/*

 * nghttp2 - HTTP/2 C Library

 *

 * Copyright (c) 2023 nghttp2 contributors

 *

 * Permission is hereby granted, free of charge, to any person obtaining

 * a copy of this software and associated documentation files (the

 * "Software"), to deal in the Software without restriction, including

 * without limitation the rights to use, copy, modify, merge, publish,

 * distribute, sublicense, and/or sell copies of the Software, and to

 * permit persons to whom the Software is furnished to do so, subject to

 * the following conditions:

 *

 * The above copyright notice and this permission notice shall be

 * included in all copies or substantial portions of the Software.

 *

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,

 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF

 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND

 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE

 * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION

 * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION

 * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

 */

#include "nghttp2_ratelim.h"

#include "nghttp2_helper.h"

void nghttp2_ratelim_init(nghttp2_ratelim *rl, uint64_t burst, uint64_t rate) {

  *rl = (nghttp2_ratelim){

    .burst = burst,

    .rate = rate,

    .val = burst,

  };

}

void nghttp2_ratelim_update(nghttp2_ratelim *rl, uint64_t tstamp) {

  uint64_t d, gain;

  if (tstamp == rl->tstamp) {

    return;

  }

  if (tstamp > rl->tstamp) {

    d = tstamp - rl->tstamp;

  } else {

    d = 1;

  }

  rl->tstamp = tstamp;

  if (UINT64_MAX / d < rl->rate) {

    rl->val = rl->burst;

    return;

  }

  gain = rl->rate * d;

  if (UINT64_MAX - gain < rl->val) {

    rl->val = rl->burst;

    return;

  }

  rl->val += gain;

  rl->val = nghttp2_min_uint64(rl->val, rl->burst);

}

int nghttp2_ratelim_drain(nghttp2_ratelim *rl, uint64_t n) {

  if (rl->val < n) {

    return -1;

  }

  rl->val -= n;

  return 0;

}