"use strict";

const Promise = require("bluebird");
const memoizee = require("memoizee");

// FIXME: Figure out a reasonable way to make this symbol its own (conflict-free) package, given that it'll be used all across both sysquery and CVM
const All = require("../graphql-interface/symbols/all");

// This generates a (memoized) source function for commands that always produce an entire list, that needs to be filtered for the desired item(s)
module.exports = function evaluateAndPick({ command, selectResult, selectID, many }) {
	let commandOnce = memoizee(command);

	return function (ids) {
		return Promise.try(() => {
			return commandOnce();
		}).then((result) => {
			if (selectResult != null) {
				return selectResult(result);
			} else {
				return result;
			}
		}).then((items) => {
			return ids.map((id) => {
				if (id === All) {
					return items;
				} else if (many === true) {
					// NOTE: This produces nested arrays! One array for each input ID.
					return items.filter((item) => selectID(item) === id);
				} else {
					// TODO: Can this be more performant? Currently it is a nested loop
					return items.find((item) => selectID(item) === id);
				}
			});
		});
	};
};