/*
 * ============LICENSE_START=======================================================
 * feature-healthcheck
 * ================================================================================
 * Copyright (C) 2017-2018 AT&T Intellectual Property. All rights reserved.
 * ================================================================================
 * 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.
 * ============LICENSE_END=========================================================
 */

package org.onap.policy.drools.healthcheck;

import java.util.ArrayList;
import java.util.List;
import java.util.Properties;

import javax.ws.rs.core.Response;

import org.onap.policy.common.capabilities.Startable;
import org.onap.policy.common.endpoints.http.client.HttpClient;
import org.onap.policy.common.endpoints.http.client.HttpClientFactory;
import org.onap.policy.common.endpoints.http.server.HttpServletServer;
import org.onap.policy.common.endpoints.http.server.HttpServletServerFactory;
import org.onap.policy.drools.persistence.SystemPersistence;
import org.onap.policy.drools.system.PolicyEngine;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Healthcheck.
 */
public interface HealthCheck extends Startable {

    /**
     * Healthcheck Monitor.
     */
    public static final HealthCheck monitor = new HealthCheckMonitor();

    /**
     * Healthcheck Report.
     */
    public static class Report {
        /**
         * Named Entity in the report.
         */
        private String name;

        /**
         * URL queried.
         */
        private String url;

        /**
         * healthy.
         */
        private boolean healthy;

        /**
         * return code.
         */
        private int code;

        /**
         * Message from remote entity.
         */
        private String message;

        @Override
        public String toString() {
            StringBuilder builder = new StringBuilder();
            builder.append("Report [name=");
            builder.append(getName());
            builder.append(", url=");
            builder.append(getUrl());
            builder.append(", healthy=");
            builder.append(isHealthy());
            builder.append(", code=");
            builder.append(getCode());
            builder.append(", message=");
            builder.append(getMessage());
            builder.append("]");
            return builder.toString();
        }

        public String getName() {
            return name;
        }

        public void setName(String name) {
            this.name = name;
        }

        public String getUrl() {
            return url;
        }

        public void setUrl(String url) {
            this.url = url;
        }

        public boolean isHealthy() {
            return healthy;
        }

        public void setHealthy(boolean healthy) {
            this.healthy = healthy;
        }

        public int getCode() {
            return code;
        }

        public void setCode(int code) {
            this.code = code;
        }

        public String getMessage() {
            return message;
        }

        public void setMessage(String message) {
            this.message = message;
        }
    }

    /**
     * Report aggregation.
     */
    public static class Reports {
        private boolean healthy;
        private List<Report> details = new ArrayList<>();

        @Override
        public String toString() {
            StringBuilder builder = new StringBuilder();
            builder.append("Reports [healthy=");
            builder.append(isHealthy());
            builder.append(", details=");
            builder.append(getDetails());
            builder.append("]");
            return builder.toString();
        }

        public boolean isHealthy() {
            return healthy;
        }

        public void setHealthy(boolean healthy) {
            this.healthy = healthy;
        }

        public List<Report> getDetails() {
            return details;
        }

        public void setDetails(List<Report> details) {
            this.details = details;
        }
    }

    /**
     * Perform a healthcheck.
     *
     * @return a report
     */
    public Reports healthCheck();
}


/**
 * Healthcheck Monitor.
 */
class HealthCheckMonitor implements HealthCheck {

    /**
     * Logger.
     */
    private static Logger logger = LoggerFactory.getLogger(HealthCheckMonitor.class);

    /**
     * Attached http servers.
     */
    protected volatile List<HttpServletServer> servers = new ArrayList<>();

    /**
     * Attached http clients.
     */
    protected volatile List<HttpClient> clients = new ArrayList<>();

    /**
     * Healthcheck configuration.
     */
    protected volatile Properties healthCheckProperties = null;

    /**
     * {@inheritDoc}.
     */
    @Override
    public Reports healthCheck() {
        Reports reports = new Reports();
        boolean thisEngineIsAlive = getEngineManager().isAlive();
        reports.setHealthy(thisEngineIsAlive);

