/**
 * Copyright (C) 2013 Open WhisperSystems
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
package org.whispersystems.textsecuregcm.limits;

import com.codahale.metrics.Meter;
import com.codahale.metrics.MetricRegistry;
import com.codahale.metrics.SharedMetricRegistries;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.whispersystems.textsecuregcm.controllers.RateLimitExceededException;
import org.whispersystems.textsecuregcm.redis.ReplicatedJedisPool;
import org.whispersystems.textsecuregcm.util.Constants;
import org.whispersystems.textsecuregcm.util.SystemMapper;

import java.io.IOException;

import static com.codahale.metrics.MetricRegistry.name;
import redis.clients.jedis.Jedis;

public class RateLimiter {

  private final Logger       logger = LoggerFactory.getLogger(RateLimiter.class);
  private final ObjectMapper mapper = SystemMapper.getMapper();

  private   final Meter               meter;
  protected final ReplicatedJedisPool cacheClient;
  protected final String              name;
  private   final int                 bucketSize;
  private   final double              leakRatePerMillis;
  private   final boolean             reportLimits;

  public RateLimiter(ReplicatedJedisPool cacheClient, String name,
                     int bucketSize, double leakRatePerMinute)
  {
    this(cacheClient, name, bucketSize, leakRatePerMinute, false);
  }

  public RateLimiter(ReplicatedJedisPool cacheClient, String name,
                     int bucketSize, double leakRatePerMinute,
                     boolean reportLimits)
  {
    MetricRegistry metricRegistry = SharedMetricRegistries.getOrCreate(Constants.METRICS_NAME);

    this.meter             = metricRegistry.meter(name(getClass(), name, "exceeded"));
    this.cacheClient       = cacheClient;
    this.name              = name;
    this.bucketSize        = bucketSize;
    this.leakRatePerMillis = leakRatePerMinute / (60.0 * 1000.0);
    this.reportLimits      = reportLimits;
  }

  public void validate(String key, int amount) throws RateLimitExceededException {
    LeakyBucket bucket = getBucket(key);

    if (bucket.add(amount)) {
      setBucket(key, bucket);
    } else {
      meter.mark();
      throw new RateLimitExceededException(key + " , " + amount);
    }
  }

  public void validate(String key) throws RateLimitExceededException {
    validate(key, 1);
  }

  public void clear(String key) {
    try (Jedis jedis = cacheClient.getWriteResource()) {
      jedis.del(getBucketName(key));
    }
  }

  private void setBucket(String key, LeakyBucket bucket) {
    try (Jedis jedis = cacheClient.getWriteResource()) {
      String serialized = bucket.serialize(mapper);
      jedis.setex(getBucketName(key), (int) Math.ceil((bucketSize / leakRatePerMillis) / 1000), serialized);
    } catch (JsonProcessingException e) {
      throw new IllegalArgumentException(e);
    }
  }

  private LeakyBucket getBucket(String key) {
    try (Jedis jedis = cacheClient.getReadResource()) {
      String serialized = jedis.get(getBucketName(key));

      if (serialized != null) {
        return LeakyBucket.fromSerialized(mapper, serialized);
      }
    } catch (IOException e) {
      logger.warn("Deserialization error", e);
    }

    return new LeakyBucket(bucketSize, leakRatePerMillis);
  }

  private String getBucketName(String key) {
    return "leaky_bucket::" + name + "::" + key;
  }
}