var error = require("http-error");

/**
 * In memory rate limiter as connect middleware
 */
module.exports = ratelimit;

function ratelimit(key, duration, max) {
    var counts = {};
    return function(req, res, next) {
        var handle = req.params[key];

        counts[handle] = counts[handle] || 0;
        if (counts[handle] >= max) {
            var err = new error.TooManyRequests("Rate limit exceeded");
            err.retryIn = Math.min(duration, 5000);
            return next(err);
        }
        
        counts[handle]++;
        setTimeout(function () {
            counts[handle]--;
            if (counts[handle] == 0) {
                delete counts[handle];
            }
        }, duration);
        
        return next();
    };
}