{-# LANGUAGE NoImplicitPrelude #-}
{-# LANGUAGE OverloadedStrings #-}
{-
Copyright (C) 2013-2018 John MacFarlane <jgm@berkeley.edu>

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
-}

{- |
   Module      : Text.Pandoc.Writers.Shared
   Copyright   : Copyright (C) 2013-2018 John MacFarlane
   License     : GNU GPL, version 2 or above

   Maintainer  : John MacFarlane <jgm@berkeley.edu>
   Stability   : alpha
   Portability : portable

Shared utility functions for pandoc writers.
-}
module Text.Pandoc.Writers.Shared (
                       metaToJSON
                     , metaToJSON'
                     , addVariablesToJSON
                     , getField
                     , setField
                     , resetField
                     , defField
                     , tagWithAttrs
                     , fixDisplayMath
                     , unsmartify
                     , gridTable
                     , metaValueToInlines
                     , stripLeadingTrailingSpace
                     )
where
import Prelude
import Control.Monad (zipWithM)
import Data.Aeson (FromJSON (..), Result (..), ToJSON (..), Value (Object),
                   encode, fromJSON)
import qualified Data.HashMap.Strict as H
import Data.List (groupBy, intersperse, transpose)
import qualified Data.Map as M
import Data.Maybe (isJust)
import qualified Data.Text as T
import qualified Data.Traversable as Traversable
import qualified Text.Pandoc.Builder as Builder
import Text.Pandoc.Definition
import Text.Pandoc.Options
import Text.Pandoc.Pretty
import Text.Pandoc.Walk (query)
import Text.Pandoc.UTF8 (toStringLazy)
import Text.Pandoc.XML (escapeStringForXML)

-- | Create JSON value for template from a 'Meta' and an association list
-- of variables, specified at the command line or in the writer.
-- Variables overwrite metadata fields with the same names.
-- If multiple variables are set with the same name, a list is
-- assigned.  Does nothing if 'writerTemplate' is Nothing.
metaToJSON :: (Functor m, Monad m, ToJSON a)
           => WriterOptions
           -> ([Block] -> m a)
           -> ([Inline] -> m a)
           -> Meta
           -> m Value
metaToJSON opts blockWriter inlineWriter meta
  | isJust (writerTemplate opts) =
    addVariablesToJSON opts <$> metaToJSON' blockWriter inlineWriter meta
  | otherwise = return (Object H.empty)

-- | Like 'metaToJSON', but does not include variables and is
-- not sensitive to 'writerTemplate'.
metaToJSON' :: (Functor m, Monad m, ToJSON a)
           => ([Block] -> m a)
           -> ([Inline] -> m a)
           -> Meta
           -> m Value
metaToJSON' blockWriter inlineWriter (Meta metamap) = do
  renderedMap <- Traversable.mapM
                 (metaValueToJSON blockWriter inlineWriter)
                 metamap
  return $ M.foldrWithKey defField (Object H.empty) renderedMap

-- | Add variables to JSON object, replacing any existing values.
-- Also include @meta-json@, a field containing a string representation
-- of the original JSON object itself, prior to addition of variables.
addVariablesToJSON :: WriterOptions -> Value -> Value
addVariablesToJSON opts metadata =
  foldl (\acc (x,y) -> setField x y acc)
       (defField "meta-json" (toStringLazy $ encode metadata) (Object mempty))
       (writerVariables opts)
    `combineMetadata` metadata
  where combineMetadata (Object o1) (Object o2) = Object $ H.union o1 o2
        combineMetadata x _                     = x

metaValueToJSON :: (Functor m, Monad m, ToJSON a)
                => ([Block] -> m a)
                -> ([Inline] -> m a)
                -> MetaValue
                -> m Value
metaValueToJSON blockWriter inlineWriter (MetaMap metamap) = toJSON <$>
  Traversable.mapM (metaValueToJSON blockWriter inlineWriter) metamap
metaValueToJSON blockWriter inlineWriter (MetaList xs) = toJSON <$>
  Traversable.mapM (metaValueToJSON blockWriter inlineWriter) xs
metaValueToJSON _ _ (MetaBool b) = return $ toJSON b
metaValueToJSON _ inlineWriter (MetaString s) = toJSON <$>
  inlineWriter (Builder.toList (Builder.text s))
metaValueToJSON blockWriter _ (MetaBlocks bs) = toJSON <$> blockWriter bs
metaValueToJSON _ inlineWriter (MetaInlines is) = toJSON <$> inlineWriter is

