module Data.Text.ParagraphLayout.Internal.ApplyBoxesSpec (spec) where

import Data.List.NonEmpty (NonEmpty, fromList, toList)
import Data.Text (empty)
import Data.Text.Glyphize (Direction (DirLTR, DirRTL))

import Test.Hspec
import Data.Text.ParagraphLayout.Internal.ApplyBoxes
import Data.Text.ParagraphLayout.Internal.BiDiLevels
import Data.Text.ParagraphLayout.Internal.BoxOptions
import Data.Text.ParagraphLayout.Internal.ResolvedBox
import Data.Text.ParagraphLayout.Internal.ResolvedSpan
import Data.Text.ParagraphLayout.Internal.TextOptions
import Data.Text.ParagraphLayout.Internal.WithSpan

trivialBox :: d -> Int -> Direction -> ResolvedBox d
trivialBox d i dir = ResolvedBox d i defaultBoxOptions dir

trivialSpan :: d -> Int -> Direction -> [ResolvedBox d] -> ResolvedSpan d
trivialSpan d i dir bs = ResolvedSpan
    { spanUserData = d
    , spanIndex = i
    , spanOffsetInParagraph = 0
    , spanText = empty
    , spanTextOptions = defaultTextOptions dir
    , spanBoxes = bs
    , spanBiDiLevels = TextLevels [] (directionLevel 0 dir)
    , spanLineBreaks = []
    , spanCharacterBreaks = []
    }

-- | Wrap nothing with the given span, since the algorithm expects `WithSpan`.
wrapNothing :: ResolvedSpan d -> WithSpan d ()
wrapNothing rs = WithSpan rs ()

buildFrags :: [ResolvedSpan d] -> NonEmpty (WithSpan d ())
buildFrags spans = fmap wrapNothing $ fromList spans

-- | Record for easy comparison of test output.
data OutputFragment = OutputFragment
    { spanData :: String
    , leftBoxesData :: [String]
    , rightBoxesData :: [String]
    }
    deriving (Show, Eq)

toOutput :: WithBoxes String (WithSpan String ()) -> OutputFragment
toOutput a = OutputFragment
    { spanData = case unwrap a of
        WithSpan rs _ -> spanUserData rs
    , leftBoxesData = map boxUserData $ leftInBoxes a
    , rightBoxesData = map boxUserData $ rightInBoxes a
    }

runTest
    :: [ResolvedBox String]
    -> [ResolvedSpan String]
    -> [ResolvedBox String]
    -> [OutputFragment]
runTest prevOpen spans nextOpen =
    map toOutput $ toList $ applyBoxes prevOpen nextOpen (buildFrags spans)

spec :: Spec
spec = do

    describe "applyBoxes" $ do

        it "handles case without boxes" $ do
            let
                spans =
                    [ trivialSpan "A" 0 DirLTR []
                    , trivialSpan "B" 1 DirLTR []
                    ]

            runTest [] spans [] `shouldBe`
                [ OutputFragment "A" [] []
                , OutputFragment "B" [] []
                ]

        it "handles discrete boxes" $ do
            let
                box1 = trivialBox "box1" 0 DirRTL
                box2 = trivialBox "box2" 1 DirRTL
                spans =
                    [ trivialSpan "Z" 0 DirRTL [box2]
                    , trivialSpan "Y" 1 DirRTL [box1]
                    , trivialSpan "X" 2 DirRTL [box1]
                    , trivialSpan "W" 3 DirRTL []
                    ]

            runTest [] spans [] `shouldBe`
                [ OutputFragment "Z" ["box2"] ["box2"]
                , OutputFragment "Y" ["box1"] []
                , OutputFragment "X" [] ["box1"]
                , OutputFragment "W" [] []
                ]

        it "handles deeply nested boxes" $ do
            let
                box1 = trivialBox "box1" 0 DirLTR
                box2 = trivialBox "box2" 1 DirRTL
                box3 = trivialBox "box3" 2 DirRTL
                box4 = trivialBox "box4" 3 DirLTR
                box5 = trivialBox "box5" 4 DirRTL
                spans =
                    [ trivialSpan "A" 0 DirRTL [box3, box2, box1]
                    , trivialSpan "B" 1 DirRTL [box5, box4, box3, box2, box1]
                    ]

            runTest [] spans [] `shouldBe`
                [ OutputFragment "A"
                    ["box3", "box2", "box1"]
                    []
                , OutputFragment "B"
                    ["box5", "box4"]
                    ["box5", "box4", "box3", "box2", "box1"]
                ]

        it "omits left edge of LTR box crossing previous line" $ do
            let
                box = trivialBox "box" 0 DirLTR
                spans = [trivialSpan "." 0 DirLTR [box]]

            runTest [box] spans [] `shouldBe` [OutputFragment "." [] ["box"]]

        it "omits right edge of RTL box crossing previous line" $ do
            let
                box = trivialBox "box" 0 DirRTL
                spans = [trivialSpan "." 0 DirRTL [box]]

            runTest [box] spans [] `shouldBe` [OutputFragment "." ["box"] []]

        it "omits right edge of LTR box crossing next line" $ do
            let
                box = trivialBox "box" 0 DirLTR
                spans = [trivialSpan "." 0 DirLTR [box]]

            runTest [] spans [box] `shouldBe` [OutputFragment "." ["box"] []]

        it "omits left edge of RTL box crossing next line" $ do
            let
                box = trivialBox "box" 0 DirRTL
                spans = [trivialSpan "." 0 DirRTL [box]]

            runTest [] spans [box] `shouldBe` [OutputFragment "." [] ["box"]]

        it "omits both edges of LTR box crossing previous and next line" $ do
            let
                box = trivialBox "box" 0 DirLTR
                spans = [trivialSpan "." 0 DirLTR [box]]

            runTest [box] spans [box] `shouldBe` [OutputFragment "." [] []]

        it "omits both edges of RTL box crossing previous and next line" $ do
            let
                box = trivialBox "box" 0 DirRTL
                spans = [trivialSpan "." 0 DirRTL [box]]

            runTest [box] spans [box] `shouldBe` [OutputFragment "." [] []]

        it "handles complex example" $ do
            let
                box1 = trivialBox "box1" 0 DirRTL
                box2 = trivialBox "box2" 1 DirLTR
                box3 = trivialBox "box3" 2 DirLTR
                box4 = trivialBox "box4" 3 DirRTL
                spans =
                    [ trivialSpan "A" 0 DirRTL [box1]
                    , trivialSpan "B" 1 DirLTR [box2, box1]
                    , trivialSpan "C" 2 DirLTR [box2, box1]
                    , trivialSpan "D" 3 DirRTL [box3, box2, box1]
                    , trivialSpan "E" 4 DirLTR [box2, box1]
                    , trivialSpan "F" 5 DirRTL [box4, box1]
                    ]

            runTest [box1] spans [box4, box1] `shouldBe`
                [ OutputFragment "A" [] []
                , OutputFragment "B" ["box2"] []
                , OutputFragment "C" [] []
                , OutputFragment "D" ["box3"] ["box3"]
                , OutputFragment "E" [] ["box2"]
                , OutputFragment "F" [] ["box4"]
                ]