com.fluxtion.runtime.dataflow.groupby.GroupBy Maven / Gradle / Ivy

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package com.fluxtion.runtime.dataflow.groupby;

import lombok.Value;

import java.util.Collection;
import java.util.Collections;
import java.util.Map;

public interface GroupBy {

    KeyValue KV_KEY_VALUE = new KeyValue<>(null, null);

    Map toMap();

    Collection values();

    default V lastValue() {
        return null;
    }

    default KeyValue lastKeyValue() {
        return emptyKey();
    }

    @SuppressWarnings("unchecked")
    static  KeyValue emptyKey() {
        return (KeyValue) KV_KEY_VALUE;
    }

    @Value
    class KeyValue {
        K key;
        V value;

        public Double getValueAsDouble() {
            return (Double) value;
        }

        public Long getValueAsLong() {
            return (Long) value;
        }

        public Integer getValueAsInt() {
            return (Integer) value;
        }
    }

    static  GroupBy emptyCollection() {
        return new EmptyGroupBy<>();
    }

    class EmptyGroupBy implements GroupBy {
        @Override
        public V lastValue() {
            return null;
        }

        @Override
        public KeyValue lastKeyValue() {
            return null;
        }

        @Override
        public Map toMap() {
            return Collections.emptyMap();
        }

        @Override
        public Collection values() {
            return Collections.emptyList();
        }
    }
}