-- | Retrieve a field value from a JSON object.
getField :: FromJSON a
         => String
         -> Value
         -> Maybe a
getField field (Object hashmap) = do
  result <- H.lookup (T.pack field) hashmap
  case fromJSON result of
       Success x -> return x
       _         -> fail "Could not convert from JSON"
getField _ _ = fail "Not a JSON object"

setField :: ToJSON a
         => String
         -> a
         -> Value
         -> Value
-- | Set a field of a JSON object.  If the field already has a value,
-- convert it into a list with the new value appended to the old value(s).
-- This is a utility function to be used in preparing template contexts.
setField field val (Object hashmap) =
  Object $ H.insertWith combine (T.pack field) (toJSON val) hashmap
  where combine newval oldval =
          case fromJSON oldval of
                Success xs -> toJSON $ xs ++ [newval]
                _          -> toJSON [oldval, newval]
setField _ _  x = x

resetField :: ToJSON a
           => String
           -> a
           -> Value
           -> Value
-- | Reset a field of a JSON object.  If the field already has a value,
-- the new value replaces it.
-- This is a utility function to be used in preparing template contexts.
resetField field val (Object hashmap) =
  Object $ H.insert (T.pack field) (toJSON val) hashmap
resetField _ _  x = x

defField :: ToJSON a
         => String
         -> a
         -> Value
         -> Value
-- | Set a field of a JSON object if it currently has no value.
-- If it has a value, do nothing.
-- This is a utility function to be used in preparing template contexts.
defField field val (Object hashmap) =
  Object $ H.insertWith f (T.pack field) (toJSON val) hashmap
    where f _newval oldval = oldval
defField _ _  x = x

-- Produce an HTML tag with the given pandoc attributes.
tagWithAttrs :: String -> Attr -> Doc
tagWithAttrs tag (ident,classes,kvs) = hsep
  ["<" <> text tag
  ,if null ident
      then empty
      else "id=" <> doubleQuotes (text ident)
  ,if null classes
      then empty
      else "class=" <> doubleQuotes (text (unwords classes))
  ,hsep (map (\(k,v) -> text k <> "=" <>
                doubleQuotes (text (escapeStringForXML v))) kvs)
  ] <> ">"

isDisplayMath :: Inline -> Bool
isDisplayMath (Math DisplayMath _) = True
isDisplayMath _                    = False

stripLeadingTrailingSpace :: [Inline] -> [Inline]
stripLeadingTrailingSpace = go . reverse . go . reverse
  where go (Space:xs)     = xs
        go (SoftBreak:xs) = xs
        go xs             = xs

-- Put display math in its own block (for ODT/DOCX).
fixDisplayMath :: Block -> Block
fixDisplayMath (Plain lst)
  | any isDisplayMath lst && not (all isDisplayMath lst) =
    -- chop into several paragraphs so each displaymath is its own
    Div ("",["math"],[]) $
       map Plain $
       filter (not . null) $
       map stripLeadingTrailingSpace $
       groupBy (\x y -> (isDisplayMath x && isDisplayMath y) ||
                         not (isDisplayMath x || isDisplayMath y)) lst
fixDisplayMath (Para lst)
  | any isDisplayMath lst && not (all isDisplayMath lst) =
    -- chop into several paragraphs so each displaymath is its own
    Div ("",["math"],[]) $
       map Para $
       filter (not . null) $
       map stripLeadingTrailingSpace $
       groupBy (\x y -> (isDisplayMath x && isDisplayMath y) ||
                         not (isDisplayMath x || isDisplayMath y)) lst
fixDisplayMath x = x

unsmartify :: WriterOptions -> String -> String
unsmartify opts ('\8217':xs) = '\'' : unsmartify opts xs
unsmartify opts ('\8230':xs) = "..." ++ unsmartify opts xs
unsmartify opts ('\8211':xs)
  | isEnabled Ext_old_dashes opts = '-' : unsmartify opts xs
  | otherwise                     = "--" ++ unsmartify opts xs
unsmartify opts ('\8212':xs)
  | isEnabled Ext_old_dashes opts = "--" ++ unsmartify opts xs
  | otherwise                     = "---" ++ unsmartify opts xs
unsmartify opts ('\8220':xs) = '"' : unsmartify opts xs
unsmartify opts ('\8221':xs) = '"' : unsmartify opts xs
unsmartify opts ('\8216':xs) = '\'' : unsmartify opts xs
unsmartify opts (x:xs) = x : unsmartify opts xs
unsmartify _ [] = []

