diff --git a/COPYING.md b/COPYING.md
new file mode 100644
--- /dev/null
+++ b/COPYING.md
@@ -0,0 +1,361 @@
+### GNU GENERAL PUBLIC LICENSE
+
+Version 2, June 1991
+
+    Copyright (C) 1989, 1991 Free Software Foundation, Inc.  
+    51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
+
+    Everyone is permitted to copy and distribute verbatim copies
+    of this license document, but changing it is not allowed.
+
+### Preamble
+
+The licenses for most software are designed to take away your freedom
+to share and change it. By contrast, the GNU General Public License is
+intended to guarantee your freedom to share and change free
+software--to make sure the software is free for all its users. This
+General Public License applies to most of the Free Software
+Foundation's software and to any other program whose authors commit to
+using it. (Some other Free Software Foundation software is covered by
+the GNU Lesser General Public License instead.) You can apply it to
+your programs, too.
+
+When we speak of free software, we are referring to freedom, not
+price. Our General Public Licenses are designed to make sure that you
+have the freedom to distribute copies of free software (and charge for
+this service if you wish), that you receive source code or can get it
+if you want it, that you can change the software or use pieces of it
+in new free programs; and that you know you can do these things.
+
+To protect your rights, we need to make restrictions that forbid
+anyone to deny you these rights or to ask you to surrender the rights.
+These restrictions translate to certain responsibilities for you if
+you distribute copies of the software, or if you modify it.
+
+For example, if you distribute copies of such a program, whether
+gratis or for a fee, you must give the recipients all the rights that
+you have. You must make sure that they, too, receive or can get the
+source code. And you must show them these terms so they know their
+rights.
+
+We protect your rights with two steps: (1) copyright the software, and
+(2) offer you this license which gives you legal permission to copy,
+distribute and/or modify the software.
+
+Also, for each author's protection and ours, we want to make certain
+that everyone understands that there is no warranty for this free
+software. If the software is modified by someone else and passed on,
+we want its recipients to know that what they have is not the
+original, so that any problems introduced by others will not reflect
+on the original authors' reputations.
+
+Finally, any free program is threatened constantly by software
+patents. We wish to avoid the danger that redistributors of a free
+program will individually obtain patent licenses, in effect making the
+program proprietary. To prevent this, we have made it clear that any
+patent must be licensed for everyone's free use or not licensed at
+all.
+
+The precise terms and conditions for copying, distribution and
+modification follow.
+
+### TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
+
+**0.** This License applies to any program or other work which
+contains a notice placed by the copyright holder saying it may be
+distributed under the terms of this General Public License. The
+"Program", below, refers to any such program or work, and a "work
+based on the Program" means either the Program or any derivative work
+under copyright law: that is to say, a work containing the Program or
+a portion of it, either verbatim or with modifications and/or
+translated into another language. (Hereinafter, translation is
+included without limitation in the term "modification".) Each licensee
+is addressed as "you".
+
+Activities other than copying, distribution and modification are not
+covered by this License; they are outside its scope. The act of
+running the Program is not restricted, and the output from the Program
+is covered only if its contents constitute a work based on the Program
+(independent of having been made by running the Program). Whether that
+is true depends on what the Program does.
+
+**1.** You may copy and distribute verbatim copies of the Program's
+source code as you receive it, in any medium, provided that you
+conspicuously and appropriately publish on each copy an appropriate
+copyright notice and disclaimer of warranty; keep intact all the
+notices that refer to this License and to the absence of any warranty;
+and give any other recipients of the Program a copy of this License
+along with the Program.
+
+You may charge a fee for the physical act of transferring a copy, and
+you may at your option offer warranty protection in exchange for a
+fee.
+
+**2.** You may modify your copy or copies of the Program or any
+portion of it, thus forming a work based on the Program, and copy and
+distribute such modifications or work under the terms of Section 1
+above, provided that you also meet all of these conditions:
+
+  
+**a)** You must cause the modified files to carry prominent notices
+stating that you changed the files and the date of any change.
+
+  
+**b)** You must cause any work that you distribute or publish, that in
+whole or in part contains or is derived from the Program or any part
+thereof, to be licensed as a whole at no charge to all third parties
+under the terms of this License.
