{-# 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, redirectCount, cachingEnabled), newSession,
    fetchURL, fetchURL', fetchURLs, mimeERR, htmlERR,
    dispatchByMIME, appsForMIME, Application(..), dispatchByApp,
    saveDownload, downloadToURI,
    -- logging API
    LogRecord(..), enableLogging, retrieveLog, writeLog) where

import Network.URI.Types

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, isJust)
import Data.Either (isLeft)
import Text.Read (readMaybe)
-- for executable extensions, all standard lib
import Data.Char (isSpace)
import System.Exit (ExitCode(..))

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

-- for logging
import Control.Concurrent.MVar
import Data.Time.Clock
import System.IO
import Control.Monad
import Data.List as L

#ifdef WITH_HTTP_URI
import qualified Network.HTTP.Client as HTTP
import qualified Network.HTTP.Client.OpenSSL as TLS
import qualified OpenSSL.Session as TLS
import           Network.HTTP.Types
import           Data.List (intercalate)
import           Control.Concurrent (forkIO)

import           Network.URI.Cache
#endif

#ifdef WITH_RAW_CONNECTIONS
import qualified OpenSSL as TLS
import qualified OpenSSL.Session as TLS
import qualified System.IO.Streams.SSL as TLSConn
import System.IO.Streams
#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

#ifdef WITH_PLUGIN_REWRITES
import Network.URI.PlugIns.Rewriters
#endif

-- | Data shared accross multiple URI requests.
data Session = Session {
#ifdef WITH_HTTP_URI
    managerHTTP :: HTTP.Manager,
#endif
#ifdef WITH_RAW_CONNECTIONS
    connCtxt :: TLS.SSLContext,
#endif
#ifdef WITH_XDG
    apps :: XDGConfig,
#endif
#ifdef WITH_PLUGIN_REWRITES
    rewriter :: Rewriter,
#endif
    -- | The languages (RFC2616-encoded) to which responses should be localized.
    locale :: [String],
    -- | Additional files to serve from about: URIs.
    aboutPages :: [(FilePath, ByteString)],
    -- | Log of timestamped/profiled URL requests
    requestLog :: Maybe (MVar [LogRecord]),
    -- | How many redirects to follow for Gemini or HTTP(S) requests
    redirectCount :: Int,
    -- | Whether to cache network responses, avoiding sending requests
    cachingEnabled :: Bool,
    -- | App-specific config subdirectory to check
    appName :: String
}

data LogRecord = LogRecord {
    url :: URI,
    accept :: [String],
    redirected :: URI,
    mimetype :: String,
    response :: Either Text ByteString,
    begin :: UTCTime,
    end :: UTCTime
  }

-- | Initializes a default Session object to support HTTPS & Accept-Language
-- if HTTP is enabled.
newSession :: IO Session
newSession = newSession' ""

-- | Variant of `newSession` which loads plugins for the named app.
newSession' :: String -> IO Session
newSession' appname = do
    (ietfLocale, unixLocale) <- rfc2616Locale
#ifdef WITH_HTTP_URI
    httpsCtxt <- TLS.context
    TLS.contextSetDefaultCiphers httpsCtxt
    TLS.contextSetCADirectory httpsCtxt "/etc/ssl/certs"
    TLS.contextSetVerificationMode httpsCtxt $ TLS.VerifyPeer True True Nothing
    managerHTTP' <- HTTP.newManager $ TLS.opensslManagerSettings $ return httpsCtxt
#endif
#ifdef WITH_RAW_CONNECTIONS
    connCtxt <- TLS.context
    TLS.contextSetDefaultCiphers connCtxt
    TLS.contextSetCADirectory connCtxt "/etc/ssl/certs"
    TLS.contextSetVerificationMode connCtxt $
        TLS.VerifyPeer True True $ Just $ \valid _ -> return valid -- FIXME: Implement Trust-On-First-Use
#endif
#ifdef WITH_XDG
    apps' <- loadXDGConfig unixLocale
#endif
#ifdef WITH_PLUGIN_REWRITES
    rewriters <- parseRewriters appname
#endif

    return Session {
#ifdef WITH_HTTP_URI
        managerHTTP = managerHTTP',
#endif
#ifdef WITH_RAW_CONNECTIONS
        connCtxt = connCtxt,
#endif
#ifdef WITH_XDG
        apps = apps',
#endif
#ifdef WITH_PLUGIN_REWRITES
        rewriter = rewriters,
#endif
        locale = ietfLocale,
        aboutPages = [],
        requestLog = Nothing,
        redirectCount = 5,
        cachingEnabled = True,
        appName = appname
    }

