Parsers.hs

{-|
Module      : PostgREST.Request.Parsers
Description : PostgREST parser combinators

This module is in charge of parsing all the querystring values in an url, e.g. the select, id, order in `/projects?select=id,name&id=eq.1&order=id,name.desc`.
-}
module PostgREST.Request.Parsers
  ( pColumns
  , pLogicPath
  , pLogicSingleVal
  , pLogicTree
  , pOrder
  , pOrderTerm
  , pRequestColumns
  , pRequestFilter
  , pRequestLogicTree
  , pRequestOnConflict
  , pRequestOrder
  , pRequestRange
  , pRequestSelect
  , pSingleVal
  , pTreePath
  ) where

import qualified Data.HashMap.Strict as M
import qualified Data.Set            as S

import Data.Either.Combinators       (mapLeft)
import Data.Foldable                 (foldl1)
import Data.List                     (init, last)
import Data.Text                     (intercalate, replace, strip)
import Data.Tree                     (Tree (..))
import Text.Parsec.Error             (errorMessages,
                                      showErrorMessages)
import Text.ParserCombinators.Parsec (GenParser, ParseError, Parser,
                                      anyChar, between, char, digit,
                                      eof, errorPos, letter,
                                      lookAhead, many1, noneOf,
                                      notFollowedBy, oneOf, option,
                                      optionMaybe, parse, sepBy1,
                                      string, try, (<?>))

import PostgREST.DbStructure.Identifiers (FieldName)
import PostgREST.Error                   (ApiRequestError (ParseRequestError))
import PostgREST.Query.SqlFragment       (ftsOperators, operators)
import PostgREST.RangeQuery              (NonnegRange)

import PostgREST.Request.Types

import Protolude hiding (intercalate, option, replace, try)

pRequestSelect :: Text -> Either ApiRequestError [Tree SelectItem]
pRequestSelect selStr =
  mapError $ parse pFieldForest ("failed to parse select parameter (" <> toS selStr <> ")") (toS selStr)

pRequestOnConflict :: Text -> Either ApiRequestError  [FieldName]
pRequestOnConflict oncStr =
  mapError $ parse pColumns ("failed to parse on_conflict parameter (" <> toS oncStr <> ")") (toS oncStr)

pRequestFilter :: (Text, Text) -> Either ApiRequestError (EmbedPath, Filter)
pRequestFilter (k, v) = mapError $ (,) <$> path <*> (Filter <$> fld <*> oper)
  where
    treePath = parse pTreePath ("failed to parser tree path (" ++ toS k ++ ")") $ toS k
    oper = parse (pOpExpr pSingleVal) ("failed to parse filter (" ++ toS v ++ ")") $ toS v
    path = fst <$> treePath
    fld = snd <$> treePath

pRequestOrder :: (Text, Text) -> Either ApiRequestError (EmbedPath, [OrderTerm])
pRequestOrder (k, v) = mapError $ (,) <$> path <*> ord'
  where
    treePath = parse pTreePath ("failed to parser tree path (" ++ toS k ++ ")") $ toS k
    path = fst <$> treePath
    ord' = parse pOrder ("failed to parse order (" ++ toS v ++ ")") $ toS v

pRequestRange :: (Text, NonnegRange) -> Either ApiRequestError (EmbedPath, NonnegRange)
pRequestRange (k, v) = mapError $ (,) <$> path <*> pure v
  where
    treePath = parse pTreePath ("failed to parser tree path (" ++ toS k ++ ")") $ toS k
    path = fst <$> treePath

pRequestLogicTree :: (Text, Text) -> Either ApiRequestError (EmbedPath, LogicTree)
pRequestLogicTree (k, v) = mapError $ (,) <$> embedPath <*> logicTree
  where
    path = parse pLogicPath ("failed to parser logic path (" ++ toS k ++ ")") $ toS k
    embedPath = fst <$> path
    logicTree = do
      op <- snd <$> path
      -- Concat op and v to make pLogicTree argument regular,
      -- in the form of "?and=and(.. , ..)" instead of "?and=(.. , ..)"
      parse pLogicTree ("failed to parse logic tree (" ++ toS v ++ ")") $ toS (op <> v)

pRequestColumns :: Maybe Text -> Either ApiRequestError (Maybe (S.Set FieldName))
pRequestColumns colStr =
  case colStr of
    Just str ->
      mapError $ Just . S.fromList <$> parse pColumns ("failed to parse columns parameter (" <> toS str <> ")") (toS str)
    _ -> Right Nothing

ws :: Parser Text
ws = toS <$> many (oneOf " \t")

