{- | UIState operations. -}

{-# LANGUAGE NamedFieldPuns    #-}
{-# LANGUAGE OverloadedStrings #-}

module Hledger.UI.UIState
where

import Brick.Widgets.Edit
import Data.Bifunctor (first)
import Data.Foldable (asum)
import Data.Either (fromRight)
import Data.List ((\\), foldl', sort)
import Data.Maybe (fromMaybe)
import Data.Semigroup (Max(..))
import qualified Data.Text as T
import Data.Text.Zipper (gotoEOL)
import Data.Time.Calendar (Day)
import Lens.Micro ((^.), over, set)

import Hledger
import Hledger.Cli.CliOptions
import Hledger.UI.UITypes

-- | Toggle between showing only unmarked items or all items.
toggleUnmarked :: UIState -> UIState
toggleUnmarked = over statuses (toggleStatus1 Unmarked)

-- | Toggle between showing only pending items or all items.
togglePending :: UIState -> UIState
togglePending = over statuses (toggleStatus1 Pending)

-- | Toggle between showing only cleared items or all items.
toggleCleared :: UIState -> UIState
toggleCleared = over statuses (toggleStatus1 Cleared)

-- TODO testing different status toggle styles

-- | Generate zero or more indicators of the status filters currently active,
-- which will be shown comma-separated as part of the indicators list.
uiShowStatus :: CliOpts -> [Status] -> [String]
uiShowStatus copts ss =
  case style of
    -- in style 2, instead of "Y, Z" show "not X"
    Just 2 | length ss == numstatuses-1
      -> map (("not "++). showstatus) $ sort $ complement ss  -- should be just one
    _ -> map showstatus $ sort ss
  where
    numstatuses = length [minBound..maxBound::Status]
    style = maybeposintopt "status-toggles" $ rawopts_ copts
    showstatus Cleared  = "cleared"
    showstatus Pending  = "pending"
    showstatus Unmarked = "unmarked"

-- various toggle behaviours:

-- 1 UPC toggles only X/all
toggleStatus1 :: Status -> [Status] -> [Status]
toggleStatus1 s ss = if ss == [s] then [] else [s]

-- 2 UPC cycles X/not-X/all
-- repeatedly pressing X cycles:
-- [] U [u]
-- [u] U [pc]
-- [pc] U []
-- pressing Y after first or second step starts new cycle:
-- [u] P [p]
-- [pc] P [p]
-- toggleStatus2 s ss
--   | ss == [s]            = complement [s]
--   | ss == complement [s] = []
--   | otherwise            = [s]  -- XXX assume only three values

-- 3 UPC toggles each X
-- toggleStatus3 s ss
--   | s `elem` ss = filter (/= s) ss
--   | otherwise   = simplifyStatuses (s:ss)

-- 4 upc sets X, UPC sets not-X
-- toggleStatus4 s ss
--  | s `elem` ss = filter (/= s) ss
--  | otherwise   = simplifyStatuses (s:ss)

-- 5 upc toggles X, UPC toggles not-X
-- toggleStatus5 s ss
--  | s `elem` ss = filter (/= s) ss
--  | otherwise   = simplifyStatuses (s:ss)

-- | Given a list of unique enum values, list the other possible values of that enum.
complement :: (Bounded a, Enum a, Eq a) => [a] -> [a]
complement = ([minBound..maxBound] \\)

--

-- | Toggle between showing all and showing only nonempty (more precisely, nonzero) items.
toggleEmpty :: UIState -> UIState
toggleEmpty = over empty__ not

-- | Toggle between showing the primary amounts or costs.
toggleConversionOp :: UIState -> UIState
toggleConversionOp = over conversionop toggleCostMode
  where
    toggleCostMode Nothing               = Just ToCost
    toggleCostMode (Just NoConversionOp) = Just ToCost
    toggleCostMode (Just ToCost)         = Just NoConversionOp

-- | Toggle between showing primary amounts or default valuation.
toggleValue :: UIState -> UIState
toggleValue = over value valuationToggleValue
  where
    -- | Basic toggling of -V, for hledger-ui.
    valuationToggleValue (Just (AtEnd _)) = Nothing
    valuationToggleValue _                = Just $ AtEnd Nothing

-- | Set hierarchic account tree mode.
setTree :: UIState -> UIState
setTree = set accountlistmode ALTree

-- | Set flat account list mode.
setList :: UIState -> UIState
setList = set accountlistmode ALFlat

