{-# LANGUAGE CPP #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE DeriveLift #-}
module Text.Collate.Collation
 ( Collation(..)
 , CollationElement(..)
 , unfoldCollation
 , insertElements
 , alterElements
 , suppressContractions
 , findLast
 , findFirst
 , matchLongestPrefix
 , getCollationElements
 , parseCollation
 , parseCJKOverrides
 )
where

import qualified Data.IntSet as IntSet
import qualified Data.Text as T
import qualified Data.Text.Read as TR
import Data.Text (Text)
import Data.Bits ( Bits((.|.), shiftR, (.&.)) )
import Data.List (foldl')
import Text.Collate.UnicodeData (readCodePoints)
import Data.Maybe
import Data.Foldable (minimumBy, maximumBy)
import Data.Word (Word16)
import Data.Binary (Binary(get, put))
import Language.Haskell.TH.Syntax (Lift(..))
import Instances.TH.Lift ()
import qualified Text.Collate.Trie as Trie
import Text.Collate.CanonicalCombiningClass (canonicalCombiningClass)
import Text.Printf
#if MIN_VERSION_base(4,11,0)
#else
import Data.Semigroup (Semigroup(..))
#endif
-- import Debug.Trace

data CollationElement =
  CollationElement
    { collationVariable :: !Bool
    , collationL1       :: {-# UNPACK #-} !Word16
    , collationL2       :: {-# UNPACK #-} !Word16
    , collationL3       :: {-# UNPACK #-} !Word16
    , collationL4       :: {-# UNPACK #-} !Word16
    } deriving (Eq, Lift)

instance Ord CollationElement where
 compare (CollationElement _ p1 s1 t1 q1) (CollationElement _ p2 s2 t2 q2) =
   compare p1 p2 <> compare s1 s2 <> compare t1 t2 <> compare q1 q2

instance Show CollationElement where
  show (CollationElement v l1 l2 l3 l4) =
    printf "CollationElement %s 0x%04X 0x%04X 0x%04X 0x%04X" (show v) l1 l2 l3 l4

instance Binary CollationElement where
   put (CollationElement v w x y z) = put (v,w,x,y,z)
   get = do
     (v,w,x,y,z) <- get
     return $ CollationElement v w x y z

newtype Collation = Collation { unCollation :: Trie.Trie [CollationElement] }
  deriving (Show, Eq, Ord, Lift, Semigroup, Monoid)

instance Binary Collation where
   put (Collation m) = put m
   get = Collation <$> get



-- | Unfold a 'Collation' into an association list.
unfoldCollation :: Collation -> [([Int], [CollationElement])]
unfoldCollation (Collation trie) = Trie.unfoldTrie trie

-- | Insert collation elements for the given code points (if there is
-- more than one code point, it is a contraction).
insertElements :: [Int] -> [CollationElement] -> Collation -> Collation
insertElements codepoints els (Collation trie) =
  Collation $ Trie.insert codepoints els trie

-- | Suppress contracts starting with any of the code points in the list.
suppressContractions :: [Int] -> Collation -> Collation
suppressContractions cps coll =
  foldr (alterElements (const Nothing)) coll
    [is | is@(i:_:_) <- collationKeys, i `elem` cps]
 where
  collationKeys = map fst $ unfoldCollation coll

-- | Change the collation elements defined for the specified code point(s).
alterElements :: (Maybe [CollationElement] -> Maybe [CollationElement])
              -> [Int] -> Collation -> Collation
alterElements f codepoints (Collation trie) =
  Collation $ Trie.alter f codepoints trie

{-# SPECIALIZE matchLongestPrefix
  :: Collation -> [Int] -> Maybe ([CollationElement], Int, Collation) #-}

-- | Find the longest matching prefix of a list of code points
-- in the collation table. This may be a single code point or
-- several (if contractions are defined).  Return the
-- collation elements for the matched code points, the code points
-- matched, and a "subcollation" which can be searched for further
-- matches. (This is needed because of "discontiguous matches";
-- see <http://www.unicode.org/reports/tr10/#Input_Matching>.)
matchLongestPrefix :: Foldable t
                   => Collation
                   -> t Int
                   -> Maybe ([CollationElement], Int, Collation)
matchLongestPrefix (Collation trie) codepoints =
  case Trie.matchLongestPrefix trie codepoints of
    Nothing -> Nothing
    Just (els, consumed, trie') -> Just (els, consumed, Collation trie')

lookupNonEmptyChild :: Collation
                    -> Int
                    -> Maybe ([CollationElement], Collation)
lookupNonEmptyChild (Collation trie) point =
  case Trie.lookupNonEmptyChild trie point of
    Nothing -> Nothing
    Just (els, trie') -> Just (els, Collation trie')

