/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.ratis.retry;

import org.apache.ratis.util.TimeDuration;

import java.util.Arrays;
import java.util.Objects;
import java.util.concurrent.TimeUnit;

/**
 * Policy abstract for retrying.
 */
@FunctionalInterface
public interface RetryPolicy {
  Action NO_RETRY_ACTION = new Action() {
    @Override
    public boolean shouldRetry() {
      return false;
    }
    @Override
    public TimeDuration getSleepTime() {
      return TimeDuration.ZERO;
    }
  };

  Action RETRY_WITHOUT_SLEEP_ACTION = () -> TimeDuration.ZERO;

  /** The action it should take. */
  @FunctionalInterface
  interface Action {
    /** @return true if it has to make another attempt; otherwise, return false. */
    default boolean shouldRetry() {
      return true;
    }

    /** @return the sleep time period before the next attempt. */
    TimeDuration getSleepTime();
  }

  /** The event triggered the failure. */
  @FunctionalInterface
  interface Event {
    /** @return the number of attempts tried so far. */
    int getAttemptCount();

    /** @return the number of attempts for the event cause. */
    default int getCauseCount() {
      return 0;
    }

    default Throwable getCause() {
      return null;
    }
  }

  /**
   * Determines whether it is supposed to retry after the operation has failed.
   *
   * @param event The failed event.
   * @return the action it should take.
   */
  Action handleAttemptFailure(Event event);

  static RetryPolicy parse(String commaSeparated, String name) {
    try {
      return parse(commaSeparated);
    } catch (Exception e) {
      throw new IllegalArgumentException("Failed to parse " + name + ": \"" + commaSeparated + "\"", e);
    }
  }

  static RetryPolicy parse(String commaSeparated) {
    Objects.requireNonNull(commaSeparated, "commaSeparated == null");
    final String[] args = commaSeparated.split(",");
    if (args.length < 1) {
      throw new IllegalArgumentException("Failed to parse RetryPolicy: empty comma separated string");
    }
    final String classname = args[0].trim();
    if (classname.equals(ExponentialBackoffRetry.class.getSimpleName())) {
      if (args.length != 4) {
        throw new IllegalArgumentException("Failed to parse ExponentialBackoffRetry: args.length = "
            + args.length + " != 4 for " + commaSeparated);
      }
      return ExponentialBackoffRetry.newBuilder()
          .setBaseSleepTime(TimeDuration.valueOf(args[1], TimeUnit.MILLISECONDS))
          .setMaxSleepTime(TimeDuration.valueOf(args[2], TimeUnit.MILLISECONDS))
          .setMaxAttempts(Integer.parseInt(args[3].trim()))
          .build();
    }
    if (classname.equals(MultipleLinearRandomRetry.class.getSimpleName())) {
      if (args.length == 1) {
        throw new IllegalArgumentException(
            "Failed to parse MultipleLinearRandomRetry: the parameter list is empty for " + commaSeparated);
      }
      final String params = String.join(",", Arrays.copyOfRange(args, 1, args.length));
      return MultipleLinearRandomRetry.parseCommaSeparated(params);
    }
    // Backward compatibility: legacy config omits class name and starts with a duration (e.g. "1ms").
    if (isLegacyMultipleLinearRandomRetryParams(classname)) {
      return MultipleLinearRandomRetry.parseCommaSeparated(commaSeparated);
    }
    // If a class name is present but unknown, fail fast to surface config errors.
    throw new IllegalArgumentException("Failed to parse RetryPolicy: unknown class "
        + classname + " for " + commaSeparated);
  }

  static boolean isLegacyMultipleLinearRandomRetryParams(String firstElement) {
    // The legacy format starts with a duration token, not a class name.
    try {
      final TimeDuration t = TimeDuration.valueOf(firstElement, TimeUnit.MILLISECONDS);
      return t.isPositive();
    } catch (RuntimeException e) {
      return false;
    }
  }
}
