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/*
 * Copyright 2019-2024 the original author or authors.
 *
 * 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
 *
 *     https://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 de.codecentric.spring.boot.chaos.monkey.component;

import de.codecentric.spring.boot.chaos.monkey.assaults.ChaosMonkeyRuntimeAssault;
import de.codecentric.spring.boot.chaos.monkey.configuration.AssaultProperties;
import java.util.*;
import java.util.function.Function;
import java.util.stream.Collectors;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.scheduling.config.CronTask;
import org.springframework.scheduling.config.ScheduledTask;
import org.springframework.scheduling.config.ScheduledTaskRegistrar;

public class ChaosMonkeyScheduler {

    private static final Logger Logger = LoggerFactory.getLogger(ChaosMonkeyScheduler.class);

    private final ScheduledTaskRegistrar scheduler;

    private final AssaultProperties config;
    private final List assaults;

    private final Map currentTasks = new HashMap<>();

    public ChaosMonkeyScheduler(ScheduledTaskRegistrar scheduler, AssaultProperties config, List assaults) {
        this.scheduler = scheduler;
        this.config = config;
        this.assaults = assaults;

        reloadConfig();
    }

    public void reloadConfig() {
        var cronExpressions = getCronExpressions();
        if (!currentTasks.isEmpty()) {
            removeUnchangedExpressions(cronExpressions);
            cancelOldTasks(cronExpressions);
        }

        scheduleNewTasks(cronExpressions);
    }

    private Map getCronExpressions() {
        return assaults.stream().collect(Collectors.toMap(Function.identity(), assault -> assault.getCronExpression(config)));
    }

    private void removeUnchangedExpressions(Map cronExpressions) {
        cronExpressions.entrySet().removeIf(entry -> {
            ScheduledTask task = currentTasks.get(entry.getKey());
            return task != null && task.getTask() instanceof CronTask
                    && Objects.equals(((CronTask) task.getTask()).getExpression(), entry.getValue());
        });
    }

    private void cancelOldTasks(Map cronExpressions) {
        cronExpressions.forEach((assault, expression) -> {
            ScheduledTask task = currentTasks.remove(assault);
            if (task != null)
                task.cancel();
        });
    }

    private void scheduleNewTasks(Map cronExpressions) {
        Logger.info("Schedule {} cron task(s)", cronExpressions.size());
        cronExpressions.forEach((assault, expression) -> {
            if (expression != null && !"OFF".equals(expression))
                scheduleRuntimeAssault(scheduler, assault, expression);
        });
    }

    private void scheduleRuntimeAssault(ScheduledTaskRegistrar scheduler, ChaosMonkeyRuntimeAssault assault, String cron) {
        final CronTask cronTask = new CronTask(() -> {
            if (assault.isActive())
                assault.attack();
        }, cron);

        final ScheduledTask scheduledTask = scheduler.scheduleCronTask(cronTask);
        currentTasks.put(assault, scheduledTask);
    }
}