{-| 

A simple text UI for hledger, based on the vty library.

-}

module Hledger.Cli.Commands.Vty
where
import Safe (headDef)
import Graphics.Vty
import Hledger.Data
import Hledger.Cli.Options
import Hledger.Cli.Commands.Balance
import Hledger.Cli.Commands.Register
import Hledger.Cli.Commands.Print


helpmsg = "(b)alance, (r)egister, (p)rint, (right) to drill down, (left) to back up, (q)uit"

instance Show Vty where show = const "a Vty"

-- | The application state when running the vty command.
data AppState = AppState {
     av :: Vty                   -- ^ the vty context
    ,aw :: Int                  -- ^ window width
    ,ah :: Int                  -- ^ window height
    ,amsg :: String              -- ^ status message
    ,aopts :: [Opt]              -- ^ command-line opts
    ,aargs :: [String]           -- ^ command-line args at startup
    ,ajournal :: Journal         -- ^ parsed journal
    ,abuf :: [String]            -- ^ lines of the current buffered view
    ,alocs :: [Loc]              -- ^ user's navigation trail within the UI
                                -- ^ never null, head is current location
    } deriving (Show)

-- | A location within the user interface.
data Loc = Loc {
     scr :: Screen               -- ^ one of the available screens
    ,sy :: Int                   -- ^ viewport y scroll position
    ,cy :: Int                   -- ^ cursor y position
    ,largs :: [String]           -- ^ command-line args, possibly narrowed for this location
    } deriving (Show)

-- | The screens available within the user interface.
data Screen = BalanceScreen     -- ^ like hledger balance, shows accounts
            | RegisterScreen    -- ^ like hledger register, shows transaction-postings
            | PrintScreen       -- ^ like hledger print, shows journal transactions
            -- | LedgerScreen      -- ^ shows the raw journal
              deriving (Eq,Show)

-- | Run the vty (curses-style) ui.
vty :: [Opt] -> [String] -> Journal -> IO ()
vty opts args j = do
  v <- mkVty
  DisplayRegion w h <- display_bounds $ terminal v
  let opts' = SubTotal:opts
  t <-  getCurrentLocalTime
  let a = enter t BalanceScreen args
          AppState {
                  av=v
                 ,aw=fromIntegral w
                 ,ah=fromIntegral h
                 ,amsg=helpmsg
                 ,aopts=opts'
                 ,aargs=args
                 ,ajournal=j
                 ,abuf=[]
                 ,alocs=[]
                 }
  go a 

-- | Update the screen, wait for the next event, repeat.
go :: AppState -> IO ()
go a@AppState{av=av,aopts=opts} = do
  when (notElem DebugVty opts) $ update av (renderScreen a)
  k <- next_event av
  t <- getCurrentLocalTime
  case k of 
    EvResize x y                -> go $ resize x y a
    EvKey (KASCII 'l') [MCtrl]  -> refresh av >> go a{amsg=helpmsg}
    EvKey (KASCII 'b') []       -> go $ resetTrailAndEnter t BalanceScreen a
    EvKey (KASCII 'r') []       -> go $ resetTrailAndEnter t RegisterScreen a
    EvKey (KASCII 'p') []       -> go $ resetTrailAndEnter t PrintScreen a
    EvKey KRight []             -> go $ drilldown t a
    EvKey KEnter []             -> go $ drilldown t a
    EvKey KLeft  []             -> go $ backout t a
    EvKey KUp    []             -> go $ moveUpAndPushEdge a
    EvKey KDown  []             -> go $ moveDownAndPushEdge a
    EvKey KHome  []             -> go $ moveToTop a
    EvKey KUp    [MCtrl]        -> go $ moveToTop a
    EvKey KUp    [MShift]       -> go $ moveToTop a
    EvKey KEnd   []             -> go $ moveToBottom a
    EvKey KDown  [MCtrl]        -> go $ moveToBottom a
    EvKey KDown  [MShift]       -> go $ moveToBottom a
    EvKey KPageUp []            -> go $ prevpage a
    EvKey KBS []                -> go $ prevpage a
    EvKey (KASCII ' ') [MShift] -> go $ prevpage a
    EvKey KPageDown []          -> go $ nextpage a
    EvKey (KASCII ' ') []       -> go $ nextpage a
    EvKey (KASCII 'q') []       -> shutdown av >> return ()
--    EvKey KEsc   []           -> shutdown av >> return ()
    _                           -> go a

