/*
    * Copyright (c) 2002-2025 Gargoyle Software Inc.
    *
    * 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 org.htmlunit.javascript.background;
  
  import java.io.IOException;
  import java.io.ObjectInputStream;
  import java.lang.ref.WeakReference;
  import java.util.ArrayList;
  import java.util.PriorityQueue;
  import java.util.concurrent.atomic.AtomicInteger;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.htmlunit.Page;
  import org.htmlunit.WebWindow;
  
  /**
   * <p>Default implementation of {@link JavaScriptJobManager}.</p>
   *
   * <p>This job manager class is guaranteed not to keep old windows in memory (no window memory leaks).</p>
   *
   * <p>This job manager is serializable, but any running jobs are transient and are not serialized.</p>
   *
   * @author Daniel Gredler
   * @author Katharina Probst
   * @author Amit Manjhi
   * @author Ronald Brill
   * @author Carsten Steul
   */
  class JavaScriptJobManagerImpl implements JavaScriptJobManager {
  
      /**
       * The window to which this job manager belongs (weakly referenced, so as not
       * to leak memory).
       */
      private final transient WeakReference<WebWindow> window_;
  
      /**
       * Queue of jobs that are scheduled to run. This is a priority queue, sorted
       * by closest target execution time.
       */
      private transient PriorityQueue<JavaScriptJob> scheduledJobsQ_ = new PriorityQueue<>();
  
      private transient ArrayList<Integer> cancelledJobs_ = new ArrayList<>();
  
      private transient JavaScriptJob currentlyRunningJob_;
  
      /** A counter used to generate the IDs assigned to {@link JavaScriptJob}s. */
      private static final AtomicInteger NEXT_JOB_ID_ = new AtomicInteger(1);
  
      /** Logging support. */
      private static final Log LOG = LogFactory.getLog(JavaScriptJobManagerImpl.class);
  
      /**
       * Creates a new instance.
       *
       * @param window the window associated with the new job manager
       */
      JavaScriptJobManagerImpl(final WebWindow window) {
          window_ = new WeakReference<>(window);
      }
  
      /** {@inheritDoc} */
      @Override
      public synchronized int getJobCount() {
          return scheduledJobsQ_.size() + (currentlyRunningJob_ != null ? 1 : 0);
      }
  
      /** {@inheritDoc} */
      @Override
      public synchronized int getJobCount(final JavaScriptJobFilter filter) {
          if (filter == null) {
              return scheduledJobsQ_.size() + (currentlyRunningJob_ != null ? 1 : 0);
          }
  
          int count = 0;
          if (currentlyRunningJob_ != null && filter.passes(currentlyRunningJob_)) {
              count++;
          }
          for (final JavaScriptJob job : scheduledJobsQ_) {
              if (filter.passes(job)) {
                  count++;
              }
          }
          return count;
      }
  
     /** {@inheritDoc} */
     @Override
     public int addJob(final JavaScriptJob job, final Page page) {
         final WebWindow w = getWindow();
         if (w == null) {
             /*
              * The window to which this job manager belongs has been garbage
              * collected. Don't spawn any more jobs for it.
              */
             return 0;
         }
         if (w.getEnclosedPage() != page) {
             /*
              * The page requesting the addition of the job is no longer contained by
              * our owner window. Don't let it spawn any more jobs.
              */
             return 0;
         }
         final int id = NEXT_JOB_ID_.getAndIncrement();
         job.setId(Integer.valueOf(id));
 
         synchronized (this) {
             scheduledJobsQ_.add(job);
 
             if (LOG.isDebugEnabled()) {
                 LOG.debug("job added to queue");
                 LOG.debug("    window is: " + w);
                 LOG.debug("    added job: " + job);
                 LOG.debug("after adding job to the queue, the queue is: ");
                 printQueue();
             }
 
             notify();
         }
 
         return id;
     }
 
     /** {@inheritDoc} */
     @Override
     public synchronized void removeJob(final int id) {
         for (final JavaScriptJob job : scheduledJobsQ_) {
             final int jobId = job.getId().intValue();
             if (jobId == id) {
                 scheduledJobsQ_.remove(job);
                 break;
             }
         }
         cancelledJobs_.add(Integer.valueOf(id));
         notify();
     }
 
     /** {@inheritDoc} */
     @Override
     public synchronized void stopJob(final int id) {
         for (final JavaScriptJob job : scheduledJobsQ_) {
             final int jobId = job.getId().intValue();
             if (jobId == id) {
                 scheduledJobsQ_.remove(job);
                 // TODO: should we try to interrupt the job if it is running?
                 break;
             }
         }
         cancelledJobs_.add(Integer.valueOf(id));
         notify();
     }
 
