    {-# OPTIONS -cpp #-}
    ---------------------------------------------------------------
    -- Colin Runciman and Andy Gill, June 2006
    ---------------------------------------------------------------

    -- |Datatypes and file-access routines for the per-module (.mix)
    --  indexes used by Hpc.
    module Trace.Hpc.Mix
            ( Mix(..)
            , MixEntry
            , BoxLabel(..)
            , CondBox(..)
            , mixCreate
            , readMix
            , Trace.Hpc.Mix.getModificationTime
            , createMixEntryDom
            , MixEntryDom
            )
      where

    import System.Time (ClockTime(..))
    import System.Directory (getModificationTime)
    import Data.Maybe (catMaybes)
    import Data.Tree
    import Data.Char

    -- a module index records the attributes of each tick-box that has
    -- been introduced in that module, accessed by tick-number position
    -- in the list

    import Trace.Hpc.Util (HpcPos, insideHpcPos, Hash, HpcHash(..))
    import Trace.Hpc.Tix

    -- | 'Mix' is the information about a modules static properties, like
    -- location of Tix's in a file.
    -- tab stops are the size of a tab in the provided line:colunm values.
    --  * In GHC, this is 1 (a tab is just a character)
    --  * With hpc-tracer, this is 8 (a tab represents several spaces).

    data Mix = Mix
                 FilePath           -- location of original file
                 Integer            -- time (in seconds) of original file's last update, since 1970.
                 Hash               -- hash of mix entry + timestamp
                 Int                -- tab stop value.
                 [MixEntry]         -- entries
            deriving (Show,Read)

    -- We would rather use ClockTime in Mix, but ClockTime has no Read instance in 6.4 and before,
    -- but does in 6.6. Definining the instance for ClockTime here is the Wrong Thing to do,
    -- because if some other program also defined that instance, we will not be able to compile.

    type MixEntry = (HpcPos, BoxLabel)

    data BoxLabel = ExpBox  Bool -- isAlt
                  | TopLevelBox [String]
                  | LocalBox [String]
                  | BinBox CondBox Bool
                  deriving (Read, Show, Eq, Ord)

    data CondBox = GuardBinBox
                 | CondBinBox
                 | QualBinBox
                  deriving (Read, Show, Eq, Ord)

    instance HpcHash BoxLabel where
       toHash (ExpBox b)       = 0x100 + toHash b
       toHash (TopLevelBox nm) = 0x200 + toHash nm
       toHash (LocalBox nm)    = 0x300 + toHash nm
       toHash (BinBox cond b)  = 0x400 + toHash (cond,b)

    instance HpcHash CondBox where
       toHash GuardBinBox = 0x10
       toHash CondBinBox  = 0x20
       toHash QualBinBox  = 0x30

    -- | Create is mix file.
    mixCreate :: String -- ^ Dir Name
              -> String -- ^ module Name
              -> Mix    -- ^ Mix DataStructure
              -> IO ()
    mixCreate dirName modName mix =
       writeFile (mixName dirName modName) (show mix)

    -- | Read a mix file.
    readMix :: [String]                 -- ^ Dir Names
            -> Either String TixModule  -- ^ module wanted
            -> IO Mix
    readMix dirNames mod' = do
       let modName = case mod' of
                        Left str -> str
                        Right tix -> tixModuleName tix
       res <- sequence [ (do contents <- readFile (mixName dirName modName)
                             case reads contents of
                               [(r@(Mix _ _ h _ _),cs)]
                                    | all isSpace cs
                                   && (case mod' of
                                         Left  _   -> True
                                         Right tix -> h == tixModuleHash tix
                                      ) -> return $ Just r
                               _ -> return $ Nothing) `catch` (\ _ -> return $ Nothing)
                       | dirName <- dirNames
                       ]
       case catMaybes res of
         [r] -> return r
         xs@(_:_) -> error $ "found " ++ show(length xs) ++ " instances of " ++ modName ++ " in " ++ show dirNames
         _        -> error $ "can not find " ++ modName ++ " in " ++ show dirNames

    mixName :: FilePath -> String -> String
    mixName dirName name = dirName ++ "/" ++ name ++ ".mix"

    -- | Get modification time of a file.

    getModificationTime :: FilePath -> IO Integer
    getModificationTime file = do
      (TOD sec _) <- System.Directory.getModificationTime file
      return $ sec

    ------------------------------------------------------------------------------

    type MixEntryDom a = Tree (HpcPos,a)

    -- A good tree has all its children fully inside its parents HpcPos.
    -- No child should have the *same* HpcPos.
    -- There is no ordering to the children

    isGoodNode :: MixEntryDom a -> Bool
    isGoodNode (Node (pos,_) sub_nodes) =
          and [ pos' `insideHpcPos` pos  | Node(pos',_)  _ <- sub_nodes ]
       && and [ pos' /= pos | Node(pos',_) _ <- sub_nodes ]
       && isGoodForest sub_nodes

    -- all sub-trees are good trees, and no two HpcPos are inside each other.
    isGoodForest :: [MixEntryDom a] -> Bool
    isGoodForest sub_nodes =
       all isGoodNode sub_nodes
       && and [  not (pos1 `insideHpcPos` pos2 ||
                      pos2 `insideHpcPos` pos1)
              | (Node (pos1,_) _,n1) <- zip sub_nodes [0..]
              , (Node (pos2,_) _,n2) <- zip sub_nodes [0..]
              , (n1 :: Int) /= n2 ]

    addNodeToTree :: (Show a) => (HpcPos,a) -> MixEntryDom [a] -> MixEntryDom [a]
    addNodeToTree (new_pos,new_a) (Node (pos,a) children)
      | pos == new_pos = Node (pos,new_a : a) children
      | new_pos `insideHpcPos` pos =
           Node (pos,a) (addNodeToList (new_pos,new_a) children)
      | pos `insideHpcPos` new_pos =
           error "precondition not met inside addNodeToNode"
      | otherwise = error "something impossible happened in addNodeToTree"

    addNodeToList :: Show a => (HpcPos,a) -> [MixEntryDom [a]] -> [MixEntryDom [a]]
    addNodeToList (new_pos,new_a) entries
      | otherwise =
      if length [ ()
              | (am_inside,am_outside,_) <- entries'
              , am_inside || am_outside
              ] == 0
         -- The case where we have a new HpcPos range
         then Node (new_pos,[new_a]) [] : entries else
      if length [ ()
                | (am_inside,_,_) <- entries'
                , am_inside
                ] > 0
         -- The case where we are recursing into a tree
         -- Note we can recurse down many branches, in the case of
         -- overlapping ranges.
         -- Assumes we have captures the new HpcPos
         -- (or the above conditional would be true)
         then [ if i_am_inside  -- or the same as
                then addNodeToTree (new_pos,new_a) node
                else node
              | (i_am_inside,_,node) <- entries'
              ] else
         -- The case of a super-range.
         ( Node (new_pos,[new_a])
                 [ node | (_,True,node) <- entries' ] :
           [ node | (_,False,node) <- entries' ]
         )
      where
        entries' = [ ( new_pos `insideHpcPos` pos
                     , pos  `insideHpcPos` new_pos
                     , node)
                   | node@(Node (pos,_) _) <- entries
                   ]

    createMixEntryDom :: (Show a) => [(HpcPos,a)] -> [MixEntryDom [a]]
    createMixEntryDom entries
        | isGoodForest forest = forest
        | otherwise = error "createMixEntryDom: bad forest"
      where forest = foldr addNodeToList [] entries