{-# LANGUAGE ExistentialQuantification, RecordWildCards, ScopedTypeVariables,
             FlexibleInstances, OverloadedStrings, PatternGuards #-}

-- | Building RQL queries in Haskell
module Database.RethinkDB.ReQL (
  ReQL(..),
  op,
  BaseReQL(..),
  BaseAttribute(..),
  buildQuery,
  BaseArray,
  Backtrace, convertBacktrace,
  Expr(..),
  QuerySettings(..),
  newVarId,
  str,
  num,
  Attribute(..),
  cons,
  arr,
  baseArray,
  withQuerySettings,
  Object(..),
  Obj(..),
  returnVals,
  canReturnVals,
  reqlToProtobuf
  ) where

import qualified Data.Vector as V
import qualified Data.HashMap.Lazy as M
import Data.Maybe (fromMaybe, catMaybes)
import Data.String (IsString(..))
import Data.List (intersperse)
import qualified Data.Sequence as S
import Control.Monad.State (State, get, put, runState)
import Control.Applicative ((<$>))
import Data.Default (Default, def)
import qualified Data.Text as T
import qualified Data.Aeson as J
import Data.Foldable (toList)
import Data.Time
import Data.Time.Clock.POSIX
import Control.Monad.Fix

import Text.ProtocolBuffers hiding (Key, cons, Default)
import Text.ProtocolBuffers.Basic hiding (Default)

import Database.RethinkDB.Protobuf.Ql2.Term
import qualified Database.RethinkDB.Protobuf.Ql2.Term as Term
import Database.RethinkDB.Protobuf.Ql2.Term.TermType as TermType
import Database.RethinkDB.Protobuf.Ql2.Term.AssocPair
import qualified Database.RethinkDB.Protobuf.Ql2.Query as Query
import Database.RethinkDB.Protobuf.Ql2.Query.QueryType
import qualified Database.RethinkDB.Protobuf.Ql2.Datum as Datum
import qualified Database.RethinkDB.Protobuf.Ql2.Datum.AssocPair as Datum
import Database.RethinkDB.Protobuf.Ql2.Datum
import qualified Database.RethinkDB.Protobuf.Ql2.Backtrace as QL
import qualified Database.RethinkDB.Protobuf.Ql2.Frame as QL
import Database.RethinkDB.Protobuf.Ql2.Datum.DatumType
import Database.RethinkDB.Protobuf.Ql2.Frame.FrameType as QL

import Database.RethinkDB.Objects as O

-- | An RQL term
data ReQL = ReQL { baseReQL :: State QuerySettings BaseReQL }

data BaseReQL = BaseReQL {
    termType :: TermType,
    termDatum :: Maybe Datum.Datum,
    termArgs :: BaseArray,
    termOptArgs :: [BaseAttribute] }

data QuerySettings = QuerySettings {
  queryToken :: Int64,
  queryDefaultDatabase :: Database,
  queryVarIndex :: Int,
  queryUseOutdated :: Maybe Bool,
  queryReturnVals :: Maybe Bool
  }

instance Default QuerySettings where
  def = QuerySettings 0 (Database "") 0 Nothing Nothing

withQuerySettings :: (QuerySettings -> ReQL) -> ReQL
withQuerySettings f = ReQL $ (baseReQL . f) =<< get

-- | Include the value of single write operations in the returned object
returnVals :: ReQL -> ReQL
returnVals (ReQL t) = ReQL $ do
  state <- get
  put state{ queryReturnVals = Just True }
  ret <- t
  state' <- get
  put state'{ queryReturnVals = queryReturnVals state }
  return ret

canReturnVals :: ReQL -> ReQL
canReturnVals (ReQL t) = ReQL $ t >>= \ret -> do
  qs <- get
  case queryReturnVals qs of
    Nothing -> return ret
    Just rv -> return ret{
      termOptArgs = BaseAttribute "return_vals" (baseBool rv) : termOptArgs ret }

baseBool :: Bool -> BaseReQL
baseBool b = BaseReQL DATUM (Just defaultValue{
                                Datum.type' = Just R_BOOL, r_bool = Just b }) [] []

newVarId :: State QuerySettings Int
newVarId = do
  QuerySettings {..} <- get
  let n = queryVarIndex + 1
  put QuerySettings {queryVarIndex = n, ..}
  return $ n

