content: {-# LANGUAGE CPP #-}
  -- |
  -- Module: Data.Map.Optics
  -- Description: Optics for working with 'Data.Map.Map's.
  --
  -- This module exists to provide documentation for lenses for working with
  -- 'Map', which might otherwise be obscured by their genericity.
  --
  -- 'Map' is an instance of 'Optics.At.Core.At' and provides 'Optics.At.Core.at'
  -- as a lens on values at keys:
  --
  -- >>> Map.fromList [(1, "world")] ^. at 1
  -- Just "world"
  --
  -- >>> Map.empty & at 1 .~ Just "world"
  -- fromList [(1,"world")]
  --
  -- >>> Map.empty & at 0 .~ Just "hello"
  -- fromList [(0,"hello")]
  --
  -- We can traverse, fold over, and map over key-value pairs in a 'Map',
  -- thanks to indexed traversals, folds and setters.
  --
  -- >>> iover imapped const $ Map.fromList [(1, "Venus")]
  -- fromList [(1,1)]
  --
  -- >>> ifoldMapOf ifolded (\i _ -> Sum i) $ Map.fromList [(2, "Earth"), (3, "Mars")]
  -- Sum {getSum = 5}
  --
  -- >>> itraverseOf_ ifolded (curry print) $ Map.fromList [(4, "Jupiter")]
  -- (4,"Jupiter")
  --
  -- >>> itoListOf ifolded $ Map.fromList [(5, "Saturn")]
  -- [(5,"Saturn")]
  --
  -- A related class, 'Optics.At.Core.Ixed', allows us to use 'Optics.At.Core.ix' to
  -- traverse a value at a particular key.
  --
  -- >>> Map.fromList [(2, "Earth")] & ix 2 %~ ("New " ++)
  -- fromList [(2,"New Earth")]
  --
  -- >>> preview (ix 8) Map.empty
  -- Nothing
  --
  module Data.Map.Optics
    ( toMapOf
    , lt
    , gt
    , le
    , ge
    ) where
  
  import Data.Map (Map)
  import qualified Data.Map as Map
  
  import Optics.IxAffineTraversal
  import Optics.IxFold
  import Optics.Optic
  
  -- $setup
  -- >>> import qualified Data.Map as Map
  -- >>> import Data.Monoid (Sum (..))
  -- >>> import Optics.Core
  
  -- | Construct a map from an 'IxFold'.
  --
  -- The construction is left-biased (see 'Map.union'), i.e. the first
  -- occurrences of keys in the fold or traversal order are preferred.
  --
  -- >>> toMapOf ifolded ["hello", "world"]
  -- fromList [(0,"hello"),(1,"world")]
  --
  -- >>> toMapOf (folded % ifolded) [('a',"alpha"),('b', "beta")]
  -- fromList [('a',"alpha"),('b',"beta")]
  --
  -- >>> toMapOf (ifolded <%> ifolded) ["foo", "bar"]
  -- fromList [((0,0),'f'),((0,1),'o'),((0,2),'o'),((1,0),'b'),((1,1),'a'),((1,2),'r')]
  --
  -- >>> toMapOf (folded % ifolded) [('a', "hello"), ('b', "world"), ('a', "dummy")]
  -- fromList [('a',"hello"),('b',"world")]
  --
  toMapOf
    :: (Is k A_Fold, is `HasSingleIndex` i, Ord i)
    => Optic' k is s a -> s -> Map i a
  toMapOf o = ifoldMapOf o Map.singleton
  {-# INLINE toMapOf #-}
  
  -- | Focus on the largest key smaller than the given one and its corresponding
  -- value.
  --
  -- >>> Map.fromList [('a', "hi"), ('b', "there")] & over (lt 'b') (++ "!")
  -- fromList [('a',"hi!"),('b',"there")]
  --
  -- >>> ipreview (lt 'a') $ Map.fromList [('a', 'x'), ('b', 'y')]
  -- Nothing
  lt :: Ord k => k -> IxAffineTraversal' k (Map k v) v
  lt k = iatraversalVL $ \point f s ->
    case Map.lookupLT k s of
      Nothing      -> point s
      Just (k', v) -> f k' v <&> \v' -> Map.insert k' v' s
  {-# INLINE lt #-}
  
  -- | Focus on the smallest key greater than the given one and its corresponding
  -- value.
  --
  -- >>> Map.fromList [('a', "hi"), ('b', "there")] & over (gt 'b') (++ "!")
  -- fromList [('a',"hi"),('b',"there")]
  --
  -- >>> ipreview (gt 'a') $ Map.fromList [('a', 'x'), ('b', 'y')]
  -- Just ('b','y')
  gt :: Ord k => k -> IxAffineTraversal' k (Map k v) v
  gt k = iatraversalVL $ \point f s ->
    case Map.lookupGT k s of
      Nothing      -> point s
      Just (k', v) -> f k' v <&> \v' -> Map.insert k' v' s
  {-# INLINE gt #-}
  
  -- | Focus on the largest key smaller or equal than the given one and its
  -- corresponding value.
  --
  -- >>> Map.fromList [('a', "hi"), ('b', "there")] & over (le 'b') (++ "!")
  -- fromList [('a',"hi"),('b',"there!")]
  --
  -- >>> ipreview (le 'a') $ Map.fromList [('a', 'x'), ('b', 'y')]
  -- Just ('a','x')
  le :: Ord k => k -> IxAffineTraversal' k (Map k v) v
  le k = iatraversalVL $ \point f s ->
    case Map.lookupLE k s of
      Nothing      -> point s
      Just (k', v) -> f k' v <&> \v' -> Map.insert k' v' s
  {-# INLINE le #-}
  
  -- | Focus on the smallest key greater or equal than the given one and its
  -- corresponding value.
  --
  -- >>> Map.fromList [('a', "hi"), ('c', "there")] & over (ge 'b') (++ "!")
  -- fromList [('a',"hi"),('c',"there!")]
  --
  -- >>> ipreview (ge 'b') $ Map.fromList [('a', 'x'), ('c', 'y')]
  -- Just ('c','y')
  ge :: Ord k => k -> IxAffineTraversal' k (Map k v) v
  ge k = iatraversalVL $ \point f s ->
    case Map.lookupGE k s of
      Nothing      -> point s
      Just (k', v) -> f k' v <&> \v' -> Map.insert k' v' s
  {-# INLINE ge #-}
  