/* BSD 2-Clause License - see OPAL/LICENSE for details. */
package org.opalj
package br
package analyses
package cg

import net.ceedubs.ficus.Ficus._

/**
 * The ''key'' object to get a traversable of entry points. Entry points are particularly relevant
 * to construct call graphs.
 * See [[InitialEntryPointsKey]] for further details.
 *
 * This ''key'' reflectively instantiates the analysis that determines the program's entry points.
 * The respective analysis has to extend the trait [[InitialEntryPointsKey]] class.
 *
 * To configure which analysis is used use the key
 * `org.opalj.br.analyses.cg.InitialEntryPointKey.analysis` to specify the name of the class which
 * implements the analysis.
 *
 * @example
 *      {{{
 *      org.opalj.br.analyses.cg {
 *          InitialEntryPointKey {
 *              analysis = "org.opalj.br.analyses.cg.ApplicationEntryPointFinder"
 *          }
 *      }
 *      }}}
 *
 * @note Please see the documentation of [[EntryPointFinder]] and its subtypes for more
 *       information.
 *
 * @author Michael Reif
 */
object InitialEntryPointsKey extends ProjectInformationKey[Iterable[Method], Nothing] {

    final val ConfigKeyPrefix = "org.opalj.br.analyses.cg.InitialEntryPointsKey."
    final val ConfigKey = ConfigKeyPrefix+"analysis"

    /**
     * The [[InitialEntryPointsKey]] depends on three other keys and queries information about closed
     * packages, must answer the question whether a method can be overridden by unknown code, and
     * performs checks whether types are extensible or not.
     *
     * @return `Nil`.
     */
    override def requirements(project: SomeProject): ProjectInformationKeys = {
        Seq(TypeExtensibilityKey, ClosedPackagesKey, IsOverridableMethodKey)
    }

    /**
     * Reflectively instantiates a ''ClosedPackagesAnalysis'' for the given project.
     * The instantiated class has to satisfy the interface and needs to provide a single
     * constructor parameterized over a Project.
     */
    override def compute(project: SomeProject): Iterable[Method] = {
        val configuredAnalysis = project.config.as[Option[String]](ConfigKey)
        val entryPointFinder = configuredAnalysis
        if (entryPointFinder.isEmpty) {
            throw new IllegalArgumentException(s"entry points cannot be computed due to missing configuration of $ConfigKey")
        }

        val fqn = entryPointFinder.get
        val epFinder = instantiateEntryPointFinder(fqn)
        epFinder.collectEntryPoints(project)
    }

    private[this] def instantiateEntryPointFinder(fqn: String): EntryPointFinder = {
        import scala.reflect.runtime.universe._
        val mirror = runtimeMirror(this.getClass.getClassLoader)
        val module = mirror.staticModule(fqn)
        mirror.reflectModule(module).instance.asInstanceOf[EntryPointFinder]
    }
}