gridTable :: Monad m
          => WriterOptions
          -> (WriterOptions -> [Block] -> m Doc)
          -> Bool -- ^ headless
          -> [Alignment]
          -> [Double]
          -> [[Block]]
          -> [[[Block]]]
          -> m Doc
gridTable opts blocksToDoc headless aligns widths headers rows = do
  -- the number of columns will be used in case of even widths
  let numcols = maximum (length aligns : length widths :
                           map length (headers:rows))
  -- handleGivenWidths wraps the given blocks in order for them to fit
  -- in cells with given widths. the returned content can be
  -- concatenated with borders and frames
  let handleGivenWidths widths' = do
        let widthsInChars' = map (
                      (\x -> if x < 1 then 1 else x) .
                      (\x -> x - 3) . floor .
                      (fromIntegral (writerColumns opts) *)
                      ) widths'
            -- replace page width (in columns) in the options with a
            -- given width if smaller (adjusting by two)
            useWidth w = opts{writerColumns = min (w - 2) (writerColumns opts)}
            -- prepare options to use with header and row cells
            columnOptions = map useWidth widthsInChars'
        rawHeaders' <- zipWithM blocksToDoc columnOptions headers
        rawRows' <- mapM
             (\cs -> zipWithM blocksToDoc columnOptions cs)
             rows
        return (widthsInChars', rawHeaders', rawRows')
  -- handleFullWidths tries to wrap cells to the page width or even
  -- more in cases where `--wrap=none`. thus the content here is left
  -- as wide as possible
  let handleFullWidths = do
        rawHeaders' <- mapM (blocksToDoc opts) headers
        rawRows' <- mapM (mapM (blocksToDoc opts)) rows
        let numChars [] = 0
            numChars xs = maximum . map offset $ xs
        let widthsInChars' =
                map numChars $ transpose (rawHeaders' : rawRows')
        return (widthsInChars', rawHeaders', rawRows')
  -- handleZeroWidths calls handleFullWidths to check whether a wide
  -- table would fit in the page. if the produced table is too wide,
  -- it calculates even widths and passes the content to
  -- handleGivenWidths
  let handleZeroWidths = do
        (widthsInChars', rawHeaders', rawRows') <- handleFullWidths
        if sum widthsInChars' > writerColumns opts
           then -- use even widths
                handleGivenWidths
                  (replicate numcols (1.0 / fromIntegral numcols) :: [Double])
           else return (widthsInChars', rawHeaders', rawRows')
  -- render the contents of header and row cells differently depending
  -- on command line options, widths given in this specific table, and
  -- cells' contents
  let handleWidths
        | writerWrapText opts == WrapNone  = handleFullWidths
        | all (== 0) widths                  = handleZeroWidths
        | otherwise                          = handleGivenWidths widths
  (widthsInChars, rawHeaders, rawRows) <- handleWidths
  let hpipeBlocks blocks = hcat [beg, middle, end]
        where h       = maximum (1 : map height blocks)
              sep'    = lblock 3 $ vcat (replicate h (text " | "))
              beg     = lblock 2 $ vcat (replicate h (text "| "))
              end     = lblock 2 $ vcat (replicate h (text " |"))
              middle  = chomp $ hcat $ intersperse sep' blocks
  let makeRow = hpipeBlocks . zipWith lblock widthsInChars
  let head' = makeRow rawHeaders
  let rows' = map (makeRow . map chomp) rawRows
  let borderpart ch align widthInChars =
           (if align == AlignLeft || align == AlignCenter
               then char ':'
               else char ch) <>
           text (replicate widthInChars ch) <>
           (if align == AlignRight || align == AlignCenter
               then char ':'
               else char ch)
  let border ch aligns' widthsInChars' =
        char '+' <>
        hcat (intersperse (char '+') (zipWith (borderpart ch)
                aligns' widthsInChars')) <> char '+'
  let body = vcat $ intersperse (border '-' (repeat AlignDefault) widthsInChars)
                    rows'
  let head'' = if headless
                  then empty
                  else head' $$ border '=' aligns widthsInChars
  if headless
     then return $
           border '-' aligns widthsInChars $$
           body $$
           border '-' (repeat AlignDefault) widthsInChars
     else return $
           border '-' (repeat AlignDefault) widthsInChars $$
           head'' $$
           body $$
           border '-' (repeat AlignDefault) widthsInChars

metaValueToInlines :: MetaValue -> [Inline]
metaValueToInlines (MetaString s)    = [Str s]
metaValueToInlines (MetaInlines ils) = ils
metaValueToInlines (MetaBlocks bs)   = query return bs
metaValueToInlines (MetaBool b)      = [Str $ show b]
metaValueToInlines _                 = []