/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.tajo.engine.function.datetime;

import org.apache.tajo.catalog.Column;
import org.apache.tajo.common.TajoDataTypes;
import org.apache.tajo.datum.Datum;
import org.apache.tajo.datum.DatumFactory;
import org.apache.tajo.datum.NullDatum;
import org.apache.tajo.datum.TimestampDatum;
import org.apache.tajo.engine.eval.FunctionEval;
import org.apache.tajo.engine.function.GeneralFunction;
import org.apache.tajo.engine.function.annotation.Description;
import org.apache.tajo.engine.function.annotation.ParamTypes;
import org.apache.tajo.storage.Tuple;
import org.joda.time.format.DateTimeFormat;
import org.joda.time.format.DateTimeFormatter;

import static org.apache.tajo.common.TajoDataTypes.Type.INT8;
import static org.apache.tajo.common.TajoDataTypes.Type.TEXT;

@Description(
  functionName = "to_char",
  description = "Convert time stamp to string",
  example = "> SELECT to_char(1389071652, 'yyyy-MM');\n"
          + "2014-01",
  returnType = TajoDataTypes.Type.TEXT,
  paramTypes = {@ParamTypes(paramTypes = {TajoDataTypes.Type.TIMESTAMP, TajoDataTypes.Type.TEXT})}
)
public class ToCharTimestamp extends GeneralFunction {
  private boolean constantFormat;
  private DateTimeFormatter formatter;

  public ToCharTimestamp() {
    super(new Column[] {
        new Column("timestamp", INT8),
        new Column("format", TEXT)
    });
  }

  @Override
  public void init(FunctionEval.ParamType[] paramTypes) {
    if (paramTypes[1] == FunctionEval.ParamType.CONSTANT) {
      constantFormat = true;
    }
  }


  @Override
  public Datum eval(Tuple params) {
    if(params.isNull(0) || params.isNull(1)) {
      return NullDatum.get();
    }

    TimestampDatum valueDatum = (TimestampDatum) params.get(0);
    Datum pattern = params.get(1);

    if (formatter == null || !constantFormat) {
      formatter = DateTimeFormat.forPattern(pattern.asChars());
    }
    return DatumFactory.createText(valueDatum.toChars(formatter));
  }
}