{-# LANGUAGE ScopedTypeVariables #-}
module Events.ManageAttachments
  ( onEventManageAttachments
  , attachmentListKeybindings
  , attachmentBrowseKeybindings
  )
where

import           Prelude ()
import           Prelude.MH

import qualified Control.Exception as E
import           Control.Monad ( void )
import qualified Brick.Widgets.FileBrowser as FB
import qualified Brick.Widgets.List as L
import qualified Data.ByteString as BS
import qualified Data.Text as T
import qualified Data.Vector as Vector
import qualified Graphics.Vty as V
import           Lens.Micro.Platform ( (%=), to )

import           Types
import           Types.KeyEvents
import           Events.Keybindings
import           State.Attachments
import           State.Common


onEventManageAttachments :: V.Event -> MH ()
onEventManageAttachments e = do
    mode <- gets appMode
    case mode of
        ManageAttachments -> onEventAttachmentList e
        ManageAttachmentsBrowseFiles -> onEventBrowseFile e
        _ -> error "BUG: onEventManageAttachments called in invalid mode"

onEventAttachmentList :: V.Event -> MH ()
onEventAttachmentList =
    handleKeyboardEvent attachmentListKeybindings $
        mhHandleEventLensed (csEditState.cedAttachmentList) L.handleListEvent

attachmentListKeybindings :: KeyConfig -> [Keybinding]
attachmentListKeybindings = mkKeybindings
    [ mkKb CancelEvent "Close attachment list"
          (setMode Main)
    , mkKb AttachmentListAddEvent "Add a new attachment to the attachment list"
          showAttachmentFileBrowser
    , mkKb AttachmentOpenEvent "Open the selected attachment using the URL open command"
          openSelectedAttachment
    , mkKb AttachmentListDeleteEvent "Delete the selected attachment from the attachment list"
          deleteSelectedAttachment
    ]

attachmentBrowseKeybindings :: KeyConfig -> [Keybinding]
attachmentBrowseKeybindings = mkKeybindings
    [ mkKb CancelEvent "Cancel attachment file browse"
      cancelAttachmentBrowse
    , mkKb AttachmentOpenEvent "Open the selected file using the URL open command"
          openSelectedBrowserEntry
    ]

openSelectedAttachment :: MH ()
openSelectedAttachment = do
    cur <- use (csEditState.cedAttachmentList.to L.listSelectedElement)
    case cur of
        Nothing -> return ()
        Just (_, entry) -> void $ openURL (OpenLocalFile $ FB.fileInfoFilePath $
                                           attachmentDataFileInfo entry)

openSelectedBrowserEntry :: MH ()
openSelectedBrowserEntry = do
    b <- use (csEditState.cedFileBrowser)
    case FB.fileBrowserCursor b of
        Nothing -> return ()
        Just entry -> void $ openURL (OpenLocalFile $ FB.fileInfoFilePath entry)

onEventBrowseFile :: V.Event -> MH ()
onEventBrowseFile e = do
    b <- use (csEditState.cedFileBrowser)
    case FB.fileBrowserIsSearching b of
        False ->
            handleKeyboardEvent attachmentBrowseKeybindings handleFileBrowserEvent e
        True ->
            handleFileBrowserEvent e

    b' <- use (csEditState.cedFileBrowser)
    case FB.fileBrowserException b' of
        Nothing -> return ()
        Just ex -> do
            mhLog LogError $ T.pack $ "FileBrowser exception: " <> show ex

cancelAttachmentBrowse :: MH ()
cancelAttachmentBrowse = do
    es <- use (csEditState.cedAttachmentList.L.listElementsL)
    case length es of
        0 -> setMode Main
        _ -> setMode ManageAttachments

handleFileBrowserEvent :: V.Event -> MH ()
handleFileBrowserEvent e = do
    mhHandleEventLensed (csEditState.cedFileBrowser) FB.handleFileBrowserEvent e
    b <- use (csEditState.cedFileBrowser)

    -- TODO: Check file browser exception state
    let entries = FB.fileBrowserSelection b
    forM_ entries $ \entry -> do
        -- Is the entry already present? If so, ignore the selection.
        es <- use (csEditState.cedAttachmentList.L.listElementsL)
        let matches = (== (FB.fileInfoFilePath entry)) .
                      FB.fileInfoFilePath .
                      attachmentDataFileInfo
        case Vector.find matches es of
            Just _ -> return ()
            Nothing -> do
                let path = FB.fileInfoFilePath entry
                readResult <- liftIO $ E.try $ BS.readFile path
                case readResult of
                    Left (_::E.SomeException) ->
                        -- TODO: report the error
                        return ()
                    Right bytes -> do
                        let a = AttachmentData { attachmentDataFileInfo = entry
                                               , attachmentDataBytes = bytes
                                               }
                        oldIdx <- use (csEditState.cedAttachmentList.L.listSelectedL)
                        let newIdx = if Vector.null es
                                     then Just 0
                                     else oldIdx
                        csEditState.cedAttachmentList %= L.listReplace (Vector.snoc es a) newIdx

    when (not $ null entries) $ setMode Main

deleteSelectedAttachment :: MH ()
deleteSelectedAttachment = do
    es <- use (csEditState.cedAttachmentList.L.listElementsL)
    mSel <- use (csEditState.cedAttachmentList.to L.listSelectedElement)
    case mSel of
        Nothing ->
            return ()
        Just (pos, _) -> do
            oldIdx <- use (csEditState.cedAttachmentList.L.listSelectedL)
            let idx = if Vector.length es == 1
                      then Nothing
                      else case oldIdx of
                          Nothing -> Just 0
                          Just old -> if pos >= old
                                      then Just $ pos - 1
                                      else Just pos
            csEditState.cedAttachmentList %= L.listReplace (deleteAt pos es) idx

deleteAt :: Int -> Vector.Vector a -> Vector.Vector a
deleteAt p as | p < 0 || p >= length as = as
              | otherwise = Vector.take p as <> Vector.drop (p + 1) as