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)

fetchURLLogged log sess mimes uri = do
    begin' <- getCurrentTime
    res@(redirected', mimetype', response') <- fetchURL' sess mimes uri
    end' <- getCurrentTime
    modifyMVar_ log $ \log' -> return (
        LogRecord uri mimes redirected' mimetype' response' begin' end' : log')
    return res

-- | Concurrently fetch given URLs.
fetchURLs :: Session -> [String] -> [URI] -> ((URI, String, Either Text ByteString) -> IO a) -> IO [(URI, a)]
fetchURLs sess mimes uris cb = do
    let fetch = case requestLog sess of {Nothing -> fetchURL'; Just log -> fetchURLLogged log}
    forConcurrently uris (\u -> fetch sess mimes u >>= cb) >>= return . L.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 {redirectCount = 0, locale = locale'} _ uri =
    return (uri, mimeERR, Left $ Txt.pack $ trans locale' ExcessiveRedirects)

#ifdef WITH_PLUGIN_REWRITES
fetchURL' session mimes uri
    | Just uri' <- applyRewriter (rewriter session) uri = fetchURL' session mimes uri'
#endif

#ifdef WITH_PLUGIN_EXEC
fetchURL' session@Session { appName = appname, locale = l } mimes
        uri@(URI "ext:" Nothing path query _) = do
    dir <- getXdgDirectory XdgData "nz.geek.adrian.hurl"
    sysdirs <- getXdgDirectoryList XdgDataDirs
    let dirs = concat [[dir' </> appname, dir'] | dir' <- dir : sysdirs]
    programs <- findExecutablesInDirectories dirs ("bin" </> path)
    case programs of
      [] -> return (uri, mimeERR, Left $ Txt.pack $ trans l $ ReadFailed "404")
      program:_ -> do
        let args = case query of {
            '?':rest -> split (== '&') rest;
            _ -> []
        }
        (exitcode, stdout, stderr) <- readProcessWithExitCode program args ""
        let response = if isSuccess exitcode then stdout else stderr
        let (header, body) = breakOn '\n' response
        case strip header of
            'm':'i':'m':'e':mimetype -> return (uri, strip mimetype, Left $ Txt.pack body)
            'u':'r':'l':header' | Just uri' <- parseURIReference $ strip header' ->
                fetchURL' (session {redirectCount = redirectCount session - 1}) mimes $
                    relativeTo uri' uri
            _ | isSuccess exitcode -> return (uri, "text/html", Left $ Txt.pack response)
            _ -> return (uri, mimeERR, Left $ Txt.pack response)
  where
    split p s = case dropWhile p s of
        "" -> []
        s' -> let (w, s'') = break p s' in w : split p s''
    strip = dropWhile isSpace . dropWhileEnd isSpace
    isSuccess ExitSuccess = True
    isSuccess _ = False
#endif

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
    cached <- if cachingEnabled session then readCacheHTTP uri else return (Nothing, Nothing)
    response <- case cached of
        (Just (mime, body), Nothing) -> return $ Right (mime, body)
        (cached, cachingHeaders) -> 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)
                    ] ++ fromMaybe [] cachingHeaders,
                    HTTP.redirectCount = 0
                } $ managerHTTP session
            case (
                    HTTP.responseStatus response,
                    HTTP.responseBody response,
                    [val | ("content-type", val) <- HTTP.responseHeaders response]
              ) of
                (Status 304 _, _, _) | Just cached'@(_, body) <- cached -> do
                    cacheHTTP uri $ response { HTTP.responseBody = body }
                    return $ Right cached'
                -- Manually handle redirects so the caller & HTTP cache gets the correct URI.
                (Status code _, _, _) | code > 300 && code < 400,
                        Just location <- lookup "location" $ HTTP.responseHeaders response,
                        Just uri' <- parseURIReference $ C8.unpack location ->
                    return $ Left $ relativeTo uri' uri
                (Status _ msg, "", _) -> return $ Right (Txt.pack mimeERR, B.fromStrict msg)
                (_, body, (mimetype:_)) -> do
                    cacheHTTP uri response
                    forkIO cleanCacheHTTP -- Try to keep diskspace down...

