asdf

import org.scalatest._

class CellTest extends FlatSpec with Matchers {

  "a cell" should "die when has less than 2 neighbours" in {
    val cell = Cell(1, true)

    val isAliveNextGeneration = cell.nextGeneration()

    isAliveNextGeneration shouldBe false
  }

  "a cell" should "survive when it has 2 neighbours" in {
    val cell = Cell(2, true)

    val isAliveNextGeneration = cell.nextGeneration()

    isAliveNextGeneration shouldBe true
  }

  "a cell" should "survive when it has 3 neighbours" in {
    val cell = Cell(3, true)

    val isAliveNextGeneration = cell.nextGeneration()

    isAliveNextGeneration shouldBe true
  }

  "a cell" should "die if has more than 3 neighbours" in {
    val cell = Cell(4, true)

    val isAliveNextGeneration = cell.nextGeneration()

    isAliveNextGeneration shouldBe false
  }

  "a dead cell" should "remain dead with 2 neighbours" in {
    val cell = Cell(2, false)

    val isAliveNextGeneration = cell.nextGeneration()

    isAliveNextGeneration shouldBe false
  }

  "a dead cell" should "become alive when it has 3 neighbours" in {
    val cell = Cell(3, false)

    val isAliveNextGeneration = cell.nextGeneration()

    isAliveNextGeneration shouldBe true
  }

  "a world that is empty" should "be empty after tick" in {
    val initialCellList = List(Cell(0, false))
    val world = World(initialCellList)

    val newDeadWorld = world.tick()

    newDeadWorld.cells shouldBe initialCellList
  }

  "a world with 1 cell" should "be dead after tick (underpopulation)" in {
    val initialCellList = List(Cell(0, true))
    val world = World(initialCellList)

    val newDeadWorld = world.tick()

    newDeadWorld.cells shouldBe List(Cell(0, false))
  }

  "a world with 4 cells" should "be dead after tick (underpopulation)" in {
    val initialCellList = List(
      Cell(1, false), Cell(1, false),
      Cell(1, false), Cell(0, true)
    )
    val world = World(initialCellList)

    val newDeadWorld = world.tick()

    newDeadWorld.cells shouldBe List(
      Cell(0, false), Cell(0, false),
      Cell(0, false), Cell(0, false)
    )
  }

  case class Cell(neighbours: List[Cell], isAlive: Boolean) {
    def nextGeneration() = {
      if (isAlive) aliveNeighbours > 1 && aliveNeighbours < 4
      else aliveNeighbours == 3
    }

    def aliveNeighbours = neighbours.filter(_.isAlive).size

    def nextAliveNeightbours() = {
      0
    }
  }

  case class World(cells: List[Cell]) {

    def tick(): World = {
      World(cells.map(a => Cell(a.nextAliveNeightbours(), a.nextGeneration())))
    }
  }

}