/*
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you 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 org.eclipse.aether.internal.impl.resolution;
  
  import javax.inject.Inject;
  import javax.inject.Named;
  import javax.inject.Singleton;
  
  import java.io.IOException;
  import java.io.UncheckedIOException;
  import java.util.HashSet;
  import java.util.List;
  import java.util.Map;
  import java.util.Objects;
  import java.util.Set;
  
  import org.eclipse.aether.RepositorySystemSession;
  import org.eclipse.aether.artifact.Artifact;
  import org.eclipse.aether.repository.ArtifactRepository;
  import org.eclipse.aether.resolution.ArtifactResult;
  import org.eclipse.aether.spi.checksums.TrustedChecksumsSource;
  import org.eclipse.aether.spi.connector.checksum.ChecksumAlgorithmFactory;
  import org.eclipse.aether.spi.connector.checksum.ChecksumAlgorithmFactorySelector;
  import org.eclipse.aether.spi.connector.checksum.ChecksumAlgorithmHelper;
  import org.eclipse.aether.transfer.ChecksumFailureException;
  import org.eclipse.aether.util.ConfigUtils;
  import org.eclipse.aether.util.artifact.ArtifactIdUtils;
  
  import static java.util.Objects.requireNonNull;
  
  /**
   * Artifact resolver processor that verifies the checksums of all resolved artifacts against trusted checksums. Is also
   * able to "record" (calculate and write them) to trusted checksum sources, that do support this operation.
   * <p>
   * It uses a list of {@link ChecksumAlgorithmFactory}ies to work with, by default SHA-1.
   * <p>
   * Configuration keys:
   * <ul>
   *     <li>{@code aether.artifactResolver.postProcessor.trustedChecksums.checksumAlgorithms} - Comma separated
   *       list of {@link ChecksumAlgorithmFactory} names to use (default "SHA-1").</li>
   *     <li>{@code aether.artifactResolver.postProcessor.trustedChecksums.failIfMissing} - To fail if artifact
   *       being validated is missing a trusted checksum (default {@code false}).</li>
   *     <li>{@code aether.artifactResolver.postProcessor.trustedChecksums.snapshots} - Should snapshot artifacts be
   *       handled (validated or recorded). Snapshots are by "best practice" in-house produced, hence should be trusted
   *       (default {@code false}).</li>
   *     <li>{@code aether.artifactResolver.postProcessor.trustedChecksums.record} - If this value set to {@code true},
   *       this component with not validate but "record" encountered artifact checksums instead
   *       (default {@code false}).</li>
   * </ul>
   * <p>
   * This component uses {@link TrustedChecksumsSource} as source of checksums for validation and also to "record" the
   * calculated checksums. To have this component usable, there must exist at least one enabled checksum source. In case
   * of multiple checksum sources enabled, ALL of them are used as source for validation or recording. This
   * implies that if two enabled checksum sources "disagree" about an artifact checksum, the validation failure is
   * inevitable.
   *
   * @since 1.9.0
   */
  @Singleton
  @Named(TrustedChecksumsArtifactResolverPostProcessor.NAME)
  public final class TrustedChecksumsArtifactResolverPostProcessor extends ArtifactResolverPostProcessorSupport {
      public static final String NAME = "trustedChecksums";
  
      private static final String CONFIG_PROPS_PREFIX =
              ArtifactResolverPostProcessorSupport.CONFIG_PROPS_PREFIX + NAME + ".";
  
      /**
       * Is post processor enabled.
       *
       * @configurationSource {@link RepositorySystemSession#getConfigProperties()}
       * @configurationType {@link java.lang.Boolean}
       * @configurationDefaultValue false
       */
      public static final String CONFIG_PROP_ENABLED = ArtifactResolverPostProcessorSupport.CONFIG_PROPS_PREFIX + NAME;
  
      /**
       * The checksum algorithms to apply during post-processing as comma separated list.
       *
       * @configurationSource {@link RepositorySystemSession#getConfigProperties()}
       * @configurationType {@link java.lang.String}
       * @configurationDefaultValue {@link #DEFAULT_CHECKSUM_ALGORITHMS}
       */
      public static final String CONFIG_PROP_CHECKSUM_ALGORITHMS = CONFIG_PROPS_PREFIX + "checksumAlgorithms";
 
     public static final String DEFAULT_CHECKSUM_ALGORITHMS = "SHA-1";
 
