/*
    * 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;
  
  import java.io.IOException;
  import java.nio.file.Files;
  import java.nio.file.Path;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.HashSet;
  import java.util.Map;
  import java.util.Objects;
  import java.util.Properties;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.regex.Pattern;
  
  import org.eclipse.aether.RepositorySystemSession;
  import org.eclipse.aether.artifact.Artifact;
  import org.eclipse.aether.metadata.Metadata;
  import org.eclipse.aether.repository.LocalArtifactRegistration;
  import org.eclipse.aether.repository.LocalArtifactRequest;
  import org.eclipse.aether.repository.LocalArtifactResult;
  import org.eclipse.aether.repository.RemoteRepository;
  import org.eclipse.aether.repository.RepositoryKeyFunction;
  import org.eclipse.aether.util.ConfigUtils;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import static java.util.Objects.requireNonNull;
  
  /**
   * These are implementation details for enhanced local repository manager, subject to change without prior notice.
   * Repositories from which a cached artifact was resolved are tracked in a properties file named
   * <code>_remote.repositories</code>, with content key as filename&gt;repo_id and value as empty string. If a file has
   * been installed in the repository, but not downloaded from a remote repository, it is tracked as empty repository id
   * and always resolved. For example:
   *
   * <pre>
   * artifact-1.0.pom>=
   * artifact-1.0.jar>=
   * artifact-1.0.pom>central=
   * artifact-1.0.jar>central=
   * artifact-1.0.zip>central=
   * artifact-1.0-classifier.zip>central=
   * artifact-1.0.pom>my_repo_id=
   * </pre>
   *
   * The repository id component of a tracking key is produced by the tracking-scoped repository key function, which
   * is URL-qualified by default: two repositories that merely share an id but point at different URLs are tracked as
   * different origins (see
   * {@link org.eclipse.aether.ConfigurationProperties#REPOSITORY_TRACKING_REPOSITORY_KEY_FUNCTION}). This does not hold
   * unconditionally when {@link EnhancedLocalRepositoryManagerFactory#CONFIG_PROP_LEGACY_LOCAL_REPOSITORY} is enabled
   * (the default): for backward compatibility with Maven 3.9 and older, a same-id fallback then also accepts an
   * artifact tracked under a different URL as long as the repository id matches (see {@link #applyTracking}).
   *
   * @see EnhancedLocalRepositoryManagerFactory
   */
  class EnhancedLocalRepositoryManager extends SimpleLocalRepositoryManager {
  
      private static final Logger LOGGER = LoggerFactory.getLogger(EnhancedLocalRepositoryManager.class);
  
      private static final String LOCAL_REPO_ID = "";
  
      private static final Pattern SHA1_HEX = Pattern.compile("[0-9a-f]{40}");
  
      /**
       * Shared sentinel for "no tracking data". Mutation is forbidden: the instance is shared
       * across threads via {@link #trackingFileCache} and returned directly from {@link #readRepos}.
       */
      private static final Properties EMPTY_PROPERTIES = new Properties() {
          @Override
          public synchronized Object put(Object key, Object value) {
              throw new UnsupportedOperationException("EMPTY_PROPERTIES is read-only");
          }
  
          @Override
          public synchronized Object remove(Object key) {
              throw new UnsupportedOperationException("EMPTY_PROPERTIES is read-only");
          }
  
          @Override
          public synchronized void clear() {
             throw new UnsupportedOperationException("EMPTY_PROPERTIES is read-only");
         }
     };
 
     private final String trackingFilename;
 
     private final boolean legacyLocalRepository;
 
     private final TrackingFileManager trackingFileManager;
 
     private final LocalPathPrefixComposer localPathPrefixComposer;
 
