-- | A BSON document is a JSON-like object with a standard binary encoding
-- defined at bsonspec.org. This implements version 1.0 of that spec.
--
-- Use the GHC language extension /OverloadedStrings/ to automatically convert
-- String literals to Text

{-# LANGUAGE DeriveDataTypeable #-}
{-# LANGUAGE ForeignFunctionInterface #-}
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE TypeSynonymInstances #-}

module Data.Bson (
  -- * Document
  Document, (!?), look, lookup, valueAt, at, include, exclude, merge,
  -- * Field
  Field(..), (=:), (=?),
  Label,
  -- * Value
  Value(..), Val(..), fval, cast, typed, typeOfVal,
  -- * Special Bson value types
  Binary(..), Function(..), UUID(..), MD5(..), UserDefined(..),
  Regex(..), Javascript(..), Symbol(..), MongoStamp(..), MinMaxKey(..),
  -- ** ObjectId
  ObjectId(..), timestamp, genObjectId, showHexLen
) where

import Prelude hiding (lookup)
#if !MIN_VERSION_base(4,8,0)
import Control.Applicative ((<$>))
#endif
import Control.Monad (foldM)
import Data.Bits (shift, (.|.))
import Data.Int (Int32, Int64)
import Data.IORef (IORef, newIORef, atomicModifyIORef)
import Data.List (find, findIndex)
import Data.Maybe (maybeToList, mapMaybe, fromMaybe)
import Data.Time.Clock (UTCTime)
import Data.Time.Clock.POSIX (POSIXTime, posixSecondsToUTCTime,
                              utcTimeToPOSIXSeconds, getPOSIXTime)
import Data.Time.Format ()  -- for Show and Read instances of UTCTime
import Data.Typeable hiding (cast)
import Data.Word (Word8, Word16, Word32, Word64)
import Numeric (readHex, showHex)
import System.IO.Unsafe (unsafePerformIO)
import Text.Read (Read(..))

import qualified Data.ByteString as S
import qualified Data.ByteString.Char8 as SC
import qualified Text.ParserCombinators.ReadP as R
import qualified Text.ParserCombinators.ReadPrec as R (lift, readS_to_Prec)

import Control.Monad.Identity (runIdentity)
import Network.BSD (getHostName)
import Data.Text (Text)

import qualified Data.Text as T
import qualified Crypto.Hash.MD5 as MD5

getProcessID :: IO Int
-- ^ Get the current process id.
getProcessID = c_getpid

foreign import ccall unsafe "getpid"
   c_getpid :: IO Int

roundTo :: (RealFrac a) => a -> a -> a
-- ^ Round second number to nearest multiple of first number. Eg: roundTo (1/1000) 0.12345 = 0.123
roundTo mult n = fromIntegral (round (n / mult) :: Integer) * mult

showHexLen :: (Show n, Integral n) => Int -> n -> ShowS
-- ^ showHex of n padded with leading zeros if necessary to fill d digits
showHexLen d n = showString (replicate (d - sigDigits n) '0') . showHex n  where
  sigDigits 0 = 1
  sigDigits n' = truncate (logBase 16 $ fromIntegral n' :: Double) + 1

-- * Document

type Document = [Field]
-- ^ A BSON document is a list of 'Field's

-- | Recursively lookup a nested field in a Document.
(!?) :: Val a => Document -> Label -> Maybe a
doc !? l = foldM (flip lookup) doc (init chunks) >>= lookup (last chunks)
  where chunks = T.split (== '.') l

look :: (Monad m) => Label -> Document -> m Value
-- ^ Value of field in document, or fail (Nothing) if field not found
look k doc = maybe notFound (return . value) (find ((k ==) . label) doc)
  where notFound = fail $ "expected " ++ show k ++ " in " ++ show doc

lookup :: (Val v, Monad m) => Label -> Document -> m v
-- ^ Lookup value of field in document and cast to expected type. Fail (Nothing) if field not found or value not of expected type.
lookup k doc = cast =<< look k doc

valueAt :: Label -> Document -> Value
-- ^ Value of field in document. Error if missing.
valueAt k = runIdentity . look k

at :: (Val v) => Label -> Document -> v
-- ^ Typed value of field in document. Error if missing or wrong type.
at k doc = result
  where
   result = fromMaybe err (lookup k doc)
   err = error $ "expected (" ++ show k ++ " :: " ++ show (typeOf result) ++ ") in " ++ show doc

