/*
 * nimbus-jose-jwt
 *
 * Copyright 2012-2016, Connect2id Ltd and contributors.
 *
 * 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.nimbusds.jose.jwk.source;


import java.util.Date;
import java.util.concurrent.TimeUnit;

import com.nimbusds.jose.jwk.JWKSet;


/**
 * JSON Web Key (JWK) set cache implementation.
 *
 * @author Vladimir Dzhuvinov
 * @author Sarvesh Sharma
 * @version 2020-03-11
 */
public class DefaultJWKSetCache implements JWKSetCache {
        
        
        /**
         * The default lifespan for cached JWK sets (15 minutes).
         */
        public static final long DEFAULT_LIFESPAN_MINUTES = 15;


        /**
         * The default refresh time for cached JWK sets (5 minutes).
         */
        public static final long DEFAULT_REFRESH_TIME_MINUTES = 5;

        
        /**
         * The lifespan of the cached JWK set, in {@link #timeUnit}s, negative
         * means no expiration.
         */
        private final long lifespan;


        /**
         * The refresh time of the cached JWK set, in {@link #timeUnit}s,
         * negative means no refresh time.
         */
        private final long refreshTime;

        
        /**
         * The time unit, may be {@code null} if no expiration / refresh time.
         */
        private final TimeUnit timeUnit;
        
        
        /**
         * The cache put timestamp, negative if not specified.
         */
        private long putTimestamp = -1;
        
        
        /**
         * Creates a new JWK set, the default lifespan of the cached JWK set is
         * set to 15 minutes, the refresh time to 5 minutes.
         */
        public DefaultJWKSetCache() {
                
                this(DEFAULT_LIFESPAN_MINUTES, DEFAULT_REFRESH_TIME_MINUTES, TimeUnit.MINUTES);
        }
        
        
        /**
         * Creates a new JWK set cache.
         *
         * @param lifespan    The lifespan of the cached JWK set before it
         *                    expires, negative means no expiration.
         * @param refreshTime The time after which the cached JWK set is marked
         *                    for refresh, negative if not specified. Should be
         *                    shorter or equal to the lifespan.
         * @param timeUnit    The lifespan time unit, may be {@code null} if no
         *                    expiration or refresh time.
         */
        public DefaultJWKSetCache(final long lifespan, final long refreshTime, final TimeUnit timeUnit) {
                
                this.lifespan = lifespan;
                this.refreshTime = refreshTime;

                if ((lifespan > -1 || refreshTime > -1) && timeUnit == null) {
                        throw new IllegalArgumentException("A time unit must be specified for non-negative lifespans or refresh times");
                }
                
                this.timeUnit = timeUnit;
        }
        
        
        /**
         * The cached JWK set, {@code null} if none.
         */
        private JWKSet jwkSet;
        
        
        @Override
        public void put(final JWKSet jwkSet) {
                
                this.jwkSet = jwkSet;
                
                if (jwkSet != null) {
                        putTimestamp = new Date().getTime();
                } else {
                        // cache cleared
                        putTimestamp = -1;
                }
        }
        
        
        @Override
        public JWKSet get() {
                
                if (isExpired()) {
                        jwkSet = null; // clear
                }
                
                return jwkSet;
        }


        @Override
        public boolean requiresRefresh() {

                return putTimestamp > -1 &&
                        refreshTime > -1 &&
                        new Date().getTime() > putTimestamp + TimeUnit.MILLISECONDS.convert(refreshTime, timeUnit);
        }

        
        /**
         * Returns the cache put timestamp.
         *
         * @return The cache put timestamp, negative if not specified.
         */
        public long getPutTimestamp() {
                
                return putTimestamp;
        }
        
        
        /**
         * Returns {@code true} if the cached JWK set is expired.
         *
         * @return {@code true} if expired.
         */
        public boolean isExpired() {
        
                return putTimestamp > -1 &&
                        lifespan > -1 &&
                        new Date().getTime() > putTimestamp + TimeUnit.MILLISECONDS.convert(lifespan, timeUnit);
        }
        
        
        /**
         * Returns the configured lifespan of the cached JWK.
         *
         * @param timeUnit The time unit to use.
         *
         * @return The configured lifespan, negative means no expiration.
         */
        public long getLifespan(final TimeUnit timeUnit) {
                
                if (lifespan < 0) {
                        return lifespan;
                }
                
                return timeUnit.convert(lifespan, timeUnit);
        }


        /**
         * Returns the configured refresh time of the cached JWK.
         *
         * @param timeUnit The time unit to use.
         *
         * @return The configured refresh time, negative means no expiration.
         */
        public long getRefreshTime(final TimeUnit timeUnit) {

                if (refreshTime < 0) {
                        return refreshTime;
                }

                return timeUnit.convert(refreshTime, timeUnit);
        }
}