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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

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 *

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package com.sun.tools.jdeps;

import static com.sun.tools.jdeps.JdepsFilter.DEFAULT_FILTER;

import static com.sun.tools.jdeps.Module.trace;

import static com.sun.tools.jdeps.Graph.*;

import java.lang.module.ModuleDescriptor.Requires;

import java.io.IOException;

import java.util.Collections;

import java.util.Deque;

import java.util.HashMap;

import java.util.HashSet;

import java.util.LinkedList;

import java.util.Map;

import java.util.Optional;

import java.util.Set;

import java.util.stream.Collectors;

import java.util.stream.Stream;

/**

 * Inverse transitive dependency analysis (compile-time view)

 */

public class InverseDepsAnalyzer extends DepsAnalyzer {

    // the end points for the resulting paths to be reported

    private final Map<Archive, Set<Archive>> endPoints = new HashMap<>();

    // target archives for inverse transitive dependence analysis

    private final Set<Archive> targets = new HashSet<>();

    public InverseDepsAnalyzer(JdepsConfiguration config,

                               JdepsFilter filter,

                               JdepsWriter writer,

                               Analyzer.Type verbose,

                               boolean apiOnly) {

        super(config, filter, writer, verbose, apiOnly);

    }

    public boolean run() throws IOException {

        try {

            if (apiOnly) {

                finder.parseExportedAPIs(rootArchives.stream());

            } else {

                finder.parse(rootArchives.stream());

            }

            archives.addAll(rootArchives);

            Set<Archive> archives = archives();

            // If -package or -regex is specified, the archives that reference

            // the matching types are used as the targets for inverse

            // transitive analysis.  If -requires is specified, the

            // specified modules are the targets.

            if (filter.requiresFilter().isEmpty()) {

                targets.addAll(archives);

            } else {

                filter.requiresFilter().stream()

                      .map(configuration::findModule)

                      .flatMap(Optional::stream)

                      .forEach(targets::add);

            }

            // If -package or -regex is specified, the end points are

            // the matching archives.  If -requires is specified,

            // the end points are the modules specified in -requires.

            if (filter.requiresFilter().isEmpty()) {

                Map<Archive, Set<Archive>> dependences = finder.dependences();

                targets.forEach(source -> endPoints.put(source, dependences.get(source)));

            } else {

                targets.forEach(t -> endPoints.put(t, Collections.emptySet()));

            }

            analyzer.run(archives, finder.locationToArchive());

            // print the first-level of dependencies

            if (writer != null) {

                writer.generateOutput(archives, analyzer);

            }

        } finally {

            finder.shutdown();

        }

        return true;

    }

    /**

     * Returns the target archives determined from the dependency analysis.

     *

     * Inverse transitive dependency will find all nodes that depend

     * upon the returned set of archives directly and indirectly.

     */

    public Set<Archive> targets() {

        return Collections.unmodifiableSet(targets);

    }

    /**

     * Finds all inverse transitive dependencies using the given requires set

     * as the targets, if non-empty.  If the given requires set is empty,

     * use the archives depending the packages specified in -regex or -p options.

     */

    public Set<Deque<Archive>> inverseDependences() throws IOException {

        // create a new dependency finder to do the analysis

        DependencyFinder dependencyFinder = new DependencyFinder(configuration, DEFAULT_FILTER);

        try {

            // parse all archives in unnamed module to get compile-time dependences

            Stream<Archive> archives =

                Stream.concat(configuration.initialArchives().stream(),

                              configuration.classPathArchives().stream());

            if (apiOnly) {

                dependencyFinder.parseExportedAPIs(archives);

            } else {

                dependencyFinder.parse(archives);

            }

            Graph.Builder<Archive> builder = new Graph.Builder<>();

            // include all target nodes

            targets().forEach(builder::addNode);

            // transpose the module graph

            configuration.getModules().values().stream()

                .forEach(m -> {

                    builder.addNode(m);

                    m.descriptor().requires().stream()

                        .map(Requires::name)

                        .map(configuration::findModule)  // must be present

                        .forEach(v -> builder.addEdge(v.get(), m));

                });

            // add the dependences from the analysis

            Map<Archive, Set<Archive>> dependences = dependencyFinder.dependences();

            dependences.entrySet().stream()

                .forEach(e -> {

                    Archive u = e.getKey();

                    builder.addNode(u);

                    e.getValue().forEach(v -> builder.addEdge(v, u));

                });

            // transposed dependence graph.

            Graph<Archive> graph = builder.build();

            trace("targets: %s%n", targets());

            // Traverse from the targets and find all paths

            // rebuild a graph with all nodes that depends on targets

            // targets directly and indirectly

            return targets().stream()

                .map(t -> findPaths(graph, t))

                .flatMap(Set::stream)

                .collect(Collectors.toSet());

        } finally {

            dependencyFinder.shutdown();

        }

    }

    /**

     * Returns all paths reachable from the given targets.

     */

    private Set<Deque<Archive>> findPaths(Graph<Archive> graph, Archive target) {

        // path is in reversed order

        Deque<Archive> path = new LinkedList<>();

        path.push(target);

        Set<Edge<Archive>> visited = new HashSet<>();

        Deque<Edge<Archive>> deque = new LinkedList<>();

        deque.addAll(graph.edgesFrom(target));

        if (deque.isEmpty()) {

            return makePaths(path).collect(Collectors.toSet());

        }

        Set<Deque<Archive>> allPaths = new HashSet<>();

        while (!deque.isEmpty()) {

            Edge<Archive> edge = deque.pop();

            if (visited.contains(edge))

                continue;

            Archive node = edge.v;

            path.addLast(node);

            visited.add(edge);

            Set<Edge<Archive>> unvisitedDeps = graph.edgesFrom(node)

                    .stream()

                    .filter(e -> !visited.contains(e))

                    .collect(Collectors.toSet());

            trace("visiting %s %s (%s)%n", edge, path, unvisitedDeps);

            if (unvisitedDeps.isEmpty()) {

                makePaths(path).forEach(allPaths::add);

                path.removeLast();

            }

            // push unvisited adjacent edges

            unvisitedDeps.stream().forEach(deque::push);

            // when the adjacent edges of a node are visited, pop it from the path

            while (!path.isEmpty()) {

                if (visited.containsAll(graph.edgesFrom(path.peekLast())))

                    path.removeLast();

                else

                    break;

            }

        }

       return allPaths;

    }

    /**

     * Prepend end point to the path

     */

    private Stream<Deque<Archive>> makePaths(Deque<Archive> path) {

        Set<Archive> nodes = endPoints.get(path.peekFirst());

        if (nodes == null || nodes.isEmpty()) {

            return Stream.of(new LinkedList<>(path));

        } else {

            return nodes.stream().map(n -> {

                Deque<Archive> newPath = new LinkedList<>();

                newPath.addFirst(n);

                newPath.addAll(path);

                return newPath;

            });

        }

    }

}