     /**
      * Repository key function used solely for the provenance tracking entries (the repository component of the
      * keys in the tracking file); path composition keeps using the (system-wide) key function held by the
      * superclass. URL-qualified by default, so two repositories merely sharing an id are not treated as the same
      * origin - see {@link org.eclipse.aether.ConfigurationProperties#REPOSITORY_TRACKING_REPOSITORY_KEY_FUNCTION}.
      * Lookups of entries written under a different key function miss and fail safe: the artifact stays tracked
      * (so the untracked inter-op fallback in {@link #checkFind} does not accept it) but unavailable, forcing a
      * checksum-validated re-fetch.
      */
     private final RepositoryKeyFunction trackingRepositoryKeyFunction;
 
     /**
      * Cache of tracking file contents, keyed by tracking file path. Eliminates redundant disk I/O
      * when multiple artifacts in the same directory are resolved — they all share the same
      * {@code _remote.repositories} tracking file. Invalidated on writes via {@link #addRepo}.
      * <p>
      * Cached {@link Properties} instances are shared across threads and must be treated as
      * read-only by callers of {@link #readRepos}. The cache is scoped to this manager instance
      * (one per session), so concurrent builds in separate JVMs each maintain independent caches.
      * If another process updates a tracking file after it has been cached here, a stale entry is
      * NOT always harmless: for a tracked artifact it merely causes a redundant download, but in the
      * untracked inter-op branch of {@link #checkFind} staleness would be trust-increasing (the file
      * would be accepted as locally installed although its recorded origin says otherwise). That
      * branch therefore re-reads the tracking file from disk before accepting, see
      * {@link #readReposFresh}.
      */
     private final ConcurrentHashMap<Path, Properties> trackingFileCache = new ConcurrentHashMap<>();
 
     EnhancedLocalRepositoryManager(
             Path basedir,
             LocalPathComposer localPathComposer,
             RepositoryKeyFunction trackingRepositoryKeyFunction,
             String trackingFilename,
             boolean legacyLocalRepository,
             TrackingFileManager trackingFileManager,
             LocalPathPrefixComposer localPathPrefixComposer) {
         super(basedir, "enhanced", localPathComposer);
         this.trackingRepositoryKeyFunction = requireNonNull(trackingRepositoryKeyFunction);
         this.trackingFilename = requireNonNull(trackingFilename);
         this.legacyLocalRepository = legacyLocalRepository;
         this.trackingFileManager = requireNonNull(trackingFileManager);
         this.localPathPrefixComposer = requireNonNull(localPathPrefixComposer);
     }
 
     private String concatPaths(String prefix, String artifactPath) {
         if (prefix == null || prefix.isEmpty()) {
             return artifactPath;
         }
         return prefix + '/' + artifactPath;
     }
 
     @Override
     public String getPathForLocalArtifact(Artifact artifact) {
         return concatPaths(
                 localPathPrefixComposer.getPathPrefixForLocalArtifact(artifact),
                 super.getPathForLocalArtifact(artifact));
     }
 
     @Override
     public String getPathForRemoteArtifact(Artifact artifact, RemoteRepository repository, String context) {
         return concatPaths(
                 localPathPrefixComposer.getPathPrefixForRemoteArtifact(artifact, repository),
                 super.getPathForRemoteArtifact(artifact, repository, context));
     }
 
     @Override
     public String getPathForLocalMetadata(Metadata metadata) {
         return concatPaths(
                 localPathPrefixComposer.getPathPrefixForLocalMetadata(metadata),
                 super.getPathForLocalMetadata(metadata));
     }
 
     @Override
     public String getPathForRemoteMetadata(Metadata metadata, RemoteRepository repository, String context) {
         requireNonNull(metadata, "metadata cannot be null");
         requireNonNull(repository, "repository cannot be null");
         if (legacyLocalRepository) {
             return concatPaths(
                     localPathPrefixComposer.getPathPrefixForRemoteMetadata(metadata, repository),
                     super.getPathForRemoteMetadata(metadata, repository, context));
         } else {
             return concatPaths(
                     localPathPrefixComposer.getPathPrefixForRemoteMetadata(metadata, repository),
                     localPathComposer.getPathForMetadata(metadata, getTrackingRepositoryKey(repository, context)));
         }
     }
 
