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package com.github.andyshao.util.stream;

import lombok.AllArgsConstructor;
import lombok.NoArgsConstructor;

import java.util.Collections;
import java.util.EnumSet;
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;

/**
 * 
 * Title:

 * Descript:

 * Copyright: Copryright(c) Jan 16, 2018

 * Encoding: UNIX UTF-8
 * 
 * @author weichuang.shao
 *
 * @param  the type of input elements to the reduction operation
 * @param  the mutable accumulation type of the reduction operation (often
 *            hidden as an implementation detail)
 * @param  the result type of the reduction operation
 * @since 3.2.9
 */
@AllArgsConstructor
@NoArgsConstructor
public class CollectorImpl implements Collector {
    private Supplier supplier;
    private BiConsumer accumulator;
    private BinaryOperator combiner;
    private Function finisher;
    private Set characteristics;
    /**CH concurrent ID*/
    public static final Set CH_CONCURRENT_ID =
        Collections.unmodifiableSet(EnumSet.of(Collector.Characteristics.CONCURRENT , Collector.Characteristics.UNORDERED , Collector.Characteristics.IDENTITY_FINISH));
    /**CH concurrent NOID*/
    public static final Set CH_CONCURRENT_NOID = Collections.unmodifiableSet(EnumSet.of(Collector.Characteristics.CONCURRENT , Collector.Characteristics.UNORDERED));
    /**CH ID*/
    public static final Set CH_ID = Collections.unmodifiableSet(EnumSet.of(Collector.Characteristics.IDENTITY_FINISH));
    /**CH Unordered ID*/
    public static final Set CH_UNORDERED_ID = Collections.unmodifiableSet(EnumSet.of(Collector.Characteristics.UNORDERED , Collector.Characteristics.IDENTITY_FINISH));
    /**CH NOID*/
    public static final Set CH_NOID = Collections.emptySet();

    @Override
    public Supplier supplier() {
        return this.supplier;
    }

    @Override
    public BiConsumer accumulator() {
        return this.accumulator;
    }

    @Override
    public BinaryOperator combiner() {
        return this.combiner;
    }

    @Override
    public Function finisher() {
        return this.finisher;
    }

    @Override
    public Set characteristics() {
        return this.characteristics;
    }

    /**
     * builder
     * @return {@link CollectorImpl.Builder}
     * @param  input type
     * @param  accumulate type
     * @param  return type
     */
    public static final  CollectorImpl.Builder builder() {
    	return new CollectorImpl.Builder();
    }

    /**
     * return type is accumulate type
     * @return {@link CollectorImpl.Builder}
     * @param  input type
     * @param  accumulate type
     */
    public static final  CollectorImpl.Builder idBuilder() {
    	return CollectorImpl.builder()
    		.withFinisher(Function.identity())
    		.withCharacteristics(CH_ID);
    }

    /**
     * return type is accumulate type, and it is concurrent mode
     * @return {@link CollectorImpl.Builder}
     * @param  input type
     * @param  accumulate type
     */
    public static final  CollectorImpl.Builder idCurrentBuilder() {
    	return CollectorImpl.builder()
        		.withFinisher(Function.identity())
        		.withCharacteristics(CH_CONCURRENT_ID);
    }

    /**
     * {@link CollectorImpl} builder
     * @param  input type
     * @param  accumulate type
     * @param  return type
     */
    public static class Builder {
        private Supplier supplier;
        private BiConsumer accumulator;
        private BinaryOperator combiner;
        private Function finisher;
        private Set characteristics;

        /**
         * set {@link java.util.stream.Collector.Characteristics}
         * @param characteristics {@link java.util.stream.Collector.Characteristics}
         * @return {@link Builder}
         */
        public Builder withCharacteristics(Set characteristics){
            this.characteristics = characteristics;
            return this;
        }

        /**
         * set accumulator to result convertor
         * @param finisher the convertor
         * @return {@link Builder}
         */
        public Builder withFinisher(Function finisher){
            this.finisher = finisher;
            return this;
        }

        /**
         * set accumulator combination
         * @param combiner combination function
         * @return {@link Builder}
         */
        public Builder withCombiner(BinaryOperator combiner){
            this.combiner = combiner;
            return this;
        }

        /**
         * set accumulator
         * @param accumulator accumulated function
         * @return {@link Builder}
         */
        public Builder withAccumulator(BiConsumer accumulator){
            this.accumulator = accumulator;
            return this;
        }

        /**
         * build operation
         * @return {@link CollectorImpl}
         */
        public CollectorImpl build() {
            return new CollectorImpl<>(supplier , accumulator , combiner , finisher , characteristics);
        }

        /**
         * set accumulator creator
         * @param supplier accumulator creator
         * @return {@link Builder}
         */
        public Builder withSupplier(Supplier supplier){
            this.supplier = supplier;
            return this;
        }
    }
}