-- | Find the first element in a 'Collation' that meets a condition.
-- Return the code points and the elements.
findFirst :: ([CollationElement] -> Bool)
          -> Collation
          -> Maybe ([Int], [CollationElement])
findFirst f (Collation trie) =
  case minimumBy comp $ Trie.unfoldTrie trie of
    (is,elts) | f elts -> Just (is,elts)
    _ -> Nothing
 where
  comp (_,x) (_,y) =  -- note Left a < Right a
    compare (if f x then Left x else Right x)
            (if f y then Left y else Right y)

-- | Find the last element in a 'Collation' that meets a condition.
-- Return the code points and the elements.
findLast :: ([CollationElement] -> Bool)
         -> Collation
         -> Maybe ([Int], [CollationElement])
findLast f (Collation trie) =
  case maximumBy comp $ Trie.unfoldTrie trie of
    (is,elts) | f elts -> Just (is,elts)
    _ -> Nothing
 where
  comp (_,x) (_,y) =  -- note Left a < Right a
    compare (if f x then Right x else Left x)
            (if f y then Right y else Left y)


-- S2.1 Find the longest initial substring S at each point that
-- has a match in the collation element table.
--
--     S2.1.1 If there are any non-starters following S, process each
--     non-starter C.
--
--     S2.1.2 If C is an unblocked non-starter with respect to S,
--     find if S + C has a match in the collation element table.
--
--     S2.1.3 If there is a match, replace S by S + C, and remove C.
--
-- Blocking Context: The presence of a character B between two characters
-- C1 and C2, where ccc(B) = 0 or ccc(B) ≥ ccc(C2).
--
-- Non-Starter: An assigned character with Canonical_Combining_Class ≠ 0.
--
-- Unblocked Non-Starter: A non-starter C2 which is not in a blocking
-- context with respect to a preceding character C1 in a string.
--
-- In the context <C1 ... B ... C2>, if there is no intervening
-- character B which meets the criterion for being a blocking context,
-- and if C2 is a non-starter, then it is also an unblocked non-starter.

-- | Retrieve the collation elements defined by a collation for
-- a sequence of code points.  These are used to construct a 'SortKey'.
getCollationElements :: Collation -> [Int] -> [CollationElement]
getCollationElements collation = go
 where
  go [] = []
  go (c:cs) =
    case matchLongestPrefix collation (c:cs) of
       Nothing -> calculateImplicitWeight c ++ go cs
       Just (elts, consumed, subcollation)
               -> elts' ++ go (unblockedNonStarters' ++ is')
          where
             getUnblockedNonStarters _ [] = ([], [])
             getUnblockedNonStarters n (x:xs)
               = case canonicalCombiningClass x of
                   ccc
                     | ccc > n,
                       (xs', rest) <- getUnblockedNonStarters ccc xs
                       -> (x : xs', rest)
                     | otherwise -> ([], x : xs)
             (unblockedNonStarters, is') = getUnblockedNonStarters 0
                                             (drop consumed (c:cs))
             (elts', unblockedNonStarters') =
               extendMatch elts unblockedNonStarters subcollation
             -- find the first unblocked non-starter that can extend
             -- the current match, also removing it from the code
             -- point list
             popExtender = popExtender' id
             popExtender' _ [] _ = Nothing
             popExtender' acc (x:xs) subc
               = case lookupNonEmptyChild subc x of
                   Just (es', subc') -> Just (es', acc xs, subc')
                   Nothing -> popExtender' (acc . (x :)) xs subc
             extendMatch es ubs subc = case popExtender ubs subc of
               Just (es', ubs', subc') -> extendMatch es' ubs' subc'
               Nothing -> (es, ubs)

