    {- |
    Module      :  XMonad.Actions.WindowGo
    License     :  Public domain

    Maintainer  :  <gwern0@gmail.com>
    Stability   :  unstable
    Portability :  unportable

    Defines a few convenient operations for raising (traveling to) windows based on XMonad's Query
    monad, such as 'runOrRaise'. runOrRaise will run a shell command unless it can
    find a specified window; you would use this to automatically travel to your
    Firefox or Emacs session, or start a new one (for example), instead of trying to
    remember where you left it or whether you still have one running. -}

    module XMonad.Actions.WindowGo (
                     -- * Usage
                     -- $usage
                     raise,
                     raiseNext,
                     runOrRaise,
                     runOrRaiseNext,
                     raiseMaybe,
                     raiseNextMaybe,

                     raiseBrowser,
                     raiseEditor,
                     runOrRaiseAndDo,
                     runOrRaiseMaster,
                     raiseAndDo,
                     raiseMaster,

                     ifWindows,
                     ifWindow,
                     raiseHook,
                     module XMonad.ManageHook
                    ) where

    import Control.Monad
    import Data.Char (toLower)
    import Data.Monoid
    import XMonad (Query(), X(), ManageHook, withWindowSet, runQuery, liftIO, ask)
    import Graphics.X11 (Window)
    import XMonad.ManageHook
    import XMonad.Operations (windows)
    import XMonad.Prompt.Shell (getBrowser, getEditor)
    import qualified XMonad.StackSet as W (allWindows, peek, swapMaster, focusWindow)
    import XMonad.Util.Run (safeSpawnProg)
    {- $usage

    Import the module into your @~\/.xmonad\/xmonad.hs@:

    > import XMonad.Actions.WindowGo

    and define appropriate key bindings:

    > , ((modm .|. shiftMask, xK_g), raise (className =? "Firefox"))
    > , ((modm .|. shiftMask, xK_b), runOrRaise "firefox" (className =? "Firefox"))

    (Note that Firefox v3 and up have a class-name of \"Firefox\" and \"Navigator\";
    lower versions use other classnames such as \"Firefox-bin\". Either choose the
    appropriate one, or cover your bases by using instead something like:

    > (className =? "Firefox" <||> className =? "Firefox-bin")

    For detailed instructions on editing your key bindings, see
    "XMonad.Doc.Extending#Editing_key_bindings". -}

    -- | If windows that satisfy the query exist, apply the supplied
    -- function to them, otherwise run the action given as
    -- second parameter.
    ifWindows :: Query Bool -> ([Window] -> X ()) -> X () -> X ()
    ifWindows qry f el = withWindowSet $ \wins -> do
      matches <- filterM (runQuery qry) $ W.allWindows wins
      case matches of
        [] -> el
        ws -> f ws

    -- | The same as ifWindows, but applies a ManageHook to the first match
    -- instead and discards the other matches
    ifWindow :: Query Bool -> ManageHook -> X () -> X ()
    ifWindow qry mh = ifWindows qry (windows . appEndo <=< runQuery mh . head)

    {- | 'action' is an executable to be run via 'safeSpawnProg' (of "XMonad.Util.Run") if the Window cannot be found.
       Presumably this executable is the same one that you were looking for.
       Note that this does not go through the shell. If you wish to run an arbitrary IO action
       (such as 'spawn', which will run its String argument through the shell), then you will want to use
       'raiseMaybe' directly. -}
    runOrRaise :: String -> Query Bool -> X ()
    runOrRaise = raiseMaybe . safeSpawnProg

    -- | See 'raiseMaybe'. If the Window can't be found, quietly give up and do nothing.
    raise :: Query Bool -> X ()
    raise = raiseMaybe $ return ()

    {- | 'raiseMaybe' queries all Windows based on a boolean provided by the
       user. Currently, there are 3 such useful booleans defined in
       "XMonad.ManageHook": 'title', 'resource', 'className'. Each one tests based pretty
       much as you would think. ManageHook also defines several operators, the most
       useful of which is (=?). So a useful test might be finding a @Window@ whose
       class is Firefox. Firefox 3 declares the class \"Firefox\", so you'd want to
       pass in a boolean like @(className =? \"Firefox\")@.

       If the boolean returns @True@ on one or more windows, then XMonad will quickly
       make visible the first result. If no @Window@ meets the criteria, then the
       first argument comes into play.

