/*
    * Licensed to The Apereo Foundation under one or more contributor license
    * agreements. See the NOTICE file distributed with this work for additional
    * information regarding copyright ownership.
    *
    *
    * The Apereo Foundation licenses this file to you under the Educational
    * Community 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://opensource.org/licenses/ecl2.txt
   *
   * 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.opencastproject.capture.admin.impl;
  
  import static org.apache.commons.lang3.StringUtils.isBlank;
  import static org.opencastproject.capture.admin.api.AgentState.KNOWN_STATES;
  import static org.opencastproject.capture.admin.api.AgentState.UNKNOWN;
  import static org.opencastproject.db.Queries.namedQuery;
  import static org.opencastproject.util.OsgiUtil.getOptContextProperty;
  
  import org.opencastproject.capture.admin.api.Agent;
  import org.opencastproject.capture.admin.api.AgentState;
  import org.opencastproject.capture.admin.api.CaptureAgentStateService;
  import org.opencastproject.db.DBSession;
  import org.opencastproject.db.DBSessionFactory;
  import org.opencastproject.security.api.Organization;
  import org.opencastproject.security.api.Role;
  import org.opencastproject.security.api.SecurityConstants;
  import org.opencastproject.security.api.SecurityService;
  import org.opencastproject.security.api.User;
  import org.opencastproject.util.NotFoundException;
  import org.opencastproject.util.data.Tuple3;
  import org.opencastproject.util.function.ThrowingFunction;
  
  import com.google.common.cache.CacheBuilder;
  import com.google.common.cache.CacheLoader;
  import com.google.common.cache.LoadingCache;
  import com.google.common.cache.RemovalCause;
  import com.google.common.cache.RemovalListener;
  import com.google.common.cache.RemovalNotification;
  
  import org.apache.commons.lang3.StringUtils;
  import org.apache.commons.lang3.tuple.Pair;
  import org.osgi.service.cm.ConfigurationException;
  import org.osgi.service.cm.ManagedServiceFactory;
  import org.osgi.service.component.ComponentContext;
  import org.osgi.service.component.annotations.Activate;
  import org.osgi.service.component.annotations.Component;
  import org.osgi.service.component.annotations.Deactivate;
  import org.osgi.service.component.annotations.Reference;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.util.Arrays;
  import java.util.Dictionary;
  import java.util.Iterator;
  import java.util.LinkedHashSet;
  import java.util.List;
  import java.util.Map;
  import java.util.Optional;
  import java.util.Properties;
  import java.util.Set;
  import java.util.TreeMap;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.TimeUnit;
  
  import javax.persistence.EntityManager;
  import javax.persistence.EntityManagerFactory;
  import javax.persistence.NoResultException;
  import javax.persistence.RollbackException;
  import javax.persistence.TypedQuery;
  
  /**
   * IMPL for the capture-admin service (MH-1336, MH-1394, MH-1457, MH-1475 and MH-1476).
   */
  @Component(
    property = {
      "service.description=Capture-Admin Service",
      "service.pid=org.opencastproject.capture.agent"
    },
    immediate = true,
    service = { CaptureAgentStateService.class , ManagedServiceFactory.class }
  )
  public class CaptureAgentStateServiceImpl implements CaptureAgentStateService, ManagedServiceFactory {
  
    private static final Logger logger = LoggerFactory.getLogger(CaptureAgentStateServiceImpl.class);
  
    /** The name of the persistence unit for this class */
    public static final String PERSISTENCE_UNIT = "org.opencastproject.capture.admin.impl.CaptureAgentStateServiceImpl";
  
   /** The delimiter for the CA configuration cache */
   private static final String DELIMITER = ";==;";
 
   /** The factory used to generate the entity manager */
   protected EntityManagerFactory emf = null;
 
   protected DBSessionFactory dbSessionFactory;
 
   protected DBSession db;
 
   /** The security service */
   protected SecurityService securityService;
 
   /** Maps the configuration PID to the agent ID, so agents can be updated via the configuration factory pattern */
   protected Map<String, String> pidMap = new ConcurrentHashMap<>();
 