     /**
      * Should post processor fail resolution if checksum is missing?
      *
      * @configurationSource {@link RepositorySystemSession#getConfigProperties()}
      * @configurationType {@link java.lang.Boolean}
      * @configurationDefaultValue false
      */
     public static final String CONFIG_PROP_FAIL_IF_MISSING = CONFIG_PROPS_PREFIX + "failIfMissing";
 
     /**
      * Should post processor process snapshots as well?
      *
      * @configurationSource {@link RepositorySystemSession#getConfigProperties()}
      * @configurationType {@link java.lang.Boolean}
      * @configurationDefaultValue false
      */
     public static final String CONFIG_PROP_SNAPSHOTS = CONFIG_PROPS_PREFIX + "snapshots";
 
     /**
      * Should post processor go into "record" mode (and collect checksums instead of validate them)?
      *
      * @configurationSource {@link RepositorySystemSession#getConfigProperties()}
      * @configurationType {@link java.lang.Boolean}
      * @configurationDefaultValue false
      */
     public static final String CONFIG_PROP_RECORD = CONFIG_PROPS_PREFIX + "record";
 
     private static final String CHECKSUM_ALGORITHMS_CACHE_KEY =
             TrustedChecksumsArtifactResolverPostProcessor.class.getName() + ".checksumAlgorithms";
 
     private final ChecksumAlgorithmFactorySelector checksumAlgorithmFactorySelector;
 
     private final Map<String, TrustedChecksumsSource> trustedChecksumsSources;
 
     @Inject
     public TrustedChecksumsArtifactResolverPostProcessor(
             ChecksumAlgorithmFactorySelector checksumAlgorithmFactorySelector,
             Map<String, TrustedChecksumsSource> trustedChecksumsSources) {
         this.checksumAlgorithmFactorySelector = requireNonNull(checksumAlgorithmFactorySelector);
         this.trustedChecksumsSources = requireNonNull(trustedChecksumsSources);
     }
 
     @Override
     protected boolean isEnabled(RepositorySystemSession session) {
         return ConfigUtils.getBoolean(session, false, CONFIG_PROP_ENABLED);
     }
 
     @SuppressWarnings("unchecked")
     @Override
     protected void doPostProcess(RepositorySystemSession session, List<ArtifactResult> artifactResults) {
         final List<ChecksumAlgorithmFactory> checksumAlgorithms = (List<ChecksumAlgorithmFactory>) session.getData()
                 .computeIfAbsent(
                         CHECKSUM_ALGORITHMS_CACHE_KEY,
                         () -> checksumAlgorithmFactorySelector.selectList(
                                 ConfigUtils.parseCommaSeparatedUniqueNames(ConfigUtils.getString(
                                         session, DEFAULT_CHECKSUM_ALGORITHMS, CONFIG_PROP_CHECKSUM_ALGORITHMS))));
 
         final boolean failIfMissing = ConfigUtils.getBoolean(session, false, CONFIG_PROP_FAIL_IF_MISSING);
         final boolean record = ConfigUtils.getBoolean(session, false, CONFIG_PROP_RECORD);
         final boolean snapshots = ConfigUtils.getBoolean(session, false, CONFIG_PROP_SNAPSHOTS);
 
         for (ArtifactResult artifactResult : artifactResults) {
             if (artifactResult.getArtifact().isSnapshot() && !snapshots) {
                 continue;
             }
             if (artifactResult.isResolved()) {
                 if (record) {
                     recordArtifactChecksums(session, artifactResult, checksumAlgorithms);
                 } else if (!validateArtifactChecksums(session, artifactResult, checksumAlgorithms, failIfMissing)) {
                     artifactResult.setArtifact(artifactResult.getArtifact().setPath(null)); // make it unresolved
                 }
             }
         }
     }
 
