{-# LANGUAGE CPP #-}
{-# LANGUAGE OverloadedStrings #-}
-- | Retrieves documents for a URL, supporting multiple URL schemes that can be
-- disabled at build-time for reduced dependencies.
module Network.URI.Fetch(Session(locale, aboutPages), newSession,
    fetchURL, fetchURL', fetchURLs, mimeERR, htmlERR,
    dispatchByMIME, saveDownload, downloadToURI) where

import qualified Data.Text as Txt
import           Data.Text (Text)
import           Network.URI
import qualified Data.ByteString as Strict
import           Data.ByteString.Lazy (ByteString)
import qualified Data.ByteString.Lazy as B
import qualified Data.ByteString.Char8 as C8
import           Network.URI.Charset
import           Control.Exception
import           System.IO.Error (isEOFError)
import           Control.Concurrent.Async (forConcurrently)

-- for about: URIs & port parsing, all standard lib
import Data.Maybe (fromMaybe, listToMaybe)
import Text.Read (readMaybe)

-- for saveDownload
import System.Directory
import System.FilePath

#ifdef WITH_HTTP_URI
import qualified Network.HTTP.Client as HTTP
import qualified Network.HTTP.Client.TLS as TLS
import           Network.HTTP.Types
import           Data.List (intercalate)
#endif

#ifdef WITH_RAW_CONNECTIONS
import Network.Connection
#endif

#ifdef WITH_DATA_URI
import qualified Data.ByteString.Base64.URL.Lazy as B64
#endif

import Network.URI.Locale
import Network.URI.Messages

#ifdef WITH_XDG
import Network.URI.XDG
#endif

-- | Data shared accross multiple URI requests.
data Session = Session {
#ifdef WITH_HTTP_URI
    managerHTTP :: HTTP.Manager,
#endif
#ifdef WITH_RAW_CONNECTIONS
    connCtxt :: ConnectionContext,
#endif
#ifdef WITH_XDG
    apps :: XDGConfig,
#endif
    -- | The languages (RFC2616-encoded) to which responses should be localized.
    locale :: [String],
    -- | Additional files to serve from about: URIs.
    aboutPages :: [(FilePath, ByteString)]
}

-- | Initializes a default Session object to support HTTPS & Accept-Language
-- if HTTP is enabled.
newSession :: IO Session
newSession = do
    (ietfLocale, unixLocale) <- rfc2616Locale
#ifdef WITH_HTTP_URI
    managerHTTP' <- HTTP.newManager TLS.tlsManagerSettings
#endif
#ifdef WITH_RAW_CONNECTIONS
    connCtxt <- initConnectionContext
#endif
#ifdef WITH_XDG
    apps' <- loadXDGConfig unixLocale
#endif

    return Session {
#ifdef WITH_HTTP_URI
        managerHTTP = managerHTTP',
#endif
#ifdef WITH_RAW_CONNECTIONS
        connCtxt = connCtxt,
#endif
#ifdef WITH_XDG
        apps = apps',
#endif
        locale = ietfLocale,
        aboutPages = []
    }

llookup key fallback map = fallback `fromMaybe` listToMaybe [v | (k, v) <- map, k == key]
parsePort fallback (':':port) = fallback `fromMaybe` readMaybe port
parsePort fallback _ = fallback

-- | Retrieves a URL-identified resource & it's MIMEtype, possibly decoding it's text.
fetchURL :: Session -- ^ The session of which this request is a part.
    -> [String] -- ^ The expected MIMEtypes in priority order.
    -> URI -- ^ The URL to retrieve
    -> IO (String, Either Text ByteString) -- ^ The MIMEtype & possibly text-decoded response.
fetchURL sess mimes uri = do
    (_, mime, resp) <- fetchURL' sess mimes uri
    return (mime, resp)

-- | Concurrently fetch given URLs.
fetchURLs :: Session -> [String] -> [URI] -> ((URI, String, Either Text ByteString) -> IO a) -> IO [(URI, a)]
fetchURLs sess mimes uris cb =
    forConcurrently uris (\u -> fetchURL' sess mimes u >>= cb) >>= return . zip uris

