/*
 * decaffeinate suggestions:
 * DS101: Remove unnecessary use of Array.from
 * DS102: Remove unnecessary code created because of implicit returns
 * DS207: Consider shorter variations of null checks
 * Full docs: https://github.com/decaffeinate/decaffeinate/blob/master/docs/suggestions.md
 */
let LockManager;
const logger = require("logger-sharelatex");

const LockState = {}; // locks for docker container operations, by container name

module.exports = (LockManager = {

	MAX_LOCK_HOLD_TIME: 15000,  // how long we can keep a lock
	MAX_LOCK_WAIT_TIME: 10000,  // how long we wait for a lock
	LOCK_TEST_INTERVAL: 1000,   // retry time

	tryLock(key, callback) {
		let lockValue;
		if (callback == null) { callback = function(err, gotLock) {}; }
		const existingLock = LockState[key];
		if (existingLock != null) { // the lock is already taken, check how old it is
			const lockAge = Date.now() - existingLock.created;
			if (lockAge < LockManager.MAX_LOCK_HOLD_TIME) {
				return callback(null, false); // we didn't get the lock, bail out
			} else {
				logger.error({key, lock: existingLock, age:lockAge}, "taking old lock by force");
			}
		}
		// take the lock
		LockState[key] = (lockValue = {created: Date.now()});
		return callback(null, true, lockValue);
	},

	getLock(key, callback) {
		let attempt;
		if (callback == null) { callback = function(error, lockValue) {}; }
		const startTime = Date.now();
		return (attempt = () =>
			LockManager.tryLock(key, function(error, gotLock, lockValue) {
				if (error != null) { return callback(error); }
				if (gotLock) {
					return callback(null, lockValue);
				} else if ((Date.now() - startTime) > LockManager.MAX_LOCK_WAIT_TIME) {
					const e = new Error("Lock timeout");
					e.key = key;
					return callback(e);
				} else {
					return setTimeout(attempt, LockManager.LOCK_TEST_INTERVAL);
				}
			})
		)();
	},

	releaseLock(key, lockValue, callback) {
		if (callback == null) { callback = function(error) {}; }
		const existingLock = LockState[key];
		if (existingLock === lockValue) { // lockValue is an object, so we can test by reference
			delete LockState[key]; // our lock, so we can free it
			return callback();
		} else if (existingLock != null) { // lock exists but doesn't match ours
			logger.error({key, lock: existingLock}, "tried to release lock taken by force");
			return callback();
		} else {
			logger.error({key, lock: existingLock}, "tried to release lock that has gone");
			return callback();
		}
	},

	runWithLock(key, runner, callback) {
		if (callback == null) { callback = function(error) {}; }
		return LockManager.getLock(key, function(error, lockValue) {
			if (error != null) { return callback(error); }
			return runner((error1, ...args) =>
				LockManager.releaseLock(key, lockValue, function(error2) {
					error = error1 || error2;
					if (error != null) { return callback(error); }
					return callback(null, ...Array.from(args));
				})
			);
		});
	}
});