     /**
      * Calculates and records checksums into trusted sources that support writing.
      */
     private void recordArtifactChecksums(
             RepositorySystemSession session,
             ArtifactResult artifactResult,
             List<ChecksumAlgorithmFactory> checksumAlgorithmFactories) {
         Artifact artifact = artifactResult.getArtifact();
         ArtifactRepository artifactRepository = artifactResult.getRepository();
         try {
             final Map<String, String> calculatedChecksums =
                     ChecksumAlgorithmHelper.calculate(artifact.getPath(), checksumAlgorithmFactories);
 
             for (TrustedChecksumsSource trustedChecksumsSource : trustedChecksumsSources.values()) {
                 TrustedChecksumsSource.Writer writer =
                         trustedChecksumsSource.getTrustedArtifactChecksumsWriter(session);
                 if (writer != null) {
                     try {
                         writer.addTrustedArtifactChecksums(
                                 artifact, artifactRepository, checksumAlgorithmFactories, calculatedChecksums);
                     } catch (IOException e) {
                         throw new UncheckedIOException(
                                 "Could not write required checksums for " + artifact.getPath(), e);
                     }
                 }
             }
         } catch (IOException e) {
             throw new UncheckedIOException("Could not calculate required checksums for " + artifact.getPath(), e);
         }
     }
 
     /**
      * Validates trusted checksums against {@link ArtifactResult}, returns {@code true} denoting "valid" checksums or
      * {@code false} denoting "invalid" checksums.
      */
     private boolean validateArtifactChecksums(
             RepositorySystemSession session,
             ArtifactResult artifactResult,
             List<ChecksumAlgorithmFactory> checksumAlgorithmFactories,
             boolean failIfMissing) {
         Artifact artifact = artifactResult.getArtifact();
         ArtifactRepository artifactRepository = artifactResult.getRepository();
         boolean valid = true;
         boolean validated = false;
         try {
             // full set: calculate all algorithms we were asked for
             final Map<String, String> calculatedChecksums =
                     ChecksumAlgorithmHelper.calculate(artifact.getPath(), checksumAlgorithmFactories);
 
             for (Map.Entry<String, TrustedChecksumsSource> entry : trustedChecksumsSources.entrySet()) {
                 final String trustedSourceName = entry.getKey();
                 final TrustedChecksumsSource trustedChecksumsSource = entry.getValue();
 
                 // upper bound set: ask source for checksums, ideally same as calculatedChecksums but may be less
                 Map<String, String> trustedChecksums = trustedChecksumsSource.getTrustedArtifactChecksums(
                         session, artifact, artifactRepository, checksumAlgorithmFactories);
 
                 if (trustedChecksums == null) {
                     continue; // not enabled
                 }
                 validated = true;
 
                 if (!calculatedChecksums.equals(trustedChecksums)) {
                     Set<String> missingTrustedAlg = new HashSet<>(calculatedChecksums.keySet());
                     missingTrustedAlg.removeAll(trustedChecksums.keySet());
 
                     if (!missingTrustedAlg.isEmpty() && failIfMissing) {
                         artifactResult.addException(
                                 artifactRepository,
                                 new ChecksumFailureException("Missing from " + trustedSourceName
                                         + " trusted checksum(s) " + missingTrustedAlg + " for artifact "
                                         + ArtifactIdUtils.toId(artifact)));
                         valid = false;
                     }
 
                     // compare values but only present ones, failIfMissing handled above
                     // we still want to report all: algX - missing, algY - mismatch, etc
                     for (ChecksumAlgorithmFactory checksumAlgorithmFactory : checksumAlgorithmFactories) {
                         String calculatedChecksum = calculatedChecksums.get(checksumAlgorithmFactory.getName());
                         String trustedChecksum = trustedChecksums.get(checksumAlgorithmFactory.getName());
                         if (trustedChecksum != null && !Objects.equals(calculatedChecksum, trustedChecksum)) {
                             artifactResult.addException(
                                     artifactRepository,
                                     new ChecksumFailureException("Artifact "
                                             + ArtifactIdUtils.toId(artifact) + " trusted checksum mismatch: "
                                             + trustedSourceName + "=" + trustedChecksum + "; calculated="
                                             + calculatedChecksum));
                             valid = false;
                         }
                     }
                 }
             }
 
             if (!validated && failIfMissing) {
                 artifactResult.addException(
                         artifactRepository,
                         new ChecksumFailureException(
                                 "There are no enabled trusted checksums" + " source(s) to validate against."));
                 valid = false;
             }
         } catch (IOException e) {
             throw new UncheckedIOException(e);
         }
         return valid;
     }
 }