/*
    * 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.apache.maven.impl;
  
  import java.io.IOException;
  import java.lang.module.ModuleDescriptor;
  import java.nio.file.Files;
  import java.nio.file.Path;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.LinkedHashMap;
  import java.util.List;
  import java.util.Map;
  import java.util.Objects;
  import java.util.Optional;
  import java.util.Set;
  import java.util.function.Predicate;
  
  import org.apache.maven.api.Dependency;
  import org.apache.maven.api.JavaPathType;
  import org.apache.maven.api.Node;
  import org.apache.maven.api.PathType;
  import org.apache.maven.api.services.DependencyResolverException;
  import org.apache.maven.api.services.DependencyResolverRequest;
  import org.apache.maven.api.services.DependencyResolverResult;
  
  /**
   * The result of collecting dependencies with a dependency resolver.
   * New instances are initially empty. Callers must populate with calls
   * to the following methods, in that order:
   *
   * <ul>
   *   <li>{@link #addOutputDirectory(Path, Path)} (optional)</li>
   *   <li>{@link #addDependency(Node, Dependency, Predicate, Path)}</li>
   * </ul>
   *
   * @see DefaultDependencyResolver#resolve(DependencyResolverRequest)
   */
  public class DefaultDependencyResolverResult implements DependencyResolverResult {
      /**
       * The corresponding request.
       */
      private final DependencyResolverRequest request;
  
      /**
       * The exceptions that occurred while building the dependency graph.
       */
      private final List<Exception> exceptions;
  
      /**
       * The root node of the dependency graph.
       */
      private final Node root;
  
      /**
       * The ordered list of the flattened dependency nodes.
       */
      private final List<Node> nodes;
  
      /**
       * The file paths of all dependencies, regardless on which Java tool option those paths should be placed.
       */
      private final List<Path> paths;
  
      /**
       * The file paths of all dependencies, dispatched according the Java options where to place them.
       */
      private final Map<PathType, List<Path>> dispatchedPaths;
  
      /**
       * The dependencies together with the path to each dependency.
       */
      private final Map<Dependency, Path> dependencies;
  
      /**
       * Information about modules in the main output. This field is initially null and is set to a non-null
       * value when the output directories have been set, or when it is too late for setting them.
       */
      private PathModularization outputModules;
  
      /**
       * Cache of module information about each dependency.
       */
     private final PathModularizationCache cache;
 
     /**
      * Creates an initially empty result with a temporary cache.
      * Callers should add path elements by calls to {@link #addDependency(Node, Dependency, Predicate, Path)}.
      *
      * <p><b>WARNING: this constructor may be removed in a future Maven release.</b>
      * The reason is because {@code DefaultDependencyResolverResult} needs a cache, which should
      * preferably be session-wide. How to manage such caches has not yet been clarified.</p>
      *
      * @param request the corresponding request
      * @param exceptions the exceptions that occurred while building the dependency graph
      * @param root the root node of the dependency graph
      * @param count estimated number of dependencies
      */
     public DefaultDependencyResolverResult(
             DependencyResolverRequest request, List<Exception> exceptions, Node root, int count) {
         this(
                 request,
                 new PathModularizationCache(DefaultDependencyResolver.getTargetVersion(request)),
                 exceptions,
                 root,
                 count);
     }
 
     /**
      * Creates an initially empty result. Callers should add path elements by calls
      * to {@link #addDependency(Node, Dependency, Predicate, Path)}.
      *
      * @param request the corresponding request
      * @param cache cache of module information about each dependency
      * @param exceptions the exceptions that occurred while building the dependency graph
      * @param root the root node of the dependency graph
      * @param count estimated number of dependencies
      */
     DefaultDependencyResolverResult(
             DependencyResolverRequest request,
             PathModularizationCache cache,
             List<Exception> exceptions,
             Node root,
             int count) {
         this.request = request;
         this.cache = Objects.requireNonNull(cache);
         this.exceptions = exceptions;
         this.root = root;
         nodes = new ArrayList<>(count);
         paths = new ArrayList<>(count);
         dispatchedPaths = new LinkedHashMap<>();
         dependencies = new LinkedHashMap<>(count + count / 3);
     }
 
     /**
      * Adds the given path element to the specified type of path.
      *
      * @param type the type of path (class-path, module-path, …)
      * @param path the path element to add
      */
     private void addPathElement(PathType type, Path path) {
         dispatchedPaths.computeIfAbsent(type, (t) -> new ArrayList<>()).add(path);
     }
 