                    let mime = Txt.toLower $ convertCharset "utf-8" mimetype
                    return $ Right (mime, body)
                (_, response, []) -> return $ Right (Txt.pack defaultMIME, response)

    case response of
        Left redirect ->
            let session' = session { redirectCount = redirectCount session - 1 }
            in fetchURL' session' accept redirect
        Right (mime, body) ->
            let mime' = L.map (Txt.unpack . Txt.strip) $ Txt.splitOn ";" mime
            in return $ resolveCharset' uri mime' body
  `catch` \e -> do return (uri, mimeERR, Left $ Txt.pack $ trans (locale session) $ Http e)
#endif

#ifdef WITH_GEMINI_URI
fetchURL' sess@Session {connCtxt = ctxt, locale = l} mimes uri@URI {
        uriScheme = "gemini:", uriAuthority = Just (URIAuth _ host port)
    } = TLSConn.withConnection ctxt host (parsePort 1965 port) $ \input output _ -> do
        writeTo output $ Just $ C8.pack $ uriToString id uri "\r\n"
        input' <- inputStreamToHandle input
        header <- hGetLine input'
        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>",
                    Txt.replace "<" "&lt;" $ Txt.replace "&" "&amp;" label,
                    "<input /></label></form>"
                ])
            ('2', _, mime) -> do
                body <- Strict.hGetContents input'
                let mime' = L.map (Txt.unpack . Txt.strip) $ Txt.splitOn ";" mime
                return $ resolveCharset' uri mime' $ B.fromStrict body
            ('3', _, redirect) | Just redirect' <- parseURIReference $ Txt.unpack redirect ->
                fetchURL' sess {
                    redirectCount = redirectCount sess - 1
                } 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)
    where
        parseHeader :: String -> (Char, Char, Text)
        parseHeader (major:minor:meta) = (major, minor, Txt.strip $ Txt.pack meta)
        parseHeader _ = ('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

appsForMIME :: Session -> String -> IO [Application]
#if WITH_XDG
appsForMIME Session { apps = a, locale = l } = queryHandlers' a l
#else
appsForMIME _ _ = []
#endif

dispatchByApp :: Session -> Application -> String -> URI -> IO Bool
#if WITH_XDG
dispatchByApp session@Session { locale = l } Application { appId = app} mime uri = do
    try1 <- launchApp' l uri app -- First try handing off the URL, feedreaders need this!
    case try1 of
        Left app -> return True
        Right False -> return False
        Right True -> do
            -- Download as temp file to open locally, the app requires it...
            temp <- canonicalizePath =<< getTemporaryDirectory
            resp <- fetchURL' session [mime] uri
            uri' <- saveDownload (URI "file:" Nothing "" "" "") temp resp
            isLeft <$> launchApp' l uri' app
#else
dispatchByApp _ _ _ _ = return False
#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)
    }

-- Logging API
enableLogging :: Session -> IO Session
enableLogging session = do
    log <- newMVar []
    return session { requestLog = Just log }

retrieveLog :: Session -> IO [LogRecord]
retrieveLog session@Session { requestLog = Just log } = swapMVar log []
retrieveLog _ = return []

writeLog :: Handle -> Session -> IO ()
writeLog out session = do
    writeRow ["URL", "Redirected", "Accept", "MIMEtype", "Size", "Begin", "End", "Duration"]
    log <- retrieveLog session
    forM log $ \record -> writeRow [
        show $ url record, show $ redirected record,
        show $ accept record, show $ mimetype record,
        case response record of
            Left txt -> show $ Txt.length txt
            Right bs -> show $ B.length bs,
        show $ begin record, show $ end record,
        show (end record `diffUTCTime` end record)
      ]
    return ()
  where
    writeRow = hPutStrLn out . L.intercalate "\t"

-- Utils

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