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-- | Module exporting convenientpandoc bindings
module Hakyll.Web.Pandoc
    ( -- * The basic building blocks
      readPandoc
    , readPandocWith
    , writePandoc
    , writePandocWith

      -- * Functions working on pages/compilers
    , pageReadPandoc
    , pageReadPandocWith
    , pageReadPandocWithA
    , pageRenderPandoc
    , pageRenderPandocWith

      -- * Default options
    , defaultHakyllParserState
    , defaultHakyllWriterOptions
    ) where


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import           Control.Arrow              ((&&&), (***), (>>>), (>>^))
import           Control.Category           (id)
import           Data.Maybe                 (fromMaybe)
import           Prelude                    hiding (id)
import           Text.Pandoc


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import           Hakyll.Core.Compiler
import           Hakyll.Core.Identifier
import           Hakyll.Core.Util.Arrow
import           Hakyll.Web.Page.Internal
import           Hakyll.Web.Pandoc.FileType


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-- | Read a string using pandoc, with the default options
readPandoc :: FileType              -- ^ Determines how parsing happens
           -> Maybe (Identifier a)  -- ^ Optional, for better error messages
           -> Page                  -- ^ String to read
           -> Pandoc                -- ^ Resulting document
readPandoc = readPandocWith defaultHakyllParserState


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-- | Read a string using pandoc, with the supplied options
readPandocWith :: ParserState           -- ^ Parser options
               -> FileType              -- ^ Determines parsing method
               -> Maybe (Identifier a)  -- ^ Optional, for better error messages
               -> Page                  -- ^ String to read
               -> Pandoc                -- ^ Resulting document
readPandocWith state fileType' id' = case fileType' of
    Html              -> readHtml state
    LaTeX             -> readLaTeX state
    LiterateHaskell t ->
        readPandocWith state {stateLiterateHaskell = True} t id'
    Markdown          -> readMarkdown state
    Rst               -> readRST state
    Textile           -> readTextile state
    t                 -> error $
        "Hakyll.Web.readPandocWith: I don't know how to read a file of the " ++
        "type " ++ show t ++ fromMaybe "" (fmap ((" for: " ++) . show) id')


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-- | Write a document (as HTML) using pandoc, with the default options
writePandoc :: Pandoc  -- ^ Document to write
            -> Page    -- ^ Resulting HTML
writePandoc = writePandocWith defaultHakyllWriterOptions


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-- | Write a document (as HTML) using pandoc, with the supplied options
writePandocWith :: WriterOptions  -- ^ Writer options for pandoc
                -> Pandoc         -- ^ Document to write
                -> Page           -- ^ Resulting HTML
writePandocWith = writeHtmlString


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-- | Read the resource using pandoc
pageReadPandoc :: Compiler Page Pandoc
pageReadPandoc = pageReadPandocWith defaultHakyllParserState


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-- | Read the resource using pandoc
pageReadPandocWith :: ParserState -> Compiler Page Pandoc
pageReadPandocWith state = constA state &&& id >>> pageReadPandocWithA


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-- | Read the resource using pandoc. This is a (rarely needed) variant, which
-- comes in very useful when the parser state is the result of some arrow.
pageReadPandocWithA :: Compiler (ParserState, Page) Pandoc
pageReadPandocWithA =
    id *** id &&& getIdentifier &&& getFileType >>^ pageReadPandocWithA'
  where
    pageReadPandocWithA' (s, (p, (i, t))) = readPandocWith s t (Just i) p


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-- | Render the resource using pandoc
pageRenderPandoc :: Compiler Page Page
pageRenderPandoc =
    pageRenderPandocWith defaultHakyllParserState defaultHakyllWriterOptions


--------------------------------------------------------------------------------
-- | Render the resource using pandoc
pageRenderPandocWith :: ParserState -> WriterOptions -> Compiler Page Page
pageRenderPandocWith state options =
    pageReadPandocWith state >>^ writePandocWith options


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-- | The default reader options for pandoc parsing in hakyll
defaultHakyllParserState :: ParserState
defaultHakyllParserState = defaultParserState
    { -- The following option causes pandoc to read smart typography, a nice
      -- and free bonus.
      stateSmart = True
    }


--------------------------------------------------------------------------------
-- | The default writer options for pandoc rendering in hakyll
defaultHakyllWriterOptions :: WriterOptions
defaultHakyllWriterOptions = defaultWriterOptions
    { -- This option causes literate haskell to be written using '>' marks in
      -- html, which I think is a good default.
      writerLiterateHaskell = True
    }