+
+  
+**c)** If the modified program normally reads commands interactively
+when run, you must cause it, when started running for such interactive
+use in the most ordinary way, to print or display an announcement
+including an appropriate copyright notice and a notice that there is
+no warranty (or else, saying that you provide a warranty) and that
+users may redistribute the program under these conditions, and telling
+the user how to view a copy of this License. (Exception: if the
+Program itself is interactive but does not normally print such an
+announcement, your work based on the Program is not required to print
+an announcement.)
+
+These requirements apply to the modified work as a whole. If
+identifiable sections of that work are not derived from the Program,
+and can be reasonably considered independent and separate works in
+themselves, then this License, and its terms, do not apply to those
+sections when you distribute them as separate works. But when you
+distribute the same sections as part of a whole which is a work based
+on the Program, the distribution of the whole must be on the terms of
+this License, whose permissions for other licensees extend to the
+entire whole, and thus to each and every part regardless of who wrote
+it.
+
+Thus, it is not the intent of this section to claim rights or contest
+your rights to work written entirely by you; rather, the intent is to
+exercise the right to control the distribution of derivative or
+collective works based on the Program.
+
+In addition, mere aggregation of another work not based on the Program
+with the Program (or with a work based on the Program) on a volume of
+a storage or distribution medium does not bring the other work under
+the scope of this License.
+
+**3.** You may copy and distribute the Program (or a work based on it,
+under Section 2) in object code or executable form under the terms of
+Sections 1 and 2 above provided that you also do one of the following:
+
+  
+**a)** Accompany it with the complete corresponding machine-readable
+source code, which must be distributed under the terms of Sections 1
+and 2 above on a medium customarily used for software interchange; or,
+
+  
+**b)** Accompany it with a written offer, valid for at least three
+years, to give any third party, for a charge no more than your cost of
+physically performing source distribution, a complete machine-readable
+copy of the corresponding source code, to be distributed under the
+terms of Sections 1 and 2 above on a medium customarily used for
+software interchange; or,
+
+  
+**c)** Accompany it with the information you received as to the offer
+to distribute corresponding source code. (This alternative is allowed
+only for noncommercial distribution and only if you received the
+program in object code or executable form with such an offer, in
+accord with Subsection b above.)
+
+The source code for a work means the preferred form of the work for
+making modifications to it. For an executable work, complete source
+code means all the source code for all modules it contains, plus any
+associated interface definition files, plus the scripts used to
+control compilation and installation of the executable. However, as a
+special exception, the source code distributed need not include
+anything that is normally distributed (in either source or binary
+form) with the major components (compiler, kernel, and so on) of the
+operating system on which the executable runs, unless that component
+itself accompanies the executable.
+
+If distribution of executable or object code is made by offering
+access to copy from a designated place, then offering equivalent
+access to copy the source code from the same place counts as
+distribution of the source code, even though third parties are not
+compelled to copy the source along with the object code.
+
+**4.** You may not copy, modify, sublicense, or distribute the Program
+except as expressly provided under this License. Any attempt otherwise
+to copy, modify, sublicense or distribute the Program is void, and
+will automatically terminate your rights under this License. However,
+parties who have received copies, or rights, from you under this
+License will not have their licenses terminated so long as such
+parties remain in full compliance.
+
+**5.** You are not required to accept this License, since you have not
+signed it. However, nothing else grants you permission to modify or
+distribute the Program or its derivative works. These actions are
+prohibited by law if you do not accept this License. Therefore, by
+modifying or distributing the Program (or any work based on the
+Program), you indicate your acceptance of this License to do so, and
+all its terms and conditions for copying, distributing or modifying
+the Program or works based on it.
+
+**6.** Each time you redistribute the Program (or any work based on
+the Program), the recipient automatically receives a license from the
+original licensor to copy, distribute or modify the Program subject to
+these terms and conditions. You may not impose any further
+restrictions on the recipients' exercise of the rights granted herein.
+You are not responsible for enforcing compliance by third parties to
+this License.
+
+**7.** If, as a consequence of a court judgment or allegation of
+patent infringement or for any other reason (not limited to patent
+issues), conditions are imposed on you (whether by court order,
+agreement or otherwise) that contradict the conditions of this
+License, they do not excuse you from the conditions of this License.
