MathFunction.scala

/**
 * Copyright (c) 2002-2012 "Neo Technology,"
 * Network Engine for Objects in Lund AB [http://neotechnology.com]
 *
 * This file is part of Neo4j.
 *
 * Neo4j 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 org.neo4j.cypher.internal.commands

import expressions.Expression
import java.lang.Math
import org.neo4j.cypher.CypherTypeException
import collection.Map
import org.neo4j.cypher.internal.symbols._

abstract class MathFunction(arg: Expression) extends Expression with NumericHelper {
  def innerExpectedType = NumberType()

  def filter(f: (Expression) => Boolean) = if (f(this))
    Seq(this) ++ arg.filter(f)
  else
    arg.filter(f)

  def calculateType(symbols: SymbolTable) = arg.evaluateType(NumberType(), symbols)

  def symbolTableDependencies = arg.symbolTableDependencies
}

trait NumericHelper {
  protected def asDouble(a: Any) = asNumber(a).doubleValue()
  protected def asInt(a: Any) = asNumber(a).intValue()

  private def asNumber(a: Any): Number = try {
    a.asInstanceOf[Number]
  }
  catch {
    case x: ClassCastException => throw new CypherTypeException("Expected a numeric value for " + toString + ", but got: " + a.toString)
  }
}

case class AbsFunction(argument: Expression) extends MathFunction(argument) {
  def apply(m: Map[String, Any]): Any = Math.abs(asDouble(argument(m)))

  def rewrite(f: (Expression) => Expression) = f(AbsFunction(argument.rewrite(f)))
}

case class RangeFunction(start: Expression, end: Expression, step: Expression) extends Expression with NumericHelper {
  def apply(m: Map[String, Any]): Any = {
    val startVal = asInt(start(m))
    val endVal = asInt(end(m))
    val stepVal = asInt(step(m))
    new Range(startVal, endVal + 1, stepVal).toList
  }

  def filter(f: (Expression) => Boolean) = {
    val inner = start.filter(f) ++ end.filter(f) ++ step.filter(f)
    if (f(this)) {
      Seq(this) ++ inner
    }
    else {
      inner
    }
  }

  def rewrite(f: (Expression) => Expression) = f(RangeFunction(start.rewrite(f), end.rewrite(f), step.rewrite(f)))

  def calculateType(symbols: SymbolTable): CypherType = {
    start.evaluateType(NumberType(), symbols)
    end.evaluateType(NumberType(), symbols)
    step.evaluateType(NumberType(), symbols)
    new IterableType(NumberType())
  }

  def symbolTableDependencies = start.symbolTableDependencies ++
        end.symbolTableDependencies ++
        step.symbolTableDependencies
}

case class SignFunction(argument: Expression) extends MathFunction(argument) {
  def apply(m: Map[String, Any]): Any = Math.signum(asDouble(argument(m)))

  def rewrite(f: (Expression) => Expression) = f(SignFunction(argument.rewrite(f)))
}

case class RoundFunction(expression: Expression) extends MathFunction(expression) {
  def apply(m: Map[String, Any]): Any = math.round(asDouble(expression(m)))

  def rewrite(f: (Expression) => Expression) = f(RoundFunction(expression.rewrite(f)))
}

case class SqrtFunction(argument: Expression) extends MathFunction(argument) {
  def apply(m: Map[String, Any]): Any = Math.sqrt(asDouble(argument(m)))

  def rewrite(f: (Expression) => Expression) = f(SqrtFunction(argument.rewrite(f)))
}