-- app state modifiers

-- | The number of lines currently available for the main data display area.
pageHeight :: AppState -> Int
pageHeight a = ah a - 1

setLocCursorY, setLocScrollY :: Int -> Loc -> Loc
setLocCursorY y l = l{cy=y}
setLocScrollY y l = l{sy=y}

cursorY, scrollY, posY :: AppState -> Int
cursorY = cy . loc
scrollY = sy . loc
posY a = scrollY a + cursorY a

setCursorY, setScrollY, setPosY :: Int -> AppState -> AppState
setCursorY _ AppState{alocs=[]} = error "shouldn't happen" -- silence warnings
setCursorY y a@AppState{alocs=(l:locs)} = a{alocs=(l':locs)} where l' = setLocCursorY y l

setScrollY _ AppState{alocs=[]} = error "shouldn't happen" -- silence warnings
setScrollY y a@AppState{alocs=(l:locs)} = a{alocs=(l':locs)} where l' = setLocScrollY y l

setPosY _ AppState{alocs=[]}    = error "shouldn't happen" -- silence warnings
setPosY y a@AppState{alocs=(l:locs)} = a{alocs=(l':locs)}
    where 
      l' = setLocScrollY sy $ setLocCursorY cy l
      ph = pageHeight a
      cy = y `mod` ph
      sy = y - cy

updateCursorY, updateScrollY, updatePosY :: (Int -> Int) -> AppState -> AppState
updateCursorY f a = setCursorY (f $ cursorY a) a
updateScrollY f a = setScrollY (f $ scrollY a) a
updatePosY f a = setPosY (f $ posY a) a

resize :: Int -> Int -> AppState -> AppState
resize x y a = setCursorY cy' a{aw=x,ah=y}
    where
      cy = cursorY a
      cy' = min cy (y-2)

moveToTop :: AppState -> AppState
moveToTop = setPosY 0

moveToBottom :: AppState -> AppState
moveToBottom a = setPosY (length $ abuf a) a

moveUpAndPushEdge :: AppState -> AppState
moveUpAndPushEdge a
    | cy > 0 = updateCursorY (subtract 1) a
    | sy > 0 = updateScrollY (subtract 1) a
    | otherwise = a
    where Loc{sy=sy,cy=cy} = head $ alocs a

moveDownAndPushEdge :: AppState -> AppState
moveDownAndPushEdge a
    | sy+cy >= bh = a
    | cy < ph-1 = updateCursorY (+1) a
    | otherwise = updateScrollY (+1) a
    where 
      Loc{sy=sy,cy=cy} = head $ alocs a
      ph = pageHeight a
      bh = length $ abuf a

-- | Scroll down by page height or until we can just see the last line,
-- without moving the cursor, or if we are already scrolled as far as
-- possible then move the cursor to the last line.
nextpage :: AppState -> AppState
nextpage (a@AppState{abuf=b})
    | sy < bh-jump = setScrollY sy' a
    | otherwise    = setCursorY (bh-sy) a
    where
      sy = scrollY a
      jump = pageHeight a - 1
      bh = length b
      sy' = min (sy+jump) (bh-jump)

-- | Scroll up by page height or until we can just see the first line,
-- without moving the cursor, or if we are scrolled as far as possible
-- then move the cursor to the first line.
prevpage :: AppState -> AppState
prevpage a
    | sy > 0    = setScrollY sy' a
    | otherwise = setCursorY 0 a
    where
      sy = scrollY a
      jump = pageHeight a - 1
      sy' = max (sy-jump) 0

