matchMetadata for examining metadata when defining rules

1 files changed, 14 insertions, 0 deletions

diff --git a/src/Hakyll/Core/Rules.hs b/src/Hakyll/Core/Rules.hs
index c248a9b..1c8b93c 100644
--- a/src/Hakyll/Core/Rules.hs
+++ b/src/Hakyll/Core/Rules.hs
@@ -19,6 +19,7 @@
 module Hakyll.Core.Rules
     ( Rules
     , match
+    , matchMetadata
     , create
     , version
     , compile
@@ -132,6 +133,19 @@ match pattern rules = do
 
 
 --------------------------------------------------------------------------------
+matchMetadata :: Pattern -> (Metadata -> Bool) -> Rules () -> Rules ()
+matchMetadata pattern metadataPred rules = do
+    tellPattern pattern
+    flush
+    idsAndMetadata <- getAllMetadata pattern
+    let ids = map fst . filter (metadataPred . snd) $ idsAndMetadata
+    tellResources ids
+    Rules $ local (setMatches ids) $ unRules $ rules >> flush
+  where
+    setMatches ids env = env {rulesMatches = ids}
+
+
+--------------------------------------------------------------------------------
 create :: [Identifier] -> Rules () -> Rules ()
 create ids rules = do
     flush