{-# LANGUAGE BangPatterns, GeneralizedNewtypeDeriving #-}
module Graphics.Vty.Widgets.Util
    ( on
    , fgColor
    , bgColor
    , style
    , mergeAttr
    , mergeAttrs
    , withWidth
    , withHeight
    , plusWidth
    , plusHeight
    , remove
    , inject
    , repl
    , takeMaxText
    , takeMaxChars
    , chWidth
    , strWidth
    , textWidth
    , regionWidth
    , regionHeight
    , Phys(..)
    )
where

import Control.Applicative
import qualified Data.Text as T
import Graphics.Vty

-- A newtype to wrap physical screen coordinates, as opposed to
-- character-logical coordinates.  Used when transforming cursor
-- coordinates to screen coordinates and when computing the physical
-- width of characters and strings.
newtype Phys = Phys Int
    deriving (Num, Eq, Show, Ord, Integral, Enum, Real)

chWidth :: Char -> Phys
chWidth = Phys . fromEnum . safeWcwidth

textWidth :: T.Text -> Phys
textWidth = strWidth . T.unpack

strWidth :: String -> Phys
strWidth = sum . (chWidth <$>)

takeMaxChars :: Phys -> [Char] -> [Char]
takeMaxChars mx xs = f' (Phys 0) xs
    where
      f' _ [] = []
      f' acc (c:cs) = let w = chWidth c
                      in if acc + w <= mx
                         then c : f' (acc + w) cs
                         else []

takeMaxText :: Phys -> T.Text -> T.Text
takeMaxText mx xs = T.pack $ takeMaxChars mx $ T.unpack xs

-- |Infix attribute constructor.  Use: foregroundColor `on`
-- backgroundColor.
on :: Color -> Color -> Attr
on a b = defAttr `withBackColor` b `withForeColor` a

-- |Foreground-only attribute constructor.  Background color and style
-- are defaulted.
fgColor :: Color -> Attr
fgColor = (defAttr `withForeColor`)

-- |Background-only attribute constructor.  Foreground color and style
-- are defaulted.
bgColor :: Color -> Attr
bgColor = (defAttr `withBackColor`)

-- |Style-only attribute constructor.  Colors are defaulted.
style :: Style -> Attr
style = (defAttr `withStyle`)

-- Left-most attribute's fields take precedence.
-- |Merge two attributes.  Leftmost attribute takes precedence where
-- it specifies any of the foreground color, background color, or
-- style.  Note that the style precedence is total: all bits of the
-- style mask will take precedence if any are set.
mergeAttr :: Attr -> Attr -> Attr
mergeAttr a b =
    let b1 = case attrStyle a of
               SetTo v -> b { attrStyle = SetTo v }
               _ -> b
        b2 = case attrForeColor a of
               SetTo v -> b1 `withForeColor` v
               _ -> b1
        b3 = case attrBackColor a of
               SetTo v -> b2 `withBackColor` v
               _ -> b2
    in b3

-- |List fold version of 'mergeAttr'.
mergeAttrs :: [Attr] -> Attr
mergeAttrs attrs = foldr mergeAttr defAttr attrs

-- |Modify the width component of a 'DisplayRegion'.
withWidth :: DisplayRegion -> Int -> DisplayRegion
withWidth (_, h) w = (w, h)

-- |Modify the height component of a 'DisplayRegion'.
withHeight :: DisplayRegion -> Int -> DisplayRegion
withHeight (w, _) h = (w, h)

-- |Modify the width component of a 'DisplayRegion'.
plusWidth :: DisplayRegion -> Int -> DisplayRegion
plusWidth (w', h) w =
    if (w' + w < 0)
    then error $ "plusWidth: would overflow on " ++ (show w') ++ " + " ++ (show w)
    else ((w + w'), h)

-- |Modify the height component of a 'DisplayRegion'.
plusHeight :: DisplayRegion -> Int -> DisplayRegion
plusHeight (w, h') h =
    if (h' + h < 0)
    then error $ "plusHeight: would overflow on " ++ (show h') ++ " + " ++ (show h)
    else (w, (h + h'))

remove :: Int -> [a] -> [a]
remove pos as = (take pos as) ++ (drop (pos + 1) as)

inject :: Int -> a -> [a] -> [a]
inject !pos !a !as = let (h, t) = (take pos as, drop pos as)
                     in h ++ (a:t)

repl :: Int -> a -> [a] -> [a]
repl !pos !a !as = inject pos a (remove pos as)

regionWidth :: DisplayRegion -> Int
regionWidth = fst

regionHeight :: DisplayRegion -> Int
regionHeight = snd