/**
 *
 * Transform which consolidates the `resolve.root` configuration option into the `resolve.modules` array
 *
 * @param {Object} j - jscodeshift top-level import
 * @param {Node} ast - jscodeshift ast to transform
 * @returns {Node} ast - jscodeshift ast
 */

module.exports = function transformer(j, ast) {
	const getRootVal = p => {
		return p.node.value.properties.filter(prop => prop.key.name === "root")[0];
	};

	const getRootIndex = p => {
		return p.node.value.properties.reduce((rootIndex, prop, index) => {
			return prop.key.name === "root" ? index : rootIndex;
		}, -1);
	};

	const isModulePresent = p => {
		const modules = p.node.value.properties.filter(
			prop => prop.key.name === "modules"
		);
		return modules.length > 0 && modules[0];
	};

	/**
	 *
	 * Add a `modules` property to the `resolve` object or update the existing one
	 * based on what is already in `resolve.root`
	 *
	 * @param {Node} p - ast node that represents the `resolve` property
	 * @returns {Node} p - ast node that represents the updated `resolve` property
	 */

	const createModuleArray = p => {
		const rootVal = getRootVal(p);
		let modulesVal = null;
		if (rootVal.value.type === "ArrayExpression") {
			modulesVal = rootVal.value.elements;
		} else {
			modulesVal = [rootVal.value];
		}
		let module = isModulePresent(p);

		if (!module) {
			module = j.property(
				"init",
				j.identifier("modules"),
				j.arrayExpression(modulesVal)
			);
			p.node.value.properties = p.node.value.properties.concat([module]);
		} else {
			module.value.elements = module.value.elements.concat(modulesVal);
		}
		const rootIndex = getRootIndex(p);
		p.node.value.properties.splice(rootIndex, 1);
		return p;
	};

	return ast
		.find(j.Property)
		.filter(p => {
			return (
				p.node.key.name === "resolve" &&
				p.node.value.properties.filter(prop => prop.key.name === "root")
					.length === 1
			);
		})
		.forEach(createModuleArray);
};