   /** A cache of CA properties, which lightens the load on the SQL server */
   private LoadingCache<String, Object> agentCache = null;
 
   /** Configuration key for capture agent timeout in minutes before being marked offline */
   public static final String CAPTURE_AGENT_TIMEOUT_KEY = "org.opencastproject.capture.admin.timeout";
 
   /** A token to store in the miss cache */
   protected Object nullToken = new Object();
 
   /** OSGi DI */
   @Reference(target = "(osgi.unit.name=org.opencastproject.capture.admin.impl.CaptureAgentStateServiceImpl)")
   void setEntityManagerFactory(EntityManagerFactory emf) {
     this.emf = emf;
   }
 
   @Reference
   public void setDBSessionFactory(DBSessionFactory dbSessionFactory) {
     this.dbSessionFactory = dbSessionFactory;
   }
 
   /**
    * @param securityService
    *          the securityService to set
    */
   @Reference
   public void setSecurityService(SecurityService securityService) {
     this.securityService = securityService;
   }
 
   public CaptureAgentStateServiceImpl() {
     logger.info("CaptureAgentStateServiceImpl starting.");
   }
 
   @Activate
   public void activate(ComponentContext cc) {
     db = dbSessionFactory.createSession(emf);
 
     // Set up the agent cache
     int timeoutInMinutes = 120;
 
     Optional<String> timeout = getOptContextProperty(cc, CAPTURE_AGENT_TIMEOUT_KEY);
 
     if (timeout.isPresent()) {
       try {
         timeoutInMinutes = Integer.parseInt(timeout.get());
       } catch (NumberFormatException e) {
         logger.warn("Invalid configuration for capture agent status timeout (minutes) ({}={})",
                 CAPTURE_AGENT_TIMEOUT_KEY, timeout.get());
       }
     }
 
     setupAgentCache(timeoutInMinutes, TimeUnit.MINUTES);
     logger.info("Capture agent status timeout is {} minutes", timeoutInMinutes);
   }
 
   @Deactivate
   public void deactivate() {
     agentCache.invalidateAll();
     db.close();
   }
 
   /**
    * {@inheritDoc}
    *
    * @see org.opencastproject.capture.admin.api.CaptureAgentStateService#getAgent(java.lang.String)
    */
   @Override
   public Agent getAgent(String name) throws NotFoundException {
     String org = securityService.getOrganization().getId();
     Agent agent = getAgent(name, org);
     return updateCachedLastHeardFrom(agent, org);
   }
 
   /**
    * Gets an agent by name and organization.
    *
    * @param name
    *          the unique agent name
    * @param org
    *          the organization identifier
    * @return the agent
    */
   protected AgentImpl getAgent(String name, String org) throws NotFoundException {
     return db.execChecked(getAgentEntityQuery(name, org));
   }
 
   /**
    * Gets an agent by name and organization, using an open entitymanager.
    *
    * @param name
    *          the unique agent name
    * @param organization
    *          the organization
    * @return the agent or <code>null</code> if no agent has been found
    */
   protected ThrowingFunction<EntityManager, AgentImpl, NotFoundException> getAgentEntityQuery(String name, String organization) {
     return em -> {
       try {
         TypedQuery<AgentImpl> q = em.createNamedQuery("Agent.get", AgentImpl.class);
         q.setParameter("id", name);
         q.setParameter("org", organization);
         return q.getSingleResult();
       } catch (NoResultException e) {
         throw new NotFoundException(e);
       }
     };
   }
 
   /**
    * Mix in the last-seen timestamp from the agent cache
    *
    * @param agent
    *          The Agent you wish to update
    * @param org
    *          the organization
    * @return the agent
    */
   protected Agent updateCachedLastHeardFrom(Agent agent, String org) {
     String agentKey = agent.getName().concat(DELIMITER).concat(org);
     Tuple3<String, Properties, Long> cachedAgent = (Tuple3) agentCache.getUnchecked(agentKey);
     if (cachedAgent != null) {
       agent.setLastHeardFrom(cachedAgent.getC());
     }
     return agent;
   }
 