-- | Push a new UI location on to the stack.
pushLoc :: Loc -> AppState -> AppState
pushLoc l a = a{alocs=(l:alocs a)}

popLoc :: AppState -> AppState
popLoc a@AppState{alocs=locs}
    | length locs > 1 = a{alocs=drop 1 locs}
    | otherwise = a

clearLocs :: AppState -> AppState
clearLocs a = a{alocs=[]}

exit :: AppState -> AppState 
exit = popLoc

loc :: AppState -> Loc
loc = head . alocs

-- | Get the filter pattern args in effect for the current ui location.
currentArgs :: AppState -> [String]
currentArgs (AppState {alocs=Loc{largs=as}:_}) = as
currentArgs (AppState {aargs=as}) = as

screen :: AppState -> Screen
screen a = scr where (Loc scr _ _ _) = loc a

-- | Enter a new screen, with possibly new args, adding the new ui location to the stack.
enter :: LocalTime -> Screen -> [String] -> AppState -> AppState
enter t scr@BalanceScreen args a  = updateData t $ pushLoc Loc{scr=scr,sy=0,cy=0,largs=args} a
enter t scr@RegisterScreen args a = updateData t $ pushLoc Loc{scr=scr,sy=0,cy=0,largs=args} a
enter t scr@PrintScreen args a    = updateData t $ pushLoc Loc{scr=scr,sy=0,cy=0,largs=args} a

resetTrailAndEnter :: LocalTime -> Screen -> AppState -> AppState
resetTrailAndEnter t scr a = enter t scr (aargs a) $ clearLocs a

-- | Regenerate the display data appropriate for the current screen.
updateData :: LocalTime -> AppState -> AppState
updateData t a@AppState{aopts=opts,ajournal=j} =
    case screen a of
      BalanceScreen  -> a{abuf=lines $ showBalanceReport opts fspec j}
      RegisterScreen -> a{abuf=lines $ showRegisterReport opts fspec j}
      PrintScreen    -> a{abuf=lines $ showTransactions fspec j}
    where fspec = optsToFilterSpec opts (currentArgs a) t

backout :: LocalTime -> AppState -> AppState
backout t a | screen a == BalanceScreen = a
            | otherwise = updateData t $ popLoc a

drilldown :: LocalTime -> AppState -> AppState
drilldown t a =
    case screen a of
      BalanceScreen  -> enter t RegisterScreen [currentAccountName a] a
      RegisterScreen -> scrollToTransaction e $ enter t PrintScreen (currentArgs a) a
      PrintScreen   -> a
    where e = currentTransaction a

-- | Get the account name currently highlighted by the cursor on the
-- balance screen. Results undefined while on other screens.
currentAccountName :: AppState -> AccountName
currentAccountName a = accountNameAt (abuf a) (posY a)

-- | Get the full name of the account being displayed at a specific line
-- within the balance command's output.
accountNameAt :: [String] -> Int -> AccountName
accountNameAt buf lineno = accountNameFromComponents anamecomponents
    where
      namestohere = map (drop 22) $ take (lineno+1) buf
      (indented, nonindented) = span (" " `isPrefixOf`) $ reverse namestohere
      thisbranch = indented ++ take 1 nonindented
      anamecomponents = reverse $ map strip $ dropsiblings thisbranch
      dropsiblings :: [AccountName] -> [AccountName]
      dropsiblings [] = []
      dropsiblings (x:xs) = x : dropsiblings xs'
          where
            xs' = dropWhile moreindented xs
            moreindented = (>= myindent) . indentof
            myindent = indentof x
            indentof = length . takeWhile (==' ')

-- | If on the print screen, move the cursor to highlight the specified entry
-- (or a reasonable guess). Doesn't work.
scrollToTransaction :: Maybe Transaction -> AppState -> AppState
scrollToTransaction Nothing a = a
scrollToTransaction (Just t) a@AppState{abuf=buf} = setCursorY cy $ setScrollY sy a
    where
      entryfirstline = head $ lines $ showTransaction t
      halfph = pageHeight a `div` 2
      y = fromMaybe 0 $ findIndex (== entryfirstline) buf
      sy = max 0 $ y - halfph
      cy = y - sy