-- | Internal MIMEtypes for error reporting
mimeERR, htmlERR :: String
mimeERR = "txt/x-error\t"
htmlERR = "html/x-error\t"

-- | As per `fetchURL`, but also returns the redirected URI.
fetchURL' :: Session -> [String] -> URI -> IO (URI, String, Either Text ByteString)
fetchURL' session mimes uri@(URI {uriScheme = "about:", uriPath = ""}) =
    fetchURL' session mimes $ uri {uriPath = "version"}
fetchURL' Session {aboutPages = pages} _ url@URI {uriScheme = "about:", uriPath = path} =
    return (url,
        Txt.unpack $ Txt.strip $ convertCharset "utf-8" $ B.toStrict $
            llookup (path ++ ".mime") "text/html" pages,
        Right $ llookup path "" pages)

#ifdef WITH_HTTP_URI
fetchURL' session accept@(defaultMIME:_) uri | uriScheme uri `elem` ["http:", "https:"] = do
    request <- HTTP.requestFromURI uri
    response <- HTTP.httpLbs request {
            HTTP.cookieJar = Nothing, -- Will only be supported by Rhapsode when submitting a form.
            HTTP.requestHeaders = [
                ("Accept", C8.pack $ intercalate ", " accept),
                ("Accept-Language", C8.pack $ intercalate ", " $ locale session)
            ]
        } $ managerHTTP session
    return $ case (
            HTTP.responseBody response,
            [val | ("content-type", val) <- HTTP.responseHeaders response]
      ) of
        ("", _) -> (uri, mimeERR, Right $ B.fromStrict $ statusMessage $ HTTP.responseStatus response)
        (response, (mimetype:_)) -> let mime = Txt.toLower $ convertCharset "utf-8" mimetype
            in resolveCharset' uri (map (Txt.unpack . Txt.strip) $ Txt.splitOn ";" mime) response
        (response, []) -> (uri, defaultMIME, Right response)
  `catches` [
    Handler $ \e -> do return (uri, mimeERR, Left $ Txt.pack $ trans (locale session) $ Http e),
    Handler $ \(ErrorCall msg) -> do return (uri, mimeERR, Left $ Txt.pack msg)
  ]
#endif

#ifdef WITH_GEMINI_URI
fetchURL' sess@Session {connCtxt = ctxt, locale = l} mimes uri@URI {
        uriScheme = "gemini:", uriAuthority = Just (URIAuth _ host port)
    } = do
        conn <- connectTo ctxt $ ConnectionParams {
            connectionHostname = host,
            connectionPort = parsePort 1965 port,
            -- TODO implement Trust-On-First-Use, client certificates
            connectionUseSecure = Just $ TLSSettingsSimple False False False,
            connectionUseSocks = Nothing
        }
        connectionPut conn $ C8.pack $ uriToString id uri "\r\n"
        header <- connectionGetLine 1024 conn
        ret <- case parseHeader header of
            -- NOTE: This case won't actually do anything until the caller (Rhapsode) implements forms.
            ('1', _, label) -> return (uri, "application/xhtml+xml", Left $ Txt.concat [
                    "<form><label for='input'>",
                    Txt.replace "<" "&lt;" $ Txt.replace "&" "&amp;" label,
                    "</label><input id='input' /></form>"
                ])
            ('2', _, mime) -> do
                chunks <- mWhile (connectionWaitForInput conn 60000 `catch` (return . not . isEOFError)) $
                    (connectionGetChunk conn `catch` handleIOErr)
                let mime' = map (Txt.unpack . Txt.strip) $ Txt.splitOn ";" mime
                return $ resolveCharset' uri mime' $ B.fromChunks chunks
            ('3', _, redirect) | Just redirect' <- parseURIReference $ Txt.unpack redirect ->
                fetchURL' sess mimes $ relativeTo redirect' uri
            -- TODO Implement client certificates, once I have a way for the user/caller to select one.
            --      And once I figure out how to configure the TLS cryptography.
            (_, _, err) -> return (uri, mimeERR, Left err)
        connectionClose conn
        return ret
    where
        parseHeader header
            | Just (major, header') <- Txt.uncons $ convertCharset "utf-8" header,
                Just (minor, meta) <- Txt.uncons header' = (major, minor, Txt.strip meta)
            | otherwise = ('4', '1', Txt.pack $ trans l MalformedResponse)
        handleIOErr :: IOError -> IO Strict.ByteString
        handleIOErr _ = return ""
#endif