-- | Toggle between flat and tree mode. If current mode is unspecified/default, assume it's flat.
toggleTree :: UIState -> UIState
toggleTree = over accountlistmode toggleTreeMode
  where
    toggleTreeMode ALTree = ALFlat
    toggleTreeMode ALFlat = ALTree

-- | Toggle between historical balances and period balances.
toggleHistorical :: UIState -> UIState
toggleHistorical = over balanceaccum toggleBalanceAccum
  where
    toggleBalanceAccum Historical = PerPeriod
    toggleBalanceAccum _          = Historical

-- | Toggle hledger-ui's "forecast/future mode". When this mode is enabled,
-- hledger-shows regular transactions which have future dates, and
-- "forecast" transactions generated by periodic transaction rules
-- (which are usually but not necessarily future-dated).
-- In normal mode, both of these are hidden.
toggleForecast :: Day -> UIState -> UIState
toggleForecast _d ui = set forecast newForecast ui
  where
    newForecast = case ui^.forecast of
      Just _  -> Nothing
      Nothing -> enableForecastPreservingPeriod ui (ui^.cliOpts) ^. forecast

-- | Ensure this CliOpts enables forecasted transactions.
-- If a forecast period was specified in the old CliOpts,
-- or in the provided UIState's startup options,
-- it is preserved.
enableForecastPreservingPeriod :: UIState -> CliOpts -> CliOpts
enableForecastPreservingPeriod ui copts = set forecast mforecast copts
  where
    mforecast = asum [mprovidedforecastperiod, mstartupforecastperiod, mdefaultforecastperiod]
      where
        mprovidedforecastperiod = copts ^. forecast
        mstartupforecastperiod  = astartupopts ui ^. forecast
        mdefaultforecastperiod  = Just nulldatespan

-- | Toggle between showing all and showing only real (non-virtual) items.
toggleReal :: UIState -> UIState
toggleReal = fromRight err . overEither real not  -- PARTIAL:
  where err = error "toggleReal: updating Real should not result in an error"

-- | Toggle the ignoring of balance assertions.
toggleIgnoreBalanceAssertions :: UIState -> UIState
toggleIgnoreBalanceAssertions = over ignore_assertions not

-- | Step through larger report periods, up to all.
growReportPeriod :: Day -> UIState -> UIState
growReportPeriod _d = updateReportPeriod periodGrow

-- | Step through smaller report periods, down to a day.
shrinkReportPeriod :: Day -> UIState -> UIState
shrinkReportPeriod d = updateReportPeriod (periodShrink d)

-- | Step the report start/end dates to the next period of same duration,
-- remaining inside the given enclosing span.
nextReportPeriod :: DateSpan -> UIState -> UIState
nextReportPeriod enclosingspan = updateReportPeriod (periodNextIn enclosingspan)

-- | Step the report start/end dates to the next period of same duration,
-- remaining inside the given enclosing span.
previousReportPeriod :: DateSpan -> UIState -> UIState
previousReportPeriod enclosingspan = updateReportPeriod (periodPreviousIn enclosingspan)

-- | If a standard report period is set, step it forward/backward if needed so that
-- it encloses the given date.
moveReportPeriodToDate :: Day -> UIState -> UIState
moveReportPeriodToDate d = updateReportPeriod (periodMoveTo d)

-- | Clear any report period limits.
resetReportPeriod :: UIState -> UIState
resetReportPeriod = setReportPeriod PeriodAll

-- | Get the report period.
reportPeriod :: UIState -> Period
reportPeriod = (^.period)

-- | Set the report period.
setReportPeriod :: Period -> UIState -> UIState
setReportPeriod p = updateReportPeriod (const p)

-- | Update report period by a applying a function.
updateReportPeriod :: (Period -> Period) -> UIState -> UIState
updateReportPeriod updatePeriod = fromRight err . overEither period updatePeriod  -- PARTIAL:
  where err = error "updateReportPeriod: updating period should not result in an error"

-- | Apply a new filter query, or return the failing query.
setFilter :: String -> UIState -> Either String UIState
setFilter s = first (const s) . setEither querystring (words'' queryprefixes $ T.pack s)

-- | Reset some filters & toggles.
resetFilter :: UIState -> UIState
resetFilter = set querystringNoUpdate [] . set realNoUpdate False . set statusesNoUpdate []
            . set empty__ True  -- set period PeriodAll
            . set rsQuery Any . set rsQueryOpts []

