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package io.protostuff.runtime;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * Field mapping implemented on top of hash for field lookup by number.
 *
 * This is the less efficient than {@code ArrayFieldMap} for almost all cases.
 * But in case when field numbers are sparse and especially when max field
 * number is big - this mapping should be used.
 *
 * @see io.protostuff.runtime.ArrayFieldMap
 *
 * @author Kostiantyn Shchepanovskyi
 */
final class HashFieldMap implements FieldMap
{
    private static final FieldComparator FIELD_COMPARATOR = new FieldComparator();
    private final List> fields;
    private final Map> fieldsByNumber;
    private final Map> fieldsByName;

    public HashFieldMap(Collection> fields)
    {
        fieldsByName = new HashMap>();
        fieldsByNumber = new HashMap>();
        for (Field f : fields)
        {
            if (fieldsByName.containsKey(f.name))
            {
                Field prev = fieldsByName.get(f.name);
                throw new IllegalStateException(prev + " and " + f + " cannot have the same name.");
            }
            if (fieldsByNumber.containsKey(f.number))
            {
                Field prev = fieldsByNumber.get(f.number);
                throw new IllegalStateException(prev + " and " + f + " cannot have the same number.");
            }
            this.fieldsByNumber.put(f.number, f);
            this.fieldsByName.put(f.name, f);
        }

        List> fieldList = new ArrayList>(fields.size());
        fieldList.addAll(fields);
        Collections.sort(fieldList, FIELD_COMPARATOR);
        this.fields = Collections.unmodifiableList(fieldList);
    }

    @Override
    public Field getFieldByNumber(int n)
    {
        return fieldsByNumber.get(n);
    }

    @Override
    public Field getFieldByName(String fieldName)
    {
        return fieldsByName.get(fieldName);
    }

    @Override
    public int getFieldCount()
    {
        return fields.size();
    }

    @Override
    public List> getFields()
    {
        return fields;
    }

    private static class FieldComparator implements Comparator>
    {
        @Override
        public int compare(Field o1, Field o2)
        {
            return compare(o1.number, o2.number);
        }

        public static int compare(int x, int y) {
            return (x < y) ? -1 : ((x == y) ? 0 : 1);
        }
    }
}