/**

  * 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, version 3 of the License.

  *

  * 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);

 			}

 		}

 	}

 }