{-# LANGUAGE FlexibleContexts, FlexibleInstances, Rank2Types
  , RecordWildCards, ScopedTypeVariables, TypeFamilies #-}
module Database.PostgreSQL.PQTypes.ToSQL (
    ParamAllocator
  , ToSQL(..)
  , put
  ) where

import Data.ByteString.Unsafe
import Data.Int
import Data.Text.Encoding
import Data.Time
import Data.Word
import Foreign.C
import Foreign.Marshal.Alloc
import Foreign.Ptr
import Foreign.Storable
import qualified Data.ByteString.Char8 as BS
import qualified Data.ByteString.Lazy.Char8 as BSL
import qualified Data.Text as T
import qualified Data.Text.Lazy as TL

import Database.PostgreSQL.PQTypes.Format
import Database.PostgreSQL.PQTypes.Internal.C.Interface
import Database.PostgreSQL.PQTypes.Internal.C.Types
import Database.PostgreSQL.PQTypes.Internal.Utils

-- | 'alloca'-like producer of 'PGparam' objects.
type ParamAllocator = forall r. (Ptr PGparam -> IO r) -> IO r

-- | Class which represents \"from Haskell type
-- to SQL (libpqtypes) type\" transformation.
class PQFormat t => ToSQL t where
  -- | Destination type (used by libpqtypes).
  type PQDest t :: *
  -- | Put supplied value into inner 'PGparam'.
  toSQL :: t -- ^ Value to be put.
        -> ParamAllocator -- ^ 'PGparam' allocator.
        -> (Ptr (PQDest t) -> IO r) -- ^ Continuation that puts
        -- converted value into inner 'PGparam'.
        -> IO r

-- | Function that abstracts away common elements of most 'ToSQL'
-- instance definitions to make them easier to write and less verbose.
put :: Storable t => t -> (Ptr t -> IO r) -> IO r
put x conv = alloca $ \ptr -> poke ptr x >> conv ptr

-- NULLables

instance ToSQL t => ToSQL (Maybe t) where
  type PQDest (Maybe t) = PQDest t
  toSQL mt allocParam conv = case mt of
    Nothing -> conv nullPtr
    Just t  -> toSQL t allocParam conv

-- NUMERICS

instance ToSQL Int16 where
  type PQDest Int16 = CShort
  toSQL n _ = put (fromIntegral n)

instance ToSQL Int32 where
  type PQDest Int32 = CInt
  toSQL n _ = put (fromIntegral n)

instance ToSQL Int64 where
  type PQDest Int64 = CLLong
  toSQL n _ = put (fromIntegral n)

instance ToSQL Int where
  type PQDest Int = CLLong
  toSQL n _ = put (fromIntegral n)

instance ToSQL Float where
  type PQDest Float = CFloat
  toSQL n _ = put (realToFrac n)

instance ToSQL Double where
  type PQDest Double = CDouble
  toSQL n _ = put (realToFrac n)

-- CHAR

instance ToSQL Char where
  type PQDest Char = CChar
  toSQL c _ conv
    | c > '\255' = hpqTypesError $ "toSQL (Char): character " ++ show c ++ " cannot be losslessly converted to CChar"
    | otherwise = put (castCharToCChar c) conv

instance ToSQL Word8 where
  type PQDest Word8 = CChar
  toSQL c _ = put (fromIntegral c)

-- VARIABLE-LENGTH CHARACTER TYPES

instance ToSQL BS.ByteString where
  type PQDest BS.ByteString = PGbytea
  toSQL bs _ conv = unsafeUseAsCStringLen bs $ \cslen ->
    -- Note: it seems that ByteString can actually store NULL pointer
    -- inside. This is bad, since NULL pointers are treated by libpqtypes
    -- as NULL values. To get around that, nullStringCStringLen is used
    -- (a static pointer to empty string defined on C level). Actually,
    -- it would be sufficient to pass any non-NULL pointer there, but
    -- this is much uglier and dangerous.
    flip put conv . cStringLenToBytea $
      if fst cslen == nullPtr
        then nullStringCStringLen
        else cslen

instance ToSQL BSL.ByteString where
  type PQDest BSL.ByteString = PGbytea
  toSQL = toSQL . BSL.toStrict

