/*

 * Copyright (c) 2016, Oracle and/or its affiliates. All rights reserved.

 * 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,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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package com.sun.tools.jdeps;

import java.io.PrintWriter;

import java.lang.module.ModuleDescriptor;

import java.util.Deque;

import java.util.HashSet;

import java.util.LinkedList;

import java.util.Map;

import java.util.Optional;

import java.util.Set;

import java.util.stream.Stream;

import static java.lang.module.ModuleDescriptor.Requires.Modifier.*;

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

/**

 * A builder to create a Graph<Module>

 */

public class ModuleGraphBuilder extends Graph.Builder<Module> {

    final JdepsConfiguration config;

    ModuleGraphBuilder(JdepsConfiguration config) {

        this.config = config;

    }

    /**

     * Adds a module to the graph.

     */

    ModuleGraphBuilder addModule(Module module) {

        addNode(module);

        return this;

    }

    /**

     * Apply transitive reduction on the resulting graph

     */

    public Graph<Module> reduced() {

        Graph<Module> graph = build();

        // transitive reduction

        Graph<Module> newGraph = buildGraph(graph.edges()).reduce();

        if (DEBUG) {

            PrintWriter log = new PrintWriter(System.err);

            System.err.println("before transitive reduction: ");

            graph.printGraph(log);

            System.err.println("after transitive reduction: ");

            newGraph.printGraph(log);

        }

        return newGraph;

    }

    public Graph<Module> buildGraph() {

        Graph<Module> graph = build();

        return buildGraph(graph.edges());

    }

    /**

     * Build a graph of module from the given dependences.

     *

     * It transitively includes all implied read edges.

     */

    private Graph<Module> buildGraph(Map<Module, Set<Module>> edges) {

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

        Set<Module> visited = new HashSet<>();

        Deque<Module> deque = new LinkedList<>();

        edges.entrySet().stream().forEach(e -> {

            Module m = e.getKey();

            deque.add(m);

            e.getValue().stream().forEach(v -> {

                deque.add(v);

                builder.addEdge(m, v);

            });

        });

        // read requires transitive from ModuleDescriptor

        Module source;

        while ((source = deque.poll()) != null) {

            if (visited.contains(source))

                continue;

            visited.add(source);

            builder.addNode(source);

            Module from = source;

            requiresTransitive(from).forEach(m -> {

                deque.add(m);

                builder.addEdge(from, m);

            });

        }

        return builder.build();

    }

    /*

     * Returns a stream of modules upon which the given module `requires transitive`

     */

    public Stream<Module> requiresTransitive(Module m) {

        // find requires transitive

        return m.descriptor()

                .requires().stream()

                .filter(req -> req.modifiers().contains(TRANSITIVE))

                .map(ModuleDescriptor.Requires::name)

                .map(config::findModule)

                .flatMap(Optional::stream);

    }

}