     /** {@inheritDoc} */
     @Override
     public synchronized void removeAllJobs() {
         if (currentlyRunningJob_ != null) {
             cancelledJobs_.add(currentlyRunningJob_.getId());
         }
         for (final JavaScriptJob job : scheduledJobsQ_) {
             cancelledJobs_.add(job.getId());
         }
         scheduledJobsQ_.clear();
         notify();
     }
 
     /** {@inheritDoc} */
     @Override
     @SuppressWarnings("PMD.GuardLogStatement")
     public int waitForJobs(final long timeoutMillis) {
         final boolean debug = LOG.isDebugEnabled();
         if (debug) {
             LOG.debug("Waiting for all jobs to finish (will wait max " + timeoutMillis + " millis).");
         }
         if (timeoutMillis > 0) {
             long now = System.currentTimeMillis();
             final long end = now + timeoutMillis;
 
             synchronized (this) {
                 while (getJobCount() > 0 && now < end) {
                     try {
                         wait(end - now);
                     }
                     catch (final InterruptedException e) {
                         LOG.error("InterruptedException while in waitForJobs", e);
 
                         // restore interrupted status
                         Thread.currentThread().interrupt();
                     }
                     // maybe a change triggers the wakup; we have to recalculate the
                     // wait time
                     now = System.currentTimeMillis();
                 }
             }
         }
         final int jobs = getJobCount();
         if (debug) {
             LOG.debug("Finished waiting for all jobs to finish (final job count is " + jobs + ").");
         }
         return jobs;
     }
 
     /** {@inheritDoc} */
     @Override
     public int waitForJobsStartingBefore(final long delayMillis) {
         return waitForJobsStartingBefore(delayMillis, null);
     }
 
     /** {@inheritDoc} */
     @Override
     @SuppressWarnings("PMD.GuardLogStatement")
     public int waitForJobsStartingBefore(final long delayMillis, final JavaScriptJobFilter filter) {
         final boolean debug = LOG.isDebugEnabled();
 
         final long latestExecutionTime = System.currentTimeMillis() + delayMillis;
         if (debug) {
             LOG.debug("Waiting for all jobs that have execution time before "
                   + delayMillis + " (" + latestExecutionTime + ") to finish");
         }
 
         final long interval = Math.max(40, delayMillis);
         synchronized (this) {
             JavaScriptJob earliestJob = getEarliestJob(filter);
             boolean pending = earliestJob != null && earliestJob.getTargetExecutionTime() < latestExecutionTime;
             pending = pending
                     || (
                             currentlyRunningJob_ != null
                             && (filter == null || filter.passes(currentlyRunningJob_))
                             && currentlyRunningJob_.getTargetExecutionTime() < latestExecutionTime
                        );
 
             while (pending) {
                 try {
                     wait(interval);
                 }
                 catch (final InterruptedException e) {
                     LOG.error("InterruptedException while in waitForJobsStartingBefore", e);
 
                     // restore interrupted status
                     Thread.currentThread().interrupt();
                 }
 
                 earliestJob = getEarliestJob(filter);
                 pending = earliestJob != null && earliestJob.getTargetExecutionTime() < latestExecutionTime;
                 pending = pending
                         || (
                                 currentlyRunningJob_ != null
                                 && (filter == null || filter.passes(currentlyRunningJob_))
                                 && currentlyRunningJob_.getTargetExecutionTime() < latestExecutionTime
                            );
             }
         }
 
         final int jobs = getJobCount(filter);
         if (debug) {
             LOG.debug("Finished waiting for all jobs that have target execution time earlier than "
                 + latestExecutionTime + ", final job count is " + jobs);
         }
         return jobs;
     }
 
     /** {@inheritDoc} */
     @Override
     public synchronized void shutdown() {
         scheduledJobsQ_.clear();
         notify();
     }
 
     /**
      * Returns the window to which this job manager belongs, or {@code null} if
      * it has been garbage collected.
      *
      * @return the window to which this job manager belongs, or {@code null} if
      *         it has been garbage collected
      */
     private WebWindow getWindow() {
         return window_.get();
     }
 
     /**
      * Utility method to print current queue.
      */
     private void printQueue() {
         if (LOG.isDebugEnabled()) {
             LOG.debug("------ printing JavaScript job queue -----");
             LOG.debug("  number of jobs on the queue: " + scheduledJobsQ_.size());
             int count = 1;
             for (final JavaScriptJob job : scheduledJobsQ_) {
                 LOG.debug("  " + count + ")  Job target execution time: " + job.getTargetExecutionTime());
                 LOG.debug("      job to string: " + job);
                 LOG.debug("      job id: " + job.getId());
                 if (job.isPeriodic()) {
                     LOG.debug("      period: " + job.getPeriod().intValue());
                 }
                 count++;
             }
             LOG.debug("------------------------------------------");
         }
     }
 