   /**
    * {@inheritDoc}
    *
    * @see org.opencastproject.capture.admin.api.CaptureAgentStateService#getAgentState(java.lang.String)
    */
   @Override
   public String getAgentState(String agentName) throws NotFoundException {
     String orgId = securityService.getOrganization().getId();
     Tuple3<String, Properties, Long> agent = getAgentFromCache(agentName, orgId);
     return agent.getA();
   }
 
   /**
    * {@inheritDoc}
    *
    * @see org.opencastproject.capture.admin.api.CaptureAgentStateService#setAgentState(java.lang.String,
    *      java.lang.String)
    */
   @Override
   public boolean setAgentState(String agentName, String state) {
     if (StringUtils.isBlank(agentName))
       throw new IllegalArgumentException("Unable to set agent state, agent name is blank or null.");
     if (StringUtils.isBlank(state))
       throw new IllegalArgumentException("Unable to set agent state, state is blank or null.");
     if (!KNOWN_STATES.contains(state))
       throw new IllegalArgumentException("Can not set agent to an invalid state: ".concat(state));
 
     logger.debug("Agent '{}' state set to '{}'", agentName, state);
     AgentImpl agent;
     String orgId = securityService.getOrganization().getId();
     try {
       //Check the return code, if it's false then we don't need to update the DB, and we should also return false
       if (!updateAgentInCache(agentName, state, orgId)) {
         return false;
       }
 
       agent = (AgentImpl) getAgent(agentName);
 
       // the agent is known, so set the state
       logger.debug("Setting Agent {} to state {}.", agentName, state);
       agent.setState(state);
       if (!AgentState.UNKNOWN.equals(state)) {
         agent.setLastHeardFrom(System.currentTimeMillis());
       }
     } catch (NotFoundException e) {
       // If the agent doesn't exists, but the name is not null nor empty, create a new one.
       logger.debug("Creating Agent {} with state {}.", agentName, state);
       agent = new AgentImpl(agentName, orgId, state, "", new Properties());
     }
     updateAgentInDatabase(agent);
     return true;
   }
 
   /**
    * Updates the agent cache, and tells you whether you need to update the database as well
    *
    * @param agentName
    *             The name of the agent in thecache
    * @param state
    *             The new state for the agent
    * @param orgId
    *             The organization the agent is a part of
    * @return
    *             True if the agent state database needs to be updated, false otherwise
    */
   private boolean updateAgentInCache(String agentName, String state, String orgId) {
     return updateAgentInCache(agentName, state, orgId, null);
   }
 
   /**
    * Updates the agent cache, and tells you whether you need to update the database as well
    *
    * @param agentName
    *             The name of the agent in thecache
    * @param state
    *             The new state for the agent
    * @param orgId
    *             The organization the agent is a part of
    * @param configuration
    *             The agent's configuration
    * @return
    *             True if the agent state database needs to be updated, false otherwise
    */
   private boolean updateAgentInCache(String agentName, String state, String orgId, Properties configuration) {
     try {
       String agentState = getAgentFromCache(agentName, orgId).getA();
       Properties config = getAgentConfiguration(agentName);
       if (configuration != null) {
         config = configuration;
       }
       if (!AgentState.UNKNOWN.equals(state)) {
         agentCache.put(agentName.concat(DELIMITER).concat(orgId),
             Tuple3.tuple3(state, config, Long.valueOf(System.currentTimeMillis())));
       } else {
         //If we're putting the agent into an unknown state we're assuming that we didn't get a check in
         // therefore we don't update the timestamp and persist to the DB
         agentCache.put(agentName.concat(DELIMITER).concat(orgId),
             Tuple3.tuple3(state, config, getAgentFromCache(agentName, orgId).getC()));
       }
       if (agentState.equals(state)) {
         return false;
       }
       return true;
     } catch (NotFoundException e) {
       agentCache.put(agentName.concat(DELIMITER).concat(orgId),
               Tuple3.tuple3(state, configuration, Long.valueOf(System.currentTimeMillis())));
       return true;
     }
   }
 
