'use strict';

var isMergeableObject = function isMergeableObject(value) {
	return isNonNullObject(value)
		&& !isSpecial(value)
};

function isNonNullObject(value) {
	return !!value && typeof value === 'object'
}

function isSpecial(value) {
	var stringValue = Object.prototype.toString.call(value);

	return stringValue === '[object RegExp]'
		|| stringValue === '[object Date]'
		|| isReactElement(value)
}

// see https://github.com/facebook/react/blob/b5ac963fb791d1298e7f396236383bc955f916c1/src/isomorphic/classic/element/ReactElement.js#L21-L25
var canUseSymbol = typeof Symbol === 'function' && Symbol.for;
var REACT_ELEMENT_TYPE = canUseSymbol ? Symbol.for('react.element') : 0xeac7;

function isReactElement(value) {
	return value.$$typeof === REACT_ELEMENT_TYPE
}

function emptyTarget(val) {
	return Array.isArray(val) ? [] : {}
}

function cloneUnlessOtherwiseSpecified(value, optionsArgument) {
	var cloneOptionWasSpecified = optionsArgument && typeof optionsArgument.clone === 'boolean';
	var clone = !cloneOptionWasSpecified || optionsArgument.clone === true;

	return (clone && isMergeableObject(value))
		? deepmerge(emptyTarget(value), value, optionsArgument)
		: value
}

function defaultArrayMerge(target, source, optionsArgument) {
	var destination = target.slice();
	source.forEach(function(e, i) {
		if (typeof destination[i] === 'undefined') {
			destination[i] = cloneUnlessOtherwiseSpecified(e, optionsArgument);
		} else if (isMergeableObject(e)) {
			destination[i] = deepmerge(target[i], e, optionsArgument);
		} else if (target.indexOf(e) === -1) {
			destination.push(cloneUnlessOtherwiseSpecified(e, optionsArgument));
		}
	});
	return destination
}

function mergeObject(target, source, optionsArgument) {
	var destination = {};
	if (isMergeableObject(target)) {
		Object.keys(target).forEach(function(key) {
			destination[key] = cloneUnlessOtherwiseSpecified(target[key], optionsArgument);
		});
	}
	Object.keys(source).forEach(function(key) {
		if (!isMergeableObject(source[key]) || !target[key]) {
			destination[key] = cloneUnlessOtherwiseSpecified(source[key], optionsArgument);
		} else {
			destination[key] = deepmerge(target[key], source[key], optionsArgument);
		}
	});
	return destination
}

function deepmerge(target, source, optionsArgument) {
	var sourceIsArray = Array.isArray(source);
	var targetIsArray = Array.isArray(target);
	var options = optionsArgument || { arrayMerge: defaultArrayMerge };
	var sourceAndTargetTypesMatch = sourceIsArray === targetIsArray;

	if (!sourceAndTargetTypesMatch) {
		return cloneUnlessOtherwiseSpecified(source, optionsArgument)
	} else if (sourceIsArray) {
		var arrayMerge = options.arrayMerge || defaultArrayMerge;
		return arrayMerge(target, source, optionsArgument)
	} else {
		return mergeObject(target, source, optionsArgument)
	}
}

deepmerge.all = function deepmergeAll(array, optionsArgument) {
	if (!Array.isArray(array) || array.length < 2) {
		throw new Error('first argument should be an array with at least two elements')
	}

	// we are sure there are at least 2 values, so it is safe to have no initial value
	return array.reduce(function(prev, next) {
		return deepmerge(prev, next, optionsArgument)
	})
};

var deepmerge_1 = deepmerge;

module.exports = deepmerge_1;
