"use strict";

const util = require("util");

const errors = require("../errors");
const createWrapper = require("../util/function-wrapper");
const getValueType = require("../util/get-value-type");

let proto = {
	_source: null,
	description: null,
	size: 0,
	add: null,
	[Symbol.iterator]: createWrapper(Symbol.iterator),
	[util.inspect.custom]: function () {
		return this.valueOf();
	},
	clear: function () {
		this._source.clear();
		this.size = 0;
	},
	entries: createWrapper("entries"),
	forEach: createWrapper("forEach"), /* FIXME: Prevent mutation from the third argument to forEach (which is the original set); maybe also needed for Map? */
	has: createWrapper("has"),
	keys: createWrapper("keys"),
	values: createWrapper("values"),
	toString: createWrapper("toString"),
	valueOf: createWrapper("valueOf"),
	delete: function (value) {
		let deleted = this._source.delete(value);
		this.size = this._source.size;

		if (deleted === false) {
			throw new errors.ValidationError("Tried to delete non-existent value from guarded set", {
				value: value,
				set: this._source
			});
		}
	}
};

module.exports = function createGuardedSet(set, guard, _, parent) {
	function generateSetSignatureError() {
		let wantedSignature = {
			_guardedCollectionType: "set",
			_itemType: guard._rule
		};

		return new errors.ValidationError(`Expected a Set or ${getValueType(wantedSignature)}, got ${getValueType(set)} instead`);
	}

	if (set._guardedCollectionType === "set") {
		if (guard === set._itemType) {
			return set;
		} else {
			throw generateSetSignatureError();
		}
	} else if (set instanceof Set) {
		function check(value) {
			let guardResult = guard.call(parent, value);

			if (guardResult === true) {
				return true;
			} else {
				throw guardResult;
			}
		}

		for (let value of set.values()) {
			check(value);
		}

		return Object.assign(Object.create(proto), {
			_source: set,
			_guardedCollectionType: "set",
			_itemType: guard,
			add: function (value) {
				if (check(value) === true) {
					this._source.add(value);
					this.size = this._source.size;
				}
			}
		});
	} else {
		throw generateSetSignatureError();
	}
};