   /**
    * {@inheritDoc}
    *
    * @see org.opencastproject.capture.admin.api.CaptureAgentStateService#setAgentUrl(String, String)
    */
   @Override
   public boolean setAgentUrl(String agentName, String agentUrl) throws NotFoundException {
     Agent agent = getAgent(agentName);
     if (agent.getUrl().equals(agentUrl))
       return false;
     agent.setUrl(agentUrl);
     updateAgentInDatabase((AgentImpl) agent);
     return true;
   }
 
   /**
    * {@inheritDoc}
    *
    * @see org.opencastproject.capture.admin.api.CaptureAgentStateService#removeAgent(java.lang.String)
    */
   @Override
   public void removeAgent(String agentName) throws NotFoundException {
     deleteAgentFromDatabase(agentName);
   }
 
   /**
    * {@inheritDoc}
    *
    * @see org.opencastproject.capture.admin.api.CaptureAgentStateService#getKnownAgents()
    */
   @Override
   public Map<String, Agent> getKnownAgents() {
     agentCache.cleanUp();
     User user = securityService.getUser();
     Organization org = securityService.getOrganization();
 
     String orgAdmin = org.getAdminRole();
     Set<Role> roles = user.getRoles();
 
     List<AgentImpl> agents = db.exec(namedQuery.findAll(
         "Agent.byOrganization",
         AgentImpl.class,
         Pair.of("org", securityService.getOrganization().getId())
     ));
 
     // Filter the results in memory if this user is not an administrator
     if (!user.hasRole(SecurityConstants.GLOBAL_ADMIN_ROLE) && !user.hasRole(orgAdmin)) {
       for (Iterator<AgentImpl> iter = agents.iterator(); iter.hasNext();) {
         AgentImpl agent = iter.next();
         Set<String> schedulerRoles = agent.getSchedulerRoles();
         // If there are no roles associated with this capture agent, it is available to anyone who can pass the
         // coarse-grained web layer security
         if (schedulerRoles == null || schedulerRoles.isEmpty()) {
           continue;
         }
         boolean hasSchedulerRole = false;
         for (Role role : roles) {
           if (schedulerRoles.contains(role.getName())) {
             hasSchedulerRole = true;
             break;
           }
         }
         if (!hasSchedulerRole) {
           iter.remove();
         }
       }
     }
 
     // Build the map that the API defines as agent name->agent
     Map<String, Agent> map = new TreeMap<>();
     for (AgentImpl agent : agents) {
       map.put(agent.getName(), updateCachedLastHeardFrom(agent, org.getId()));
     }
     return map;
   }
 
   /**
    * {@inheritDoc}
    *
    * @see org.opencastproject.capture.admin.api.CaptureAgentStateService#getAgentCapabilities(java.lang.String)
    */
   @Override
   public Properties getAgentCapabilities(String agentName) throws NotFoundException {
     return getAgent(agentName).getCapabilities();
   }
 
   /**
    * {@inheritDoc}
    *
    * @see org.opencastproject.capture.admin.api.CaptureAgentStateService#getAgentConfiguration(java.lang.String)
    */
   @Override
   public Properties getAgentConfiguration(String agentName) throws NotFoundException {
     String orgId = securityService.getOrganization().getId();
     Tuple3<String, Properties, Long> agent = getAgentFromCache(agentName, orgId);
     return agent.getB();
   }
 
   @SuppressWarnings("unchecked")
   private Tuple3<String, Properties, Long> getAgentFromCache(String agentName, String orgId) throws NotFoundException {
     Object agent = agentCache.getUnchecked(agentName.concat(DELIMITER).concat(orgId));
     if (agent == nullToken) {
       throw new NotFoundException();
     } else {
       return (Tuple3<String, Properties, Long>) agent;
     }
   }
 