     @Override
     public LocalArtifactResult find(RepositorySystemSession session, LocalArtifactRequest request) {
         Artifact artifact = request.getArtifact();
         LocalArtifactResult result = new LocalArtifactResult(request);
 
         boolean verifyRealPath = ConfigUtils.getBoolean(
                 session,
                 EnhancedLocalRepositoryManagerFactory.DEFAULT_VERIFY_REAL_PATH,
                 EnhancedLocalRepositoryManagerFactory.CONFIG_PROP_VERIFY_REAL_PATH);
 
         Path filePath;
 
         // Local repository CANNOT have timestamped installed, they are created only during deploy
         if (Objects.equals(artifact.getVersion(), artifact.getBaseVersion())) {
             filePath = getAbsolutePathForLocalArtifact(artifact);
             checkFind(
                     getPrefixDirectory(localPathPrefixComposer.getPathPrefixForLocalArtifact(artifact)),
                     filePath,
                     result,
                     verifyRealPath);
         }
 
         if (!result.isAvailable()) {
             for (RemoteRepository repository : request.getRepositories()) {
                 filePath = getAbsolutePathForRemoteArtifact(artifact, repository, request.getContext());
 
                 checkFind(
                         getPrefixDirectory(
                                 localPathPrefixComposer.getPathPrefixForRemoteArtifact(artifact, repository)),
                         filePath,
                         result,
                         verifyRealPath);
 
                 if (result.isAvailable()) {
                     break;
                 }
             }
         }
 
         return result;
     }
 
     private Path getPrefixDirectory(String prefix) {
         Path basePath = getRepository().getBasePath();
         return prefix == null || prefix.isEmpty() ? basePath : basePath.resolve(prefix);
     }
 
     /**
      * Verifies that the real (on-disk) spelling of the given artifact path matches the requested spelling,
      * relative to the directory of its local path prefix. On case-insensitive or normalization-preserving
      * filesystems (the macOS and Windows defaults) a cached file whose stored name differs from the requested one
      * - for example one cached for case-colliding coordinates - still passes the file-existence check, while the
      * tracking data in the tracking file is compared exactly: the aliased file would then be treated as
      * present-but-untracked and accepted with no download and no checksum verification. Such aliases are treated
      * as "not present" instead (fail closed), forcing a proper download for the requested coordinates. Only the
      * coordinate-derived part of the path is compared, as a suffix of the real path: the base directory and the
      * prefix directories are configuration, not coordinates, so they may be symbolic links - see
      * {@link EnhancedLocalRepositoryManagerFactory#CONFIG_PROP_VERIFY_REAL_PATH} to opt out.
      */
     private boolean hasFaithfulRealPath(Path prefixDirectory, Path path) {
         try {
             String requested = prefixDirectory.relativize(path).toString();
             String real = path.toRealPath().toString();
             // compare strings: Path comparison ignores case on Windows
             if (!real.endsWith(path.getFileSystem().getSeparator() + requested)) {
                 LOGGER.warn(
                         "Rejecting locally cached artifact {}: its on-disk path {} does not match the requested"
                                 + " coordinates (filesystem case/normalization alias); treating it as not present",
                         path,
                         real);
                 return false;
             }
             return true;
         } catch (IOException | IllegalArgumentException e) {
             // the real identity of the file cannot be established: fail closed, forcing a re-download
             return false;
         }
     }
 
     private void checkFind(Path prefixDirectory, Path path, LocalArtifactResult result, boolean verifyRealPath) {
         if (Files.isRegularFile(path) && (!verifyRealPath || hasFaithfulRealPath(prefixDirectory, path))) {
             result.setPath(path);
 
             Properties props = readRepos(path);
 
             if (!applyTracking(path, result, props) && !isTracked(props, path)) {
                 /*
                  * The (possibly cached) state claims the artifact is untracked, and the untracked inter-op
                  * branch below is trust-increasing: it accepts the file as locally installed. That decision
                  * must never rest on tracking state that may be older than the file it judges (another process
                  * sharing this local repository may have recorded the true origin of the file after our cache
                  * entry was populated), so re-read the tracking file from disk before concluding untracked.
                  */
                 props = readReposFresh(path);
                 if (!applyTracking(path, result, props) && !isTracked(props, path)) {
                     /*
                      * NOTE: The artifact is present but not tracked at all, for inter-op with simple local repo, assume
                      * the artifact was locally installed.
                      */
                     result.setAvailable(true);
                 }
             }
         }
     }
 
