module Data.Text.ParagraphLayout.Internal.Rich.ParagraphLayout
    ( ParagraphLayout (..)
    , appendContents
    , emptyParagraphLayout
    , filterLine
    , paragraphOriginX
    , paragraphOriginY
    , paragraphSafeWidth
    , shapedRuns
    , shiftContents
    , topDistance
    )
where

import Data.Int (Int32)

import Data.Text.ParagraphLayout.Internal.Fragment
import Data.Text.ParagraphLayout.Internal.Line
import Data.Text.ParagraphLayout.Internal.LineNumbers
import Data.Text.ParagraphLayout.Internal.LinePagination
import Data.Text.ParagraphLayout.Internal.ParagraphExtents
import Data.Text.ParagraphLayout.Internal.Rect

-- | The resulting layout of the whole paragraph.
data ParagraphLayout d = ParagraphLayout
    { paragraphRect :: Rect Int32
    -- ^ The containing block (CSS3).
    , paragraphLines :: [Line]
    -- ^ Information about line boxes (CSS).
    -- May describe additional empty space around text fragments.
    , paragraphFragments :: [Fragment d]
    -- ^ The resulting layout of all input text, divided into fragments as
    -- required by the input structure, line breaking, text writing direction,
    -- and changes of script.
    }
    deriving (Eq, Read, Show)

instance LineNumbers (ParagraphLayout d) where
    lineNumbersWithDuplication pl = map fragmentLine $ paragraphFragments pl

instance LineHeight (ParagraphLayout d) where
    lineHeight pl = height $ paragraphRect pl

-- | A `ParagraphLayout` with no fragments and no lines.
-- Useful as an identity element for `appendContents`.
emptyParagraphLayout :: ParagraphLayout a
emptyParagraphLayout = ParagraphLayout emptyRect [] []

-- | Distance from the paragraph origin to its topmost line.
topDistance :: ParagraphLayout d -> Int32
topDistance pl = case paragraphLines pl of
    [] -> 0
    ls -> maximum $ map (y_origin . lineRect) ls

-- | Keep the line with the given number and its fragments,
-- and remove everything else.
filterLine :: Int -> ParagraphLayout d -> ParagraphLayout d
filterLine num (ParagraphLayout _ ls frags) =
    ParagraphLayout pRect' ls' frags'
    where
        pRect' = containRects $ map lineRect ls
        ls' = filter ((== num) . lineNumber) ls
        frags' = filter ((== num) . fragmentLine) frags

-- | Add @dx@ and @dy@ to the origins of each line and fragment,
-- effectively shifting the whole paragraph by the given amount.
shiftContents :: Int32 -> Int32 -> ParagraphLayout d -> ParagraphLayout d
shiftContents dx dy (ParagraphLayout _ ls frags) =
    ParagraphLayout pRect' ls' frags'
    where
        pRect' = containRects $ map lineRect ls
        ls' = map (shiftLine dx dy) ls
        frags' = map (shiftFragment dx dy) frags

-- | Combine fragments from two `ParagraphLayout`s.
appendContents :: ParagraphLayout d -> ParagraphLayout d -> ParagraphLayout d
appendContents (ParagraphLayout _ ls1 frags1) (ParagraphLayout _ ls2 frags2) =
    ParagraphLayout pRect ls frags
    where
        pRect = containRects $ map lineRect ls
        ls = ls1 ++ ls2
        frags = frags1 ++ frags2

-- | Return all shaped runs in the paragraph.
shapedRuns :: ParagraphLayout d -> [ShapedRun]
shapedRuns pl = map shapedRun $ paragraphFragments pl

-- | Width of the widest line, including spacing.
--
-- This is the smallest `Data.Text.ParagraphLayout.Rich.paragraphMaxWidth`
-- that will not introduce new line breaks.
--
-- When `Data.Text.ParagraphLayout.Rich.paragraphMaxWidth` is set to `maxBound`,
-- `paragraphSafeWidth` can be used to determine the @max-content@ width of the
-- paragraph for CSS.
paragraphSafeWidth :: ParagraphLayout d -> Int32
paragraphSafeWidth pl = maximum $ map (lineWidth pl) $ lineNumbers pl

lineWidth :: ParagraphLayout d -> Int -> Int32
lineWidth pl line = sum $ map fragmentWidth $ lineFragments pl line

fragmentWidth :: Fragment d -> Int32
fragmentWidth f = width $ fragmentSpacedRect f

lineFragments :: ParagraphLayout d -> Int -> [Fragment d]
lineFragments pl line = filter byLine $ paragraphFragments pl
    where
        byLine frag = line == fragmentLine frag