-- | Encodes underlying C string as UTF-8, so if you are working
-- with a different encoding, you should not rely on this instance.
instance ToSQL T.Text where
  type PQDest T.Text = PGbytea
  toSQL = toSQL . encodeUtf8

-- | Encodes underlying C string as UTF-8, so if you are working
-- with a different encoding, you should not rely on this instance.
instance ToSQL TL.Text where
  type PQDest TL.Text = PGbytea
  toSQL = toSQL . TL.toStrict

-- | Encodes underlying C string as UTF-8, so if you are working
-- with a different encoding, you should not rely on this instance.
instance ToSQL String where
  type PQDest String = PGbytea
  toSQL = toSQL . T.pack

-- DATE

instance ToSQL Day where
  type PQDest Day = PGdate
  toSQL day _ = put (dayToPGdate day)

-- TIME

instance ToSQL TimeOfDay where
  type PQDest TimeOfDay = PGtime
  toSQL tod _ = put (timeOfDayToPGtime tod)

-- TIMESTAMP

instance ToSQL LocalTime where
  type PQDest LocalTime = PGtimestamp
  toSQL LocalTime{..} _ = put PGtimestamp {
    pgTimestampEpoch = 0
  , pgTimestampDate = dayToPGdate localDay
  , pgTimestampTime = timeOfDayToPGtime localTimeOfDay
  }

-- TIMESTAMPTZ

instance ToSQL UTCTime where
  type PQDest UTCTime = PGtimestamp
  toSQL UTCTime{..} _ = put PGtimestamp {
    pgTimestampEpoch = 0
  , pgTimestampDate = dayToPGdate utctDay
  , pgTimestampTime = timeOfDayToPGtime $ timeToTimeOfDay utctDayTime
  }

instance ToSQL ZonedTime where
  type PQDest ZonedTime = PGtimestamp
  toSQL ZonedTime{..} _ = put PGtimestamp {
    pgTimestampEpoch = 0
  , pgTimestampDate = dayToPGdate $ localDay zonedTimeToLocalTime
  , pgTimestampTime = (timeOfDayToPGtime $ localTimeOfDay zonedTimeToLocalTime) {
      pgTimeGMTOff = fromIntegral (timeZoneMinutes zonedTimeZone) * 60
    }
  }

-- BOOL

instance ToSQL Bool where
  type PQDest Bool = CInt
  toSQL True  _ = put 1
  toSQL False _ = put 0

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

timeOfDayToPGtime :: TimeOfDay -> PGtime
timeOfDayToPGtime TimeOfDay{..} = PGtime {
    pgTimeHour   = fromIntegral todHour
  , pgTimeMin    = fromIntegral todMin
  , pgTimeSec    = sec
  , pgTimeUSec   = usec
  , pgTimeWithTZ = 0
  , pgTimeIsDST  = 0
  , pgTimeGMTOff = 0
  , pgTimeTZAbbr = BS.empty
  }
  where
    (sec, usec) = floor ((toRational todSec) * 1000000) `divMod` 1000000

dayToPGdate :: Day -> PGdate
dayToPGdate day = PGdate {
    pgDateIsBC  = isBC
  , pgDateYear  = fromIntegral $ adjustBC year
  , pgDateMon   = fromIntegral $ mon - 1
  , pgDateMDay  = fromIntegral mday
  , pgDateJDay  = 0
  , pgDateYDay  = 0
  , pgDateWDay  = 0
  }
  where
    (year, mon, mday) = toGregorian day

    -- Note: inverses of appropriate functions
    -- in pgDateToDay defined in FromSQL module
    isBC = if year <= 0 then 1 else 0
    adjustBC = if isBC == 1 then succ . negate else id