include :: [Label] -> Document -> Document
-- ^ Only include fields of document in label list
include keys doc = mapMaybe (\k -> find ((k ==) . label) doc) keys

exclude :: [Label] -> Document -> Document
-- ^ Exclude fields from document in label list
exclude keys = filter (\(k := _) -> notElem k keys)

merge :: Document -> Document -> Document
-- ^ Merge documents with preference given to first one when both have the same label. I.e. for every (k := v) in first argument, if k exists in second argument then replace its value with v, otherwise add (k := v) to second argument.
merge es docInitial = foldl f docInitial es
  where f doc (k := v) = case findIndex ((k ==) . label) doc of
                          Nothing -> doc ++ [k := v]
                          Just i -> let (x, _ : y) = splitAt i doc in x ++ [k := v] ++ y

-- * Field

infix 0 :=, =:, =?

data Field = (:=) {label :: !Label, value :: Value}  deriving (Typeable, Eq, Ord)
-- ^ A BSON field is a named value, where the name (label) is a string and the value is a BSON 'Value'

(=:) :: (Val v) => Label -> v -> Field
-- ^ Field with given label and typed value
k =: v = k := val v

(=?) :: (Val a) => Label -> Maybe a -> Document
-- ^ If Just value then return one field document, otherwise return empty document
k =? ma = maybeToList (fmap (k =:) ma)

instance Show Field where
  showsPrec d (k := v) = showParen (d > 0) $ showString (' ' : T.unpack k) . showString ": " . showsPrec 1 v

type Label = Text
-- ^ The name of a BSON field

-- * Value

-- | A BSON value is one of the following types of values
data Value = Float Double
           | String Text
           | Doc Document
           | Array [Value]
           | Bin Binary
           | Fun Function
           | Uuid UUID
           | Md5 MD5
           | UserDef UserDefined
           | ObjId ObjectId
           | Bool Bool
           | UTC UTCTime
           | Null
           | RegEx Regex
           | JavaScr Javascript
           | Sym Symbol
           | Int32 Int32
           | Int64 Int64
           | Stamp MongoStamp
           | MinMax MinMaxKey
           deriving (Typeable, Eq, Ord)

instance Show Value where
  showsPrec d = fval (showsPrec d)

fval :: (forall a . (Val a) => a -> b) -> Value -> b
-- ^ Apply generic function to typed value
fval f v = case v of
            Float x   -> f x
            String x  -> f x
            Doc x     -> f x
            Array x   -> f x
            Bin x     -> f x
            Fun x     -> f x
            Uuid x    -> f x
            Md5 x     -> f x
            UserDef x -> f x
            ObjId x   -> f x
            Bool x    -> f x
            UTC x     -> f x
            Null      -> f (Nothing :: Maybe Value)
            RegEx x   -> f x
            JavaScr x -> f x
            Sym x     -> f x
            Int32 x   -> f x
            Int64 x   -> f x
            Stamp x   -> f x
            MinMax x  -> f x

-- * Value conversion

cast :: (Val a, Monad m) => Value -> m a
-- ^ Convert Value to expected type, or fail (Nothing) if not of that type
cast v = maybe notType return castingResult
  where
    castingResult = cast' v
    unMaybe :: Maybe a -> a
    unMaybe = undefined
    notType = fail $ "expected " ++ show (typeOf $ unMaybe castingResult) ++ ": " ++ show v

typed :: (Val a) => Value -> a
-- ^ Convert Value to expected type. Error if not that type.
typed = runIdentity . cast

typeOfVal :: Value -> TypeRep
-- ^ Type of typed value
typeOfVal = fval typeOf

-- ** conversion class

-- | Haskell types of this class correspond to BSON value types
class (Typeable a, Show a, Eq a) => Val a where
  val :: a -> Value
  valList :: [a] -> Value
  valList = Array . map val
  valMaybe :: Maybe a -> Value
  valMaybe = maybe Null val
  cast' :: Value -> Maybe a
  cast'List :: Value -> Maybe [a]
  cast'List (Array x) = mapM cast x
  cast'List _         = Nothing
  cast'Maybe :: Value -> Maybe (Maybe a)
  cast'Maybe Null = Just Nothing
  cast'Maybe v    = fmap Just (cast' v)

