{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE UndecidableInstances #-}
--------------------------------------------------------------------------------
-- |
-- Module      :  Data.Geometry.LineSegment
-- Copyright   :  (C) Frank Staals
-- License     :  see the LICENSE file
-- Maintainer  :  Frank Staals
--
-- Line segment data type and some basic functions on line segments
--
--------------------------------------------------------------------------------
module Data.Geometry.LineSegment( LineSegment
                                , pattern LineSegment
                                , pattern LineSegment'
                                , pattern ClosedLineSegment

                                , _SubLine
                                , module Data.Geometry.Interval


                                , toLineSegment
                                , onSegment
                                , orderedEndPoints
                                , segmentLength
                                , sqDistanceToSeg, sqDistanceToSegArg
                                , flipSegment
                                ) where

import           Control.Arrow ((&&&))
import           Control.Lens
import           Data.Bifunctor
import           Data.Ext
import qualified Data.Foldable as F
import           Data.Geometry.Box.Internal
import           Data.Geometry.Interval hiding (width, midPoint)
import           Data.Geometry.Line.Internal
import           Data.Geometry.Point
import           Data.Geometry.Properties
import           Data.Geometry.SubLine
import           Data.Geometry.Transformation
import           Data.Geometry.Vector
import           Data.Ord (comparing)
import           Data.Vinyl
import           Data.Vinyl.CoRec
import           GHC.TypeLits

--------------------------------------------------------------------------------
-- * d-dimensional LineSegments


-- | Line segments. LineSegments have a start and end point, both of which may
-- contain additional data of type p. We can think of a Line-Segment being defined as
--
--
-- >>>  data LineSegment d p r = LineSegment (EndPoint (Point d r :+ p)) (EndPoint (Point d r :+ p))
newtype LineSegment d p r = GLineSegment { _unLineSeg :: Interval p (Point d r)}

makeLenses ''LineSegment

-- | Pattern that essentially models the line segment as a:
--
-- >>> data LineSegment d p r = LineSegment (EndPoint (Point d r :+ p)) (EndPoint (Point d r :+ p))
pattern LineSegment           :: EndPoint (Point d r :+ p)
                              -> EndPoint (Point d r :+ p)
                              -> LineSegment d p r
pattern LineSegment       s t = GLineSegment (Interval s t)
{-# COMPLETE LineSegment #-}

-- | Gets the start and end point, but forgetting if they are open or closed.
pattern LineSegment'          :: Point d r :+ p
                              -> Point d r :+ p
                              -> LineSegment d p r
pattern LineSegment'      s t <- ((^.start) &&& (^.end) -> (s,t))
{-# COMPLETE LineSegment' #-}

pattern ClosedLineSegment     :: Point d r :+ p
                              -> Point d r :+ p
                              -> LineSegment d p r
pattern ClosedLineSegment s t = GLineSegment (ClosedInterval s t)
{-# COMPLETE ClosedLineSegment #-}

type instance Dimension (LineSegment d p r) = d
type instance NumType   (LineSegment d p r) = r

instance HasStart (LineSegment d p r) where
  type StartCore  (LineSegment d p r) = Point d r
  type StartExtra (LineSegment d p r) = p
  start = unLineSeg.start

instance HasEnd (LineSegment d p r) where
  type EndCore  (LineSegment d p r) = Point d r
  type EndExtra (LineSegment d p r) = p
  end = unLineSeg.end


_SubLine :: (Num r, Arity d) => Iso' (LineSegment d p r) (SubLine d p r r)
_SubLine = iso segment2SubLine subLineToSegment
{-# INLINE _SubLine #-}

segment2SubLine    :: (Num r, Arity d)
                   => LineSegment d p r -> SubLine d p r r
segment2SubLine ss = SubLine (Line p (q .-. p)) (Interval s e)
  where
    p = ss^.start.core
    q = ss^.end.core
    (Interval a b)  = ss^.unLineSeg
    s = a&unEndPoint.core .~ 0
    e = b&unEndPoint.core .~ 1

subLineToSegment    :: (Num r, Arity d) => SubLine d p r r -> LineSegment d p r
subLineToSegment sl = let (Interval s' e') = (fixEndPoints sl)^.subRange
                          s = s'&unEndPoint %~ (^.extra)
                          e = e'&unEndPoint %~ (^.extra)
                      in LineSegment s e

instance (Num r, Arity d) => HasSupportingLine (LineSegment d p r) where
  supportingLine s = lineThrough (s^.start.core) (s^.end.core)


instance (Show r, Show p, Arity d) => Show (LineSegment d p r) where
  show ~(LineSegment p q) = concat ["LineSegment (", show p, ") (", show q, ")"]

deriving instance (Eq r, Eq p, Arity d)     => Eq (LineSegment d p r)
-- deriving instance (Ord r, Ord p, Arity d)   => Ord (LineSegment d p r)
deriving instance Arity d                   => Functor (LineSegment d p)

instance PointFunctor (LineSegment d p) where
  pmap f ~(LineSegment s e) = LineSegment (s&unEndPoint.core %~ f)
                                          (e&unEndPoint.core %~ f)

instance Arity d => IsBoxable (LineSegment d p r) where
  boundingBox l = boundingBox (l^.start.core) <> boundingBox (l^.end.core)

instance (Fractional r, Arity d, Arity (d + 1)) => IsTransformable (LineSegment d p r) where
  transformBy = transformPointFunctor

instance Arity d => Bifunctor (LineSegment d) where
  bimap f g (GLineSegment i) = GLineSegment $ bimap f (fmap g) i



