{-# LANGUAGE CPP #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE OverloadedStrings #-}
module Commonmark.Extensions.RebaseRelativePaths
  ( rebaseRelativePathsSpec )
where
import Commonmark.Types
import Commonmark.Syntax
import Commonmark.Inlines
import Data.Text (Text)
import qualified Data.Text as T
import Data.Maybe (fromMaybe)
import Text.Parsec (getPosition)
import Text.Parsec.Pos (sourceName)
import System.FilePath
import Network.URI (URI (uriScheme), parseURI)
import qualified Data.Set as Set
#if !MIN_VERSION_base(4,11,0)
import Data.Semigroup (Semigroup(..))
#endif

rebaseRelativePathsSpec
  :: forall m bl il . (Monad m , IsInline il , IsBlock il bl)
  => SyntaxSpec m il bl
rebaseRelativePathsSpec =
  defaultSyntaxSpec {
     syntaxBracketedSpecs = [rebasedImageSpec, rebasedLinkSpec] }

 where

  rebasedImageSpec :: BracketedSpec il
  rebasedImageSpec =BracketedSpec
            { bracketedName = "Image"
            , bracketedNests = True
            , bracketedPrefix = Just '!'
            , bracketedSuffixEnd = Just ')'
            , bracketedSuffix = newImageSuffix
            }

  rebasedLinkSpec :: BracketedSpec il
  rebasedLinkSpec = BracketedSpec
           { bracketedName = "Link"
           , bracketedNests = False  -- links don't nest inside links
           , bracketedPrefix = Nothing
           , bracketedSuffixEnd = Just ')'
           , bracketedSuffix = newLinkSuffix
           }

  newImageSuffix rm key = do
    pos <- getPosition
    LinkInfo target title attrs mbpos <- pLink rm key
    let pos' = fromMaybe pos mbpos
    return $! addAttributes attrs . image (rebasePath pos' target) title

  newLinkSuffix rm key = do
    pos <- getPosition
    LinkInfo target title attrs mbpos <- pLink rm key
    let pos' = fromMaybe pos mbpos
    return $! addAttributes attrs . link (rebasePath pos' target) title

-- | Rebase a relative path, by adding the (relative) directory
-- of the containing source position.  Absolute links and URLs
-- are untouched.
rebasePath :: SourcePos -> Text -> Text
rebasePath pos path = do
  let fp = sourceName pos
      isFragment = T.take 1 path == "#"
   in if T.null path || isFragment || isAbsolute (T.unpack path) || isURI path
         then path
         else
           case takeDirectory fp of
             ""  -> path
             "." -> path
             d   -> T.pack d <> "/" <> path

-- | Schemes from http://www.iana.org/assignments/uri-schemes.html plus
-- the unofficial schemes doi, javascript, isbn, pmid.
schemes :: Set.Set T.Text
schemes = Set.fromList
  -- Official IANA schemes
  [ "aaa", "aaas", "about", "acap", "acct", "acr", "adiumxtra", "afp", "afs"
  , "aim", "appdata", "apt", "attachment", "aw", "barion", "beshare", "bitcoin"
  , "blob", "bolo", "browserext", "callto", "cap", "chrome", "chrome-extension"
  , "cid", "coap", "coaps", "com-eventbrite-attendee", "content", "crid", "cvs"
  , "data", "dav", "dict", "dis", "dlna-playcontainer", "dlna-playsingle"
  , "dns", "dntp", "dtn", "dvb", "ed2k", "example", "facetime", "fax", "feed"
  , "feedready", "file", "filesystem", "finger", "fish", "ftp", "geo", "gg"
  , "git", "gizmoproject", "go", "gopher", "graph", "gtalk", "h323", "ham"
  , "hcp", "http", "https", "hxxp", "hxxps", "hydrazone", "iax", "icap", "icon"
  , "im", "imap", "info", "iotdisco", "ipn", "ipp", "ipps", "irc", "irc6"
  , "ircs", "iris", "iris.beep", "iris.lwz", "iris.xpc", "iris.xpcs"
  , "isostore", "itms", "jabber", "jar", "jms", "keyparc", "lastfm", "ldap"
  , "ldaps", "lvlt", "magnet", "mailserver", "mailto", "maps", "market"
  , "message", "mid", "mms", "modem", "mongodb", "moz", "ms-access"
  , "ms-browser-extension", "ms-drive-to", "ms-enrollment", "ms-excel"
  , "ms-gamebarservices", "ms-getoffice", "ms-help", "ms-infopath"
  , "ms-media-stream-id", "ms-officeapp", "ms-project", "ms-powerpoint"
  , "ms-publisher", "ms-search-repair", "ms-secondary-screen-controller"
  , "ms-secondary-screen-setup", "ms-settings", "ms-settings-airplanemode"
  , "ms-settings-bluetooth", "ms-settings-camera", "ms-settings-cellular"
  , "ms-settings-cloudstorage", "ms-settings-connectabledevices"
  , "ms-settings-displays-topology", "ms-settings-emailandaccounts"
  , "ms-settings-language", "ms-settings-location", "ms-settings-lock"
  , "ms-settings-nfctransactions", "ms-settings-notifications"
  , "ms-settings-power", "ms-settings-privacy", "ms-settings-proximity"
  , "ms-settings-screenrotation", "ms-settings-wifi", "ms-settings-workplace"
  , "ms-spd", "ms-sttoverlay", "ms-transit-to", "ms-virtualtouchpad"
  , "ms-visio", "ms-walk-to", "ms-whiteboard", "ms-whiteboard-cmd", "ms-word"
  , "msnim", "msrp", "msrps", "mtqp", "mumble", "mupdate", "mvn", "news", "nfs"
  , "ni", "nih", "nntp", "notes", "ocf", "oid", "onenote", "onenote-cmd"
  , "opaquelocktoken", "pack", "palm", "paparazzi", "pkcs11", "platform", "pop"
  , "pres", "prospero", "proxy", "pwid", "psyc", "qb", "query", "redis"
  , "rediss", "reload", "res", "resource", "rmi", "rsync", "rtmfp", "rtmp"
  , "rtsp", "rtsps", "rtspu", "secondlife", "service", "session", "sftp", "sgn"
  , "shttp", "sieve", "sip", "sips", "skype", "smb", "sms", "smtp", "snews"
  , "snmp", "soap.beep", "soap.beeps", "soldat", "spotify", "ssh", "steam"
  , "stun", "stuns", "submit", "svn", "tag", "teamspeak", "tel", "teliaeid"
  , "telnet", "tftp", "things", "thismessage", "tip", "tn3270", "tool", "turn"
  , "turns", "tv", "udp", "unreal", "urn", "ut2004", "v-event", "vemmi"
  , "ventrilo", "videotex", "vnc", "view-source", "wais", "webcal", "wpid"
  , "ws", "wss", "wtai", "wyciwyg", "xcon", "xcon-userid", "xfire"
  , "xmlrpc.beep", "xmlrpc.beeps", "xmpp", "xri", "ymsgr", "z39.50", "z39.50r"
  , "z39.50s"
  -- Unofficial schemes
  , "doi", "isbn", "javascript", "pmid"
  ]

-- | Check if the string is a valid URL with a IANA or frequently used but
-- unofficial scheme (see @schemes@).
isURI :: T.Text -> Bool
isURI = maybe False hasKnownScheme . parseURI . T.unpack
  where
    hasKnownScheme = (`Set.member` schemes) . T.toLower .
                     T.filter (/= ':') . T.pack . uriScheme