     /**
      * <span style="color:red">INTERNAL API - SUBJECT TO CHANGE AT ANY TIME - USE AT YOUR OWN RISK.</span><br>
      */
     @Override
     public synchronized String jobStatusDump(final JavaScriptJobFilter filter) {
         final String lineSeparator = System.lineSeparator();
 
         final StringBuilder status = new StringBuilder(110)
                 .append("------ JavaScript job status -----")
                 .append(lineSeparator);
 
         if (null != currentlyRunningJob_ && (filter == null || filter.passes(currentlyRunningJob_))) {
             status.append("  current running job: ").append(currentlyRunningJob_.toString())
                 .append("      job id: ").append(currentlyRunningJob_.getId())
                 .append(lineSeparator)
                 .append(lineSeparator)
                 .append(lineSeparator);
         }
         status.append("  number of jobs on the queue: ")
             .append(scheduledJobsQ_.size())
             .append(lineSeparator);
 
         int count = 1;
         for (final JavaScriptJob job : scheduledJobsQ_) {
             if (filter == null || filter.passes(job)) {
                 final long now = System.currentTimeMillis();
                 final long execTime = job.getTargetExecutionTime();
                 status.append("  ").append(count).append(")  Job target execution time: ")
                         .append(execTime).append(" (should start in ")
                         .append((execTime - now) / 1000d).append("s)")
                         .append(lineSeparator)
                         .append("      job to string: ").append(job)
                         .append(lineSeparator).append("      job id: ").append(job.getId())
                     .append(lineSeparator);
                 if (job.isPeriodic()) {
                     status.append("      period: ")
                         .append(job.getPeriod().toString())
                         .append(lineSeparator);
                 }
                 count++;
             }
         }
         status.append("------------------------------------------")
             .append(lineSeparator);
 
         return status.toString();
     }
 
     /**
      * {@inheritDoc}
      */
     @Override
     public JavaScriptJob getEarliestJob() {
         return scheduledJobsQ_.peek();
     }
 
     /**
      * {@inheritDoc}
      */
     @Override
     public synchronized JavaScriptJob getEarliestJob(final JavaScriptJobFilter filter) {
         if (filter == null) {
             return scheduledJobsQ_.peek();
         }
 
         for (final JavaScriptJob job : scheduledJobsQ_) {
             if (filter.passes(job)) {
                 return job;
             }
         }
         return null;
     }
 
     /**
      * {@inheritDoc}
      */
     @Override
     @SuppressWarnings("PMD.GuardLogStatement")
     public boolean runSingleJob(final JavaScriptJob givenJob) {
         assert givenJob != null;
         final JavaScriptJob job = getEarliestJob();
         if (job != givenJob) {
             return false;
         }
 
         final long currentTime = System.currentTimeMillis();
         if (job.getTargetExecutionTime() > currentTime) {
             return false;
         }
         synchronized (this) {
             if (scheduledJobsQ_.remove(job)) {
                 currentlyRunningJob_ = job;
             }
             // no need to notify if processing is started
         }
 
         final boolean debug = LOG.isDebugEnabled();
         final boolean isPeriodicJob = job.isPeriodic();
         if (isPeriodicJob) {
             final long jobPeriod = job.getPeriod().longValue();
 
             // reference: http://ejohn.org/blog/how-javascript-timers-work/
             long timeDifference = currentTime - job.getTargetExecutionTime();
             timeDifference = (timeDifference / jobPeriod) * jobPeriod + jobPeriod;
             job.setTargetExecutionTime(job.getTargetExecutionTime() + timeDifference);
 
             // queue
             synchronized (this) {
                 if (!cancelledJobs_.contains(job.getId())) {
                     if (debug) {
                         LOG.debug("Reschedulling job " + job);
                     }
                     scheduledJobsQ_.add(job);
                     notify();
                 }
             }
         }
         if (debug) {
             final String periodicJob = isPeriodicJob ? "interval " : "";
             LOG.debug("Starting " + periodicJob + "job " + job);
         }
         try {
             job.run();
         }
         catch (final RuntimeException e) {
             LOG.error("Job run failed with unexpected RuntimeException: " + e.getMessage(), e);
         }
         finally {
             synchronized (this) {
                 if (job == currentlyRunningJob_) {
                     currentlyRunningJob_ = null;
                 }
                 notify();
             }
         }
         if (debug) {
             final String periodicJob = isPeriodicJob ? "interval " : "";
             LOG.debug("Finished " + periodicJob + "job " + job);
         }
         return true;
     }
 
     /**
      * Our own serialization (to handle the weak reference)
      * @param in the stream to read form
      * @throws IOException in case of error
      * @throws ClassNotFoundException in case of error
      */
     private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
         in.defaultReadObject();
 
         // we do not store the jobs (at the moment)
         scheduledJobsQ_ = new PriorityQueue<>();
         cancelledJobs_ = new ArrayList<>();
         currentlyRunningJob_ = null;
     }
 }