+If you cannot distribute so as to satisfy simultaneously your
+obligations under this License and any other pertinent obligations,
+then as a consequence you may not distribute the Program at all. For
+example, if a patent license would not permit royalty-free
+redistribution of the Program by all those who receive copies directly
+or indirectly through you, then the only way you could satisfy both it
+and this License would be to refrain entirely from distribution of the
+Program.
+
+If any portion of this section is held invalid or unenforceable under
+any particular circumstance, the balance of the section is intended to
+apply and the section as a whole is intended to apply in other
+circumstances.
+
+It is not the purpose of this section to induce you to infringe any
+patents or other property right claims or to contest validity of any
+such claims; this section has the sole purpose of protecting the
+integrity of the free software distribution system, which is
+implemented by public license practices. Many people have made
+generous contributions to the wide range of software distributed
+through that system in reliance on consistent application of that
+system; it is up to the author/donor to decide if he or she is willing
+to distribute software through any other system and a licensee cannot
+impose that choice.
+
+This section is intended to make thoroughly clear what is believed to
+be a consequence of the rest of this License.
+
+**8.** If the distribution and/or use of the Program is restricted in
+certain countries either by patents or by copyrighted interfaces, the
+original copyright holder who places the Program under this License
+may add an explicit geographical distribution limitation excluding
+those countries, so that distribution is permitted only in or among
+countries not thus excluded. In such case, this License incorporates
+the limitation as if written in the body of this License.
+
+**9.** The Free Software Foundation may publish revised and/or new
+versions of the General Public License from time to time. Such new
+versions will be similar in spirit to the present version, but may
+differ in detail to address new problems or concerns.
+
+Each version is given a distinguishing version number. If the Program
+specifies a version number of this License which applies to it and
+"any later version", you have the option of following the terms and
+conditions either of that version or of any later version published by
+the Free Software Foundation. If the Program does not specify a
+version number of this License, you may choose any version ever
+published by the Free Software Foundation.
+
+**10.** If you wish to incorporate parts of the Program into other
+free programs whose distribution conditions are different, write to
+the author to ask for permission. For software which is copyrighted by
+the Free Software Foundation, write to the Free Software Foundation;
+we sometimes make exceptions for this. Our decision will be guided by
+the two goals of preserving the free status of all derivatives of our
+free software and of promoting the sharing and reuse of software
+generally.
+
+**NO WARRANTY**
+
+**11.** BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO
+WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW.
+EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR
+OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY OF ANY
+KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE
+PROGRAM IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME
+THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
+
+**12.** IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN
+WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY
+AND/OR REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU
+FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR
+CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE
+PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING
+RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A
+FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), EVEN IF
+SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
+DAMAGES.
+
+### END OF TERMS AND CONDITIONS
+
+### How to Apply These Terms to Your New Programs
+
+If you develop a new program, and you want it to be of the greatest
+possible use to the public, the best way to achieve this is to make it
+free software which everyone can redistribute and change under these
+terms.
+
+To do so, attach the following notices to the program. It is safest to
+attach them to the start of each source file to most effectively
+convey the exclusion of warranty; and each file should have at least
+the "copyright" line and a pointer to where the full notice is found.
+
+    one line to give the program's name and an idea of what it does.
+    Copyright (C) yyyy  name of author
+
+    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., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+
+Also add information on how to contact you by electronic and paper
+mail.
+
+If the program is interactive, make it output a short notice like this
+when it starts in an interactive mode:
+
+    Gnomovision version 69, Copyright (C) year name of author
+    Gnomovision comes with ABSOLUTELY NO WARRANTY; for details
+    type `show w'.  This is free software, and you are welcome
+    to redistribute it under certain conditions; type `show c' 
+    for details.
+
+The hypothetical commands \`show w' and \`show c' should show the
+appropriate parts of the General Public License. Of course, the
+commands you use may be called something other than \`show w' and
+\`show c'; they could even be mouse-clicks or menu items--whatever
+suits your program.
+
+You should also get your employer (if you work as a programmer) or
+your school, if any, to sign a "copyright disclaimer" for the program,
+if necessary. Here is a sample; alter the names:
+
+    Yoyodyne, Inc., hereby disclaims all copyright
+    interest in the program `Gnomovision'
+    (which makes passes at compilers) written 
+    by James Hacker.
