"use strict";

const defaultValue = require("default-value");
const asExpression = require("as-expression");

// FIXME: Move to stand-alone package, clearly document that it is not order-sensitive

function ensureObject(object, property) {
	if (object[property] == null) {
		object[property] = {};
	}
}

module.exports = function createNamedTreeBuilder(options = {}) {
	let parentKey = options.parentKey;
	let childrenKey = options.childrenKey;
	let treatRootAsParent = defaultValue(options.treatRootAsParent, true);
	let root = {};
	let done = false;

	return {
		add: function (path, item) {
			if (done === true) {
				throw new Error(`done() was called on the builder; no further modifications are possible`);
			} else {
				let lastItem = root;

				for (let i = 0; i < path.length; i++) {
					let segment = path[i];
					
					// eslint-disable-next-line no-loop-func
					let childrenContainer = asExpression(() => {
						if (childrenKey != null) {
							ensureObject(lastItem, childrenKey);
							return lastItem[childrenKey];
						} else {
							return lastItem;
						}
					});
					
					ensureObject(childrenContainer, segment);
					let child = childrenContainer[segment];
					
					let setParent = (
						parentKey != null
						&& child[parentKey] == null
						&& (treatRootAsParent || i >= 1)
					);

					if (setParent) {
						child[parentKey] = lastItem;
					}
					
					if (i === path.length - 1) {
						// Last segment, this is where we want to put the item data
						child = childrenContainer[segment] = {
							... item,
							... child
						};
					}
					
					lastItem = child;
				}
			}
		},
		done: function () {
			done = true;
			return root;
		}
	};
};

// let builder = module.exports({ childrenKey: "children", parentKey: "parent" });
// builder.add([], { description: "root" });
// builder.add(["a"], { description: "root -> a" });
// builder.add(["b", "c"], { description: "root -> b -> c" });
// builder.add(["b"], { description: "root -> b" });
// builder.add(["a", "c"], { description: "root -> a -> c" });
// builder.add(["a", "c", "d"], { description: "root -> a -> c -> d" });
// console.dir(builder.done(), { depth: null });