     /**
      * Applies the tracking-state based acceptance rules to given result: an artifact installed into the local
      * repository is always accepted, an artifact downloaded from a remote repository is accepted only if
      * downloaded from one of the request repositories.
      *
      * @return {@code true} if the result was made available, {@code false} otherwise.
      */
     private boolean applyTracking(Path path, LocalArtifactResult result, Properties props) {
         if (props.get(getKey(path, LOCAL_REPO_ID)) != null) {
             // artifact installed into the local repo is always accepted
             result.setAvailable(true);
             return true;
         }
         String context = result.getRequest().getContext();
         for (RemoteRepository repository : result.getRequest().getRepositories()) {
             String trackingKey = getTrackingRepositoryKey(repository, context);
             if (props.get(getKey(path, trackingKey)) != null) {
                 // artifact downloaded from remote repository is accepted only downloaded from request
                 // repositories
                 result.setAvailable(true);
                 result.setRepository(repository);
                 return true;
             }
             if (legacyLocalRepository) {
                 // Backward compatibility fallback: if the tracking key function is URL-qualified (e.g. nid_hurl)
                 // but the tracking file was written by an older resolver using the system-wide key function
                 // (e.g. nid, producing ID-only entries like "artifact>central="), the URL-qualified lookup above
                 // misses. Try the system-wide key function as a fallback: if it matches, the artifact was genuinely
                 // downloaded from this repository under the old key scheme. Accept it and log a migration notice.
                 String legacyKey = simpleRepositoryKeyFunction.apply(repository, context);
                 if (!legacyKey.equals(trackingKey) && props.get(getKey(path, legacyKey)) != null) {
                     LOGGER.debug(
                             "Accepting locally cached artifact {} via legacy tracking key '{}'"
                                     + " (current key function would produce '{}'); the entry will be"
                                     + " upgraded on next download",
                             path.getFileName(),
                             legacyKey,
                             trackingKey);
                     result.setAvailable(true);
                     result.setRepository(repository);
                     return true;
                 }
                 // Same-ID-different-URL fallback: if the tracking file contains a URL-qualified entry for the
                 // same repository ID but with a different URL hash (e.g. real Central tracked as
                 // "central-<sha1(realUrl)>=" but the current build overrides central to "file:target/null"),
                 // the exact lookup misses because sha1(realUrl) != sha1(file:target/null). Match by repo-ID
                 // prefix: any entry starting with "filename>repoId-" is accepted as originating from the same
                 // logical repository. The remainder must be exactly one SHA-1 hash, otherwise a different repository
                 // whose ID merely starts with "repoId-" (e.g. "central-snapshots") would be accepted as well.
                 String repoIdPrefix = getKey(path, legacyKey + "-");
                 for (Object key : props.keySet()) {
                     String k = key.toString();
                     if (k.startsWith(repoIdPrefix) && isSha1(k.substring(repoIdPrefix.length()))) {
                         LOGGER.debug(
                                 "Accepting locally cached artifact {} via same-id tracking entry '{}'"
                                         + " (current URL-qualified key would be '{}')",
                                 path.getFileName(),
                                 k,
                                 getKey(path, trackingKey));
                         result.setAvailable(true);
                         result.setRepository(repository);
                         return true;
                     }
                 }
             }
         }
         return false;
     }
 
     private static boolean isSha1(String s) {
         return SHA1_HEX.matcher(s).matches();
     }
 