     /**
      * Adds main and test output directories to the result. This method adds the main output directory
      * to the module path if it contains a {@code module-info.class}, or to the class path otherwise.
      * For the test output directory, the rules are more complex and are governed by the fact that
      * Java does not accept the placement of two modules of the same name on the module path.
      * So the modular test output directory usually needs to be placed in a {@code --path-module} option.
      *
      * <ul>
      *   <li>If the test output directory is modular, then:
      *     <ul>
      *       <li>If a test module name is identical to a main module name,
      *           place the test directory in a {@code --patch-module} option.</li>
      *       <li>Otherwise, place the test directory on the module path. However, this case
      *           (a module existing only in test output, not in main output) should be uncommon.</li>
      *     </ul>
      *   </li>
      *   <li>Otherwise (test output contains no module information), then:
      *     <ul>
      *       <li>If the main output is on the module path, place the test output
      *           on a {@code --patch-module} option.</li>
      *       <li>Otherwise (main output on the class path), place the test output on the class path too.</li>
      *     </ul>
      *   </li>
      * </ul>
      *
      * This method must be invoked before {@link #addDependency(Node, Dependency, Predicate, Path)}
      * if output directories are desired on the class path or module path.
      * This method can be invoked at most once.
      *
      * @param main the main output directory, or {@code null} if none
      * @param test the test output directory, or {@code null} if none
      * @throws IOException if an error occurred while reading module information
      *
      * TODO: this is currently not called. This is intended for use by Surefire and may move there.
      */
     void addOutputDirectory(Path main, Path test) throws IOException {
         if (outputModules != null) {
             throw new IllegalStateException("Output directories must be set first and only once.");
         }
         if (main != null) {
             outputModules = cache.getModuleInfo(main);
             addPathElement(outputModules.getPathType(), main);
         } else {
             outputModules = PathModularization.NONE;
         }
         if (test != null) {
             boolean addToClasspath = true;
             PathModularization testModules = cache.getModuleInfo(test);
             boolean isModuleHierarchy = outputModules.isModuleHierarchy || testModules.isModuleHierarchy;
             for (Object value : outputModules.descriptors.values()) {
                 String moduleName = name(value);
                 Path subdir = test;
                 if (isModuleHierarchy) {
                     // If module hierarchy is used, the directory names shall be the module names.
                     Path path = test.resolve(moduleName);
                     if (!Files.isDirectory(path)) {
                         // Main module without tests. It is okay.
                         continue;
                     }
                     subdir = path;
                 }
                 // When the same module is found in main and test output, the latter is patching the former.
                 addPathElement(JavaPathType.patchModule(moduleName), subdir);
                 addToClasspath = false;
             }
             /*
              * If the test output directory provides some modules of its own, add them.
              * Except for this unusual case, tests should never be added to the module-path.
              */
             for (Map.Entry<Path, Object> entry : testModules.descriptors.entrySet()) {
                 if (!outputModules.containsModule(name(entry.getValue()))) {
                     addPathElement(JavaPathType.MODULES, entry.getKey());
                     addToClasspath = false;
                 }
             }
             if (addToClasspath) {
                 addPathElement(JavaPathType.CLASSES, test);
             }
         }
     }
 
     /**
      * Adds a dependency node to the result.
      *
      * @param node the dependency node
      */
     void addNode(Node node) {
         nodes.add(node);
     }
 
     /**
      * Adds a dependency to the result. This method populates the {@link #nodes}, {@link #paths},
      * {@link #dispatchedPaths} and {@link #dependencies} collections with the given arguments.
      *
      * @param node the dependency node
      * @param dep the dependency for the given node, or {@code null} if none
      * @param filter filter the paths accepted by the tool which will consume the path.
      * @param path the path to the dependency, or {@code null} if the dependency was null
      * @throws IOException if an error occurred while reading module information
      */
     void addDependency(Node node, Dependency dep, Predicate<PathType> filter, Path path) throws IOException {
         nodes.add(node);
         if (dep == null) {
             return;
         }
         if (dependencies.put(dep, path) != null) {
             throw new IllegalStateException("Duplicated key: " + dep);
         }
         if (path == null) {
             return;
         }
         paths.add(path);
         /*
          * Dispatch the dependency to class path, module path, patch-module path, etc.
          * according the dependency properties. We need to process patch-module first,
          * because this type depends on whether a module of the same name has already
          * been added on the module-type.
          */
         // DependencyProperties properties = dep.getDependencyProperties();
         Set<PathType> pathTypes = dep.getType().getPathTypes();
         if (containsPatches(pathTypes)) {
             if (outputModules == null) {
                 // For telling users that it is too late for setting the output directory.
                 outputModules = PathModularization.NONE;
             }
             PathType type = null;
             for (Map.Entry<Path, Object> info :
                     cache.getModuleInfo(path).descriptors.entrySet()) {
                 String moduleName = name(info.getValue());
                 type = JavaPathType.patchModule(moduleName);
                 if (!containsModule(moduleName)) {
                     /*
                      * Not patching an existing module. This case should be unusual. If it nevertheless
                      * happens, add to class path or module path if allowed, or keep patching otherwise.
                      * The latter case (keep patching) is okay if the main module will be defined later.
                      */
                     type = cache.selectPathType(pathTypes, filter, path).orElse(type);
                 }
                 addPathElement(type, info.getKey());
                 // There is usually no more than one element, but nevertheless allow multi-modules.
             }
             /*
              * If the dependency has no module information, search for an artifact of the same groupId
              * and artifactId. If one is found, we are patching that module. If none is found, add the
              * dependency as a normal dependency.
              */
             if (type == null) {
                 Path main = findArtifactPath(dep.getGroupId(), dep.getArtifactId());
                 if (main != null) {
                     for (Map.Entry<Path, Object> info :
                             cache.getModuleInfo(main).descriptors.entrySet()) {
                         type = JavaPathType.patchModule(name(info.getValue()));
                         addPathElement(type, info.getKey());
                         // There is usually no more than one element, but nevertheless allow multi-modules.
                     }
                 }
             }
             if (type != null) {
                 return; // Dependency added, we are done.
             }
         }
         addPathElement(cache.selectPathType(pathTypes, filter, path).orElse(PathType.UNRESOLVED), path);
     }
 
