Aquarium

/*

 * Copyright 2011-2012 GRNET S.A. All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or

 * without modification, are permitted provided that the following

 * conditions are met:

 *

 *   1. Redistributions of source code must retain the above

 *      copyright notice, this list of conditions and the following

 *      disclaimer.

 *

 *   2. Redistributions in binary form must reproduce the above

 *      copyright notice, this list of conditions and the following

 *      disclaimer in the documentation and/or other materials

 *      provided with the distribution.

 *

 * THIS SOFTWARE IS PROVIDED BY GRNET S.A. ``AS IS'' AND ANY EXPRESS

 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED

 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR

 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL GRNET S.A OR

 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT

 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF

 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED

 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT

 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN

 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE

 * POSSIBILITY OF SUCH DAMAGE.

 *

 * The views and conclusions contained in the software and

 * documentation are those of the authors and should not be

 * interpreted as representing official policies, either expressed

 * or implied, of GRNET S.A.

 */

package gr.grnet.aquarium

import com.ckkloverdos.resource.{StreamResource, CompositeStreamResourceContext, ClassLoaderStreamResourceContext, FileStreamResourceContext}

import com.ckkloverdos.maybe.{Failed, Just, Maybe, NoVal}

import com.ckkloverdos.sys.{SysEnv, SysProp}

import java.io.File

import gr.grnet.aquarium.util.justForSure

/**

 * Used to locate configuration files.

 *

 * This code was initially in [[gr.grnet.aquarium.Configurator]].

 *

 * @author Christos KK Loverdos <loverdos@gmail.com>

 */

object ResourceLocator {

  /**

   * This is normally exported from the shell script that starts Aquarium.

   */

  final val AQUARIUM_HOME = SysEnv("AQUARIUM_HOME")

  lazy val AQUARIUM_HOME_FOLDER: File = {

    AQUARIUM_HOME.value match {

      case Just(home) ⇒

        val file = new File(home)

        if(!file.isDirectory) {

          throw new Exception("%s (%s) is not a folder".format(AQUARIUM_HOME.name, home))

        }

        file.getCanonicalFile()

      case _ ⇒

        throw new Exception("%s is not set".format(AQUARIUM_HOME.name))

    }

  }

  /**

   * This exists in order to have a feeling of where we are.

   */

  final val HERE = justForSure(getResource(".")).get.url.toExternalForm

  /**

   * Current directory resource context.

   */

  private[this] final val AppBaseResourceContext = new FileStreamResourceContext(".")

  /**

   * Default config context for Aquarium distributions

   */

  private[this] final val LocalConfigResourceContext = new FileStreamResourceContext("conf")

  /**

   * The venerable /etc resource context. Applicable in Unix environments

   */

  private[this] final val SlashEtcResourceContext = new FileStreamResourceContext("/etc/aquarium")

  /**

   * Class loader resource context.

   * This has the lowest priority.

   */

  private[this] final val ClasspathBaseResourceContext = new ClassLoaderStreamResourceContext(Thread.currentThread().getContextClassLoader)

  /**

   * Use this property to override the place where aquarium configuration resides.

   *

   * The value of this property is a folder that defines the highest-priority resource context.

   */

  private[this] final val ConfBaseFolderSysProp = SysProp("aquarium.conf.base.folder")

  private[this] final val BasicResourceContext = new CompositeStreamResourceContext(

    NoVal,

    SlashEtcResourceContext,

    LocalConfigResourceContext,

    AppBaseResourceContext,

    ClasspathBaseResourceContext)

  /**

   * The resource context used in the application.

   */

  private[this] final val MasterResourceContext = {

    ConfBaseFolderSysProp.value match {

      case Just(value) ⇒

        // We have a system override for the configuration location

        new CompositeStreamResourceContext(Just(BasicResourceContext), new FileStreamResourceContext(value))

      case NoVal ⇒

        BasicResourceContext

      case Failed(e, m) ⇒

        throw new RuntimeException(m , e)

    }

  }

  def getResource(what: String): Maybe[StreamResource] =

    MasterResourceContext.getResource(what)

}