/**
 * Copyright (c) 2017 mol* contributors, licensed under MIT, See LICENSE file for more info.
 *
 * @author David Sehnal <david.sehnal@gmail.com>
 */

const hasOwnProperty = Object.prototype.hasOwnProperty;

/** Create new object if any property in "update" changes in "source". */
export function shallowMerge2<T>(source: T, update: Partial<T>): T {
    // Adapted from LiteMol (https://github.com/dsehnal/LiteMol)
    let changed = false;
    for (let k of Object.keys(update)) {
        if (!hasOwnProperty.call(update, k)) continue;

        if ((update as any)[k] !== (source as any)[k]) {
            changed = true;
            break;
        }
    }

    if (!changed) return source;
    return Object.assign({}, source, update);
}

export function shallowEqual<T>(a: T, b: T) {
    if (!a) {
        if (!b) return true;
        return false;
    }
    if (!b) return false;

    let keys = Object.keys(a);
    if (Object.keys(b).length !== keys.length) return false;
    for (let k of keys) {
        if (!hasOwnProperty.call(a, k) || (a as any)[k] !== (b as any)[k]) return false;
    }

    return true;
}

export function shallowMerge<T>(source: T, ...rest: (Partial<T> | undefined)[]): T {
    // Adapted from LiteMol (https://github.com/dsehnal/LiteMol)
    let ret: any = source;

    for (let s = 0; s < rest.length; s++) {
        if (!rest[s]) continue;
        ret = shallowMerge2(source, rest[s] as T);
        if (ret !== source) {
            for (let i = s + 1; i < rest.length; i++) {
                ret = Object.assign(ret, rest[i]);
            }
            break;
        }
    }
    return ret;
}