/**

 * SQL-DK

 * Copyright © 2013 František Kučera (frantovo.cz)

 *

 * This program is free software: you can redistribute it and/or modify

 * it under the terms of the GNU General Public License as published by

 * the Free Software Foundation, either version 3 of the License, or

 * (at your option) any later version.

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the

 * GNU General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program. If not, see <http://www.gnu.org/licenses/>.

 */

package info.globalcode.sql.dk.formatting;

import info.globalcode.sql.dk.Parameter;

import java.io.OutputStream;

import java.util.EmptyStackException;

import java.util.EnumSet;

import java.util.List;

import java.util.Stack;

/**

 *

 * @author Ing. František Kučera (frantovo.cz)

 */

public abstract class AbstractFormatter implements Formatter {

	private Stack<State> state = new Stack<>();

	private OutputStream outputStream;

	private ColumnsHeader currentColumnsHeader;

	private String currentQuery;

	private int currentColumnsCount;

	public AbstractFormatter(OutputStream outputStream) {

		this.outputStream = outputStream;

		state.push(State.ROOT);

	}

	/*

	 * root

	 * .database

	 * ..resultSet

	 * ...@query

	 * ...@parameters

	 * ...@columnsHeader

	 * ...row

	 * ....@columnValue

	 * ..updatesResult

	 * ...@query

	 * ...@parameters

	 * ...@updatedRowsCount

	 * ...generatedKeys

	 * ....resultSet (see above)

	 */

	protected enum State {

		ROOT,

		DATABASE,

		RESULT_SET,

		ROW,

		UPDATES_RESULT,

		GENERATED_KEYS

	}

	/**

	 * Go down in hierarchy.

	 * Pushes new state and verifies the old one.

	 *

	 * @param current the new state – currently entering

	 * @param expected expected previous states (any of them is valid)

	 * @return previous state

	 * @throws IllegalStateException if previous state was not one from expected

	 */

	private State pushState(State current, EnumSet expected) {

		State previous = state.peek();

		if (expected.contains(previous)) {

			state.push(current);

			return previous;

		} else {

			throw new IllegalStateException("Formatter was in wrong state: " + previous + " when it should be in one of: " + expected);

		}

	}

	protected State peekState(EnumSet expected) {

		State current = state.peek();

		if (expected.contains(current)) {

			return current;

		} else {

			throw new IllegalStateException("Formatter is in wrong state: " + current + " when it should be in one of: " + expected);

		}

	}

	/**

	 * Go up in hierarchy.

	 * Pops the superior state/branch.

	 *

	 * @param expected expected superior state

	 * @return the superior state

	 * @throws IllegalStateException if superior state was not one from expected or if there is no

	 * more superior state (we are at root level)

	 */

	private State popState(EnumSet expected) {

		try {

			State superior = state.pop();

			if (expected.contains(superior)) {

				return superior;

			} else {

				throw new IllegalStateException("Formatter had wrong superior state: " + superior + " when it should be in one of: " + expected);

			}

		} catch (EmptyStackException e) {

			throw new IllegalStateException("Formatter was already at root level – there is nothing above that.", e);

		}

	}

	@Override

	public void writeStartDatabase() {

		pushState(State.DATABASE, EnumSet.of(State.ROOT));

	}

	@Override

	public void writeEndDatabase() {

		popState(EnumSet.of(State.ROOT));

	}

	@Override

	public void writeStartResultSet() {

		pushState(State.RESULT_SET, EnumSet.of(State.DATABASE, State.GENERATED_KEYS));

	}

	@Override

	public void writeEndResultSet() {

		popState(EnumSet.of(State.DATABASE, State.GENERATED_KEYS));

		currentColumnsHeader = null;

	}

	@Override

	public void writeQuery(String sql) {

		peekState(EnumSet.of(State.RESULT_SET, State.UPDATES_RESULT));

		if (currentColumnsHeader == null) {

			currentQuery = sql;

		} else {

			throw new IllegalStateException("Query string '" + sql + "' must be set before columns header – was already set: " + currentColumnsHeader);

		}

	}

	@Override

	public void writeParameters(List<Parameter> parameters) {

		peekState(EnumSet.of(State.RESULT_SET, State.UPDATES_RESULT));

		if (currentColumnsHeader != null) {

			throw new IllegalStateException("Parameters '" + parameters + "' must be set before columns header – was already set: " + currentColumnsHeader);

		}

		if (currentQuery == null) {

			throw new IllegalStateException("Parameters '" + parameters + "' must be set after query – was not yet set.");

		}

	}

	@Override

	public void writeColumnsHeader(ColumnsHeader header) {

		peekState(EnumSet.of(State.RESULT_SET, State.UPDATES_RESULT));

		if (currentColumnsHeader == null) {

			currentColumnsHeader = header;

		} else {

			throw new IllegalStateException("Columns header can be set only once per result set – was already set: " + currentColumnsHeader);

		}

	}

	@Override

	public void writeStartRow() {

		pushState(State.ROW, EnumSet.of(State.RESULT_SET));

		currentColumnsCount = 0;

	}

	@Override

	public void writeEndRow() {

		popState(EnumSet.of(State.RESULT_SET));

	}

	@Override

	public void writeColumnValue(Object value) {

		peekState(EnumSet.of(State.ROW));

		currentColumnsCount++;

		int declaredCount = currentColumnsHeader.getColumnCount();

		if (currentColumnsCount > declaredCount) {

			throw new IllegalStateException("Current columns count is " + currentColumnsCount + " which is more than declared " + declaredCount + " in header.");

		}

	}

	@Override

	public void writeStartUpdatesResult() {

		pushState(State.RESULT_SET, EnumSet.of(State.DATABASE));

	}

	@Override

	public void writeEndUpdatesResult() {

		popState(EnumSet.of(State.DATABASE));

		currentColumnsHeader = null;

	}

	@Override

	public void writeUpdatedRowsCount(int updatedRowsCount) {

		peekState(EnumSet.of(State.UPDATES_RESULT));

	}

	@Override

	public void writeStartGeneratedKeys() {

		pushState(State.GENERATED_KEYS, EnumSet.of(State.UPDATES_RESULT));

	}

	@Override

	public void writeEndGeneratedKeys() {

		popState(EnumSet.of(State.UPDATES_RESULT));

	}

	protected OutputStream getOutputStream() {

		return outputStream;

	}

	protected ColumnsHeader getCurrentColumnsHeader() {

		return currentColumnsHeader;

	}

	protected int getCurrentColumnsCount() {

		return currentColumnsCount;

	}

	/**

	 * TODO: write SQLWarning

	 */

}