com.github.paganini2008.devtools.beans.streaming.Groups Maven / Gradle / Ivy

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package com.github.paganini2008.devtools.beans.streaming;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.function.Function;
import java.util.function.Predicate;
import java.util.stream.Collectors;

import com.github.paganini2008.devtools.jdbc.ResultSetSlice;

/**
 * 
 * Groups
 * 
 * @author Fred Feng
 * 
 * 
 * @version 1.0
 */
public class Groups implements Groupable {

	private List> groups = new ArrayList>();

	Groups(List elements) {
		groups.add(new GroupImpl(new LinkedHashMap<>(), elements, null));
	}

	public Groupable having(Predicate> predicate) {
		groups = groups.stream().filter(predicate).collect(Collectors.toList());
		return this;
	}

	public Groupable orderBy(Sort> sort) {
		this.groups.sort(sort);
		return this;
	}

	public  Groupable groupBy(Function function, String attributeName) {
		List> updated = new ArrayList>();
		for (Group group : new ArrayList>(groups)) {
			updated.addAll(divide(group, function, attributeName));
		}
		groups.clear();
		groups.addAll(updated);
		return this;
	}

	public  ResultSetSlice setTransformer(Transformer, T> transformer) {
		return new MemoryResultSetSlice<>(groups, transformer);
	}

	private  List> divide(Group group, Function function, String attributeName) {
		List> groups = new ArrayList>();
		Map> data = group.elements().stream().collect(Collectors.groupingBy(function, Collectors.toList()));
		for (Map.Entry> entry : data.entrySet()) {
			Map attributes = new LinkedHashMap(group.getAttributes());
			attributes.put(attributeName, entry.getKey());
			groups.add(new GroupImpl(attributes, entry.getValue(), group));
		}
		return groups;
	}

	/**
	 * 
	 * GroupImpl
	 * 
	 * @author Fred Feng
	 * 
	 * @version 1.0
	 */
	static class GroupImpl implements Group, Serializable {

		private static final long serialVersionUID = -5752728250597378290L;
		private final Map attributes;
		private final List elements;
		private final Group rollup;

		GroupImpl(Map attributes, List elements, Group rollup) {
			this.attributes = attributes;
			this.elements = elements;
			this.rollup = rollup;
		}

		public  T summarize(Calculation calculation) {
			return calculation.getResult(elements);
		}

		public Map getAttributes() {
			return attributes;
		}

		public List elements() {
			return elements;
		}

		public Group rollup() {
			return rollup;
		}

	}

}