relational

import org.specs._
import Relation._
class RelationalSpec extends Specification {
  
  "Any Relation" should {
    "have a restrict operator to filter tuples" in {
      type PT = {def name: String; def state: String; def city: String; def zipCode: Int}
      var relVar = relation[PT](new {def name = "Nilanjan"; def state = "OH"; def city = "Columbus"; def zipCode = 43230}, 
          new {def name = "Manisha"; def state = "OH"; def city = "Westerville"; def zipCode = 43333})
      relVar = relVar where { _.city == "Columbus" }
      relVar.body must exist({ t => t.name == "Nilanjan" && t.state == "OH" && t.city == "Columbus" && t.zipCode == 43230})
    }
    "have a project operator to create new relations " in {
      var relVar = relation(PersonTuple("Nilanjan", "OH", "Columbus", 43230), PersonTuple("Manisha", "OH", "Westerville", 43333))
      var nameRelVar = relVar project { t: PersonTuple => NameTuple(t.name) }
      nameRelVar.body must contain(NameTuple("Nilanjan"))
      nameRelVar.body must contain(NameTuple("Manisha"))
    }
    "have a project operator to create same relation again " in {
      var relVar = relation(PersonTuple("Nilanjan", "OH", "Columbus", 43230), PersonTuple("Manisha", "OH", "Westerville", 43333))
      var newRelVar = relVar project { t => t }
      newRelVar.body must contain(PersonTuple("Nilanjan", "OH", "Columbus", 43230))
      newRelVar.body must contain(PersonTuple("Manisha", "OH", "Westerville", 43333))
    }
    "have a project operator to create new relations with restriction " in {
      var relVar = relation(PersonTuple("Nilanjan", "OH", "Columbus", 43230), PersonTuple("Manisha", "OH", "Westerville", 43333))
      var nameRelVar = relVar where { _.city == "Columbus" } project { t: PersonTuple => NameTuple(t.name) }
      nameRelVar.body must contain(NameTuple("Nilanjan"))
      nameRelVar.body must notContain(NameTuple("Manisha"))
    }
  } 
}

case class NameTuple(name: String)
case class PersonTuple(name: String, state: String, city: String, zipCode: Int)

class Relation[H](val body: Seq[H]) {
  def where(restrict : (H) => Boolean): Relation[H] = {
    def matches = body filter restrict
    relation(matches:_*)
  }
  
  def project[H1](f: (H) => H1): Relation[H1] = {
    def projection = body map f
    relation(projection:_*)
  }
}

object Relation {
  def relation[H](body: H*) = new Relation(body)
}