"use strict";

const Promise = require("bluebird");
const memoizee = require("memoizee");
const asExpression = require("as-expression");
const fs = Promise.promisifyAll(require("fs"));
const lsblk = require("../../packages/exec-lsblk");
const All = require("../../packages/graphql-interface/symbols/all");
const treecutter = require("../../packages/treecutter");
const findInTree = require("../../packages/find-in-tree");
const shallowMerge = require("../../packages/shallow-merge");
const unreachable = require("../../packages/unreachable");

module.exports = function () {
	let lsblkOnce = memoizee(() => {
		return Promise.try(() => {
			return lsblk();
		}).then((tree) => {
			return treecutter.flatten(tree);
		}).map((device) => {
			return Promise.try(() => {
				return fs.realpathAsync(device.path);
			}).then((actualPath) => {
				return shallowMerge(device, {
					path: actualPath
				});
			});
		}).then((devices) => {
			return {
				tree: treecutter.rebuild(devices),
				list: devices
			};
		});
	});

	return function (selectors) {
		return Promise.try(() => {
			return lsblkOnce();
		}).then(({tree, list}) => {
			return selectors.map((selector) => {
				if (selector === All) {
					// return tree;
					return list;
				} else {
					let { path, name } = selector;

					let predicate = asExpression(() => {
						if (path != null) {
							return (device) => device.path === path;
						} else if (name != null) {
							return (device) => device.name === name;
						} else {
							unreachable("No selector specified for lsblk");
						}
					});

					return findInTree({ tree, predicate });
				}
			});
		});
	};
};