/*
 * MIT License
 *
 * Copyright (c) 2020-present Cloudogu GmbH and Contributors
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

package sonia.scm.admin;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Strings;
import com.google.common.util.concurrent.ThreadFactoryBuilder;
import io.micrometer.core.instrument.MeterRegistry;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import sonia.scm.metrics.Metrics;
import sonia.scm.net.ahc.AdvancedHttpClient;
import sonia.scm.version.Version;

import javax.inject.Inject;
import javax.inject.Singleton;
import java.util.Comparator;
import java.util.Optional;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;

@Singleton
public class ReleaseFeedParser {

  public static final int DEFAULT_TIMEOUT_IN_MILLIS = 5000;

  private static final Logger LOG = LoggerFactory.getLogger(ReleaseFeedParser.class);

  @VisibleForTesting
  static final String SPAN_KIND = "Release Feed";

  private final AdvancedHttpClient client;
  private final ExecutorService executorService;
  private final long timeoutInMillis;
  private Future<Optional<UpdateInfo>> updateInfoFuture;

  @Inject
  public ReleaseFeedParser(AdvancedHttpClient client, MeterRegistry registry) {
    this(client, registry, DEFAULT_TIMEOUT_IN_MILLIS);
  }

  public ReleaseFeedParser(AdvancedHttpClient client, MeterRegistry registry, long timeoutInMillis) {
    this.client = client;
    this.timeoutInMillis = timeoutInMillis;
    this.executorService = createExecutorService(registry);
  }

  private ExecutorService createExecutorService(MeterRegistry registry) {
    ExecutorService executor = Executors.newSingleThreadExecutor(
      new ThreadFactoryBuilder()
        .setNameFormat("ReleaseFeedParser")
        .build()
    );
    Metrics.executor(registry, executor, "ReleaseFeedParser", "single");
    return executor;
  }

  Optional<UpdateInfo> findLatestRelease(String url) {
    Future<Optional<UpdateInfo>> currentUpdateInfoFuture;
    boolean updateInfoFutureCreated = false;
    try {
      synchronized (this) {
        currentUpdateInfoFuture = this.updateInfoFuture;
        if (currentUpdateInfoFuture == null) {
          currentUpdateInfoFuture = submitRequest(url);
          this.updateInfoFuture = currentUpdateInfoFuture;
          updateInfoFutureCreated = true;
        }
      }
      try {
        return currentUpdateInfoFuture.get(timeoutInMillis, TimeUnit.MILLISECONDS);
      } catch (Exception e) {
        LOG.error("Could not read release feed", e);
        return Optional.empty();
      }
    } finally {
      if (updateInfoFutureCreated) {
        synchronized (this) {
          this.updateInfoFuture = null;
        }
      }
    }
  }

  private Future<Optional<UpdateInfo>> submitRequest(String url) {
    return executorService.submit(() -> {
      LOG.info("Search for newer versions of SCM-Manager");
      Optional<ReleaseFeedDto.Release> latestRelease = parseLatestReleaseFromRssFeed(url);
      return latestRelease.map(release -> new UpdateInfo(release.getTitle(), release.getLink()));
    });
  }

  private Optional<ReleaseFeedDto.Release> parseLatestReleaseFromRssFeed(String url) {
    try {
      if (Strings.isNullOrEmpty(url)) {
        return Optional.empty();
      }
      ReleaseFeedDto releaseFeed = client.get(url)
        .spanKind(SPAN_KIND)
        .request()
        .contentFromXml(ReleaseFeedDto.class);
      return filterForLatestRelease(releaseFeed);
    } catch (Exception e) {
      LOG.error("Could not parse release feed from {}", url, e);
      return Optional.empty();
    }
  }

  private Optional<ReleaseFeedDto.Release> filterForLatestRelease(ReleaseFeedDto releaseFeed) {
    return releaseFeed.getChannel().getReleases()
      .stream()
      .min(Comparator.comparing(release -> Version.parse(release.getTitle().trim())));
  }
}