+
+    signature of Ty Coon, 1 April 1989
+    Ty Coon, President of Vice
+
+This General Public License does not permit incorporating your program
+into proprietary programs. If your program is a subroutine library,
+you may consider it more useful to permit linking proprietary
+applications with the library. If this is what you want to do, use the
+[GNU Lesser General Public
+License](https://www.gnu.org/licenses/lgpl.html) instead of this
+License.
diff --git a/pandoc-server.cabal b/pandoc-server.cabal
new file mode 100644
--- /dev/null
+++ b/pandoc-server.cabal
@@ -0,0 +1,70 @@
+cabal-version:   2.4
+name:            pandoc-server
+version:         0.1
+build-type:      Simple
+license:         GPL-2.0-or-later
+license-file:    COPYING.md
+copyright:       (c) 2006-2022 John MacFarlane
+author:          John MacFarlane <jgm@berkeley.edu>
+maintainer:      John MacFarlane <jgm@berkeley.edu>
+bug-reports:     https://github.com/jgm/pandoc/issues
+stability:       alpha
+homepage:        https://pandoc.org
+category:        Text
+tested-with:     GHC == 8.6.5, GHC == 8.8.4, GHC == 8.10.7, GHC == 9.0.2,
+                 GHC == 9.2.5, GHC == 9.4.4
+synopsis:        Pandoc document conversion as an HTTP servant-server
+description:     Pandoc-server provides pandoc's document conversion functions
+                 in an HTTP server.
+source-repository head
+  type:          git
+  location:      git://github.com/jgm/pandoc.git
+
+common common-options
+  default-language: Haskell2010
+  build-depends:    base         >= 4.12 && < 5
+  ghc-options:      -Wall -fno-warn-unused-do-bind
+                    -Wincomplete-record-updates
+                    -Wnoncanonical-monad-instances
+                    -Wcpp-undef
+                    -Wincomplete-uni-patterns
+                    -Widentities
+                    -Wpartial-fields
+                    -Wmissing-signatures
+                    -fhide-source-paths
+                    -- -Wmissing-export-lists
+
+  if impl(ghc >= 8.10)
+    ghc-options:    -Wunused-packages
+
+  if impl(ghc >= 9.0)
+    ghc-options:    -Winvalid-haddock
+
+  if os(windows)
+    cpp-options:      -D_WINDOWS
+
+common common-executable
+  import:           common-options
+  ghc-options:      -rtsopts -with-rtsopts=-A8m -threaded
+
+library
+  import:        common-options
+  build-depends: pandoc                >= 3.0,
+                 pandoc-types          >= 1.22     && < 1.24,
+                 containers            >= 0.6.0.1  && < 0.7,
+                 aeson                 >= 2.0      && < 2.2,
+                 bytestring            >= 0.9      && < 0.12,
+                 base64                >= 0.4      && < 0.5,
+                 doctemplates          >= 0.11     && < 0.12,
+                 data-default          >= 0.4      && < 0.8,
+                 text                  >= 1.1.1.0  && < 2.1,
+                 unicode-collation     >= 0.1.1    && < 0.2,
+                 servant-server        >= 0.19     && < 0.20,
+                 skylighting           >= 0.13     && < 0.14,
+                 wai                   >= 3.2      && < 3.3,
+                 wai-cors              >= 0.2.7    && < 0.3
+
+  hs-source-dirs:  src
+
+  exposed-modules: Text.Pandoc.Server
+  buildable:       True
diff --git a/src/Text/Pandoc/Server.hs b/src/Text/Pandoc/Server.hs
new file mode 100644
--- /dev/null
+++ b/src/Text/Pandoc/Server.hs
@@ -0,0 +1,429 @@
+{-# LANGUAGE DataKinds       #-}
+{-# LANGUAGE DeriveGeneric   #-}
+{-# LANGUAGE TypeOperators   #-}
+{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE OverloadedStrings #-}
+module Text.Pandoc.Server
+    ( app
+    , API
+    , ServerOpts(..)
+    , Params(..)
+    , Blob(..)