-- ** Converting between Lines and LineSegments

-- | Directly convert a line into a line segment.
toLineSegment            :: (Monoid p, Num r, Arity d) => Line d r -> LineSegment d p r
toLineSegment (Line p v) = ClosedLineSegment (p       :+ mempty)
                                             (p .+^ v :+ mempty)

-- *** Intersecting LineSegments

type instance IntersectionOf (LineSegment 2 p r) (LineSegment 2 p r) = [ NoIntersection
                                                                       , Point 2 r
                                                                       , LineSegment 2 p r
                                                                       ]

type instance IntersectionOf (LineSegment 2 p r) (Line 2 r) = [ NoIntersection
                                                              , Point 2 r
                                                              , LineSegment 2 p r
                                                              ]


instance (Ord r, Fractional r) =>
         (LineSegment 2 p r) `IsIntersectableWith` (LineSegment 2 p r) where
  nonEmptyIntersection = defaultNonEmptyIntersection

  a `intersect` b = match ((a^._SubLine) `intersect` (b^._SubLine)) $
         (H coRec)
      :& (H coRec)
      :& (H $ coRec . subLineToSegment)
      :& RNil


instance (Ord r, Fractional r) =>
         (LineSegment 2 p r) `IsIntersectableWith` (Line 2 r) where
  nonEmptyIntersection = defaultNonEmptyIntersection

  s `intersect` l = let ubSL = s^._SubLine.re _unBounded.to dropExtra
                    in match (ubSL `intersect` (fromLine l)) $
                            (H   coRec)
                         :& (H $ coRec)
                         :& (H $ const (coRec s))
                         :& RNil

-- * Functions on LineSegments

-- | Test if a point lies on a line segment.
--
-- >>> (point2 1 0) `onSegment` (ClosedLineSegment (origin :+ ()) (point2 2 0 :+ ()))
-- True
-- >>> (point2 1 1) `onSegment` (ClosedLineSegment (origin :+ ()) (point2 2 0 :+ ()))
-- False
-- >>> (point2 5 0) `onSegment` (ClosedLineSegment (origin :+ ()) (point2 2 0 :+ ()))
-- False
-- >>> (point2 (-1) 0) `onSegment` (ClosedLineSegment (origin :+ ()) (point2 2 0 :+ ()))
-- False
-- >>> (point2 1 1) `onSegment` (ClosedLineSegment (origin :+ ()) (point2 3 3 :+ ()))
-- True
--
-- Note that the segments are assumed to be closed. So the end points lie on the segment.
--
-- >>> (point2 2 0) `onSegment` (ClosedLineSegment (origin :+ ()) (point2 2 0 :+ ()))
-- True
-- >>> origin `onSegment` (ClosedLineSegment (origin :+ ()) (point2 2 0 :+ ()))
-- True
--
--
-- This function works for arbitrary dimensons.
--
-- >>> (point3 1 1 1) `onSegment` (ClosedLineSegment (origin :+ ()) (point3 3 3 3 :+ ()))
-- True
-- >>> (point3 1 2 1) `onSegment` (ClosedLineSegment (origin :+ ()) (point3 3 3 3 :+ ()))
-- False
onSegment       :: (Ord r, Fractional r, Arity d)
                => Point d r -> LineSegment d p r -> Bool
p `onSegment` l = let s          = l^.start.core
                      t          = l^.end.core
                      inRange' x = 0 <= x && x <= 1
                  in
                  if s == t -- zero length segment
                  then p == s
                  else maybe False inRange' $ scalarMultiple (p .-. s) (t .-. s)


-- | The left and right end point (or left below right if they have equal x-coords)
orderedEndPoints   :: Ord r => LineSegment 2 p r -> (Point 2 r :+ p, Point 2 r :+ p)
orderedEndPoints s = if pc <= qc then (p, q) else (q,p)
  where
    p@(pc :+ _) = s^.start
    q@(qc :+ _) = s^.end


-- | Length of the line segment
segmentLength                     :: (Arity d, Floating r) => LineSegment d p r -> r
segmentLength ~(LineSegment' p q) = distanceA (p^.core) (q^.core)


-- | Squared distance from the point to the Segment s. The same remark as for
-- the 'sqDistanceToSegArg' applies here.
sqDistanceToSeg   :: (Arity d, Fractional r, Ord r) => Point d r -> LineSegment d p r -> r
sqDistanceToSeg p = fst . sqDistanceToSegArg p


-- | Squared distance from the point to the Segment s, and the point on s
-- realizing it.  Note that if the segment is *open*, the closest point
-- returned may be one of the (open) end points, even though technically the
-- end point does not lie on the segment. (The true closest point then lies
-- arbitrarily close to the end point).
sqDistanceToSegArg     :: (Arity d, Fractional r, Ord r)
                       => Point d r -> LineSegment d p r -> (r, Point d r)
sqDistanceToSegArg p s = let m  = sqDistanceToArg p (supportingLine s)
                             xs = m : map (\(q :+ _) -> (qdA p q, q)) [s^.start, s^.end]
                         in   F.minimumBy (comparing fst)
                            . filter (flip onSegment s . snd) $ xs

-- | flips the start and end point of the segment
flipSegment   :: LineSegment d p r -> LineSegment d p r
flipSegment s = let p = s^.start
                    q = s^.end
                in (s&start .~ q)&end .~ p

-- testSeg :: LineSegment 2 () Rational
-- testSeg = LineSegment (Open $ ext origin)  (Closed $ ext (point2 10 0))

-- horL' :: Line 2 Rational
-- horL' = horizontalLine 0

-- testI = testSeg `intersect` horL'


-- ff = bimap (fmap Val) (const ())

-- ss' = let (LineSegment p q) = testSeg in
--       LineSegment (p&unEndPoint %~ ff)
--                   (q&unEndPoint %~ ff)

-- ss'' = ss'^._SubLine