add File.containsBlock

1 files changed, 17 insertions, 0 deletions

diff --git a/src/Propellor/Property/File.hs b/src/Propellor/Property/File.hs
index b6f1a8d6..f57480a3 100644
--- a/src/Propellor/Property/File.hs
+++ b/src/Propellor/Property/File.hs
@@ -6,6 +6,7 @@ import Propellor.Base
 import Utility.FileMode
 
 import qualified Data.ByteString.Lazy as L
+import Data.List (isInfixOf, isPrefixOf)
 import System.Posix.Files
 import System.Exit
 
@@ -32,6 +33,22 @@ f `containsLines` ls = fileProperty (f ++ " contains:" ++ show ls) go f
   where
 	go content = content ++ filter (`notElem` content) ls
 
+-- | Ensures that a block of consecutive lines is present in a file, adding it
+-- to the end if not.  Revert to ensure that the block is not present (though
+-- the lines it contains could be present, non-consecutively).
+containsBlock :: FilePath -> [Line] -> RevertableProperty UnixLike UnixLike
+f `containsBlock` ls =
+	fileProperty (f ++ " contains block:" ++ show ls) add f
+	<!> fileProperty (f ++ " lacks block:" ++ show ls) remove f
+  where
+	add content
+		| ls `isInfixOf` content = content
+		| otherwise              = content ++ ls
+	remove [] = []
+	remove content@(x:xs)
+		| ls `isPrefixOf` content = x : remove (drop (length ls) xs)
+		| otherwise = x : remove xs
+
 -- | Ensures that a line is not present in a file.
 -- Note that the file is ensured to exist, so if it doesn't, an empty
 -- file will be written.