gambas-source-code/app/examples/Games/Invaders/.src/Enemy.class

' Gambas class file

' Types in ascending difficulty
Public Enum Normal = 1, Tough, Borg, BorgQueen
' See looking strings below
Public Const AverageWidth As Integer = 5

Property X As Integer
Property Y As Integer
'' Shift distance from 0,0 (may *not* equal Y * Window.Width + X)
Property Read Shifted As Integer
Property Read Width As Integer
Property Read Type As Integer

Event Destroyed
Event SuperDestroyed

Private $iType As Integer
Private $sLook As String
Private $iWidth As Integer
Private $iColor As Integer

Private $hWnd As Window
Private $iX As Integer
Private $iY As Integer
Private $iShifted As Integer

Public Sub _new(Optional iType As Integer)
  ' Calculate a fair share of enemies
  If Not iType Then
    Select Case CInt(Rnd(0, 100))
      Case 0 To 69
        iType = Normal
      Case 70 To 94
        iType = Tough
      Case 95 To 98
        iType = Borg
      Case 99
        iType = BorgQueen
    End Select
  Endif
  Select Case iType
    Case Normal
      $sLook = " -o- "
      $iColor = Color.Green
    Case Tough
      $sLook = " ,^, "
      $iColor = Color.Cyan
    Case Borg
      $sLook = " [%] "
      $iColor = Color.Magenta
    Case BorgQueen
      $sLook = " <Q> "
      $iColor = Color.Red
  End Select
  $iWidth = Len($sLook)
  $iType = iType
End

Public Sub Init(hWnd As Window, Optional iShift As Integer)
  $hWnd = hWnd
  $iX = 0
  $iY = 0
  $iShifted = 0
  If iShift Then Shift(iShift)
End

Public Sub Draw()
  $hWnd.Print($sLook, $iX, $iY,, Pair[$iColor, $hWnd.Background])
End

Public Sub Undraw()
  $hWnd.Print(Space$($iWidth), $iX, $iY)
End

Public Sub Move(Optional iShift As Integer = 1)
  Undraw()
  Shift(iShift)
  '' FIXME: Value is arbitrary but works kind of
  If CInt(Rnd(0, 2000)) = 0 Then
    ' Resistance is futile
    Missiles.Shoot(Missile.Borg, $iX, $iY + 1)
  Endif
End

'' Shift this ship some places in its row (probably into some other row).
'' Even very huge values are supported.
'' 
'' The mathematics in this function should guarantee that no ship ever
'' covers another (accidentally) and that they always stay togehter
'' tightly.
Public Sub Shift(iShift As Integer)
  Dim iCur As Integer

  $iShifted += iShift
  While iShift <> 0
    ' Handle one row at max at a time
    If iShift > $hWnd.Width Then
      iCur = $hWnd.Width
    Else
      iCur = iShift
    Endif
    iShift -= iCur
    ' All even rows go to the right, all odd lines to the left
    Select Case $iY % 2
      Case 0
        $iX += iCur
        If $iX + $iWidth >= $hWnd.Width Then
          ' Goes to an odd row, must start at the end of the row
          While $iX + $iWidth >= $hWnd.Width
            $iX = ($iX + $iWidth) % $hWnd.Width
          Wend
          $iX = $hWnd.Width - $iX - $iWidth
          Inc $iY
        Endif
      Case 1
        $iX -= iCur
        If $iX < 0 Then
          ' Goes to an even row, must start at the beginning
          $iX = (- $iX) % $hWnd.Width
          Inc $iY
        Endif
    End Select
  Wend
End

Public Sub Destroy()
  Raise Destroyed
End

Public Sub SuperDestroy()
  Raise SuperDestroyed
End

Private Function X_Read() As Integer
  Return $iX
End

Private Sub X_Write(Value As Integer)
  $iX = Value
End

Private Function Y_Read() As Integer
  Return $iY
End

Private Sub Y_Write(Value As Integer)
  $iY = Value
End

Private Function Width_Read() As Integer
  Return $iWidth
End

Private Function Type_Read() As Integer
  Return $iType
End

Private Function Shifted_Read() As Integer
  Return $iShifted
End