+    , parseServerOptsFromArgs
+    ) where
+
+import Data.Aeson
+import qualified Data.Aeson.KeyMap as KeyMap
+import Network.Wai
+import Servant
+import Text.DocTemplates as DocTemplates
+import Text.Pandoc
+import Text.Pandoc.Writers.Shared (lookupMetaString)
+import Text.Pandoc.Citeproc (processCitations)
+import Text.Pandoc.Highlighting (lookupHighlightingStyle)
+import qualified Text.Pandoc.UTF8 as UTF8
+import Data.Text (Text)
+import qualified Data.Text as T
+import qualified Data.Text.Lazy as TL
+import qualified Data.Text.Lazy.Encoding as TLE
+import Data.Maybe (fromMaybe)
+import qualified Data.ByteString as BS
+import qualified Data.ByteString.Lazy as BL
+import Data.ByteString.Base64 (decodeBase64, encodeBase64)
+import Data.Default
+import Control.Monad (when, unless, foldM)
+import qualified Data.Set as Set
+import Skylighting (defaultSyntaxMap)
+import qualified Data.Map as M
+import Text.Collate.Lang (Lang (..), parseLang)
+import System.Console.GetOpt
+import System.Environment (getProgName)
+import qualified Control.Exception as E
+import Text.Pandoc.Shared (safeStrRead, headerShift, filterIpynbOutput,
+                           eastAsianLineBreakFilter)
+import Text.Pandoc.App ( IpynbOutput (..), Opt(..), defaultOpts )
+import Text.Pandoc.Builder (setMeta)
+import Text.Pandoc.Format (parseFlavoredFormat, formatName)
+import Text.Pandoc.SelfContained (makeSelfContained)
+import System.Exit
+import GHC.Generics (Generic)
+import Network.Wai.Middleware.Cors ( cors,
+           simpleCorsResourcePolicy, CorsResourcePolicy(corsRequestHeaders) )
+
+data ServerOpts =
+  ServerOpts
+    { serverPort    :: Int
+    , serverTimeout :: Int }
+  deriving (Show)
+
+defaultServerOpts :: ServerOpts
+defaultServerOpts = ServerOpts { serverPort = 3030, serverTimeout = 2 }
+
+cliOptions :: [OptDescr (ServerOpts -> IO ServerOpts)]
+cliOptions =
+  [ Option ['p'] ["port"]
+      (ReqArg (\s opts -> case safeStrRead s of
+                            Just i -> return opts{ serverPort = i }
+                            Nothing ->
+                              E.throwIO $ PandocOptionError $ T.pack
+                                s <> " is not a number") "NUMBER")
+      "port number"
+  , Option ['t'] ["timeout"]
+      (ReqArg (\s opts -> case safeStrRead s of
+                            Just i -> return opts{ serverTimeout = i }
+                            Nothing ->
+                              E.throwIO $ PandocOptionError $ T.pack
+                                s <> " is not a number") "NUMBER")
+      "timeout (seconds)"
+
+  , Option ['h'] ["help"]
+      (NoArg (\_ -> do
+        prg <- getProgName
+        let header = "Usage: " <> prg <> " [OPTION...]"
+        putStrLn $ usageInfo header cliOptions
+        exitSuccess))
+      "help message"
+
+  , Option ['v'] ["version"]
+      (NoArg (\_ -> do
+        prg <- getProgName
+        putStrLn $ prg <> " " <> T.unpack pandocVersionText
+        exitSuccess))
+      "version info"
+
+  ]
+
+parseServerOptsFromArgs :: [String] -> IO ServerOpts
+parseServerOptsFromArgs args = do
+  let handleUnknownOpt x = "Unknown option: " <> x
+  case getOpt' Permute cliOptions args of
+    (os, ns, unrecognizedOpts, es) -> do
+      when (not (null es) || not (null unrecognizedOpts)) $
+        E.throwIO $ PandocOptionError $ T.pack $
+          concat es ++ unlines (map handleUnknownOpt unrecognizedOpts) ++
+          ("Try --help for more information.")