instance Show BaseReQL where
  show (BaseReQL DATUM (Just dat) _ _) = showD dat
  show (BaseReQL MAKE_ARRAY _ x []) = "[" ++ (concat $ intersperse ", " $ map show x) ++ "]"
  show (BaseReQL MAKE_OBJ _ [] x) = "{" ++ (concat $ intersperse ", " $ map show x) ++ "}"
  show (BaseReQL VAR _ [BaseReQL DATUM (Just d) [] []] []) | Just x <- toDouble d =
    "x" ++ show (round x)
  show (BaseReQL FUNC _ [BaseReQL DATUM (Just d) [] [], body] []) | Just vars <- toDoubles d =
    "(\\" ++ (concat $ intersperse " " $ map (("x"++) . show . round) $ vars)
    ++ " -> " ++ show body ++ ")"
  show (BaseReQL GET_FIELD _ [o, k] []) = show o ++ "!" ++ show k
  show (BaseReQL fun _ args optargs) =
    show fun ++ "(" ++
    concat (intersperse ", " (map show args ++ map show optargs)) ++ ")"

showD :: Datum.Datum -> String
showD d = case Datum.type' d of
  Just R_NUM -> show' $ r_num d
  Just R_BOOL -> show' $ r_bool d
  Just R_STR -> show' $ r_str d
  Just R_ARRAY -> "[" ++ (concat $ intersperse ", " $ map showD $ toList $ r_array d) ++ "]"
  Just R_OBJECT ->
    "{" ++ (concat $ intersperse ", " $ map showDatumAttr $ toList $ r_object d) ++ "}"
  Just R_NULL -> "null"
  Nothing -> "Nothing"
  where show' Nothing = "Nothing"
        show' (Just a) = show a

showDatumAttr:: Datum.AssocPair -> String
showDatumAttr (Datum.AssocPair (Just k) (Just v)) = uToString k ++ ": " ++ showD v
showDatumAttr x = show x

-- | Convert other types into ReqL expressions
class Expr e where
  expr :: e -> ReQL

instance Expr ReQL where
  expr t = t

-- | A list of terms
data Array = Array { baseArray :: State QuerySettings BaseArray }

type BaseArray = [BaseReQL]

-- | Build arrays of exprs
class Arr a where
  arr :: a -> Array

cons :: Expr e => e -> Array -> Array
cons x xs = Array $ do
  bt <- baseReQL (expr x)
  xs' <- baseArray xs
  return $ bt : xs'

instance Arr () where
  arr () = Array $ return []

instance Expr a => Arr [a] where
  arr [] = Array $ return []
  arr (x:xs) = cons x (arr xs)

instance (Expr a, Expr b) => Arr (a, b) where
  arr (a,b) = cons a $ cons b $ arr ()

instance (Expr a, Expr b, Expr c) => Arr (a, b, c) where
  arr (a,b,c) = cons a $ cons b $ cons c $ arr ()

instance (Expr a, Expr b, Expr c, Expr d) => Arr (a, b, c, d) where
  arr (a,b,c,d) = cons a $ cons b $ cons c $ cons d $ arr ()

instance Arr Array where
  arr = id

-- | A list of key/value pairs
data Object = Object { baseObject :: State QuerySettings [BaseAttribute] }

-- | A key/value pair used for building objects
data Attribute = forall e . (Expr e) => T.Text := e

data BaseAttribute = BaseAttribute T.Text BaseReQL

mapBaseAttribute :: (BaseReQL -> BaseReQL) -> BaseAttribute -> BaseAttribute
mapBaseAttribute f (BaseAttribute k v) = BaseAttribute k (f v)

instance Show BaseAttribute where
  show (BaseAttribute a b) = T.unpack a ++ ": " ++ show b

-- | Convert into a ReQL object
class Obj o where
  obj :: o -> Object

instance Obj [Attribute] where
  obj = Object . mapM base
    where base (k := e) = BaseAttribute k <$> baseReQL (expr e)

instance Obj Object where
  obj = id

instance Obj () where
  obj _ = Object $ return []

