Shared: introduce blocksToInlines function

This is a lossy function for converting `[Block] -> [Inline]`. Its main
use, at the moment, is for docx comments, which can contain arbitrary
blocks (except for footnotes), but which will be converted to spans.

This is, at the moment, pretty useless for everything but the basic
`Para` and `Plain` comments. It can be improved, but the docx reader
should probably emit a warning if the comment contains more than this.

src/Text/Pandoc/Shared.hs

@@ -89,6 +89,8 @@ module Text.Pandoc.Shared (
                      warn,
                      mapLeft,
                      hush,
+                     -- * for squashing blocks
+                     blocksToInlines,
                      -- * Safe read
                      safeRead,
                      -- * Temp directory
@@ -1020,6 +1022,41 @@ collapseFilePath = Posix.joinPath . reverse . foldl go [] . splitDirectories
     isSingleton _ = Nothing
     checkPathSeperator = fmap isPathSeparator . isSingleton
 
+---
+--- Squash blocks into inlines
+---
+
+blockToInlines :: Block -> [Inline]
+blockToInlines (Plain ils) = ils
+blockToInlines (Para ils) = ils
+blockToInlines (CodeBlock attr str) = [Code attr str]
+blockToInlines (RawBlock fmt str) = [RawInline fmt str]
+blockToInlines (OrderedList _ blkslst) =
+  concatMap blocksToInlines blkslst
+blockToInlines (BulletList blkslst) =
+  concatMap blocksToInlines blkslst
+blockToInlines (DefinitionList pairslst) =
+  concatMap f pairslst
+  where
+    f (ils, blkslst) = ils ++
+      [Str ":", Space] ++
+      (concatMap blocksToInlines blkslst)
+blockToInlines (Header _ _  ils) = ils
+blockToInlines (HorizontalRule) = []
+blockToInlines (Table _ _ _ headers rows) =
+  intercalate [LineBreak] $ map (concatMap blocksToInlines) tbl
+  where
+    tbl = headers : rows
+blockToInlines (Div _ blks) = blocksToInlines blks
+blockToInlines Null = []
+
+blocksToInlinesWithSep :: [Inline] -> [Block] -> [Inline]
+blocksToInlinesWithSep sep blks = intercalate sep $ map blockToInlines blks
+
+blocksToInlines :: [Block] -> [Inline]
+blocksToInlines = blocksToInlinesWithSep [Space, Str "¶", Space]
+        
+
 --
 -- Safe read
 --