       The first argument is an arbitrary IO function which will be executed if the
       tests fail. This is what enables 'runOrRaise' to use 'raiseMaybe': it simply runs
       the desired program if it isn't found. But you don't have to do that. Maybe
       you want to do nothing if the search fails (the definition of 'raise'), or
       maybe you want to write to a log file, or call some prompt function, or
       something crazy like that. This hook gives you that flexibility. You can do
       some cute things with this hook. Suppose you want to do the same thing for
       Mutt which you just did for Firefox - but Mutt runs inside a terminal window?
       No problem: you search for a terminal window calling itself \"mutt\", and if
       there isn't you run a terminal with a command to run Mutt! Here's an example
       (borrowing 'runInTerm' from "XMonad.Util.Run"):

      > , ((modm, xK_m), raiseMaybe (runInTerm "-title mutt" "mutt") (title =? "mutt"))
    -}
    raiseMaybe :: X () -> Query Bool -> X ()
    raiseMaybe f qry = ifWindow qry raiseHook f

    -- | A manage hook that raises the window.
    raiseHook :: ManageHook
    raiseHook = ask >>= doF . W.focusWindow

    -- | See 'runOrRaise' and 'raiseNextMaybe'. Version that allows cycling through matches.
    runOrRaiseNext :: String -> Query Bool -> X ()
    runOrRaiseNext = raiseNextMaybe . safeSpawnProg

    -- | See 'raise' and 'raiseNextMaybe'. Version that allows cycling through matches.
    raiseNext :: Query Bool -> X ()
    raiseNext = raiseNextMaybe $ return ()

    {- | See 'raiseMaybe'.
         'raiseNextMaybe' is an alternative version that allows cycling
         through the matching windows. If the focused window matches the
         query the next matching window is raised. If no matches are found
         the function f is executed.
    -}

    raiseNextMaybe :: X () -> Query Bool -> X ()
    raiseNextMaybe f qry = flip (ifWindows qry) f $ \ws -> do
      foc <- withWindowSet $ return . W.peek
      case foc of
        Just w | w `elem` ws -> let (_:y:_) = dropWhile (/=w) $ cycle ws -- cannot fail to match
                                in windows $ W.focusWindow y
        _ -> windows . W.focusWindow . head $ ws

    -- | Given a function which gets us a String, we try to raise a window with that classname,
    --   or we then interpret that String as a executable name.
    raiseVar :: IO String -> X ()
    raiseVar getvar = liftIO getvar >>= \var -> runOrRaise var (fmap (map toLower) className =? var)

    {- | 'raiseBrowser' and 'raiseEditor' grab $BROWSER and $EDITOR respectively and they either
         take you to the specified program's window, or they try to run it. This is most useful
         if your variables are simple and look like \"firefox\" or \"emacs\". -}
    raiseBrowser, raiseEditor :: X ()
    raiseBrowser = raiseVar getBrowser
    raiseEditor  = raiseVar getEditor

    {- | If the window is found the window is focused and the third argument is called
         otherwise, the first argument is called
         See 'raiseMaster' for an example. -}
    raiseAndDo :: X () -> Query Bool -> (Window -> X ()) -> X ()
    raiseAndDo f qry after = ifWindow qry (afterRaise `mappend` raiseHook) f
        where afterRaise = ask >>= (>> idHook) . liftX . after

    {- | If a window matching the second argument is found, the window is focused and the third argument is called;
         otherwise, the first argument is called. -}
    runOrRaiseAndDo :: String -> Query Bool -> (Window -> X ()) -> X ()
    runOrRaiseAndDo = raiseAndDo . safeSpawnProg

    {- | if the window is found the window is focused and set to master
         otherwise, the first argument is called.

         > raiseMaster (runInTerm "-title ghci"  "zsh -c 'ghci'") (title =? "ghci") -}
    raiseMaster :: X () -> Query Bool -> X ()
    raiseMaster raisef thatUserQuery = raiseAndDo raisef thatUserQuery (\_ -> windows W.swapMaster)

    {- |  If the window is found the window is focused and set to master
          otherwise, action is run.

          > runOrRaiseMaster "firefox" (className =? "Firefox"))
      -}
    runOrRaiseMaster :: String -> Query Bool -> X ()
    runOrRaiseMaster run query = runOrRaiseAndDo run query (\_ -> windows W.swapMaster)