-- | Build a term
op :: (Arr a, Obj o) => TermType -> a -> o -> ReQL
op t a b = ReQL $ do
  a' <- baseArray (arr a)
  b' <- baseObject (obj b)
  case (t, a') of
    (FUNCALL, (BaseReQL FUNC Nothing [argsFunDatum, fun] [] : argsCall)) |
      BaseReQL DATUM (Just argsFunArray) [] [] <- argsFunDatum,
      Just varsFun <- toDoubles argsFunArray,
      length varsFun == length argsCall,
      Just varsCall <- varsOf argsCall ->
        return $ alphaRename (zip varsFun varsCall) fun
    _ -> return $ BaseReQL t Nothing a' b'

toDoubles :: Datum.Datum -> Maybe [Double]
toDoubles Datum.Datum{
  Datum.type' = Just R_ARRAY,
  r_array = seq } =
  sequence . map toDouble . toList $ seq
toDoubles _ = Nothing

toDouble :: Datum.Datum -> Maybe Double
toDouble Datum.Datum{ type' = Just R_NUM, r_num = Just n } = Just n
toDouble _ = Nothing

varsOf :: [BaseReQL] -> Maybe [Double]
varsOf = sequence . map varOf
    
varOf :: BaseReQL -> Maybe Double
varOf (BaseReQL VAR Nothing [BaseReQL DATUM (Just d) [] []] []) = toDouble d
varOf _ = Nothing

datumNumberArray :: [Int] -> Datum.Datum
datumNumberArray a =
  defaultValue{
    Datum.type' = Just R_ARRAY,
    r_array = S.fromList $ map datumInt a }

datumInt :: Int -> Datum.Datum
datumInt n =
  defaultValue{
    Datum.type' = Just R_NUM,
    r_num = Just $ fromIntegral n }

alphaRename :: [(Double, Double)] -> BaseReQL -> BaseReQL
alphaRename assoc = fix $ \f x ->
  case varOf x of
    Just n
      | Just n' <- lookup n assoc ->
      BaseReQL VAR Nothing
      [BaseReQL DATUM
       (Just $ defaultValue{ Datum.type' = Just R_NUM, r_num = Just n' }) [] []] []
      | otherwise -> x
    _ -> updateChildren x f

updateChildren :: BaseReQL -> (BaseReQL -> BaseReQL) -> BaseReQL
updateChildren (BaseReQL t d a o) f = BaseReQL t d (map f a) (map (mapBaseAttribute f) o)

datumTerm :: DatumType -> Datum.Datum -> ReQL
datumTerm t d = ReQL $ return $ BaseReQL DATUM (Just d { Datum.type' = Just t }) [] []

-- | A shortcut for inserting strings into ReQL expressions
-- Useful when OverloadedStrings makes the type ambiguous
str :: String -> ReQL
str s = datumTerm R_STR defaultValue { r_str = Just (uFromString s) }

-- | A shortcut for inserting numbers into ReQL expressions
num :: Double -> ReQL
num = expr

instance Expr Int64 where
  expr i = datumTerm R_NUM defaultValue { r_num = Just (fromIntegral i) }

instance Expr Int where
  expr i = datumTerm R_NUM defaultValue { r_num = Just (fromIntegral i) }

instance Expr Integer where
  expr i = datumTerm R_NUM defaultValue { r_num = Just (fromIntegral i) }

instance Num ReQL where
  fromInteger x = datumTerm R_NUM defaultValue { r_num = Just (fromInteger x) }
  a + b = op ADD (a, b) ()
  a * b = op MUL (a, b) ()
  abs n = op BRANCH (op TermType.LT (n, 0 :: Double) (), negate n, n) ()
  signum n = op BRANCH (op TermType.LT (n, 0 :: Double) (),
                        -1 :: Double,
                        op BRANCH (op TermType.EQ (n, 0 :: Double) (), 0 :: Double, 1 :: Double) ()) ()

instance Expr T.Text where
  expr t = datumTerm R_STR defaultValue { r_str = Just (uFromString $ T.unpack t) }

instance Expr Bool where
  expr b = datumTerm R_BOOL defaultValue { r_bool = Just b }

instance Expr () where
  expr _ = datumTerm R_NULL defaultValue

instance IsString ReQL where
  fromString s = datumTerm R_STR defaultValue { r_str = Just (uFromString $ s) }

