@known-as-bmf/hookable/dist/index.es.js

Function hooking utility.

/**
 * Setup a subscription and save it to provided `Map`.
 *
 * @param map - The map to save the subscription to.
 *
 * @internal
 */
const hookInto = (map) => (subscription) => {
    // symbol used to uniquely identify this subscription
    const symbol = Symbol();
    const unsubscribe = () => {
        map.delete(symbol);
    };
    map.set(symbol, subscription(unsubscribe));
};
/**
 * Create a hookable function.
 *
 * @param fn - The function to make hookable.
 *
 * @public
 */
function createHookable(fn) {
    const transformInput = new Map();
    const enter = new Map();
    const transformOutput = new Map();
    const leave = new Map();
    return Object.assign(((...initialArgs) => {
        // apply input transformations - `TransformInput`
        const tArgs = Array.from(transformInput.values()).reduce((args, ti) => ti(...args), initialArgs);
        // "entering" function with transformed inputs - `TapInput`
        enter.forEach((e) => e(...tArgs));
        const initialResult = fn(...tArgs);
        // apply output transformations - TransformOutput
        const tResult = Array.from(transformOutput.values()).reduce((result, a) => a(result), initialResult);
        // "leaving" function with transformed output - TapOutput
        leave.forEach((e) => e(tResult));
        return tResult;
    }), {
        transformInput: hookInto(transformInput),
        enter: hookInto(enter),
        transformOutput: hookInto(transformOutput),
        leave: hookInto(leave),
    });
}

/**
 * Create a hook subscriber that never unsubscribes.
 *
 * @param fn - The hook to register.
 *
 * @public
 */
const every = (fn) => () => {
    return ((...args) => fn(...args));
};
/**
 * Create a hook subscriber that unsubscribes after the first call.
 *
 * @param fn - The hook to register.
 *
 * @public
 */
const once = (fn) => (unsub) => {
    return ((...args) => {
        unsub();
        return fn(...args);
    });
};

export { createHookable, every, once };
//# sourceMappingURL=index.es.js.map