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package org.cloudfoundry.identity.uaa.util;

import java.util.Collections;
import java.util.HashMap;
import java.util.Set;
import java.util.function.BiConsumer;
import java.util.function.BinaryOperator;
import java.util.function.Function;
import java.util.function.Supplier;
import java.util.stream.Collector;

public class MapCollector implements Collector, HashMap> {

    private final Function keyMapper;
    private final Function valueMapper;

    public MapCollector(Function keyMapper, Function valueMapper) {

        this.keyMapper = keyMapper;
        this.valueMapper = valueMapper;
    }

    @Override
    public Supplier> supplier() {
        return HashMap::new;
    }

    @Override
    public BiConsumer, T> accumulator() {
        return (m, item) -> m.put(keyMapper.apply(item), valueMapper.apply(item));
    }

    @Override
    public BinaryOperator> combiner() {
        return (left, right) -> { throw new IllegalStateException(String.format("Duplicate key %s", left)); };
    }

    @Override
    public Function, HashMap> finisher() {
        return m -> m;
    }

    @Override
    public Set characteristics() {
        return Collections.singleton(Characteristics.UNORDERED);
    }
}