instance Val Double where
  val             = Float
  cast' (Float x) = Just x
  cast' (Int32 x) = Just (fromIntegral x)
  cast' (Int64 x) = Just (fromIntegral x)
  cast' _         = Nothing

instance Val Float where
  val             = Float . realToFrac
  cast' (Float x) = Just (realToFrac x)
  cast' (Int32 x) = Just (fromIntegral x)
  cast' (Int64 x) = Just (fromIntegral x)
  cast' _         = Nothing

instance Val Text where
  val                    = String
  cast' (String x)       = Just x
  cast' (Sym (Symbol x)) = Just x
  cast' _                = Nothing

instance Val Char where
  val x   = valList [x]
  valList = String . T.pack
  cast' v = cast'List v >>= safeHead
    where safeHead list = case list of
                           x:_ -> Just x
                           _   -> Nothing
  cast'List (String x)       = Just $ T.unpack x
  cast'List (Sym (Symbol x)) = Just $ T.unpack x
  cast'List _                = Nothing

instance Val Field where
  val x   = valList [x]
  valList = Doc
  cast' _ = Nothing
  cast'List v = case v of
                 Doc x -> Just x
                 _     -> Nothing

instance Val Value where
  val   = id
  cast' = Just

instance (Val a) => Val [a] where
  val   = valList
  cast' = cast'List

instance Val Binary where
  val           = Bin
  cast' (Bin x) = Just x
  cast' _       = Nothing

instance Val Function where
  val           = Fun
  cast' (Fun x) = Just x
  cast' _       = Nothing

instance Val UUID where
  val            = Uuid
  cast' (Uuid x) = Just x
  cast' _         = Nothing

instance Val MD5 where
  val           = Md5
  cast' (Md5 x) = Just x
  cast' _       = Nothing

instance Val UserDefined where
  val               = UserDef
  cast' (UserDef x) = Just x
  cast' _           = Nothing

instance Val ObjectId where
  val             = ObjId
  cast' (ObjId x) = Just x
  cast' _         = Nothing

instance Val Bool where
  val            = Bool
  cast' (Bool x) = Just x
  cast' _        = Nothing

instance Val UTCTime where
  val           = UTC
  cast' (UTC x) = Just x
  cast' _       = Nothing

instance Val POSIXTime where
  val           = UTC . posixSecondsToUTCTime . roundTo (1/1000)
  cast' (UTC x) = Just (utcTimeToPOSIXSeconds x)
  cast' _       = Nothing

instance (Val a) => Val (Maybe a) where
  val   = valMaybe
  cast' = cast'Maybe

instance Val Regex where
  val             = RegEx
  cast' (RegEx x) = Just x
  cast' _         = Nothing

instance Val Javascript where
  val               = JavaScr
  cast' (JavaScr x) = Just x
  cast' _           = Nothing

instance Val Symbol where
  val              = Sym
  cast' (Sym x)    = Just x
  cast' (String x) = Just (Symbol x)
  cast' _          = Nothing

instance Val Int32 where
  val             = Int32
  cast' (Int32 x) = Just x
  cast' (Int64 x) = fitInt x
  cast' (Float x) = Just (round x)
  cast' _         = Nothing

instance Val Int64 where
  val             = Int64
  cast' (Int64 x) = Just x
  cast' (Int32 x) = Just (fromIntegral x)
  cast' (Float x) = Just (round x)
  cast' _         = Nothing

instance Val Int where
  val n           = maybe (Int64 $ fromIntegral n) Int32 (fitInt n)
  cast' (Int32 x) = Just (fromIntegral x)
  cast' (Int64 x) = Just (fromEnum x)
  cast' (Float x) = Just (round x)
  cast' _         = Nothing

instance Val Integer where
  val n           = maybe (maybe err Int64 $ fitInt n) Int32 (fitInt n)
    where err = error $ show n ++ " is too large for Bson Int Value"
  cast' (Int32 x) = Just (fromIntegral x)
  cast' (Int64 x) = Just (fromIntegral x)
  cast' (Float x) = Just (round x)
  cast' _         = Nothing

instance Val MongoStamp where
  val             = Stamp
  cast' (Stamp x) = Just x
  cast' _         = Nothing

instance Val MinMaxKey where
  val              = MinMax
  cast' (MinMax x) = Just x
  cast' _          = Nothing

fitInt :: (Integral n, Integral m, Bounded m) => n -> Maybe m
-- ^ If number fits in type m then cast to m, otherwise Nothing
fitInt n =
  if fromIntegral (minBound `asTypeOf` result) <= n && n <= fromIntegral (maxBound `asTypeOf` result)
  then Just result
  else Nothing
    where result = fromIntegral n

