/* BSD 2-Clause License - see OPAL/LICENSE for details. */
package org.opalj
package ai
package fpcf
package properties

import org.opalj.br.Method
import org.opalj.br.analyses.SomeProject
import org.opalj.fpcf.FallbackReason
import org.opalj.fpcf.Property
import org.opalj.fpcf.PropertyKey
import org.opalj.fpcf.PropertyMetaInformation
import org.opalj.fpcf.PropertyStore
import org.opalj.si.Project
import org.opalj.util.elidedAssert
import org.opalj.value.ValueInformation

sealed trait MethodReturnValuePropertyMetaInformation extends PropertyMetaInformation {

    final type Self = MethodReturnValue
}

trait MethodReturnValue extends Property with MethodReturnValuePropertyMetaInformation {

    def returnValue: Option[ValueInformation]

    override final def key: PropertyKey[MethodReturnValue] = MethodReturnValue.key

}

/**
 * Stores the information about the value (always) returned by a specific method. '''Overridden
 * methods are generally not taken into account.''' For a method that always end with an exception
 * `returnValue` will be `None`.
 *
 * In the worst case the information about the return value is just the declared type.
 *
 * @param theReturnValue The value returned by the method when the method does not throw
 *                       an exception. If the method always throws an exception, then the
 *                       returnValue is `None`.
 */
case class TheMethodReturnValue(theReturnValue: ValueInformation) extends MethodReturnValue {

    elidedAssert(theReturnValue ne null, "returnValue must not be null")

    override def returnValue: Option[ValueInformation] = Some(theReturnValue)

}

// Used for methods which throw an exception.
case object NoMethodReturnValue extends MethodReturnValue {

    override def returnValue: Option[ValueInformation] = None

}

object MethodReturnValue extends MethodReturnValuePropertyMetaInformation {

    def apply(mrvOption: Option[ValueInformation]): MethodReturnValue = {
        mrvOption match {
            case Some(vi)   => TheMethodReturnValue(vi)
            case _ /*None*/ => NoMethodReturnValue
        }
    }

    /**
     * The key associated with every purity property.
     */
    final val key = PropertyKey.create[Method, MethodReturnValue](
        "opalj.MethodReturnValue",
        (ps: PropertyStore, _: FallbackReason, m: Method) => {
            val p = ps.context(classOf[Project]).asInstanceOf[SomeProject]
            MethodReturnValue(
                Some(ValueInformation.forProperValue(m.descriptor.returnType)(using p.classHierarchy))
            )
        }
    )

}