Powerpoint writer: simplify replaceNamedChildren function

A lot of work in the powerpoint writer is replacing XML from within
slidelayouts from templates. This function does a good deal of that
work, and this makes it preserve element order, as well as making it a
bit easier to understand.

1 files changed, 17 insertions, 9 deletions

diff --git a/src/Text/Pandoc/Writers/Powerpoint.hs b/src/Text/Pandoc/Writers/Powerpoint.hs
index bf80b8afb..50b48fd87 100644
--- a/src/Text/Pandoc/Writers/Powerpoint.hs
+++ b/src/Text/Pandoc/Writers/Powerpoint.hs
@@ -820,16 +820,24 @@ getContentShape ns spTreeElem
   filterChild (\e -> (isElem ns "p" "sp" e) && (shapeHasName ns "Content Placeholder 2" e)) spTreeElem
   | otherwise = Nothing
 
-contentIsElem :: NameSpaces -> String -> String -> Content -> Bool
-contentIsElem ns prefix name (Elem element) = isElem ns prefix name element
-contentIsElem _ _ _ _ = False
-
-replaceNamedChildren :: NameSpaces -> String -> String -> [Element] -> Element -> Element
+replaceChildren :: (Element -> [Element]) -> Element -> Element
+replaceChildren fun element =
+  element{elContent = concatMap fun' $ elContent element}
+  where fun' :: Content -> [Content]
+        fun' (Elem e) = map Elem $ fun e
+        fun' content  = [content]
+
+replaceNamedChildren :: NameSpaces
+                   -> String
+                   -> String
+                   -> [Element]
+                   -> Element
+                   -> Element
 replaceNamedChildren ns prefix name newKids element =
-  let content = elContent element
-      content' = filter (\c -> not (contentIsElem ns prefix name c)) content
-  in
-    element{elContent = content' ++ map Elem newKids}
+  let fun :: Element -> [Element]
+      fun e | isElem ns prefix name e = newKids
+            | otherwise = [e]
+  in replaceChildren fun element
 
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