// Copyright (C) 2017 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License"),
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package com.googlesource.gerrit.plugins.ratelimiter;

import com.google.common.annotations.VisibleForTesting;
import com.google.gerrit.exceptions.NoSuchAccountException;
import com.google.inject.Inject;
import com.google.inject.assistedinject.Assisted;
import java.time.LocalTime;
import java.time.format.DateTimeFormatter;
import java.util.Optional;
import java.util.concurrent.TimeUnit;
import org.slf4j.Logger;

class WarningRateLimiter implements RateLimiter {
  @FunctionalInterface
  interface Factory {
    WarningRateLimiter create(RateLimiter delegate, String key, int warnLimit);
  }

  private static final Logger rateLimitLog = RateLimiterStatsLog.getLogger();
  private static final DateTimeFormatter format = DateTimeFormatter.ofPattern("mm 'min' ss 'sec'");

  private final UserResolver userResolver;
  private final RateLimiter delegate;
  private final RateLimitReachedSender.Factory rateLimitReachedSenderFactory;
  private final int warnLimit;
  private final String key;

  private volatile boolean wasLogged;
  private volatile boolean warningWasLogged = false;

  @Inject
  WarningRateLimiter(
      UserResolver userResolver,
      RateLimitReachedSender.Factory rateLimitReachedSenderFactory,
      @Assisted RateLimiter delegate,
      @Assisted String key,
      @Assisted int warnLimit) {
    this.userResolver = userResolver;
    this.delegate = delegate;
    this.rateLimitReachedSenderFactory = rateLimitReachedSenderFactory;
    this.warnLimit = warnLimit;
    this.key = key;
  }

  @Override
  public int permitsPerHour() {
    return delegate.permitsPerHour();
  }

  @Override
  public synchronized boolean acquirePermit() {
    boolean acquirePermit = delegate.acquirePermit();
    if (usedPermits() == warnLimit) {
      String emailMessage =
          String.format(
              "User %s reached the warning limit of %s %s per %s minutes.",
              userResolver.getUserName(key).orElse(key), warnLimit, delegate.getType(), delegate.getTimeLapse());
      rateLimitLog.info(emailMessage);
      warningWasLogged = true;
      sendEmail(key, emailMessage, acquirePermit);
    }

    if (!acquirePermit && !wasLogged) {
      String emailMessage =
          String.format(
              "User %s was blocked due to exceeding the limit of %s %s per %s minutes. %s remaining to permits replenishing.",
              userResolver.getUserName(key).orElse(key),
              permitsPerHour(),
              delegate.getType(),
              delegate.getTimeLapse(),
              secondsToMsSs(remainingTime(TimeUnit.SECONDS)));
      rateLimitLog.info(emailMessage);
      wasLogged = true;
      sendEmail(key, emailMessage, acquirePermit);
    }
    return acquirePermit;
  }

  protected void sendEmail(String key, String emailMessage, boolean acquirePermit) {
    try {
      RateLimitReachedSender sender =
          rateLimitReachedSenderFactory.create(
              userResolver
                  .getIdentifiedUser(key)
                  .orElseThrow(() -> new NoSuchAccountException("User not found")),
              emailMessage,
              acquirePermit);
      sender.send();
    } catch (Exception e) {
      rateLimitLog.error("Error with exception while sending email: " + e);
    }
  }

  @Override
  public int availablePermits() {
    return delegate.availablePermits();
  }

  @Override
  public long remainingTime(TimeUnit timeUnit) {
    return delegate.remainingTime(timeUnit);
  }

  @Override
  public void replenishPermits() {
    warningWasLogged = false;
    delegate.replenishPermits();
  }

  @Override
  public Optional<Integer> getTimeLapse() {
    return delegate.getTimeLapse();
  }

  @Override
  public String getType() {
    return delegate.getType();
  }

  @Override
  public void close() {
    delegate.close();
  }

  @Override
  public int usedPermits() {
    return delegate.usedPermits();
  }

  private String secondsToMsSs(long seconds) {
    return LocalTime.MIN.plusSeconds(seconds).format(format);
  }

  @Override
  public Optional<Integer> getWarnLimit() {
    return Optional.of(warnLimit);
  }

  @VisibleForTesting
  public boolean getWarningFlagState() {
    return warningWasLogged;
  }
}