Aquarium

/*

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

 *

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 * without modification, are permitted provided that the following

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 *

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 *

 *   2. Redistributions in binary form must reproduce the above

 *      copyright notice, this list of conditions and the following

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 *      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,

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 * interpreted as representing official policies, either expressed

 * or implied, of GRNET S.A.

 */

package gr.grnet.aquarium.logic.accounting.dsl

import java.util.Date

import scala.collection.mutable

/**

 * A representation of a timeslot with a start and end date.

 *

 * @author Georgios Gousios <gousiosg@gmail.com>

 */

case class Timeslot(from: Date, to: Date) extends Ordered[Timeslot] {

  /* Preconditions to ensure correct object creations */

  assert(from != null)

  assert(to != null)

  assert(from.before(to))

  def startsBefore(t: Timeslot) : Boolean = this.from.before(t.from)

  def startsAfter(t: Timeslot) : Boolean = this.from.after(t.from)

  def endsBefore(t: Timeslot) : Boolean = this.to.before(t.to)

  def endsAfter(t: Timeslot) : Boolean = this.to.after(t.to)

  /**

   * Check whether this time slot fully contains the provided one.

   */

  def contains(t: Timeslot) : Boolean = t.startsAfter(this) && t.endsBefore(this)

  /**

   * Check whether this timeslot contains the provided time instant.

   */

  def includes(t: Date) : Boolean =

    if (from.before(t) && to.after(t)) true else false

  /**

   * Check whether this timeslot overlaps with the provided one.

   */

  def overlaps(t: Timeslot) : Boolean = {

    if (contains(t) || t.contains(this))

      return true

    if (this.includes(t.from) || this.includes(t.to))

      return true

    false

  }

  /**

   * Merges this timeslot with the provided one. If the timeslots overlap,

   * a list with the resulting merge is returned. If the timeslots do not

   * overlap, the returned list contains both timeslots in increasing start

   * date order.

   */

  def merge(t: Timeslot) : List[Timeslot] = {

    if (overlaps(t)) {

      val nfrom = if (from.before(t.from)) from else t.from

      val nto   = if (to.after(t.to)) to else t.to

      List(Timeslot(nfrom, nto))

    } else

      if (this.from.before(t.from))

        List(this, t)

      else

        List(t, this)

  }

  /**

   * Split the timeslot in two parts at the provided timestamp, if the

   * timestamp falls within the timeslot boundaries.

   */

  def slice(d: Date) : List[Timeslot] =

    if (includes(d))

      List(Timeslot(from, d), Timeslot(d,to))

    else

      List(this)

  /**

   * Find and return the timeslots whithin which this Timeslot overrides

   * with the provided list of timeslots. For example if:

   * 

   *  - `this == Timeslot(7,20)`

   *  - `list == List(Timeslot(1,3), Timeslot(6,8), Timeslot(11,15))`

   *

   * the result will be: `List(Timeslot(7,8), Timeslot(11,15))`

   */

  def overlappingTimeslots(list: List[Timeslot]) : List[Timeslot] = {

    val result = new mutable.ListBuffer[Timeslot]()

    list.foreach {

      t =>

        if (t.contains(this)) result += this

        else if (this.contains(t)) result += t

        else if (t.overlaps(this) && t.startsBefore(this)) result += this.slice(t.to).head

        else if (t.overlaps(this) && t.startsAfter(this)) result += this.slice(t.from).tail.head

    }

    result.toList

  }

  /**

   * Find and return the timeslots whithin which this Timeslot does not

   * override with the provided list of timeslots. For example if:

   *

   *  - `this == Timeslot(7,20)`

   *  - `list == List(Timeslot(1,3), Timeslot(6,8), Timeslot(11,15))`

   *

   * the result will be: `List(Timeslot(9,10), Timeslot(15,20))`

   */

  def nonOverlappingTimeslots(list: List[Timeslot]): List[Timeslot] = {

    val overlaps = list.filter(t => this.overlaps(t))

    if (overlaps.isEmpty)

      return List(this)

    def build(acc: List[Timeslot], listPart: List[Timeslot]): List[Timeslot] = {

      listPart match {

        case Nil => acc

        case x :: Nil => build(acc, List())

        case x :: y :: rest =>

          build(acc ++ List(Timeslot(x.to,  y.from)), y :: rest)

      }

    }

    val head = overlaps.head

    val last = overlaps.reverse.head

    val start = if (head.startsAfter(this)) List(Timeslot(this.from, head.from)) else List()

    val end = if (last.endsBefore(this)) List(Timeslot(last.to, this.to)) else List()

    start ++ build(List(), overlaps) ++ end

  }

  /**

   * Compares the starting times of two timeslots.

   */

  def compare(that: Timeslot): Int = {

    if (this.startsBefore(that)) -1

    else if (this.startsAfter(that)) 1

    else 0

  }

  /**

   * Converts the timeslot to the amount of hours it represents

   */

  def hours: Float = ((to.getTime - from.getTime)/1000)/60F/60F

}