        HealthCheck.Report engineReport = new Report();
        engineReport.setHealthy(thisEngineIsAlive);
        engineReport.setName("PDP-D");
        engineReport.setUrl("self");
        engineReport.setCode(thisEngineIsAlive ? 200 : 500);
        engineReport.setMessage(thisEngineIsAlive ? "alive" : "not alive");
        reports.getDetails().add(engineReport);

        for (HttpClient client : clients) {
            HealthCheck.Report report = new Report();
            report.setName(client.getName());
            report.setUrl(client.getBaseUrl());
            report.setHealthy(true);
            try {
                Response response = client.get();
                report.setCode(response.getStatus());
                if (report.getCode() != 200) {
                    report.setHealthy(false);
                    reports.setHealthy(false);
                }

                report.setMessage(getHttpBody(response, client));
            } catch (Exception e) {
                logger.warn("{}: cannot contact http-client {}", this, client, e);

                report.setHealthy(false);
                reports.setHealthy(false);
            }
            reports.getDetails().add(report);
        }
        return reports;
    }

    /**
     * {@inheritDoc}.
     */
    @Override
    public boolean start() {

        try {
            this.healthCheckProperties = getPersistentProperties(HealthCheckFeature.CONFIGURATION_PROPERTIES_NAME);
            this.servers = getServerFactory().build(healthCheckProperties);
            this.clients = getClientFactory().build(healthCheckProperties);

            for (HttpServletServer server : servers) {
                startServer(server);
            }
        } catch (Exception e) {
            logger.warn("{}: cannot start {}", this, e);
            return false;
        }

        return true;
    }

    /**
     * {@inheritDoc}.
     */
    @Override
    public boolean stop() {

        for (HttpServletServer server : servers) {
            try {
                server.stop();
            } catch (Exception e) {
                logger.warn("{}: cannot stop http-server {}", this, server, e);
            }
        }

        for (HttpClient client : clients) {
            try {
                client.stop();
            } catch (Exception e) {
                logger.warn("{}: cannot stop http-client {}", this, client, e);
            }
        }

        return true;
    }

    /**
     * {@inheritDoc}.
     */
    @Override
    public void shutdown() {
        this.stop();
    }

    /**
     * {@inheritDoc}.
     */
    @Override
    public synchronized boolean isAlive() {
        return this.healthCheckProperties != null;
    }

    /**
     * Get servers.
     *
     * @return list of attached Http Servers
     */
    public List<HttpServletServer> getServers() {
        return this.servers;
    }

    /**
     * Get clients.
     *
     * @return list of attached Http Clients
     */
    public List<HttpClient> getClients() {
        return this.clients;
    }

    public String getHttpBody(Response response, HttpClient client) {

        String body = null;
        try {
            body = HttpClient.getBody(response, String.class);
        } catch (Exception e) {
            logger.info("{}: cannot get body from http-client {}", this, client, e);
        }

        return body;
    }

    public void startServer(HttpServletServer server) {
        try {
            server.start();
        } catch (Exception e) {
            logger.warn("{}: cannot start http-server {}", this, server, e);
        }
    }

    @Override
    public String toString() {
        StringBuilder builder = new StringBuilder();
        builder.append("HealthCheckMonitor [servers=");
        builder.append(servers);
        builder.append(", clients=");
        builder.append(clients);
        builder.append("]");
        return builder.toString();
    }

    // the following methods may be overridden by junit tests

    protected PolicyEngine getEngineManager() {
        return PolicyEngine.manager;
    }

    protected HttpServletServerFactory getServerFactory() {
        return HttpServletServer.factory;
    }

    protected HttpClientFactory getClientFactory() {
        return HttpClient.factory;
    }

    protected Properties getPersistentProperties(String propertyName) {
        return SystemPersistence.manager.getProperties(propertyName);
    }
}