/**

 * SQL-DK

 * Copyright © 2014 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.batch;

import info.globalcode.sql.dk.Parameter;

import info.globalcode.sql.dk.SQLCommand;

import info.globalcode.sql.dk.SQLCommandNumbered;

import java.io.DataInputStream;

import java.io.InputStream;

import static info.globalcode.sql.dk.batch.BatchConstants.*;

import static info.globalcode.sql.dk.Functions.toHex;

import info.globalcode.sql.dk.SQLType;

import java.io.IOException;

import java.util.ArrayList;

import java.util.Arrays;

import java.util.List;

/**

 *

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

 */

public class BatchDecoder {

	public Batch decode(InputStream in) throws BatchException {

		return new BatchFromStream(new DataInputStream(in));

	}

	private class BatchFromStream implements Batch {

		private DataInputStream in;

		private boolean hasNext;

		public BatchFromStream(DataInputStream in) throws BatchException {

			this.in = in;

			hasNext = verifyHeader();

		}

		@Override

		public boolean hasNext() throws BatchException {

			return hasNext;

		}

		@Override

		public SQLCommand next() throws BatchException {

			try {

				String sql = readNextString();

				int paramCount = in.readInt();

				List<Parameter> parameters = new ArrayList<>(paramCount);

				for (int i = 0; i < paramCount; i++) {

					SQLType type = SQLType.valueOf(in.readInt());

					String value = readNextString();

					parameters.add(new Parameter(value, type));

				}

				hasNext = verifyHeader();

				SQLCommand sqlCommand = new SQLCommandNumbered(sql, parameters);

				return sqlCommand;

			} catch (IOException e) {

				throw new BatchException("Unable to read batch", e);

			}

		}

		private String readNextString() throws IOException {

			byte[] buffer = new byte[in.readInt()];

			in.read(buffer);

			return new String(buffer, CHARSET);

		}

		/**

		 * @return true if correct batch header was found | false if EOF was found

		 * @throws BatchException if unexpected data was found (not batch header nor EOF)

		 */

		private boolean verifyHeader() throws BatchException {

			try {

				byte[] buffer = new byte[BATCH_HEADER.length];

				int bytesRead = in.read(buffer);

				if (bytesRead == BATCH_HEADER.length && Arrays.equals(buffer, BATCH_HEADER)) {

					return true;

				} else if (bytesRead == -1) {

					return false;

				} else {

					throw new BatchException("This is not SQL-DK batch: " + toHex(buffer));

				}

			} catch (IOException e) {

				throw new BatchException("Unable to read batch header", e);

			}

		}

	}

}