+      unless (null ns) $
+        E.throwIO $ PandocOptionError $ T.pack $
+                     "Unknown arguments: " <> unwords ns
+      foldM (flip ($)) defaultServerOpts os
+
+newtype Blob = Blob BL.ByteString
+  deriving (Show, Eq)
+
+instance ToJSON Blob where
+  toJSON (Blob bs) = toJSON (encodeBase64 $ BL.toStrict bs)
+
+instance FromJSON Blob where
+ parseJSON = withText "Blob" $ \t -> do
+   let inp = UTF8.fromText t
+   case decodeBase64 inp of
+        Right bs -> return $ Blob $ BL.fromStrict bs
+        Left _ -> -- treat as regular text
+                    return $ Blob $ BL.fromStrict inp
+
+-- This is the data to be supplied by the JSON payload
+-- of requests.  Maybe values may be omitted and will be
+-- given default values.
+data Params = Params
+  { options               :: Opt
+  , text                  :: Text
+  , files                 :: Maybe (M.Map FilePath Blob)
+  , citeproc              :: Maybe Bool
+  } deriving (Show)
+
+instance Default Params where
+  def = Params
+    { options = defaultOpts
+    , text = mempty
+    , files = Nothing
+    , citeproc = Nothing
+    }
+
+-- Automatically derive code to convert to/from JSON.
+instance FromJSON Params where
+ parseJSON = withObject "Params" $ \o ->
+   Params
+     <$> parseJSON (Object o)
+     <*> o .: "text"
+     <*> o .:? "files"
+     <*> o .:? "citeproc"
+
+instance ToJSON Params where
+ toJSON params =
+   case toJSON (options params) of
+     (Object o) -> Object $
+       KeyMap.insert "text" (toJSON $ text params)
+       . KeyMap.insert "files" (toJSON $ files params)
+       . KeyMap.insert "citeproc" (toJSON $ citeproc params)
+       $ o
+     x -> x
+
+data Message =
+  Message
+  { verbosity :: Verbosity
+  , message   :: Text }
+  deriving (Generic, Show)
+
+instance ToJSON Message where
+ toEncoding = genericToEncoding defaultOptions
+
+type Base64 = Bool
+
+data Output = Succeeded Text Base64 [Message]
+            | Failed Text
+  deriving (Generic, Show)
+
+instance ToJSON Output where
+  toEncoding (Succeeded o b m) = pairs
+    ( "output" .= o  <>
+      "base64" .= b  <>
+      "messages" .= m )
+  toEncoding (Failed errmsg) = pairs
+    ( "error" .= errmsg )
+
+-- This is the API.  The "/convert" endpoint takes a request body
+-- consisting of a JSON-encoded Params structure and responds to
+-- Get requests with either plain text or JSON, depending on the
+-- Accept header.
+type API =
+  ReqBody '[JSON] Params :> Post '[OctetStream] BS.ByteString
+  :<|>
+  ReqBody '[JSON] Params :> Post '[PlainText] Text
+  :<|>
+  ReqBody '[JSON] Params :> Post '[JSON] Output
+  :<|>
+  "batch" :> ReqBody '[JSON] [Params] :> Post '[JSON] [Output]
+  :<|>
+  "babelmark" :> QueryParam' '[Required] "text" Text :> QueryParam "from" Text :> QueryParam "to" Text :> QueryFlag "standalone" :> Get '[JSON] Value
+  :<|>
+  "version" :> Get '[PlainText, JSON] Text
+
+app :: Application
+app = corsWithContentType $ serve api server
+
+-- | Allow Content-Type header with values other then allowed by simpleCors.
+corsWithContentType :: Middleware
+corsWithContentType = cors (const $ Just policy)
+    where
+      policy = simpleCorsResourcePolicy
+        { corsRequestHeaders = ["Content-Type"] }
+
+api :: Proxy API
+api = Proxy
+
+server :: Server API
+server = convertBytes
+    :<|> convertText
+    :<|> convertJSON
+    :<|> mapM convertJSON
+    :<|> babelmark  -- for babelmark which expects {"html": "", "version": ""}
+    :<|> pure pandocVersionText
+ where
+  babelmark text' from' to' standalone' = do
+    res <- convertText def{
+                        text = text',
+                        options = defaultOpts{
+                          optFrom = from',
+                          optTo = to',
+                          optStandalone = standalone' }
+                      }
+    return $ toJSON $ object [ "html" .= res, "version" .= pandocVersion ]
+
+  -- We use runPure for the pandoc conversions, which ensures that
+  -- they will do no IO.  This makes the server safe to use.  However,
+  -- it will mean that features requiring IO, like RST includes, will not work.