-- | Reset all options state to exactly what it was at startup
-- (preserving any command-line options/arguments).
resetOpts :: UIState -> UIState
resetOpts ui@UIState{astartupopts} = ui{aopts=astartupopts}

resetDepth :: UIState -> UIState
resetDepth = updateReportDepth (const Nothing)

-- | Get the maximum account depth in the current journal.
maxDepth :: UIState -> Int
maxDepth UIState{ajournal=j} = getMax . foldMap (Max . accountNameLevel) $ journalAccountNamesDeclaredOrImplied j

-- | Decrement the current depth limit towards 0. If there was no depth limit,
-- set it to one less than the maximum account depth.
decDepth :: UIState -> UIState
decDepth ui = updateReportDepth dec ui
  where
    dec (Just d) = Just $ max 0 (d-1)
    dec Nothing  = Just $ maxDepth ui - 1

-- | Increment the current depth limit. If this makes it equal to the
-- the maximum account depth, remove the depth limit.
incDepth :: UIState -> UIState
incDepth = updateReportDepth (fmap succ)

-- | Set the current depth limit to the specified depth, or remove the depth limit.
-- Also remove the depth limit if the specified depth is greater than the current
-- maximum account depth. If the specified depth is negative, reset the depth limit
-- to whatever was specified at uiartup.
setDepth :: Maybe Int -> UIState -> UIState
setDepth mdepth = updateReportDepth (const mdepth)

getDepth :: UIState -> Maybe Int
getDepth = (^.depth)

-- | Update report depth by a applying a function. If asked to set a depth less
-- than zero, it will leave it unchanged.
updateReportDepth :: (Maybe Int -> Maybe Int) -> UIState -> UIState
updateReportDepth updateDepth ui = over reportSpec update ui
  where
    update = fromRight (error "updateReportDepth: updating depth should not result in an error")  -- PARTIAL:
           . updateReportSpecWith (\ropts -> ropts{depth_=updateDepth (depth_ ropts) >>= clipDepth ropts})
    clipDepth ropts d | d < 0            = depth_ ropts
                      | d >= maxDepth ui = Nothing
                      | otherwise        = Just d

-- | Open the minibuffer, setting its content to the current query with the cursor at the end.
showMinibuffer :: T.Text -> Maybe String -> UIState -> UIState
showMinibuffer label moldq ui = setMode (Minibuffer label e) ui
  where
    e = applyEdit gotoEOL $ editor MinibufferEditor (Just 1) oldq
    oldq = fromMaybe (T.unpack . T.unwords . map textQuoteIfNeeded $ ui^.querystring) moldq

-- | Close the minibuffer, discarding any edit in progress.
closeMinibuffer :: UIState -> UIState
closeMinibuffer = setMode Normal

setMode :: Mode -> UIState -> UIState
setMode m ui = ui{aMode=m}

-- | Regenerate the content for the current and previous screens, from a new journal and current date.
regenerateScreens :: Journal -> Day -> UIState -> UIState
regenerateScreens j d ui@UIState{aScreen=s,aPrevScreens=ss} =
  -- XXX clumsy due to entanglement of UIState and Screen.
  -- sInit operates only on an appstate's current screen, so
  -- remove all the screens from the appstate and then add them back
  -- one at a time, regenerating as we go.
  let
    frst:rest = reverse $ s:ss :: [Screen]
    ui0 = ui{ajournal=j, aScreen=frst, aPrevScreens=[]} :: UIState

    ui1 = (sInit frst) d False ui0 :: UIState
    ui2 = foldl' (\ui' s' -> (sInit s') d False $ pushScreen s' ui') ui1 rest :: UIState
  in
    ui2

pushScreen :: Screen -> UIState -> UIState
pushScreen scr ui = ui{aPrevScreens=(aScreen ui:aPrevScreens ui)
                      ,aScreen=scr
                      }

popScreen :: UIState -> UIState
popScreen ui@UIState{aPrevScreens=s:ss} = ui{aScreen=s, aPrevScreens=ss}
popScreen ui = ui

resetScreens :: Day -> UIState -> UIState
resetScreens d ui@UIState{aScreen=s,aPrevScreens=ss} =
  (sInit topscreen) d True $
  resetOpts $
  closeMinibuffer ui{aScreen=topscreen, aPrevScreens=[]}
  where
    topscreen = case ss of _:_ -> last ss
                           []  -> s

-- | Enter a new screen, saving the old screen & state in the
-- navigation history and initialising the new screen's state.
screenEnter :: Day -> Screen -> UIState -> UIState
screenEnter d scr ui = (sInit scr) d True $
                       pushScreen scr
                       ui