import { assign, assignWith, merge as _merge, mergeWith } from 'lodash';
import { MergeOptions } from '../types';

export type MergeHandler = <T extends {} = {}>(settings: T[], options?: MergeOptions) => T;

export const merge = <T extends {} = {}>(settings: T[], options?: MergeOptions): T => {
    const overwrite = options && options.overwrite === true;
    const concatArrays = options && options.concatArrays === true;
    if (overwrite) {
        return concatArrays ? assignConcatArrays(...settings) : assign({}, ...settings);
    } else {
        return concatArrays ? mergeConcatArrays(...settings) : _merge({}, ...settings);
    }
};

const mergeConcatArrays = <T extends {} = {}>(...settings: T[]): T => {
    return mergeWith({}, ...settings, (objValue, srcValue) => {
        if (Array.isArray(objValue)) {
            return objValue.concat(srcValue);
        }
    });
};

const assignConcatArrays = <T extends {} = {}>(...settings: T[]): T => {
    return assignWith({}, ...settings, (objValue, srcValue) => {
        if (Array.isArray(objValue)) {
            return objValue.concat(srcValue);
        }
    });
};