+  -- Changing this to
+  --    handleErr =<< liftIO (runIO (convert' params))
+  -- will allow the IO operations.
+  convertText params = handleErr $
+    runPure (convert' return (return . encodeBase64 . BL.toStrict) params)
+
+  convertBytes params = handleErr $
+    runPure (convert' (return . UTF8.fromText) (return . BL.toStrict) params)
+
+  convertJSON params = handleErrJSON $
+    runPure
+      (convert'
+        (\t -> Succeeded t False . map toMessage <$> getLog)
+        (\bs -> Succeeded (encodeBase64 (BL.toStrict bs)) True
+                 . map toMessage <$> getLog)
+        params)
+
+  toMessage m = Message { verbosity = messageVerbosity m
+                        , message = showLogMessage m }
+
+  convert' :: (Text -> PandocPure a)
+           -> (BL.ByteString -> PandocPure a)
+           -> Params -> PandocPure a
+  convert' textHandler bsHandler params = do
+    curtime <- getCurrentTime
+    -- put files params in ersatz file system
+    let addFile :: FilePath -> Blob -> FileTree -> FileTree
+        addFile fp (Blob lbs) =
+          insertInFileTree fp FileInfo{ infoFileMTime = curtime
+                                      , infoFileContents = BL.toStrict lbs }
+    case files params of
+      Nothing -> return ()
+      Just fs -> do
+        let filetree = M.foldrWithKey addFile mempty fs
+        modifyPureState $ \st -> st{ stFiles = filetree }
+
+    let opts = options params
+    readerFormat <- parseFlavoredFormat <$> fromMaybe "markdown" $ optFrom opts
+    writerFormat <- parseFlavoredFormat <$> fromMaybe "html" $ optTo opts
+    (readerSpec, readerExts) <- getReader readerFormat
+    (writerSpec, writerExts) <- getWriter writerFormat
+
+    let isStandalone = optStandalone opts
+    let toformat = formatName writerFormat
+    hlStyle <- traverse (lookupHighlightingStyle . T.unpack)
+                  $ optHighlightStyle opts
+
+    mbTemplate <- if isStandalone
+                     then case optTemplate opts of
+                            Nothing -> Just <$>
+                              compileDefaultTemplate toformat
+                            Just t  -> Just <$>
+                              compileCustomTemplate toformat t
+                     else return Nothing
+
+    abbrevs <- Set.fromList . filter (not . T.null) . T.lines . UTF8.toText <$>
+                 case optAbbreviations opts of
+                      Nothing -> readDataFile "abbreviations"
+                      Just f  -> readFileStrict f
+
+    let readeropts = def{ readerExtensions = readerExts
+                        , readerStandalone = isStandalone
+                        , readerTabStop = optTabStop opts
+                        , readerIndentedCodeClasses =
+                            optIndentedCodeClasses opts
+                        , readerAbbreviations = abbrevs
+                        , readerDefaultImageExtension =
+                            optDefaultImageExtension opts
+                        , readerTrackChanges = optTrackChanges opts
+                        , readerStripComments = optStripComments opts
+                        }
+
+    let writeropts =
+          def{ writerExtensions = writerExts
+             , writerTabStop = optTabStop opts
+             , writerWrapText = optWrap opts
+             , writerColumns = optColumns opts
+             , writerTemplate = mbTemplate
+             , writerSyntaxMap = defaultSyntaxMap
+             , writerVariables = optVariables opts
+             , writerTableOfContents = optTableOfContents opts
+             , writerIncremental = optIncremental opts
+             , writerHTMLMathMethod = optHTMLMathMethod opts
+             , writerNumberSections = optNumberSections opts
+             , writerNumberOffset = optNumberOffset opts
+             , writerSectionDivs = optSectionDivs opts
+             , writerReferenceLinks = optReferenceLinks opts
+             , writerDpi = optDpi opts
+             , writerEmailObfuscation = optEmailObfuscation opts
+             , writerIdentifierPrefix = optIdentifierPrefix opts
+             , writerCiteMethod = optCiteMethod opts
+             , writerHtmlQTags = optHtmlQTags opts
+             , writerSlideLevel = optSlideLevel opts
+             , writerTopLevelDivision = optTopLevelDivision opts
+             , writerListings = optListings opts
+             , writerHighlightStyle = hlStyle