-- see 10.1.3, Implicit Weights
-- from allkeys.txt:
-- @implicitweights 17000..18AFF; FB00 # Tangut and Tangut Components
-- @implicitweights 18D00..18D8F; FB00 # Tangut Supplement
-- @implicitweights 1B170..1B2FF; FB01 # Nushu
-- @implicitweights 18B00..18CFF; FB02 # Khitan Small Script
calculateImplicitWeight :: Int -> [CollationElement]
calculateImplicitWeight cp =
  [CollationElement False (fromIntegral aaaa) 0x0020 0x0002 0xFFFF,
   CollationElement False (fromIntegral bbbb) 0 0 0xFFFF]
 where
  range x y = IntSet.fromList [x..y]
  singleton = IntSet.singleton
  union = IntSet.union
  -- from PropList.txt in unicode data:
  unifiedIdeographs =    range 0x3400 0x4DBF `union`
                         range 0x4E00 0x9FFC `union`
                         range 0xFA0E 0xFA0F `union`
                         singleton 0xFA11 `union`
                         range 0xFA13 0xFA14 `union`
                         singleton 0xFA1F `union`
                         singleton 0xFA21 `union`
                         range 0xFA23 0xFA24 `union`
                         range 0xFA27 0xFA29 `union`
                         range 0x20000 0x2A6DD `union`
                         range 0x2A700 0x2B734 `union`
                         range 0x2B740 0x2B81D `union`
                         range 0x2B820 0x2CEA1 `union`
                         range 0x2CEB0 0x2EBE0 `union`
                         range 0x2CEB0 0x2EBE0 `union`
                         range 0x30000 0x3134A
  -- from Blocks.txt in unicode data:
  cjkCompatibilityIdeographs = range 0xF900 0xFAFF
  cjkUnifiedIdeographs = range 0x4E00 0x9FFF
  (aaaa, bbbb) =
    case cp of
    _ | cp >= 0x17000 , cp <= 0x18AFF -- Tangut and Tangut Components
        -> (0xFB00, (cp - 0x17000) .|. 0x8000)
      | cp >= 0x18D00 , cp <= 0x18D8F -- Tangut Supplement
        -> (0xFB00, (cp - 0x17000) .|. 0x8000)
      | cp >= 0x1B170 , cp <= 0x1B2FF -- Nushu
        -> (0xFB01, (cp - 0x1B170) .|. 0x8000)
      | cp >= 0x18B00 , cp <= 0x18CFF -- Khitan Small Script
        -> (0xFB02, (cp - 0x18B00) .|. 0x8000)
      | cp `IntSet.member` unifiedIdeographs &&
        (cp `IntSet.member` cjkUnifiedIdeographs ||
         cp `IntSet.member` cjkCompatibilityIdeographs)  -- Core Han
        -> (0xFB40 + (cp `shiftR` 15), (cp .&. 0x7FFF) .|. 0x8000)
      | cp `IntSet.member` unifiedIdeographs -- All Other Han Unified ?
        -> (0xFB80 + (cp `shiftR` 15), (cp .&. 0x7FFF) .|. 0x8000)
      | otherwise
        -> (0xFBC0 + (cp `shiftR` 15), (cp .&. 0x7FFFF) .|. 0x8000)

-- | Parse a 'Collation' from a 'ByteString' in the format of
-- @allkeys.txt@.
parseCollation :: Text -> Collation
parseCollation = foldl' processLine mempty . T.lines
 where
  processLine trie t =
    case readCodePoints t of
      ([],_) -> trie
      (c:cs, rest) -> insertElements (c:cs) (go rest) trie
  go t =
    case T.break (== ']') (T.drop 1 $ T.dropWhile (/= '[') t) of
      (contents, rest)
         | T.null rest -> []
         | otherwise   -> parseContents contents : go rest
  parseContents t =
    let isVariable = not (T.null t) && T.head t == '*'
        isIgnorable (0,0,0) = True
        isIgnorable _       = False
    in case map TR.hexadecimal $ filter (not . T.null)
                                  (T.split isSep t) of
              [Right (x,_), Right (y,_), Right (z,_)]
                -> CollationElement isVariable x y z
                                    (if isVariable || isIgnorable (x,y,z)
                                        then 0
                                        else 0xFFFF)
              _ -> CollationElement isVariable 0 0 0 0
  isSep '*' = True
  isSep '.' = True
  isSep _   = False

-- the result is a list of code points; the first will be assigned
-- the colllation element [0x8000, 0x0020, 0x0002], the next
-- [0x8001, 0x0020, 0x0002], and so on.
parseCJKOverrides :: Text -> [Int]
parseCJKOverrides = mapMaybe chunkToCp . T.words
 where
  chunkToCp t =
    case TR.hexadecimal t of
      Right (x,rest)
        | T.null rest -> Just x
      _ -> Nothing -- like the perl module we ignore e.g. FDD0-0041