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/*
 * 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.hadoop.hive.ql.exec.vector.expressions;

import org.apache.hadoop.hive.common.type.Date;
import org.apache.hadoop.hive.ql.exec.vector.BytesColumnVector;
import org.apache.hadoop.hive.ql.exec.vector.LongColumnVector;
import org.apache.hadoop.hive.ql.exec.vector.VectorExpressionDescriptor;
import org.apache.hadoop.hive.ql.exec.vector.VectorizedRowBatch;
import org.apache.hadoop.hive.ql.metadata.HiveException;
import org.apache.hadoop.hive.serde2.io.DateWritableV2;
import org.apache.hive.common.util.DateParser;

import java.nio.charset.StandardCharsets;
import java.util.Arrays;

/**
 * Casts a string vector to a date vector.
 */
public class CastStringToDate extends VectorExpression {
  private static final long serialVersionUID = 1L;

  public CastStringToDate() {
    super();
  }

  public CastStringToDate(int inputColumn, int outputColumnNum) {
    super(inputColumn, outputColumnNum);
  }

  @Override
  public void evaluate(VectorizedRowBatch batch) throws HiveException {

    if (childExpressions != null) {
      super.evaluateChildren(batch);
    }

    BytesColumnVector inV = (BytesColumnVector) batch.cols[inputColumnNum[0]];
    int[] sel = batch.selected;
    int n = batch.size;
    LongColumnVector outputColVector = (LongColumnVector) batch.cols[outputColumnNum];

    boolean[] inputIsNull = inV.isNull;
    boolean[] outputIsNull = outputColVector.isNull;

    if (n == 0) {

      // Nothing to do
      return;
    }

    // We do not need to do a column reset since we are carefully changing the output.
    outputColVector.isRepeating = false;

    if (inV.isRepeating) {
      if (inV.noNulls || !inputIsNull[0]) {
        // Set isNull before call in case it changes it mind.
        outputIsNull[0] = false;
        evaluate(outputColVector, inV, 0);
      } else {
        outputIsNull[0] = true;
        outputColVector.noNulls = false;
      }
      outputColVector.isRepeating = true;
      return;
    }

    if (inV.noNulls) {
      if (batch.selectedInUse) {

        // CONSIDER: For large n, fill n or all of isNull array and use the tighter ELSE loop.

        if (!outputColVector.noNulls) {
          for(int j = 0; j != n; j++) {
           final int i = sel[j];
           // Set isNull before call in case it changes it mind.
           outputIsNull[i] = false;
           evaluate(outputColVector, inV, i);
         }
        } else {
          for(int j = 0; j != n; j++) {
            final int i = sel[j];
            evaluate(outputColVector, inV, i);
          }
        }
      } else {
        if (!outputColVector.noNulls) {

          // Assume it is almost always a performance win to fill all of isNull so we can
          // safely reset noNulls.
          Arrays.fill(outputIsNull, false);
          outputColVector.noNulls = true;
        }
        for(int i = 0; i != n; i++) {
          evaluate(outputColVector, inV, i);
        }
      }
    } else /* there are NULLs in the inputColVector */ {

      // Carefully handle NULLs...
      outputColVector.noNulls = false;

      if (batch.selectedInUse) {
        for(int j = 0; j != n; j++) {
          int i = sel[j];
          if (!inputIsNull[i]) {
            // Set isNull before call in case it changes it mind.
            outputColVector.isNull[i] = false;
            evaluate(outputColVector, inV, i);
          } else {
            outputColVector.isNull[i] = true;
            outputColVector.noNulls = false;
          }
        }
      } else {
        for(int i = 0; i != n; i++) {
          if (!inputIsNull[i]) {
            // Set isNull before call in case it changes it mind.
            outputColVector.isNull[i] = false;
            evaluate(outputColVector, inV, i);
          } else {
            outputColVector.isNull[i] = true;
            outputColVector.noNulls = false;
          }
        }
      }
    }
  }

  protected void evaluate(LongColumnVector outputColVector, BytesColumnVector inV, int i) {
    String dateString = new String(inV.vector[i], inV.start[i], inV.length[i], StandardCharsets.UTF_8);
    Date hDate = DateParser.parseDate(dateString);
    if (hDate != null) {
      outputColVector.vector[i] = DateWritableV2.dateToDays(hDate);
      return;
    }
    setNull(outputColVector, i);
  }

  protected void setNull(LongColumnVector outputColVector, int i) {
    outputColVector.vector[i] = 1;
    outputColVector.isNull[i] = true;
    outputColVector.noNulls = false;
  }

  @Override
  public String vectorExpressionParameters() {
    return getColumnParamString(0, inputColumnNum[0]);
  }

  @Override
  public VectorExpressionDescriptor.Descriptor getDescriptor() {
    VectorExpressionDescriptor.Builder b = new VectorExpressionDescriptor.Builder();
    b.setMode(VectorExpressionDescriptor.Mode.PROJECTION)
        .setNumArguments(1)
        .setArgumentTypes(
            VectorExpressionDescriptor.ArgumentType.STRING_FAMILY)
        .setInputExpressionTypes(
            VectorExpressionDescriptor.InputExpressionType.COLUMN);
    return b.build();
  }
}