+             , writerSetextHeaders = optSetextHeaders opts
+             , writerEpubSubdirectory = T.pack $ optEpubSubdirectory opts
+             , writerEpubMetadata = T.pack <$> optEpubMetadata opts
+             , writerEpubFonts = optEpubFonts opts
+             , writerSplitLevel = optSplitLevel opts
+             , writerTOCDepth = optTOCDepth opts
+             , writerReferenceDoc = optReferenceDoc opts
+             , writerReferenceLocation = optReferenceLocation opts
+             , writerPreferAscii = optAscii opts
+             }
+
+    let reader = case readerSpec of
+                TextReader r -> r readeropts
+                ByteStringReader r -> \t -> do
+                  let eitherbs = decodeBase64 $ UTF8.fromText t
+                  case eitherbs of
+                    Left errt -> throwError $ PandocSomeError errt
+                    Right bs -> r readeropts $ BL.fromStrict bs
+
+    let writer d@(Pandoc meta _) = do
+          case lookupMetaString "lang" meta of
+              ""      -> setTranslations $
+                            Lang "en" Nothing (Just "US") [] [] []
+              l       -> case parseLang l of
+                              Left _   -> report $ InvalidLang l
+                              Right l' -> setTranslations l'
+          case writerSpec of
+                TextWriter w ->
+                  w writeropts d >>=
+                    (if optEmbedResources opts && htmlFormat (optTo opts)
+                        then makeSelfContained
+                        else return) >>=
+                    textHandler
+                ByteStringWriter w ->
+                  w writeropts d >>= bsHandler
+
+    let transforms :: Pandoc -> Pandoc
+        transforms = (case optShiftHeadingLevelBy opts of
+                        0             -> id
+                        x             -> headerShift x) .
+                   (if extensionEnabled Ext_east_asian_line_breaks
+                          readerExts &&
+                       not (extensionEnabled Ext_east_asian_line_breaks
+                              writerExts &&
+                            optWrap opts == WrapPreserve)
+                       then eastAsianLineBreakFilter
+                       else id) .
+                   (case optIpynbOutput opts of
+                     IpynbOutputAll  -> id
+                     IpynbOutputNone -> filterIpynbOutput Nothing
+                     IpynbOutputBest -> filterIpynbOutput (Just $
+                       case optTo opts of
+                            Just "latex"  -> Format "latex"
+                            Just "beamer" -> Format "latex"
+                            Nothing       -> Format "html"
+                            Just f
+                              | htmlFormat (optTo opts) -> Format "html"
+                              | otherwise -> Format f))
+
+    let meta =   (case optBibliography opts of
+                   [] -> id
+                   fs -> setMeta "bibliography" (MetaList
+                            (map (MetaString . T.pack) fs))) .
+                 maybe id (setMeta "csl" . MetaString . T.pack)
+                   (optCSL opts) .
+                 maybe id (setMeta "citation-abbreviations" . MetaString .
+                              T.pack)
+                   (optCitationAbbreviations opts) $
+                 optMetadata opts
+
+    let addMetadata m' (Pandoc m bs) = Pandoc (m <> m') bs
+
+    reader (text params) >>=
+      return . transforms . addMetadata meta >>=
+        (case citeproc params of
+          Just True -> processCitations
+          _ -> return) >>=
+      writer
+
+  htmlFormat :: Maybe Text -> Bool
+  htmlFormat Nothing = True
+  htmlFormat (Just f) =
+    any (`T.isPrefixOf` f)
+      ["html","html4","html5","s5","slidy", "slideous","dzslides","revealjs"]
+
+  handleErr (Right t) = return t
+  handleErr (Left err) = throwError $
+    err500 { errBody = TLE.encodeUtf8 $ TL.fromStrict $ renderError err }
+
+  handleErrJSON (Right o) = return o
+  handleErrJSON (Left err) =
+    return $ Failed (renderError err)
+
+  compileCustomTemplate toformat t = do
+    res <- runWithPartials $ compileTemplate ("custom." <> T.unpack toformat)
+               (T.pack t)
+    case res of
+      Left e -> throwError $ PandocTemplateError (T.pack e)
+      Right tpl -> return tpl
