/*
 * Copyright 2004-2019 H2 Group. Multiple-Licensed under the MPL 2.0,
 * and the EPL 1.0 (http://h2database.com/html/license.html).
 * Initial Developer: H2 Group
 */
package org.h2.result;

import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;

import org.h2.util.Utils;
import org.h2.value.Value;

Merged result. Used to combine several results into one. Merged result will contain rows from all appended results. Results are not required to have the same lists of columns, but required to have compatible column definitions, for example, if one result has a Types.VARCHAR column NAME then another results that have NAME column should also define it with the same type. /**
 * Merged result. Used to combine several results into one. Merged result will
 * contain rows from all appended results. Results are not required to have the
 * same lists of columns, but required to have compatible column definitions,
 * for example, if one result has a {@link java.sql.Types#VARCHAR} column
 * {@code NAME} then another results that have {@code NAME} column should also
 * define it with the same type.
 */
public final class MergedResult {
    private final ArrayList<Map<SimpleResult.Column, Value>> data = Utils.newSmallArrayList();

    private final ArrayList<SimpleResult.Column> columns = Utils.newSmallArrayList();

    
Appends a result.
Params:
result – 
           result to append/**
     * Appends a result.
     *
     * @param result
     *            result to append
     */
    public void add(ResultInterface result) {
        int count = result.getVisibleColumnCount();
        if (count == 0) {
            return;
        }
        SimpleResult.Column[] cols = new SimpleResult.Column[count];
        for (int i = 0; i < count; i++) {
            SimpleResult.Column c = new SimpleResult.Column(result.getAlias(i), result.getColumnName(i),
                    result.getColumnType(i));
            cols[i] = c;
            if (!columns.contains(c)) {
                columns.add(c);
            }
        }
        while (result.next()) {
            if (count == 1) {
                data.add(Collections.singletonMap(cols[0], result.currentRow()[0]));
            } else {
                HashMap<SimpleResult.Column, Value> map = new HashMap<>();
                for (int i = 0; i < count; i++) {
                    SimpleResult.Column ci = cols[i];
                    map.put(ci, result.currentRow()[i]);
                }
                data.add(map);
            }
        }
    }

    
Returns merged results.
Returns:
result with rows from all appended result sets/**
     * Returns merged results.
     *
     * @return result with rows from all appended result sets
     */
    public SimpleResult getResult() {
        SimpleResult result = new SimpleResult();
        for (SimpleResult.Column c : columns) {
            result.addColumn(c);
        }
        for (Map<SimpleResult.Column, Value> map : data) {
            Value[] row = new Value[columns.size()];
            for (Map.Entry<SimpleResult.Column, Value> entry : map.entrySet()) {
                row[columns.indexOf(entry.getKey())] = entry.getValue();
            }
            result.addRow(row);
        }
        return result;
    }

    @Override
    public String toString() {
        return columns + ": " + data.size();
    }

}