   /**
    * {@inheritDoc}
    *
    * @see org.opencastproject.capture.admin.api.CaptureAgentStateService#setAgentConfiguration
    */
   @Override
   public boolean setAgentConfiguration(String agentName, Properties configuration) {
     if (StringUtils.isBlank(agentName))
       throw new IllegalArgumentException("Unable to set agent state, agent name is blank or null.");
 
     String orgId = securityService.getOrganization().getId();
     AgentImpl agent;
     try {
       Properties agentConfig = getAgentFromCache(agentName, orgId).getB();
       if (agentConfig.equals(configuration)) {
         agentCache.put(agentName.concat(DELIMITER).concat(orgId),
                 Tuple3.tuple3(getAgentState(agentName), agentConfig, Long.valueOf(System.currentTimeMillis())));
         return false;
       }
 
       agent = (AgentImpl) getAgent(agentName);
       logger.debug("Setting Agent {}'s capabilities", agentName);
       agent.setConfiguration(configuration);
     } catch (NotFoundException e) {
       // If the agent doesn't exists, but the name is not null nor empty, create a new one.
       logger.debug("Creating Agent {} with state {}.", agentName, UNKNOWN);
       agent = new AgentImpl(agentName, orgId, UNKNOWN, "", configuration);
     }
 
     updateAgentInDatabase(agent);
     return true;
   }
 
   /**
    * Updates or adds an agent to the database.
    *
    * @param agent
    *          The Agent you wish to modify or add in the database.
    */
   protected void updateAgentInDatabase(AgentImpl agent) {
     updateAgentInDatabase(agent, true, 10);
   }
 
   /**
    * Updates or adds an agent to the database.
    *
    * @param agent
    *          The Agent you wish to modify or add in the database.
    * @param updateFromCache
    *          True to update the last heard from timestamp from the agentCache, false to avoid this.
    *          Note that you should nearly always update the cache, this was added to avoid deadlocks when removing agents from the cache.
    */
   private void updateAgentInDatabase(AgentImpl agent, boolean updateFromCache, int retries) {
     try {
       db.execTx(retries, em -> {
         //This is the cached last-heard-from time
         Long cachedLastHeardFrom = -1L;
         // Update the last seen property from the agent cache
         if (updateFromCache) {
           try {
             cachedLastHeardFrom = getAgentFromCache(agent.getName(), agent.getOrganization()).getC();
           } catch (NotFoundException e) {
             // That's fine
           }
         }
 
         try {
           AgentImpl existing = getAgentEntityQuery(agent.getName(), agent.getOrganization()).apply(em);
           existing.setConfiguration(agent.getConfiguration());
           if (!AgentState.UNKNOWN.equals(agent.getState())) {
             existing.setLastHeardFrom(Math.max(cachedLastHeardFrom, agent.getLastHeardFrom()));
           }
           existing.setState(agent.getState());
           existing.setSchedulerRoles(agent.getSchedulerRoles());
           existing.setUrl(agent.getUrl());
           em.merge(existing);
         } catch (NotFoundException e) {
           em.persist(agent);
         }
       });
 
       if (updateFromCache) {
         updateAgentInCache(agent.getName(), agent.getState(), agent.getOrganization(), agent.getConfiguration());
       }
     } catch (RollbackException e) {
       throw new RollbackException("Maximum number of retries exceeded", e);
     }
   }
 
   /**
    * Removes an agent from the database.
    *
    * @param agentName
    *          The name of the agent you wish to remove.
    */
   private void deleteAgentFromDatabase(String agentName) throws NotFoundException {
     try {
       String org = securityService.getOrganization().getId();
       db.execTxChecked(em -> {
         Agent existing = getAgentEntityQuery(agentName, org).apply(em);
         if (existing == null)
           throw new NotFoundException();
         em.remove(existing);
       });
       agentCache.invalidate(agentName.concat(DELIMITER).concat(org));
     } catch (RollbackException e) {
       logger.warn("Unable to commit to DB in deleteAgent.");
     }
   }
 
