-- Example binding and helpers to cycleRecentWS with nonempty workspaces only

import XMonad
import qualified XMonad.StackSet as W
import XMonad.Actions.CycleRecentWS
import XMonad.Util.EZConfig -- optional but used in the example

main = xmonad $ defaultConfig
        { modMask = mod4Mask -- on Super
        -- skipped
        }
        `additionalKeysP` myKeys

myKeys =
    [ ("M-<Tab>", cycleWindowSets nonEmptyRecents [xK_Super_L] xK_Tab xK_grave)
    -- skipped
    ]
    --   for additionalKeys or default keybinding style
    -- (modm xK_Tab, cycleWindowSets nonEmptyRecents [xK_Super_L] xK_Tab xK_grave)

-- Build a list of windowsets with current swapped in turn with each
-- "most recent" workspace as given by nonEmptyTags
nonEmptyRecents :: (Eq s, Eq i) => W.StackSet i l a s sd -> [W.StackSet i l a s sd]
nonEmptyRecents ws = map (W.view `flip` ws) (rotUp $ nonEmptyTags ws)

-- Given a windowset grab a list of the workspace tags, in the default order:
-- current, visibles in screen order, hiddens from most to least recently accessed.
nonEmptyTags ::  W.StackSet i l a s sd -> [i]
nonEmptyTags ws = [ tag | W.Workspace tag _ (Just _) <- W.workspaces ws]

-- rotUp and rotDown are actually exported by Actions.CycleWindows,
-- but written in an unsafe form using head tail init last :((
-- Shall have to send patch to fix that.
rotUp ::  [a] -> [a]
rotUp l = drop 1 l ++ take 1