    -----------------------------------------------------------------------------
    -- |
    -- Module      :  XMonad.Actions.FindEmptyWorkspace
    -- Copyright   :  (c) Miikka Koskinen 2007
    -- License     :  BSD3-style (see LICENSE)
    --
    -- Maintainer  :  arcatan@kapsi.fi
    -- Stability   :  stable
    -- Portability :  unportable
    --
    -- Find an empty workspace.
    --
    -----------------------------------------------------------------------------

    module XMonad.Actions.FindEmptyWorkspace (
        -- * Usage
        -- $usage
        viewEmptyWorkspace, tagToEmptyWorkspace
      ) where

    import Data.List
    import Data.Maybe ( isNothing )

    import XMonad
    import XMonad.StackSet

    -- $usage
    --
    -- To use, import this module into your @~\/.xmonad\/xmonad.hs@:
    --
    -- >   import XMonad.Actions.FindEmptyWorkspace
    --
    -- and add the desired keybindings, for example:
    --
    --  >   , ((modm,                xK_m    ), viewEmptyWorkspace)
    --  >   , ((modm .|. shiftMask,  xK_m    ), tagToEmptyWorkspace)
    --
    -- Now you can jump to an empty workspace with @mod-m@. @Mod-shift-m@
    -- will tag the current window to an empty workspace and view it.
    --
    -- For detailed instructions on editing your key bindings, see
    -- "XMonad.Doc.Extending#Editing_key_bindings".

    -- | Find the first hidden empty workspace in a StackSet. Returns
    -- Nothing if all workspaces are in use. Function searches currently
    -- focused workspace, other visible workspaces (when in Xinerama) and
    -- hidden workspaces in this order.
    findEmptyWorkspace :: StackSet i l a s sd -> Maybe (Workspace i l a)
    findEmptyWorkspace = find (isNothing . stack) . allWorkspaces
      where
        allWorkspaces ss = (workspace . current) ss :
                           (map workspace . visible) ss ++ hidden ss

    withEmptyWorkspace :: (WorkspaceId -> X ()) -> X ()
    withEmptyWorkspace f = do
        ws <- gets windowset
        whenJust (findEmptyWorkspace ws) (f . tag)

    -- | Find and view an empty workspace. Do nothing if all workspaces are
    -- in use.
    viewEmptyWorkspace :: X ()
    viewEmptyWorkspace = withEmptyWorkspace (windows . view)

    -- | Tag current window to an empty workspace and view it. Do nothing if
    -- all workspaces are in use.
    tagToEmptyWorkspace :: X ()
    tagToEmptyWorkspace = withEmptyWorkspace $ \w -> windows $ view w . shift w