Pandoc filter: convert horizontal rules into section breaks for Word output

pandoc-word-sectionbreak.hs

#!/usr/bin/env runhaskell

{- 
Pandoc filter to replace horizontal rules with hard section breaks when output is in Word format.

Credits: This is a very lightly adapted version of a `\newpage` filter
previously described on pandoc-discuss:
	https://groups.google.com/forum/#!topic/pandoc-discuss/FzLrhk0vVbU

	
Usage: 
	pandoc --filter pandoc-word-sectionbreak.hs  input.md -o output.docx

Alternately, compile the filter, store it anywhere you like, 
add it to your PATH, and call the compiled version:
	ghc --make pandoc-word-sectionbreak.hs
	rm pandoc-word-sectionbreak.hi pandoc-word-sectionbreak.o
	mv pandoc-word-sectionbreak /path/to/your/binaries/pandoc-word-sectionbreak
	export PATH=$PATH:/path/to/your/binaries

	pandoc --filter pandoc-word-sectionbreak  input.md -o output.docx

N.B.: 
  As far as I know, this filter ONLY works correctly when output is a Word document. 
  It *may* work with other xml formats, but I haven't tried. 
  When run with other output formats, it removes the horizonal rules entirely. 
  This is probably not what you want.

-}

import Text.Pandoc.JSON

secBrkXml :: String
secBrkXml = "<w:p><w:pPr><w:sectPr><w:type w:val=\"nextPage\"/></w:sectPr></w:pPr></w:p>"

secBrkBlock :: Block
secBrkBlock = RawBlock (Format "openxml") secBrkXml

insertSecBrks :: Block -> Block

insertSecBrks HorizontalRule = secBrkBlock 
insertSecBrks blk = blk

main = toJSONFilter insertSecBrks