    {-# LANGUAGE CPP #-}
    {-
    Copyright (c) 2006-2023, John MacFarlane

    All rights reserved.

    Redistribution and use in source and binary forms, with or without
    modification, are permitted provided that the following conditions are met:

        * Redistributions of source code must retain the above copyright
          notice, this list of conditions and the following disclaimer.

        * Redistributions in binary form must reproduce the above
          copyright notice, this list of conditions and the following
          disclaimer in the documentation and/or other materials provided
          with the distribution.

        * Neither the name of John MacFarlane nor the names of other
          contributors may be used to endorse or promote products derived
          from this software without specific prior written permission.

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    "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
    LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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    OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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    LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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    THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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    -}

    {- |
       Module      : Text.Pandoc.Generic
       Copyright   : Copyright (C) 2006-2023 John MacFarlane
       License     : BSD3

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

    Generic functions for manipulating 'Pandoc' documents.
    (Note:  the functions defined in @Text.Pandoc.Walk@ should be used instead,
    when possible, as they are much faster.)

    Here's a simple example, defining a function that replaces all the level 3+
    headers in a document with regular paragraphs in ALL CAPS:

    > import Text.Pandoc.Definition
    > import Text.Pandoc.Generic
    > import Data.Char (toUpper)
    >
    > modHeader :: Block -> Block
    > modHeader (Header n _ xs) | n >= 3 = Para $ bottomUp allCaps xs
    > modHeader x = x
    >
    > allCaps :: Inline -> Inline
    > allCaps (Str xs) = Str $ map toUpper xs
    > allCaps x = x
    >
    > changeHeaders :: Pandoc -> Pandoc
    > changeHeaders = bottomUp modHeader

    'bottomUp' is so called because it traverses the @Pandoc@ structure from
    bottom up. 'topDown' goes the other way. The difference between them can be
    seen from this example:

    > normal :: [Inline] -> [Inline]
    > normal (Space : Space : xs) = Space : xs
    > normal (Emph xs : Emph ys : zs) = Emph (xs ++ ys) : zs
    > normal xs = xs
    >
    > myDoc :: Pandoc
    > myDoc =  Pandoc nullMeta
    >  [ Para [Str "Hi",Space,Emph [Str "world",Space],Emph [Space,Str "emphasized"]]]

    Here we want to use 'topDown' to lift @normal@ to @Pandoc -> Pandoc@.
    The top down strategy will collapse the two adjacent @Emph@s first, then
    collapse the resulting adjacent @Space@s, as desired. If we used 'bottomUp',
    we would end up with two adjacent @Space@s, since the contents of the
    two @Emph@ inlines would be processed before the @Emph@s were collapsed
    into one.

    > topDown normal myDoc ==
    >   Pandoc nullMeta
    >    [Para [Str "Hi",Space,Emph [Str "world",Space,Str "emphasized"]]]
    >
    > bottomUp normal myDoc ==
    >   Pandoc nullMeta
    >    [Para [Str "Hi",Space,Emph [Str "world",Space,Space,Str "emphasized"]]]

    'bottomUpM' is a monadic version of 'bottomUp'.  It could be used,
    for example, to replace the contents of delimited code blocks with
    attribute @include=FILENAME@ with the contents of @FILENAME@:

    > doInclude :: Block -> IO Block
    > doInclude cb@(CodeBlock (id, classes, namevals) contents) =
    >   case lookup "include" namevals of
    >        Just f  -> return . (CodeBlock (id, classes, namevals)) =<< readFile f
    >        Nothing -> return cb
    > doInclude x = return x
    >
    > processIncludes :: Pandoc -> IO Pandoc
    > processIncludes = bottomUpM doInclude

    'queryWith' can be used, for example, to compile a list of URLs
    linked to in a document:

    > extractURL :: Inline -> [String]
    > extractURL (Link _ (u,_)) = [u]
    > extractURL (Image _ _ (u,_)) = [u]
    > extractURL _ = []
    >
    > extractURLs :: Pandoc -> [String]
    > extractURLs = queryWith extractURL

    -}
    module Text.Pandoc.Generic where

    import Data.Generics

    -- | Applies a transformation on @a@s to matching elements in a @b@,
    -- moving from the bottom of the structure up.
    bottomUp :: (Data a, Data b) => (a -> a) -> b -> b
    bottomUp :: forall a b. (Data a, Data b) => (a -> a) -> b -> b
    bottomUp a -> a
    f = (forall a. Data a => a -> a) -> forall a. Data a => a -> a
    everywhere ((a -> a) -> a -> a
    forall a b. (Typeable a, Typeable b) => (b -> b) -> a -> a
    mkT a -> a
    f)

    -- | Applies a transformation on @a@s to matching elements in a @b@,
    -- moving from the top of the structure down.
    topDown :: (Data a, Data b) => (a -> a) -> b -> b
    topDown :: forall a b. (Data a, Data b) => (a -> a) -> b -> b
    topDown a -> a
    f = (forall a. Data a => a -> a) -> forall a. Data a => a -> a
    everywhere' ((a -> a) -> a -> a
    forall a b. (Typeable a, Typeable b) => (b -> b) -> a -> a
    mkT a -> a
    f)

    -- | Like 'bottomUp', but with monadic transformations.
    bottomUpM :: (Monad m, Data a, Data b) => (a -> m a) -> b -> m b
    bottomUpM :: forall (m :: * -> *) a b.
    (Monad m, Data a, Data b) =>
    (a -> m a) -> b -> m b
    bottomUpM a -> m a
    f = GenericM m -> GenericM m
    forall (m :: * -> *). Monad m => GenericM m -> GenericM m
    everywhereM ((a -> m a) -> a -> m a
    forall (m :: * -> *) a b.
    (Monad m, Typeable a, Typeable b) =>
    (b -> m b) -> a -> m a
    mkM a -> m a
    f)

    -- | Runs a query on matching @a@ elements in a @c@.  The results
    -- of the queries are combined using 'mappend'.
    queryWith :: (Data a, Monoid b, Data c) => (a -> b) -> c -> b
    queryWith :: forall a b c. (Data a, Monoid b, Data c) => (a -> b) -> c -> b
    queryWith a -> b
    f = (b -> b -> b) -> GenericQ b -> GenericQ b
    forall r. (r -> r -> r) -> GenericQ r -> GenericQ r
    everything b -> b -> b
    forall a. Monoid a => a -> a -> a
    mappend (b
    forall a. Monoid a => a
    mempty b -> (a -> b) -> a -> b
    forall a b r. (Typeable a, Typeable b) => r -> (b -> r) -> a -> r
    `mkQ` a -> b
    f)