-- * Haskell types corresponding to special Bson value types

-- ** Binary types

newtype Binary = Binary S.ByteString  deriving (Typeable, Show, Read, Eq, Ord)

newtype Function = Function S.ByteString  deriving (Typeable, Show, Read, Eq, Ord)

newtype UUID = UUID S.ByteString  deriving (Typeable, Show, Read, Eq, Ord)

newtype MD5 = MD5 S.ByteString  deriving (Typeable, Show, Read, Eq, Ord)

newtype UserDefined = UserDefined S.ByteString  deriving (Typeable, Show, Read, Eq, Ord)

-- ** Regex

data Regex = Regex Text Text  deriving (Typeable, Show, Read, Eq, Ord)
-- ^ The first string is the regex pattern, the second is the regex options string. Options are identified by characters, which must be listed in alphabetical order. Valid options are *i* for case insensitive matching, *m* for multiline matching, *x* for verbose mode, *l* to make \\w, \\W, etc. locale dependent, *s* for dotall mode (\".\" matches everything), and *u* to make \\w, \\W, etc. match unicode.

-- ** Javascript

data Javascript = Javascript Document Text deriving (Typeable, Show, Eq, Ord)
-- ^ Javascript code with possibly empty environment mapping variables to values that the code may reference

-- ** Symbol

newtype Symbol = Symbol Text  deriving (Typeable, Show, Read, Eq, Ord)

-- ** MongoStamp

newtype MongoStamp = MongoStamp Int64  deriving (Typeable, Show, Read, Eq, Ord)

-- ** MinMax

data MinMaxKey = MinKey | MaxKey  deriving (Typeable, Show, Read, Eq, Ord)

-- ** ObjectId

data ObjectId = Oid {-# UNPACK #-} !Word32 {-# UNPACK #-} !Word64  deriving (Typeable, Eq, Ord)
-- ^ A BSON ObjectID is a 12-byte value consisting of a 4-byte timestamp (seconds since epoch), a 3-byte machine id, a 2-byte process id, and a 3-byte counter. Note that the timestamp and counter fields must be stored big endian unlike the rest of BSON. This is because they are compared byte-by-byte and we want to ensure a mostly increasing order.

instance Show ObjectId where
  showsPrec _ (Oid x y) = showHexLen 8 x . showHexLen 16 y

instance Read ObjectId where
  readPrec = do
    [(x, "")] <- readHex <$> R.lift (R.count 8 R.get)
    y <- R.readS_to_Prec $ const readHex
    return (Oid x y)

timestamp :: ObjectId -> UTCTime
-- ^ Time when objectId was created
timestamp (Oid time _) = posixSecondsToUTCTime (fromIntegral time)

genObjectId :: IO ObjectId
-- ^ Create a fresh ObjectId
genObjectId = do
  time <- truncate <$> getPOSIXTime
  pid <- fromIntegral <$> getProcessID
  inc <- nextCount
  return $ Oid time (composite machineId pid inc)
 where
  machineId :: Word24
  machineId = unsafePerformIO (makeWord24 . S.unpack . S.take 3 . MD5.hash . SC.pack <$> getHostName)
  {-# NOINLINE machineId #-}
  counter :: IORef Word24
  counter = unsafePerformIO (newIORef 0)
  {-# NOINLINE counter #-}
  nextCount :: IO Word24
  nextCount = atomicModifyIORef counter $ \n -> (wrap24 (n + 1), n)

composite :: Word24 -> Word16 -> Word24 -> Word64
composite mid pid inc = fromIntegral mid `shift` 40 .|. fromIntegral pid `shift` 24 .|. fromIntegral inc

type Word24 = Word32
-- ^ low 3 bytes only, high byte must be zero

wrap24 :: Word24 -> Word24
wrap24 n = n `mod` 0x1000000

makeWord24 :: [Word8] -> Word24
-- ^ Put last 3 bytes into a Word24. Expected to be called on very short list
makeWord24 = foldl (\a b -> a `shift` 8 .|. fromIntegral b) 0

{- Authors: Tony Hannan <tony@10gen.com>
   Copyright 2010 10gen Inc.
   Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at: http://www.apache.org/licenses/LICENSE-2.0. Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. -}