapshot.length = 0;
console.assert(internal.length === 1);

A detached snapshot protects ownership; the service still has to validate and commit a coherent transition.