# RowIterator.java

    package org.codefilarete.stalactite.sql.result;

    import javax.annotation.Nullable;
    import java.sql.ResultSet;
    import java.sql.SQLException;
    import java.util.Comparator;
    import java.util.Map;
    import java.util.TreeSet;

    import org.codefilarete.stalactite.sql.statement.binder.ParameterBinderIndex;
    import org.codefilarete.stalactite.sql.statement.binder.ResultSetReader;
    import org.codefilarete.stalactite.sql.statement.SQLStatement.BindingException;

    /**
     * {@link ResultSetIterator} specialized in {@link Row} building for each {@link ResultSet} line.
     *
     * @author Guillaume Mary
     */
    public class RowIterator extends ResultSetIterator<Row> {

    	/** Readers for each column of the {@link ResultSet}, by name (may contain double but doesn't matter, causes only extra conversion) */
    	private final Iterable<Decoder> decoders;

    	/**
    	 * Constructs an instance without {@link ResultSet} : it shall be set further with {@link #setResultSet(ResultSet)}.
    	 *
    	 * @param columnNameBinders columns and associated {@link ResultSetReader} to use for {@link ResultSet} reading
    	 */
    	public RowIterator(Map<String, ? extends ResultSetReader<?>> columnNameBinders) {
    		this(null, columnNameBinders);
    	}

    	/**
    	 * Constructs an instance that will iterate over the given {@link ResultSet}. It can be changed with {@link #setResultSet(ResultSet)}.
    	 *
    	 * @param rs a ResultSet to wrap into an {@link java.util.Iterator}
    	 * @param columnNameBinders column names and associated {@link ResultSetReader} to use for {@link ResultSet} reading
    	 */
    	public RowIterator(@Nullable ResultSet rs, Map<String, ? extends ResultSetReader<?>> columnNameBinders) {
    		super(rs);
    		decoders = Decoder.decoders(columnNameBinders.entrySet());
    	}

    	/**
    	 * Constructs an instance that will iterate over the given {@link ResultSet}. It can be changed with {@link #setResultSet(ResultSet)}.
    	 *
    	 * @param rs a ResultSet to wrap into an {@link java.util.Iterator}
    	 * @param columnNameBinders object to extract column names and associated {@link ResultSetReader} to use for <t>ResultSet</t> reading
    	 */
    	public RowIterator(ResultSet rs, ParameterBinderIndex<String, ? extends ResultSetReader> columnNameBinders) {
    		super(rs);
    		decoders = Decoder.decoders(columnNameBinders.all());
    	}

    	/**
    	 * Implementation that converts current {@link ResultSet} line into a {@link Row} according to {@link ResultSetReader}s given at construction time.
    	 *
    	 * @param rs {@link ResultSet} positioned at line that must be converted
    	 * @return a {@link Row} containing values given by {@link ResultSetReader}s
    	 * @throws SQLException if a read error occurs
    	 * @throws BindingException if a binding doesn't match its ResultSet value
    	 */
    	@Override
    	public Row convert(ResultSet rs) throws SQLException {
    		Row toReturn = new Row();
    		for (Decoder columnEntry : decoders) {
    			String columnName = columnEntry.getColumnName();
    			Object columnValue = columnEntry.getReader().get(rs, columnName);
    			toReturn.put(columnName, columnValue);
    		}
    		return toReturn;
    	}

    	/**
    	 * Simple storage of mapping between column name and their {@link ResultSetReader}
    	 */
    	private static class Decoder {

    		private static Iterable<Decoder> decoders(Iterable<? extends Map.Entry<String, ? extends ResultSetReader>> input) {
    			// NB: we don't expect duplicate in entry column names, so we don't apply any case-insensitive sort
    			TreeSet<Decoder> result = new TreeSet<>(Comparator.comparing(Decoder::getColumnName));
    			input.forEach(e -> result.add(new Decoder(e.getKey(), e.getValue())));
    			return result;
    		}

    		private final String columnName;

    		private final ResultSetReader<?> reader;

    		private Decoder(String columnName, ResultSetReader<?> reader) {
    			this.columnName = columnName;
    			this.reader = reader;
    		}

    		private String getColumnName() {
    			return columnName;
    		}

    		private ResultSetReader<?> getReader() {
    			return reader;
    		}
    	}
    }