{- Event handlers for Lazymail
 -
 - Copyright 2013 Raúl Benencia <rul@kalgan.cc>
 -
 - Licensed under the GNU GPL version 3 or higher
 -}

module Lazymail.Handlers where

import Codec.MIME.Parse(parseMIMEMessage)
import Codec.MIME.Type(MIMEValue(..))
import Control.Exception(evaluate)
import Control.Monad.State
import Data.List(intercalate, stripPrefix, sort)
import System.FilePath(FilePath, takeFileName, dropTrailingPathSeparator)
import System.IO(openFile, IOMode(..), hClose)
import System.Locale(rfc822DateFormat)
import Data.DateTime(parseDateTime, startOfTime, formatDateTime)
import qualified System.IO.UTF8 as UTF8

import Lazymail.Email(lookupField, getBody, formatBody)
import Lazymail.Maildir
import Lazymail.Print
import Lazymail.State
import Lazymail.Types

previousMode :: LazymailCurses ()
previousMode = get >>= \st -> previousMode' (mode st)

previousMode' MaildirMode = (=<<) put $ get >>= \st -> return st { exitRequested = True }
previousMode' EmailMode   = do
  st <- get
  if (triggerUpdateIn . indexState $ st)
  then do
    advanceMode
    solveIndexUpdate
  else put $ st { mode = IndexMode }
previousMode' IndexMode   = do
  st <- get
  let ist = (indexState st) { selectedRowIn = 0, scrollRowIn = 0 }
  put $ st { mode = MaildirMode, indexState = ist }

advanceMode :: LazymailCurses ()
advanceMode = get >>= \st -> advanceMode' (mode st)

advanceMode' IndexMode   = do
  st <- get
  let fp = selectedEmailPath . indexState $ st
  nfp <- if (isNew fp)
         then liftIO $ markAsRead fp
         else return fp
  when (fp /= nfp) triggerIndexUpdate
  st <- get
  msg <- liftIO $ UTF8.readFile nfp
  let email = parseMIMEMessage msg
  let body = getBody $ email
  let el = formatBody body $ screenColumns st
  let est = (emailState st) { currentEmail = email, emailLines = el, scrollRowEm = 0 }
  put $ st { mode = EmailMode, emailState = est }

advanceMode' MaildirMode =  do
  st <- get
  unsortedEmails <- liftIO $ do
    freeOldHandlers st
    let md = (selectedMD . maildirState) $ st
    emails <- getMaildirEmails md
    mapM toEmail emails
  let selectedEmails' = reverse $ sort unsortedEmails
  let scrollRow = scrollRowIn . indexState $ st
  let scrRows = screenRows st
  let indexState' = (indexState st) {
          selectedEmails = selectedEmails'
        , currentInLen   = length selectedEmails'
        , scrollBufferIn = formatIndexModeRows st $ scrollCrop scrollRow scrRows selectedEmails'
        }
  put $ st { mode = IndexMode, indexState = indexState' }

  where
    toEmail fp = do
      handle <- openFile fp ReadMode
      msg <- UTF8.hGetContents handle
      let value = parseMIMEMessage msg
      let headers = mime_val_headers value
      let date = maybe startOfTime id $ parseDateTime rfc822DateFormat $ takeWhile (/= '(') $ lookupField "date" headers
      return (Email value date fp handle)

advanceMode' _  = return ()

freeOldHandlers st = mapM (hClose . emailHandle) $ selectedEmails . indexState $ st

scrollDown :: LazymailCurses ()
scrollDown = get >>= \st -> scrollDown' (mode st)

-- Boilerplate code
scrollDown' IndexMode = do
  st <- get
  let inSt = indexState st
  let selRow = selectedRowIn inSt
  let topScrollRow = scrollRowIn inSt
  let startScrolling = (div (screenRows st) 4) * 3
  let totalRows = currentInLen inSt

  if selRow > startScrolling && (topScrollRow <= (totalRows - (screenRows st)))
     then do -- Scroll emails
       let scrollRowIn'    = scrollRowIn inSt + 1
       let scrollBufferIn' = formatIndexModeRows st $ scrollCrop scrollRowIn' (screenRows st) $ selectedEmails inSt
       let inSt'           = inSt { scrollRowIn = scrollRowIn', scrollBufferIn = scrollBufferIn' }
       put st { indexState = inSt' }
     else -- Move the selected row
       put $ incrementSelectedRow st

scrollDown' MaildirMode = do
  st <- get
  let mdSt = maildirState st
  let selRow = selectedRowMD mdSt
  let topScrollRow = scrollRowMD mdSt
  let startScrolling = (div (screenRows st) 4) * 3
  let totalRows = length $ detectedMDs mdSt

  if selRow > startScrolling && (topScrollRow <= (totalRows - (screenRows st)))
     then do -- Scroll emails
       let scrollRowMD'    = topScrollRow + 1
       let scrollBufferMD' = scrollCrop scrollRowMD' (screenRows st) $ detectedMDs mdSt
       let mdSt'           = mdSt { scrollRowMD = scrollRowMD', scrollBufferMD = scrollBufferMD' }
       put st { maildirState = mdSt' }
     else -- Move the selected row
       put $ incrementSelectedRow st

{- Down-scrolling in Email mode -}
scrollDown' EmailMode = do
  st <- get
  let est = emailState st
  let cur = scrollRowEm est
  let scrRows = screenRows st
  let totalRows = length $ emailLines est
  let est' = est { scrollRowEm = (cur + 1) }

  when ((totalRows - scrRows + (bodyStartRow est) - 1) > (scrollRowEm est)) $
    put $ st { emailState = est' }

scrollDown' _ = (=<<) put $ get >>= \st -> return $ incrementSelectedRow st

scrollUp :: LazymailCurses ()
scrollUp = get >>= \st -> scrollUp' (mode st)

