package com.fasterxml.jackson.core.json;

import java.util.*;

import com.fasterxml.jackson.core.*;

Helper class used if Feature.STRICT_DUPLICATE_DETECTION is enabled. Optimized to try to limit memory usage and processing overhead for smallest entries, but without adding trashing (immutable objects would achieve optimal memory usage but lead to significant number of discarded temp objects for scopes with large number of entries). Another consideration is trying to limit actual number of compiled classes as it contributes significantly to overall jar size (due to linkage etc). 
Since:
2.3/**
 * Helper class used if
 * {@link com.fasterxml.jackson.core.JsonParser.Feature#STRICT_DUPLICATE_DETECTION}
 * is enabled.
 * Optimized to try to limit memory usage and processing overhead for smallest
 * entries, but without adding trashing (immutable objects would achieve optimal
 * memory usage but lead to significant number of discarded temp objects for
 * scopes with large number of entries). Another consideration is trying to limit
 * actual number of compiled classes as it contributes significantly to overall
 * jar size (due to linkage etc).
 * 
 * @since 2.3
 */
public class DupDetector
{
    
We need to store a back-reference here to parser/generator.
/**
     * We need to store a back-reference here to parser/generator.
     */
    protected final Object _source;

    protected String _firstName;

    protected String _secondName;
    
    
Lazily constructed set of names already seen within this context.
/**
     * Lazily constructed set of names already seen within this context.
     */
    protected HashSet<String> _seen;

    private DupDetector(Object src) {
        _source = src;
    }

    public static DupDetector rootDetector(JsonParser p) {
        return new DupDetector(p);
    }

    public static DupDetector rootDetector(JsonGenerator g) {
        return new DupDetector(g);
    }
    
    public DupDetector child() {
        return new DupDetector(_source);
    }

    public void reset() {
        _firstName = null;
        _secondName = null;
        _seen = null;
    }

    public JsonLocation findLocation() {
        // ugly but:
        if (_source instanceof JsonParser) {
            return ((JsonParser)_source).getCurrentLocation();
        }
        // do generators have a way to provide Location? Apparently not...
        return null;
    }

    
Since:
2.7/**
     * @since 2.7
     */
    public Object getSource() {
        return _source;
    }

    public boolean isDup(String name) throws JsonParseException
    {
        if (_firstName == null) {
            _firstName = name;
            return false;
        }
        if (name.equals(_firstName)) {
            return true;
        }
        if (_secondName == null) {
            _secondName = name;
            return false;
        }
        if (name.equals(_secondName)) {
            return true;
        }
        if (_seen == null) {
            _seen = new HashSet<String>(16); // 16 is default, seems reasonable
            _seen.add(_firstName);
            _seen.add(_secondName);
        }
        return !_seen.add(name);
    }
}