// Copyright 2012 Mark Cavage, Inc.  All rights reserved.

'use strict';

var assert = require('assert-plus');
var errors = require('restify-errors');

///--- Globals

var InvalidHeaderError = errors.InvalidHeaderError;
var RequestExpiredError = errors.RequestExpiredError;

var BAD_MSG = 'Date header is invalid';
var OLD_MSG = 'Date header %s is too old';

///--- API

/**
 * Parses out the HTTP Date header (if present) and checks for clock skew.
 * If the header is invalid, a `InvalidHeaderError` (`400`) is returned.
 * If the clock skew exceeds the specified value,
 * a `RequestExpiredError` (`400`) is returned.
 * Where expired means the request originated at a time
 * before (`$now - $clockSkew`).
 * The default clockSkew allowance is 5m (thanks
 * Kerberos!)
 *
 * @public
 * @function dateParser
 * @throws   {RequestExpiredError}
 * @throws   {InvalidHeaderError}
 * @param    {Number}    [clockSkew=300] - allowed clock skew in seconds.
 * @returns  {Function}                    restify handler.
 * @example
 * // Allows clock skew of 1m
 * server.use(restify.plugins.dateParser(60));
 */
function dateParser(clockSkew) {
    var normalizedClockSkew = clockSkew || 300;
    assert.number(normalizedClockSkew, 'normalizedClockSkew');

    normalizedClockSkew = normalizedClockSkew * 1000;

    function parseDate(req, res, next) {
        if (!req.headers.date) {
            return next();
        }

        var e;
        var date = req.headers.date;
        var log = req.log;

        try {
            var now = Date.now();
            var sent = new Date(date).getTime();

            if (log.trace()) {
                log.trace(
                    {
                        allowedSkew: normalizedClockSkew,
                        now: now,
                        sent: sent
                    },
                    'Checking clock skew'
                );
            }

            if (now - sent > normalizedClockSkew) {
                e = new RequestExpiredError(OLD_MSG, date);
                return next(e);
            }
        } catch (err) {
            log.trace(
                {
                    err: err
                },
                'Bad Date header: %s',
                date
            );

            e = new InvalidHeaderError(BAD_MSG, date);
            return next(e);
        }

        return next();
    }

    return parseDate;
}

module.exports = dateParser;