/*
    * Copyright 2021 TiKV Project Authors.
    *
    * Licensed 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.tikv.common.expression;
  
  import com.google.common.collect.ImmutableList;
  import com.google.common.primitives.UnsignedLong;
  import java.math.BigDecimal;
  import java.sql.Date;
  import java.sql.Timestamp;
  import java.util.List;
  import java.util.Objects;
  import org.joda.time.DateTime;
  import org.tikv.common.exception.TiExpressionException;
  import org.tikv.common.types.*;
  
  // Refactor needed.
  // Refer to https://github.com/pingcap/tipb/blob/master/go-tipb/expression.pb.go
  // TODO: This might need a refactor to accept an DataType?
  public class Constant extends Expression {
    private final Object value;
    private final BigDecimal UNSIGNED_LONG_MAX =
        new BigDecimal(UnsignedLong.fromLongBits(-1).toString());
  
    public Constant(Object value, DataType type) {
      this.value = value;
      this.dataType = (type == null && value != null) ? getDefaultType(value) : type;
      this.resolved = true;
    }
  
    public static Constant create(Object value, DataType type) {
      return new Constant(value, type);
    }
  
    @Deprecated
    public static Constant create(Object value) {
      return new Constant(value, null);
    }
  
    protected static boolean isIntegerType(Object value) {
      return value instanceof Long
          || value instanceof Integer
          || value instanceof Short
          || value instanceof Byte;
    }
  
    private static DataType getDefaultType(Object value) {
      if (value == null) {
        throw new TiExpressionException("NULL constant has no type");
      } else if (isIntegerType(value)) {
        return IntegerType.BIGINT;
      } else if (value instanceof String) {
        return StringType.VARCHAR;
      } else if (value instanceof Float) {
        return RealType.FLOAT;
      } else if (value instanceof Double) {
        return RealType.DOUBLE;
      } else if (value instanceof BigDecimal) {
        int prec = ((BigDecimal) value).precision();
        int frac = ((BigDecimal) value).scale();
        return new DecimalType(prec, frac);
      } else if (value instanceof DateTime) {
        return DateTimeType.DATETIME;
      } else if (value instanceof Date) {
        return DateType.DATE;
      } else if (value instanceof Timestamp) {
        return TimestampType.TIMESTAMP;
      } else if (value instanceof byte[]) {
        return BytesType.TEXT;
      } else {
        throw new TiExpressionException(
            "Constant type not supported:" + value.getClass().getSimpleName());
      }
    }
  
    public void setType(DataType type) {
      this.dataType = type;
    }
  
    public Object getValue() {
      return value;
    }
  
    @Override
    public String toString() {
     if (value == null) {
       return "null";
     }
     if (value instanceof String) {
       return String.format("\"%s\"", value);
     }
     return value.toString();
   }
 
   @Override
   public boolean equals(Object other) {
     if (other instanceof Constant) {
       return Objects.equals(value, ((Constant) other).value);
     }
     return false;
   }
 
   @Override
   public int hashCode() {
     return Objects.hashCode(value);
   }
 
   @Override
   public List<Expression> getChildren() {
     return ImmutableList.of();
   }
 
   @Override
   public <R, C> R accept(Visitor<R, C> visitor, C context) {
     return visitor.visit(this, context);
   }
 
   public boolean isOverflowed() {
     if (this.dataType instanceof IntegerType) {
       if (((IntegerType) this.dataType).isUnsignedLong()) {
         return ((BigDecimal) value).min(UNSIGNED_LONG_MAX).signum() > 0
             || ((BigDecimal) value).signum() < 0;
       }
     }
     return false;
   }
 }