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/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 * 
 *    Copyright (c) [2017] Payara Foundation and/or its affiliates. All rights reserved.
 * 
 *     The contents of this file are subject to the terms of either the GNU
 *     General Public License Version 2 only ("GPL") or the Common Development
 *     and Distribution License("CDDL") (collectively, the "License").  You
 *     may not use this file except in compliance with the License.  You can
 *     obtain a copy of the License at
 *     https://github.com/payara/Payara/blob/master/LICENSE.txt
 *     See the License for the specific
 *     language governing permissions and limitations under the License.
 * 
 *     When distributing the software, include this License Header Notice in each
 *     file and include the License file at glassfish/legal/LICENSE.txt.
 * 
 *     GPL Classpath Exception:
 *     The Payara Foundation designates this particular file as subject to the "Classpath"
 *     exception as provided by the Payara Foundation in the GPL Version 2 section of the License
 *     file that accompanied this code.
 * 
 *     Modifications:
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 *     Version 2] license."  If you don't indicate a single choice of license, a
 *     recipient has the option to distribute your version of this file under
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 */
package fish.payara.microprofile.faulttolerance.state;

import java.util.concurrent.BlockingQueue;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * Class that represents the state of a CircuitBreaker.
 * @author Andrew Pielage
 */
public class CircuitBreakerState {  
        
    private static final Logger logger = Logger.getLogger(CircuitBreakerState.class.getName());
    
    public enum CircuitState {
        OPEN, CLOSED, HALF_OPEN
    }
    
    private final BlockingQueue closedResultsQueue;
    private volatile int halfOpenSuccessfulResultsCounter;
    private volatile CircuitState circuitState = CircuitState.CLOSED;
    
    public CircuitBreakerState(int requestVolumeThreshold) {
        closedResultsQueue = new LinkedBlockingQueue<>(requestVolumeThreshold);
        halfOpenSuccessfulResultsCounter = 0;
    }
    
    /**
     * Gets the current circuit state.
     * @return The current circuit state
     */
    public CircuitState getCircuitState() {
        return circuitState;
    }
    
    /**
     * Sets the CircuitBreaker state to the provided enum value.
     * @param circuitState The state to set the CIrcuitBreaker to.
     */
    public void setCircuitState(CircuitState circuitState) {
        this.circuitState = circuitState;
    }
    
    /**
     * Records a success or failure result to the CircuitBreaker.
     * @param result True for a success, false for a failure
     */
    public void recordClosedResult(Boolean result) {
        // If the queue is full, remove the oldest result and add
        if (!closedResultsQueue.offer(result)) {
            closedResultsQueue.poll();
            closedResultsQueue.offer(result);
        }
    }
    
    /**
     * Clears the results queue.
     */
    public void resetResults() {
        closedResultsQueue.clear();
    }
    
    /**
     * Increments the successful results counter for the half open state.
     */
    public void incrementHalfOpenSuccessfulResultCounter() {
        halfOpenSuccessfulResultsCounter++;
    }
    
    /**
     * Resets the successful results counter for the half open state.
     */
    public void resetHalfOpenSuccessfulResultCounter() {
        halfOpenSuccessfulResultsCounter = 0;
    }
    
    /**
     * Gets the successful results counter for the half open state.
     * @return The number of consecutive successful results.
     */
    public int getHalfOpenSuccessFulResultCounter() {
        return halfOpenSuccessfulResultsCounter;
    }
    
    /**
     * Checks to see if the CircuitBreaker is over the given failure threshold.
     * @param failureThreshold The number of failures before the circuit breaker should open
     * @return True if the CircuitBreaker is over the failure threshold
     */
    public Boolean isOverFailureThreshold(long failureThreshold) {
        Boolean over = false;
        int failures = 0;
        
        // Only check if the queue is full
        if (closedResultsQueue.remainingCapacity() == 0) {
            for (Boolean success : closedResultsQueue) {
                if (!success) {
                    failures++;

                    if (failures == failureThreshold) {
                        over = true;
                        break;
                    }
                }
            }
        } else {
            logger.log(Level.FINE, "CircuitBreaker results queue isn't full yet.");
        }
        
        return over;
    }
}