{-
Copyright (C) 2022 Yuchen Pei.

This file is part of f2md.

f2md is free software: you can redistribute it and/or modify it under
the terms of the GNU Affero General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

f2md 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 Affero General
Public License for more details.

You should have received a copy of the GNU Affero General Public
License along with f2md.  If not, see <https://www.gnu.org/licenses/>.

-}

{-# LANGUAGE OverloadedStrings #-}

module F2Md.Export (writeMessage) where

import F2Md.Types
import Data.Text (Text)
import qualified Data.Text as T
import System.Posix.Process
import System.Posix.Files
import Data.Time
import Network.HostName
import System.Random
import System.FilePath


formatMessage :: Message -> Text
formatMessage (Message from subject date messageId body _) =
  "MIME-Version: 1.0\n" <> "Date: " <> T.pack (show date) <> "\nSubject: " <> subject <>
  "\nFrom: " <> from <> "\nMessage-ID: " <> messageId <>
  "\nContent-Type: text/html" <> "\n\n" <> body

genFilename :: FilePath -> IO String
genFilename root = do
  epoch <- formatTime defaultTimeLocale "%s" <$> getCurrentTime
  pid <- getProcessID
  host <- getHostName
  rand <- randomRIO (10000, 99999) :: IO Int
  return $ root </> "new" </> epoch <> "." <> show pid <> "." <>
    host <> "." <> show rand

genUniqFilename :: FilePath -> IO String
genUniqFilename root = do
  filename <- genFilename root
  exists <- fileExist filename
  if exists then genUniqFilename root else return filename

writeMessage :: FilePath -> Message -> IO ()
writeMessage root msg =
  genUniqFilename root >>=
  \filename -> writeFile filename $ T.unpack (formatMessage msg)