     @Override
     public void add(RepositorySystemSession session, LocalArtifactRegistration request) {
         Collection<String> repositories;
         // no contexts would record nothing, leaving the artifact untracked, hence later accepted as locally installed
         Collection<String> contexts =
                 request.getContexts().isEmpty() ? Collections.singleton("") : request.getContexts();
         if (request.getRepository() == null) {
             repositories = Collections.singleton(LOCAL_REPO_ID);
         } else {
             repositories = getRepositoryKeys(request.getRepository(), contexts);
         }
         if (request.getRepository() == null) {
             addArtifact(request.getArtifact(), repositories, null, null);
         } else {
             for (String context : contexts) {
                 addArtifact(request.getArtifact(), repositories, request.getRepository(), context);
             }
         }
     }
 
     private Collection<String> getRepositoryKeys(RemoteRepository repository, Collection<String> contexts) {
         Collection<String> keys = new HashSet<>();
 
         if (contexts != null) {
             for (String context : contexts) {
                 keys.add(getTrackingRepositoryKey(repository, context));
             }
         }
 
         return keys;
     }
 
     private void addArtifact(
             Artifact artifact, Collection<String> repositories, RemoteRepository repository, String context) {
         requireNonNull(artifact, "artifact cannot be null");
         Path file = repository == null
                 ? getAbsolutePathForLocalArtifact(artifact)
                 : getAbsolutePathForRemoteArtifact(artifact, repository, context);
         addRepo(file, repositories);
     }
 
     private Properties readRepos(Path artifactPath) {
         Path trackingFile = getTrackingFile(artifactPath);
         return trackingFileCache.computeIfAbsent(trackingFile, tf -> {
             Properties props = trackingFileManager.read(tf);
             return (props != null) ? props : EMPTY_PROPERTIES;
         });
     }
 
     /**
      * Reads the tracking file for given artifact directly from disk, bypassing (and deliberately not populating)
      * {@link #trackingFileCache}: callers use the result for a trust-increasing decision, which must not be taken
      * on — nor allowed to re-cache — possibly stale state.
      */
     private Properties readReposFresh(Path artifactPath) {
         Properties props = trackingFileManager.read(getTrackingFile(artifactPath));
         return (props != null) ? props : EMPTY_PROPERTIES;
     }
 
     private void addRepo(Path artifactPath, Collection<String> repositories) {
         Map<String, String> updates = new HashMap<>();
         for (String repository : repositories) {
             updates.put(getKey(artifactPath, repository), "");
         }
 
         Path trackingPath = getTrackingFile(artifactPath);
 
         // Invalidate cache before AND after the write. Before: using put() with the returned Properties
         // would be racy — two concurrent addRepo() calls could reorder their puts, leaving stale data.
         // After: a reader may re-populate the cache with the pre-write contents between the first
         // invalidation and the write completing; without a post-write invalidation that stale entry —
         // which is trust-affecting, see checkFind — would survive for the whole session.
         trackingFileCache.remove(trackingPath);
         try {
             trackingFileManager.update(trackingPath, updates);
         } finally {
             trackingFileCache.remove(trackingPath);
         }
     }
 
     private Path getTrackingFile(Path artifactPath) {
         return artifactPath.getParent().resolve(trackingFilename);
     }
 
     private String getKey(Path path, String repository) {
         return path.getFileName() + ">" + repository;
     }
 
     /**
      * Returns the tracking key of given repository, derived with the tracking-scoped key function (URL-qualified
      * by default). Deliberately distinct from {@link #simpleRepositoryKeyFunction}, which follows
      * the Maven 3.9 (Resolver 1.x) key function and is used for path composition: tracking must bind an artifact to the full
      * identity of its origin, while on-disk layout and repository aggregation identity stay unchanged.
      */
     private String getTrackingRepositoryKey(RemoteRepository repository, String context) {
         return trackingRepositoryKeyFunction.apply(repository, context);
     }
 
     private boolean isTracked(Properties props, Path path) {
         if (props != null) {
             String keyPrefix = path.getFileName() + ">";
             for (Object key : props.keySet()) {
                 if (key.toString().startsWith(keyPrefix)) {
                     return true;
                 }
             }
         }
         return false;
     }
 }