instance Expr (ReQL -> ReQL) where
  expr f = ReQL $ do
    v <- newVarId
    baseReQL $ op FUNC (datumNumberArray [v], f (op VAR [v] ())) ()

instance Expr (ReQL -> ReQL -> ReQL) where
  expr f = ReQL $ do
    a <- newVarId
    b <- newVarId
    baseReQL $ op FUNC (datumNumberArray [a, b], f (op VAR [a] ()) (op VAR [b] ())) ()

instance Expr Datum.Datum where
  expr d = ReQL $ return $ BaseReQL DATUM (Just d) [] []

instance Expr Table where
  expr (Table mdb name _) = withQuerySettings $ \QuerySettings {..} ->
    op TABLE (fromMaybe queryDefaultDatabase mdb, name) $ catMaybes [
      fmap ("use_outdated" :=) queryUseOutdated ]

instance Expr Database where
  expr (Database name) = op DB [name] ()

instance Expr J.Value where
  expr J.Null = expr ()
  expr (J.Bool b) = expr b
  expr (J.Number n) = expr (fromRational (toRational n) :: Double)
  expr (J.String t) = expr t
  expr (J.Array a) = expr a
  expr (J.Object o) = expr o

instance Expr Double where
  expr d = datumTerm R_NUM defaultValue { r_num = Just d }

instance Expr Rational where
  expr x = expr (fromRational x :: Double)

instance Expr x => Expr (V.Vector x) where
  expr v = expr (V.toList v)

instance Expr a => Expr [a] where
  expr a = expr $ arr a

instance Expr Array where
  expr a = op MAKE_ARRAY a ()

instance Expr e => Expr (M.HashMap T.Text e) where
  expr m = expr $ obj $ map (uncurry (:=)) $ M.toList m

instance Expr Object where
  expr o = op MAKE_OBJ () o

buildBaseReQL :: BaseReQL -> Term
buildBaseReQL BaseReQL {..} = defaultValue {
    Term.type' = Just termType,
    datum = termDatum,
    args = buildBaseArray termArgs,
    optargs = buildTermAssoc termOptArgs }

buildBaseArray :: BaseArray -> Seq Term
buildBaseArray [] = S.empty
buildBaseArray (x:xs) = buildBaseReQL x S.<| buildBaseArray xs

buildTermAssoc :: [BaseAttribute] -> Seq AssocPair
buildTermAssoc = S.fromList . map buildTermAttribute

buildTermAttribute :: BaseAttribute -> AssocPair
buildTermAttribute (BaseAttribute k v) = AssocPair (Just $ uFromString $ T.unpack k) (Just $ buildBaseReQL v)

buildQuery :: ReQL -> Int64 -> Database -> (Query.Query, BaseReQL)
buildQuery term token db = (defaultValue {
                              Query.type' = Just START,
                              Query.query = Just pterm },
                            bterm)
  where bterm =
         fst $ runState (baseReQL term) (def {queryToken = token,
                                              queryDefaultDatabase = db })
        pterm = buildBaseReQL bterm

instance Show ReQL where
  show t = show . snd $ buildQuery t 0 (Database "")

reqlToProtobuf :: ReQL -> Query.Query
reqlToProtobuf t = fst $ buildQuery t 0 (Database "")

type Backtrace = [Frame]

data Frame = FramePos Int64 | FrameOpt T.Text

instance Show Frame where
    show (FramePos n) = show n
    show (FrameOpt k) = show k

convertBacktrace :: QL.Backtrace -> Backtrace
convertBacktrace = concatMap convertFrame . toList . QL.frames
    where convertFrame QL.Frame { type' = Just QL.POS, pos = Just n } = [FramePos n]
          convertFrame QL.Frame { type' = Just QL.OPT, opt = Just k } = [FrameOpt (T.pack $ uToString k)]
          convertFrame _ = []

instance Expr UTCTime where
  expr t = op EPOCH_TIME [expr . toRational $ utcTimeToPOSIXSeconds t] ()

instance Expr ZonedTime where
  expr (ZonedTime
        (LocalTime
         date
         (TimeOfDay hour minute seconds))
        timezone) = let
    (year, month, day) = toGregorian date
    in  op TIME [
      expr year, expr month, expr day, expr hour, expr minute, expr (toRational seconds),
      str $ timeZoneOffsetString timezone] ()