   // // ManagedServiceFactory Methods ////
 
   /**
    * {@inheritDoc}
    *
    * @see org.osgi.service.cm.ManagedServiceFactory#getName()
    */
   @Override
   public String getName() {
     return "org.opencastproject.capture.agent";
   }
 
   protected void setupAgentCache(int count, TimeUnit unit) {
     // Setup the agent cache
     RemovalListener<String, Object> removalListener = new RemovalListener<String, Object>() {
       private Set<String> ignoredStates = new LinkedHashSet<>(Arrays.asList(AgentState.UNKNOWN, AgentState.OFFLINE));
       @Override
       public void onRemoval(RemovalNotification<String, Object> removal) {
         if (RemovalCause.EXPIRED.equals(removal.getCause())) {
           String org = securityService.getOrganization().getId();
           try {
             String agentName = removal.getKey().split(DELIMITER)[0];
             AgentImpl agent = getAgent(agentName, org);
             if (!ignoredStates.contains(agent.getState())) {
               agent.setState(AgentState.OFFLINE);
               updateAgentInDatabase(agent, false, 2);
             }
           } catch (NotFoundException e) {
             //Ignore this
             //It should not happen, and if it does we just don't update the non-existant agent in the DB
           }
         }
       }
     };
     agentCache = CacheBuilder.newBuilder().expireAfterWrite(count, unit).removalListener(removalListener).build(new CacheLoader<String, Object>() {
       @Override
       public Object load(String id) {
         String[] key = id.split(DELIMITER);
         AgentImpl agent;
         try {
           agent = getAgent(key[0], key[1]);
         } catch (NotFoundException e) {
           return nullToken;
         }
         return Tuple3.tuple3(agent.getState(), agent.getConfiguration(), agent.getLastHeardFrom());
       }
     });
   }
 
   /**
    * {@inheritDoc}
    *
    * @see org.osgi.service.cm.ManagedServiceFactory#updated(java.lang.String, java.util.Dictionary)
    */
   @Override
   public void updated(String pid, Dictionary<String, ?> properties) throws ConfigurationException {
     // Get the agent properties
     String nameConfig = (String) properties.get("id");
     if (isBlank(nameConfig))
       throw new ConfigurationException("id", "must be specified");
 
     nameConfig = nameConfig.trim();
 
     String urlConfig = (String) properties.get("url");
     if (isBlank(urlConfig))
       throw new ConfigurationException("url", "must be specified");
     urlConfig = urlConfig.trim();
 
     String orgConfig = (String) properties.get("organization");
     if (isBlank(orgConfig))
       throw new ConfigurationException("organization", "must be specified");
     orgConfig = orgConfig.trim();
 
     String schedulerRolesConfig = (String) properties.get("schedulerRoles");
     if (isBlank(schedulerRolesConfig))
       throw new ConfigurationException("schedulerRoles", "must be specified");
     String[] schedulerRoles = schedulerRolesConfig.trim().split(",");
 
     // If we don't already have a mapping for this PID, create one
     if (!pidMap.containsKey(pid)) {
       pidMap.put(pid, nameConfig);
     }
 
     AgentImpl agent;
     try {
       agent = getAgent(nameConfig, orgConfig);
       agent.setUrl(urlConfig);
       agent.setState(UNKNOWN);
     } catch (NotFoundException e) {
       agent = new AgentImpl(nameConfig, orgConfig, UNKNOWN, urlConfig, new Properties());
     }
 
     for (String role : schedulerRoles) {
       agent.schedulerRoles.add(role.trim());
     }
 
     // Update the database
     logger.info("Roles '{}' may schedule '{}'", schedulerRolesConfig, agent.name);
     updateAgentInDatabase(agent);
   }
 
   /**
    * {@inheritDoc}
    *
    * @see org.osgi.service.cm.ManagedServiceFactory#deleted(java.lang.String)
    */
   @Override
   public void deleted(String pid) {
     String agentId = pidMap.remove(pid);
     if (agentId == null) {
       logger.warn("{} was not a managed capture agent pid", pid);
     } else {
       try {
         deleteAgentFromDatabase(agentId);
       } catch (NotFoundException e) {
         logger.warn("Unable to delete capture agent '{}'", agentId);
       }
     }
   }
 }