-- More boilerplate code
scrollUp' IndexMode = do
  st <- get
  let inSt = indexState st
  let selRow = selectedRowIn inSt
  let startScrolling = (div (screenRows st) 4)
  let topScrollRow = scrollRowIn inSt
  if topScrollRow > 0 && selRow < startScrolling
     then do
       let scrollRowIn'    = scrollRowIn inSt - 1
       let scrollBufferIn' = formatIndexModeRows st $ scrollCrop scrollRowIn' (screenRows st) $ selectedEmails inSt
       let inSt'           = inSt { scrollRowIn = scrollRowIn', scrollBufferIn = scrollBufferIn' }
       put st { indexState = inSt' }
      else
        put $ decrementSelectedRow st

scrollUp' MaildirMode = do
  st <- get
  let mdSt = maildirState st
  let selRow = selectedRowMD mdSt
  let startScrolling = (div (screenRows st) 4)
  let topScrollRow = scrollRowMD mdSt
  if topScrollRow > 0 && selRow < startScrolling
     then do
       let scrollRowMD'    = scrollRowMD mdSt - 1
       let scrollBufferMD' = scrollCrop scrollRowMD' (screenRows st) $ detectedMDs mdSt
       let mdSt'           = mdSt { scrollRowMD = scrollRowMD', scrollBufferMD = scrollBufferMD' }
       put st { maildirState = mdSt' }
      else
        put $ decrementSelectedRow st

scrollUp' EmailMode = do
  st <- get
  let est = emailState st
  let cur = scrollRowEm est
  let scrRows = screenRows st
  let totalRows = length $ emailLines est
  let est' = est { scrollRowEm = (cur - 1) }

  when (cur > 0) $
    put $ st { emailState = est' }

scrollUp' _ = (=<<) put $ get >>= \st -> return $ decrementSelectedRow st

incrementSelectedRow st | (selectedRow st) < limit =
  case (mode st) of
    MaildirMode ->
      let
        sr = (selectedRowMD . maildirState) st
        maildirState' = (maildirState st) { selectedRowMD = sr + 1 }
      in
       st { maildirState = maildirState' }
    IndexMode ->
      let
        sr = (selectedRowIn . indexState) st
        indexState' = (indexState st) { selectedRowIn = sr + 1 }
      in
       st { indexState = indexState' }
    _ -> st
                        | otherwise = st
  where
    scrRows = screenRows st
    curInLen = length $ selectedEmails . indexState $ st
    curMDLen = length $ detectedMDs . maildirState $ st
    limit' = case (mode st) of
      MaildirMode -> if curMDLen < scrRows then curMDLen - 1 else scrRows
      IndexMode   -> if curInLen < scrRows then curInLen - 1 else scrRows
    limit = if (statusBar st) && (limit' == scrRows)
            then fromIntegral $ limit' - 2
            else fromIntegral limit'

decrementSelectedRow st | (selectedRow st) > 0 =
  case (mode st) of
    MaildirMode ->
      let
        sr = (selectedRowMD . maildirState) st
        maildirState' = (maildirState st) { selectedRowMD = sr - 1 }
      in
       st { maildirState = maildirState' }
    IndexMode ->
      let
        sr = (selectedRowIn . indexState) st
        indexState' = (indexState st) { selectedRowIn = sr - 1 }
      in
       st { indexState = indexState' }
    _ -> st
                        | otherwise = st


{- Given a list, it returns the elements that will be in the next screen refresh
 - TODO: find a better name -}
scrollCrop top rows xs = take rows $ drop top xs

formatIndexModeRows :: LazymailState -> [Email] -> [(FilePath, String)]
formatIndexModeRows st = map formatRow where
  formatRow e =
    let fp = emailPath e
        email = emailValue e
        hs = mime_val_headers email
        str = normalizeLen (screenColumns st) $ intercalate ppSep $
              [ "[" ++ normalizeLen maxFlags (ppFlags . getFlags $ fp) ++ "]"
              , formatDateTime "%b %d" $ emailDate e
              , normalizeLen fromLen $ ppField $ lookupField "from" hs
              , ppField $ lookupField "subject" hs
              ]
    in (fp, str)

formatMaildirModeRows st = mapM formatRow where
  formatRow fp = return $ (fp, (concat $ replicate (numPads - 1) pad) ++ name) where
    bp      = basePath st
    str     = case (stripPrefix bp fp) of
                Nothing  -> fp
                Just s    -> s
    name'   = takeFileName . dropTrailingPathSeparator $ str
    name    = takeFileName $ map (\x -> if x `elem` imapSep then '/' else x) name'
    pad     = "  "
    numPads = (length $ filter (== '/') str) + (length $ filter (`elem` imapSep) str)
    imapSep = ['.'] -- IMAP usually separates its directories with dots

triggerIndexUpdate :: LazymailCurses ()
triggerIndexUpdate = do
  st <- get
  let ist = indexState st
  put $ st { indexState = (ist { triggerUpdateIn = True }) }

solveIndexUpdate :: LazymailCurses ()
solveIndexUpdate = do
  st <- get
  let ist = indexState st
  put $ st { indexState = (ist { triggerUpdateIn = False }) }

triggerMaildirUpdate :: LazymailCurses ()
triggerMaildirUpdate = do
  st <- get
  let mst = maildirState st
  put $ st { maildirState = (mst { triggerUpdateMD = True }) }

solveMaildirUpdate :: LazymailCurses ()
solveMaildirUpdate = do
  st <- get
  let mst = maildirState st
  put $ st { maildirState = (mst { triggerUpdateMD = False }) }