Utilities for dealing with config and data directories

1 files changed, 84 insertions, 12 deletions

diff --git a/src/Xmobar/App/Config.hs b/src/Xmobar/App/Config.hs
index 86bc9cb..7b1171f 100644
--- a/src/Xmobar/App/Config.hs
+++ b/src/Xmobar/App/Config.hs
@@ -10,16 +10,21 @@
 -- Created: Sun Nov 25, 2018 22:26
 --
 --
--- Default values for Xmobar configurations
+-- Default values for Xmobar configurations and functions to access
+-- configuration files and directories.
 --
 ------------------------------------------------------------------------------
 
 
-module Xmobar.App.Config (defaultConfig, getXdgConfigFile) where
+module Xmobar.App.Config (defaultConfig,
+                          xmobarConfigDir,
+                          xmobarDataDir,
+                          xmobarConfigFile) where
 
 import System.Environment
-import System.Directory (getHomeDirectory)
+import System.Directory
 import System.FilePath ((</>))
+import System.Posix.Files (fileExist)
 
 import Xmobar.Plugins.Date
 import Xmobar.Plugins.StdinReader
@@ -58,14 +63,81 @@ defaultConfig =
                         "<fc=#00FF00>%uname%</fc> * <fc=#FF0000>%theDate%</fc>"
            }
 
-xdgConfigDir :: IO String
-xdgConfigDir = do env <- getEnvironment
-                  case lookup "XDG_CONFIG_HOME" env of
-                       Just val -> return val
-                       Nothing  -> fmap (</> ".config") getHomeDirectory
+-- | Return the path to the xmobar configuration directory.  This
+-- directory is where user configuration files are stored (e.g, the
+-- xmobar.hs file).  You may also create a @lib@ subdirectory in the
+-- configuration directory and the default recompile command will add
+-- it to the GHC include path.
+--
+-- Several directories are considered.  In order of
+-- preference:
+--
+--   1. The directory specified in the @XMOBAR_CONFIG_DIR@ environment variable.
+--   2. The @~\/.xmobar@ directory.
+--   3. The @XDG_CONFIG_HOME/xmobar@ directory.
+--
+-- The first directory that exists will be used.  If none of the
+-- directories exist then (1) will be used if it is set, otherwise (2)
+-- will be used.  Either way, a directory will be created if necessary.
+xmobarConfigDir :: IO String
+xmobarConfigDir =
+    findFirstDirWithEnv "XMOBAR_CONFIG_DIR"
+      [ getAppUserDataDirectory "xmobar"
+      , getXdgDirectory XdgConfig "xmobar"
+      ]
+
+-- | Return the path to the xmobar data directory.  This directory is
+-- used by Xmobar to store data files such as the run-time state file
+-- and the configuration binary generated by GHC.
+--
+-- Several directories are considered.  In order of preference:
+--
+--   1. The directory specified in the @XMOBAR_DATA_DIR@ environment variable.
+--   2. The @~\/.xmobar@ directory.
+--   3. The @XDG_DATA_HOME/xmobar@ directory.
+--
+-- The first directory that exists will be used.  If none of the
+-- directories exist then (1) will be used if it is set, otherwise (2)
+-- will be used.  Either way, a directory will be created if
+-- necessary.
+xmobarDataDir :: IO String
+xmobarDataDir =
+    findFirstDirWithEnv "XMOBAR_DATA_DIR"
+      [ getAppUserDataDirectory "xmobar"
+      , getXdgDirectory XdgData "xmobar"
+      ]
+
+-- | Helper function that will find the first existing directory and
+-- return its path.  If none of the directories can be found, create
+-- and return the first from the list.  If the list is empty this
+-- function returns the historical @~\/.xmobar@ directory.
+findFirstDirOf :: [IO FilePath] -> IO FilePath
+findFirstDirOf [] = findFirstDirOf [getAppUserDataDirectory "xmobar"]
+findFirstDirOf possibles = do
+    found <- go possibles
+    case found of
+      Just path -> return path
+      Nothing ->  do
+        primary <- head possibles
+        createDirectoryIfMissing True primary
+        return primary
+  where
+    go [] = return Nothing
+    go (x:xs) = do
+      exists <- x >>= doesDirectoryExist
+      if exists then x >>= return . Just else go xs
 
-xmobarConfigDir :: IO FilePath
-xmobarConfigDir = fmap (</> "xmobar") xdgConfigDir
+-- | Simple wrapper around @findFirstDirOf@ that allows the primary
+-- path to be specified by an environment variable.
+findFirstDirWithEnv :: String -> [IO FilePath] -> IO FilePath
+findFirstDirWithEnv envName paths = do
+    envPath' <- lookupEnv envName
+    case envPath' of
+      Nothing -> findFirstDirOf paths
+      Just envPath -> findFirstDirOf (return envPath:paths)
 
-getXdgConfigFile :: IO FilePath
-getXdgConfigFile = fmap (</> "xmobarrc") xmobarConfigDir
+xmobarConfigFile :: IO FilePath
+xmobarConfigFile = do
+  f <- fmap (</> "xmobarrc") xmobarConfigDir
+  fe <- fileExist f
+  if fe then return f else fmap (</> ".xmobarrc") getHomeDirectory