-- | Get the transaction containing the posting currently highlighted by
-- the cursor on the register screen (or best guess). Results undefined
-- while on other screens.
currentTransaction :: AppState -> Maybe Transaction
currentTransaction a@AppState{ajournal=j,abuf=buf} = ptransaction p
    where
      p = headDef nullposting $ filter ismatch $ journalPostings j
      ismatch p = postingDate p == parsedate (take 10 datedesc)
                  && take 70 (showPostingWithBalance False p nullmixedamt) == (datedesc ++ acctamt)
      datedesc = take 32 $ fromMaybe "" $ find (not . (" " `isPrefixOf`)) $ headDef "" rest : reverse above
      acctamt = drop 32 $ headDef "" rest
      (above,rest) = splitAt y buf
      y = posY a

-- renderers

renderScreen :: AppState -> Picture
renderScreen (a@AppState{aw=w,ah=h,abuf=buf,amsg=msg}) =
    Picture {pic_cursor = Cursor (fromIntegral cx) (fromIntegral cy)
            ,pic_image = mainimg
                         <->
                         renderStatus w msg
            ,pic_background = Background ' ' def_attr
            }
    where 
      (cx, cy) = (0, cursorY a)
      sy = scrollY a
--       mainimg = (renderString attr $ unlines $ above)
--           <->
--           (renderString reverseattr $ thisline)
--           <->
--           (renderString attr $ unlines $ below)
--       (above,(thisline:below))
--           | null ls   = ([],[""])
--           | otherwise = splitAt y ls
--       ls = lines $ fitto w (h-1) $ unlines $ drop as $ buf
-- trying for more speed
      mainimg = vert_cat (map (string defaultattr) above)
               <->
               string currentlineattr thisline
               <->
               vert_cat (map (string defaultattr) below)
      (thisline,below) | null rest = (blankline,[])
                       | otherwise = (head rest, tail rest)
      (above,rest) = splitAt cy linestorender
      linestorender = map padclipline $ take (h-1) $ drop sy $ buf ++ replicate h blankline
      padclipline = take w . (++ blankline)
      blankline = replicate w ' '

padClipString :: Int -> Int -> String -> [String]
padClipString h w s = rows
    where
      rows = map padclipline $ take h $ lines s ++ replicate h blankline
      padclipline = take w . (++ blankline)
      blankline = replicate w ' '

renderString :: Attr -> String -> Image
renderString attr s = vert_cat $ map (string attr) rows
    where
      rows = lines $ fitto w h s
      w = maximum $ map length ls
      h = length ls
      ls = lines s

renderStatus :: Int -> String -> Image
renderStatus w = string statusattr . take w . (++ repeat ' ')

-- the all-important theming engine!

theme = Restrained

data UITheme = Restrained | Colorful | Blood

(defaultattr, 
 currentlineattr, 
 statusattr
 ) = case theme of
       Restrained -> (def_attr
                    ,def_attr `with_style` bold
                    ,def_attr `with_style` reverse_video
                    )
       Colorful   -> (def_attr `with_style` reverse_video
                    ,def_attr `with_fore_color` white `with_back_color` red
                    ,def_attr `with_fore_color` black `with_back_color` green
                    )
       Blood      -> (def_attr `with_style` reverse_video
                    ,def_attr `with_fore_color` white `with_back_color` red
                    ,def_attr `with_style` reverse_video
                    )

halfbrightattr = def_attr `with_style` dim
reverseattr = def_attr `with_style` reverse_video
redattr = def_attr `with_fore_color` red
greenattr = def_attr `with_fore_color` green
reverseredattr = def_attr `with_style` reverse_video `with_fore_color` red
reversegreenattr= def_attr `with_style` reverse_video `with_fore_color` green