     /**
      * Returns whether the given set of path types contains at least one patch for a module.
      */
     private boolean containsPatches(Set<PathType> types) {
         for (PathType type : types) {
             if (type instanceof JavaPathType.Modular modular) {
                 type = modular.rawType();
             }
             if (JavaPathType.PATCH_MODULE.equals(type)) {
                 return true;
             }
         }
         return false;
     }
 
     /**
      * Returns whether at least one previously added modular dependency contains a module of the given name.
      *
      * @param moduleName name of the module to search
      */
     private boolean containsModule(String moduleName) throws IOException {
         for (Path path : dispatchedPaths.getOrDefault(JavaPathType.MODULES, Collections.emptyList())) {
             if (cache.getModuleInfo(path).containsModule(moduleName)) {
                 return true;
             }
         }
         return false;
     }
 
     /**
      * Searches an artifact of the given group and artifact identifiers, and returns its path
      *
      * @param group the group identifier to search
      * @param artifact the artifact identifier to search
      * @return path to the desired artifact, or {@code null} if not found
      */
     private Path findArtifactPath(String group, String artifact) throws IOException {
         for (Map.Entry<Dependency, Path> entry : dependencies.entrySet()) {
             Dependency dep = entry.getKey();
             if (group.equals(dep.getGroupId()) && artifact.equals(dep.getArtifactId())) {
                 return entry.getValue();
             }
         }
         return null;
     }
 
     @Override
     public DependencyResolverRequest getRequest() {
         return request;
     }
 
     @Override
     public List<Exception> getExceptions() {
         return Collections.unmodifiableList(exceptions);
     }
 
     @Override
     public Node getRoot() {
         return root;
     }
 
     @Override
     public List<Node> getNodes() {
         return Collections.unmodifiableList(nodes);
     }
 
     @Override
     public List<Path> getPaths() {
         return Collections.unmodifiableList(paths);
     }
 
     @Override
     public Map<PathType, List<Path>> getDispatchedPaths() {
         return Collections.unmodifiableMap(dispatchedPaths);
     }
 
     @Override
     public Map<Dependency, Path> getDependencies() {
         return Collections.unmodifiableMap(dependencies);
     }
 
     @Override
     public Optional<ModuleDescriptor> getModuleDescriptor(Path dependency) throws IOException {
         Object value = cache.getModuleInfo(dependency).descriptors.get(dependency);
         return (value instanceof ModuleDescriptor moduleDescriptor) ? Optional.of(moduleDescriptor) : Optional.empty();
     }
 
     @Override
     public Optional<String> getModuleName(Path dependency) throws IOException {
         return Optional.ofNullable(
                 name(cache.getModuleInfo(dependency).descriptors.get(dependency)));
     }
 
     /**
      * Returns the module name for the given value of the {@link PathModularization#descriptors} map.
      */
     private static String name(final Object value) {
         if (value instanceof String string) {
             return string;
         } else if (value instanceof ModuleDescriptor moduleDescriptor) {
             return moduleDescriptor.name();
         } else {
             return null;
         }
     }
 
     @Override
     public Optional<String> warningForFilenameBasedAutomodules() {
         try {
             return cache.warningForFilenameBasedAutomodules(dispatchedPaths.get(JavaPathType.MODULES));
         } catch (IOException e) {
             throw new DependencyResolverException("Cannot read module information.", e);
         }
     }
 }