#ifdef WITH_FILE_URI
fetchURL' Session {locale = l} (defaultMIME:_) uri@URI {uriScheme = "file:"} = do
    response <- B.readFile $ uriPath uri
    return (uri, defaultMIME, Right response)
  `catch` \e -> do
    return (uri, mimeERR,
        Left $ Txt.pack $ trans l $ ReadFailed $ displayException (e :: IOException))
#endif

#ifdef WITH_DATA_URI
fetchURL' _ (defaultMIME:_) uri@URI {uriScheme = "data:"} =
    let request = uriPath uri ++ uriQuery uri ++ uriFragment uri
    in case breakOn ',' $ unEscapeString request of
        ("", response) -> return (uri, defaultMIME, Left $ Txt.pack response)
        (mime', response) | '4':'6':'e':'s':'a':'b':';':mime <- reverse mime' ->
            return $ case B64.decode $ B.fromStrict $ C8.pack response of
                Left str -> (uri, mimeERR, Left $ Txt.pack $ unEscapeString str)
                Right bytes -> (uri, reverse mime, Right bytes)
        (mime, response) -> return (uri, mime, Left $ Txt.pack response)
#endif

#ifdef WITH_XDG
fetchURL' Session {locale = l, apps = a} _ uri@(URI {uriScheme = s}) = do
        app <- dispatchURIByMIME a uri ("x-scheme-handler/" ++ init s)
        return (uri, htmlERR, Left $ Txt.pack $ trans l $ app)
#else
fetchURL' Session {locale = l} _ URI {uriScheme = scheme} =
    return (uri, mimeERR, Left $ Txt.pack $ trans l $ UnsupportedScheme scheme)
#endif

dispatchByMIME :: Session -> String -> URI -> IO (Maybe String)
#if WITH_XDG
dispatchByMIME Session {locale = l, apps = a} mime uri = do
    err <- dispatchURIByMIME a uri mime
    return $ case err of
        UnsupportedMIME _ -> Nothing
        _ -> Just $ trans l err
#else
dispatchByMIME _ _ _ = return Nothing
#endif

-- Downloads utilities
-- | write download to a file in the given directory.
saveDownload :: URI -> FilePath -> (URI, String, Either Text ByteString) -> IO URI
saveDownload baseURI dir (URI {uriPath = path}, mime, resp) = do
    dest <- unusedFilename (dir </> takeFileName' path)
    case resp of
        Left txt -> writeFile dest $ Txt.unpack txt
        Right bytes -> B.writeFile dest bytes
    -- TODO set user.mime file attribute.
    return $ baseURI {uriPath = dest}
  where
    takeFileName' s = case takeFileName s of { "" -> "index";  f -> f}

unusedFilename path = do
        exists <- doesFileExist path
        if exists then go 0 else return path
    where
        go n = do
            let path' = path ++ show n
            exists <- doesFileExist path'
            if exists then go (n+1) else return path'

-- | Convert a download into a data: URI
downloadToURI :: (URI, String, Either Text ByteString) -> URI
downloadToURI (_, mime, Left txt) = nullURI {
        uriScheme = "data:",
        uriPath = mime ++ "," ++ escapeURIString isReserved (Txt.unpack txt)
    }
downloadToURI (_, mime, Right bytes) = nullURI {
        uriScheme = "data:",
        uriPath = mime ++ ";base64," ++ C8.unpack (B.toStrict $ B64.encode bytes)
    }

-- Utils

#ifdef WITH_DATA_URI
breakOn c (a:as) | c == a = ([], as)
    | otherwise = let (x, y) = breakOn c as in (a:x, y)
breakOn _ [] = ([], [])
#endif

#ifdef WITH_GEMINI_URI
mWhile test body = do
    cond <- test
    if cond then do
        x <- body
        xs <- mWhile test body
        return (x:xs)
    else return []
#endif