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

module Handlers where

import Data.List(intercalate)
import Control.Monad.State
import Data.List(stripPrefix)
import System.FilePath(FilePath, takeFileName, dropTrailingPathSeparator)

import Email(parseEmail, getFields, getSubject, getFrom, getBody, formatBody)
import Maildir
import Print
import State
import qualified System.IO.UTF8 as UTF8
import Types (LazymailCurses)

previousMode :: Mode -> LazymailCurses ()
previousMode MaildirMode = (=<<) put $ get >>= \st -> return st { exitRequested = True }
previousMode EmailMode   = (=<<) put $ get >>= \st -> return st { mode = IndexMode }
previousMode IndexMode   = do
  st <- get
  let ist = (indexState st) { selectedRowIn = 0, scrollRowIn = 0 }
  put $ st { mode = MaildirMode, indexState = ist }

changeMode :: Mode -> LazymailCurses ()
changeMode EmailMode   = return ()
changeMode IndexMode   = do
  st <- get
  msg <- liftIO $ UTF8.readFile . selectedEmailPath . indexState $ st
  let email = parseEmail 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 }

changeMode MaildirMode =  do
  st <- get
  selectedEmails' <- liftIO $ do
    let md = (selectedMD . maildirState) $ st
    emails <- getMaildirEmails md
    formatIndexModeRows st emails
  let indexState' = (indexState st) {
          selectedEmails = selectedEmails'
        , currentInLen   = length selectedEmails'
        , scrollBufferIn = scrollCrop (scrollRowIn . indexState $ st) (screenRows st)  selectedEmails'
        }
  put $ st { mode = IndexMode, indexState = indexState' }

{- Boilerplate code -}
incSelectedRow 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' = 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

incSelectedRow 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

incSelectedRow 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) > (scrollRowEm est)) $
    put $ st { emailState = est' }

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

{- More boilerplate code -}
decSelectedRow 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' = scrollCrop scrollRowIn' (screenRows st) $ selectedEmails inSt
       let inSt'           = inSt { scrollRowIn = scrollRowIn', scrollBufferIn = scrollBufferIn' }
       put st { indexState = inSt' }
      else
        put $ decrementSelectedRow st

decSelectedRow 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

decSelectedRow 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 + cur)) > 0) $
    put $ st { emailState = est' }

decSelectedRow _ = (=<<) put $ get >>= \st -> return $ decrementSelectedRow 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 st = mapM formatRow where
  formatRow fp = do
    msg <- UTF8.readFile fp
    let email = parseEmail msg
    let fs = getFields email
    let str = normalizeLen (screenColumns st) $ intercalate ppSep $
              [ ppFlags . getFlags $ fp
              , ppIndexNameAddr . getFrom $ fs
              , ppSubject . getSubject $ fs
              ]
    return (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

-- TODO: Improve this rancidness
mailHeaderLength = 4