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A DNS client that can iteratively resolve resource records

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/*
 * Copyright 2015-2024 the original author or authors
 *
 * This software is licensed under the Apache License, Version 2.0,
 * the GNU Lesser General Public License version 2 or later ("LGPL")
 * and the WTFPL.
 * You may choose either license to govern your use of this software only
 * upon the condition that you accept all of the terms of either
 * the Apache License 2.0, the LGPL 2.1+ or the WTFPL.
 */
package org.minidns.iterative;

import java.net.InetAddress;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Set;

import org.minidns.dnsmessage.DnsMessage;
import org.minidns.dnsmessage.Question;
import org.minidns.iterative.IterativeClientException.LoopDetected;
import org.minidns.iterative.IterativeClientException.MaxIterativeStepsReached;

public class ResolutionState {

    private final IterativeDnsClient recursiveDnsClient;
    private final HashMap> map = new HashMap<>();
    private int steps;

    ResolutionState(IterativeDnsClient recursiveDnsClient) {
        this.recursiveDnsClient = recursiveDnsClient;
    }

    void recurse(InetAddress address, DnsMessage query) throws LoopDetected, MaxIterativeStepsReached {
        Question question = query.getQuestion();
        if (!map.containsKey(address)) {
            map.put(address, new HashSet());
        } else if (map.get(address).contains(question)) {
            throw new IterativeClientException.LoopDetected(address, question);
        }

        if (++steps > recursiveDnsClient.maxSteps) {
            throw new IterativeClientException.MaxIterativeStepsReached(); 
        }

        boolean isNew = map.get(address).add(question);
        assert isNew;
    }

    void decrementSteps() {
        steps--;
    }

}