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/*
 * Copyright 2010-2015 JetBrains s.r.o.
 *
 * Licensed 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 kotlin.reflect.jvm.internal.impl.utils;

import org.jetbrains.annotations.NotNull;

import java.util.*;

public class DFS {
    public static  R dfs(@NotNull Collection nodes, @NotNull Neighbors neighbors, @NotNull Visited visited, @NotNull NodeHandler handler) {
        for (N node : nodes) {
            doDfs(node, neighbors, visited, handler);
        }
        return handler.result();
    }

    public static  R dfs(
        @NotNull Collection nodes,
        @NotNull Neighbors neighbors,
        @NotNull NodeHandler handler
    ) {
        return dfs(nodes, neighbors, new VisitedWithSet(), handler);
    }

    public static  R dfsFromNode(@NotNull N node, @NotNull Neighbors neighbors, @NotNull Visited visited, @NotNull NodeHandler handler) {
        doDfs(node, neighbors, visited, handler);
        return handler.result();
    }

    public static  void dfsFromNode(
            @NotNull N node,
            @NotNull Neighbors neighbors,
            @NotNull Visited visited
    ) {
        dfsFromNode(node, neighbors, visited, new AbstractNodeHandler() {
            @Override
            public Void result() {
                return null;
            }
        });
    }

    public static  List topologicalOrder(@NotNull Iterable nodes, @NotNull Neighbors neighbors, @NotNull Visited visited) {
        TopologicalOrder handler = new TopologicalOrder();
        for (N node : nodes) {
            doDfs(node, neighbors, visited, handler);
        }
        return handler.result();
    }

    public static  List topologicalOrder(@NotNull Iterable nodes, @NotNull Neighbors neighbors) {
        return topologicalOrder(nodes, neighbors, new VisitedWithSet());
    }

    private static  void doDfs(@NotNull N current, @NotNull Neighbors neighbors, @NotNull Visited visited, @NotNull NodeHandler handler) {
        if (!visited.checkAndMarkVisited(current)) return;
        if (!handler.beforeChildren(current)) return;

        for (N neighbor : neighbors.getNeighbors(current)) {
            doDfs(neighbor, neighbors, visited, handler);
        }
        handler.afterChildren(current);
    }

    public interface NodeHandler {
        boolean beforeChildren(N current);

        void afterChildren(N current);

        R result();
    }

    public interface Neighbors {
        @NotNull
        Iterable getNeighbors(N current);
    }

    public interface Visited {
        boolean checkAndMarkVisited(N current);
    }

    public static abstract class AbstractNodeHandler implements NodeHandler {
        @Override
        public boolean beforeChildren(N current) {
            return true;
        }

        @Override
        public void afterChildren(N current) {
        }
    }

    public static class VisitedWithSet implements Visited {
        private final Set visited;

        public VisitedWithSet() {
            this(new HashSet());
        }

        public VisitedWithSet(@NotNull Set visited) {
            this.visited = visited;
        }

        @Override
        public boolean checkAndMarkVisited(N current) {
            return visited.add(current);
        }
    }

    public static abstract class CollectingNodeHandler> extends AbstractNodeHandler {
        @NotNull
        protected final C result;

        protected CollectingNodeHandler(@NotNull C result) {
            this.result = result;
        }

        @Override
        @NotNull
        public C result() {
            return result;
        }
    }

    public static abstract class NodeHandlerWithListResult extends CollectingNodeHandler> {
        protected NodeHandlerWithListResult() {
            super(new LinkedList());
        }
    }

    public static class TopologicalOrder extends NodeHandlerWithListResult {
        @Override
        public void afterChildren(N current) {
            result.addFirst(current);
        }
    }
}