-- 
-- DynamicLog
--
-- Log events in:
--
--      1 2 [3] 4 8
--
-- format. suitable to pipe into dzen.
--
-- To use, set:
--
--      import XMonadContrib.DynamicLog
--      logHook = dynamicLog
--
-- Don Stewart

module XMonadContrib.DynamicLog (dynamicLog, dynamicLogXinerama) where

-- 
-- Useful imports
--
import XMonad
import Data.Maybe ( isJust )
import Data.List
import qualified StackSet as S

--
-- Perform an arbitrary action on each state change.
-- Examples include:
--      * do nothing
--      * log the state to stdout

--
-- An example logger, print a status bar output to dzen, in the form:
--
--  1 2 [3] 4 7
--  

dynamicLog :: X ()
dynamicLog = withWindowSet $ io . putStrLn . ppr
  where
    ppr s =  concatMap fmt $ sortBy (compare `on` S.tag)
                (map S.workspace (S.current s : S.visible s) ++ S.hidden s)
       where this     = S.tag (S.workspace (S.current s))
             visibles = map (S.tag . S.workspace) (S.visible s)

             fmt w | S.tag w == this         = "[" ++ pprTag w ++ "]"
                   | S.tag w `elem` visibles = "<" ++ pprTag w ++ ">"
                   | isJust (S.stack w)      = " " ++ pprTag w ++ " "
                   | otherwise               = ""

--
-- Workspace logger with a format designed for Xinerama:
--
-- [1 9 3] 2 7
--
-- where 1, 9, and 3 are the workspaces on screens 1, 2 and 3, respectively,
-- and 2 and 7 are non-visible, non-empty workspaces
--
dynamicLogXinerama :: X ()
dynamicLogXinerama = withWindowSet $ io . putStrLn . ppr
  where
    ppr ws = "[" ++ unwords onscreen ++ "] " ++ unwords offscreen
      where onscreen  = map (pprTag . S.workspace)
                            . sortBy (compare `on` S.screen) $ S.current ws : S.visible ws
            offscreen = map pprTag . filter (isJust . S.stack)
                            . sortBy (compare `on` S.tag) $ S.hidden ws

-- util functions
pprTag :: Integral i => S.Workspace i a -> String
pprTag = show . (+(1::Int)) . fromIntegral . S.tag

on :: (a -> a -> c) -> (b -> a) -> b -> b -> c
on f g a b = (g a) `f` (g b)