support custom metadata per build

Closes #13

1 files changed, 18 insertions, 1 deletions

diff --git a/Types.hs b/Types.hs
index bff0491..17be93e 100644
--- a/Types.hs
+++ b/Types.hs
@@ -21,7 +21,8 @@
 module Types where
 
 import Control.Monad.Trans.State.Lazy
-import Data.List.NonEmpty
+import qualified Data.ByteString.UTF8
+import Data.List.NonEmpty (nonEmpty, toList)
 import qualified Data.Map as M
 import qualified Data.Set as S
 import qualified Data.Yaml as Y
@@ -73,6 +74,7 @@ data SiteState =
     , _redirectTemplate :: FilePath -- ^ Name of the template for redirect pages
     , _tagTemplate :: FilePath -- ^ Name of the template for category pages
     , _listTemplate :: FilePath -- ^ Name of the template for listing pages
+    , _extraMeta :: [(String, Y.Value)] -- ^ Extra metadata added to rendering of all templates
     , _timestampSuffix :: FilePath -- ^ File to search for a timestamp (e.g., if the prefix is ".ts", a timestamp for file "page.md" will be looked for in "page.md.ts"). These are best autogenerated with a script that sources the data from git or so.
     , _urlBase :: FilePath -- ^ "Root route" to prepend to all absolute links.
     , _appendUrlIndex :: Bool -- ^ Append full @index.html@ to all page URLs
@@ -146,6 +148,21 @@ siteOptions' = do
     long "timestamp-prefix" <>
     help "Timestamp file suffix for markdowns" <>
     value ".timestamp" <> showDefault
+  _extraMeta <-
+    let processKeyVal :: String -> (String, Y.Value)
+        processKeyVal opt =
+          case break (== ':') opt of
+            (k, ':':v) ->
+              case Y.decodeEither' $ Data.ByteString.UTF8.fromString v of
+                Right v -> (k, v :: Y.Value)
+                Left err ->
+                  error $
+                  "cannot parse key:val in --extra-metadata: " ++ show err
+            _ -> error "cannot process key:val in --extra-metadata"
+     in fmap (map processKeyVal) . many . strOption $
+        long "extra-metadata" <>
+        help
+          "Extra metadata to add to pages rendering in format `key:<yaml>'. May be specified multiple times."
   _urlBase <-
     strOption $
     long "url-base" <>