lexeme :: Parser a -> Parser a
lexeme p = ws *> p <* ws

pTreePath :: Parser (EmbedPath, Field)
pTreePath = do
  p <- pFieldName `sepBy1` pDelimiter
  jp <- option [] pJsonPath
  return (init p, (last p, jp))

pFieldForest :: Parser [Tree SelectItem]
pFieldForest = pFieldTree `sepBy1` lexeme (char ',')
  where
    pFieldTree :: Parser (Tree SelectItem)
    pFieldTree =  try (Node <$> pRelationSelect <*> between (char '(') (char ')') pFieldForest) <|>
                  Node <$> pFieldSelect <*> pure []

pStar :: Parser Text
pStar = string "*" $> "*"

pFieldName :: Parser Text
pFieldName =
  pQuotedValue <|>
  intercalate "-" . map toS <$> (many1 (letter <|> digit <|> oneOf "_ ") `sepBy1` dash) <?>
  "field name (* or [a..z0..9_])"
  where
    isDash :: GenParser Char st ()
    isDash = try ( char '-' >> notFollowedBy (char '>') )
    dash :: Parser Char
    dash = isDash $> '-'

pJsonPath :: Parser JsonPath
pJsonPath = many pJsonOperation
  where
    pJsonOperation :: Parser JsonOperation
    pJsonOperation = pJsonArrow <*> pJsonOperand

    pJsonArrow   =
      try (string "->>" $> J2Arrow) <|>
      try (string "->" $> JArrow)

    pJsonOperand =
      let pJKey = JKey . toS <$> pFieldName
          pJIdx = JIdx . toS <$> ((:) <$> option '+' (char '-') <*> many1 digit) <* pEnd
          pEnd = try (void $ lookAhead (string "->")) <|>
                 try (void $ lookAhead (string "::")) <|>
                 try eof in
      try pJIdx <|> try pJKey

pField :: Parser Field
pField = lexeme $ (,) <$> pFieldName <*> option [] pJsonPath

aliasSeparator :: Parser ()
aliasSeparator = char ':' >> notFollowedBy (char ':')

pRelationSelect :: Parser SelectItem
pRelationSelect = lexeme $ try ( do
    alias <- optionMaybe ( try(pFieldName <* aliasSeparator) )
    fld <- pField
    prm1 <- optionMaybe pEmbedParam
    prm2 <- optionMaybe pEmbedParam
    return (fld, Nothing, alias, embedParamHint prm1 <|> embedParamHint prm2, embedParamJoin prm1 <|> embedParamJoin prm2)
  )
  where
    pEmbedParam :: Parser EmbedParam
    pEmbedParam =
      char '!' *> (
        try (string "left"  $> EPJoinType JTLeft)  <|>
        try (string "inner" $> EPJoinType JTInner) <|>
        try (EPHint <$> pFieldName))
    embedParamHint prm = case prm of
      Just (EPHint hint) -> Just hint
      _                  -> Nothing
    embedParamJoin prm = case prm of
      Just (EPJoinType jt) -> Just jt
      _                    -> Nothing

pFieldSelect :: Parser SelectItem
pFieldSelect = lexeme $
  try (
    do
      alias <- optionMaybe ( try(pFieldName <* aliasSeparator) )
      fld <- pField
      cast' <- optionMaybe (string "::" *> many letter)
      return (fld, toS <$> cast', alias, Nothing, Nothing)
  )
  <|> do
    s <- pStar
    return ((s, []), Nothing, Nothing, Nothing, Nothing)

pOpExpr :: Parser SingleVal -> Parser OpExpr
pOpExpr pSVal = try ( string "not" *> pDelimiter *> (OpExpr True <$> pOperation)) <|> OpExpr False <$> pOperation
  where
    pOperation :: Parser Operation
    pOperation =
          Op . toS <$> foldl1 (<|>) (try . ((<* pDelimiter) . string) . toS <$> M.keys ops) <*> pSVal
      <|> In <$> (try (string "in" *> pDelimiter) *> pListVal)
      <|> Is <$> (try (string "is" *> pDelimiter) *> pTriVal)
      <|> pFts
      <?> "operator (eq, gt, ...)"

    pTriVal = try (ciString "null"    $> TriNull)
          <|> try (ciString "unknown" $> TriUnknown)
          <|> try (ciString "true"    $> TriTrue)
          <|> try (ciString "false"   $> TriFalse)
          <?> "null or trilean value (unknown, true, false)"

    pFts = do
      op   <- foldl1 (<|>) (try . string . toS <$> ftsOps)
      lang <- optionMaybe $ try (between (char '(') (char ')') (many (letter <|> digit <|> oneOf "_")))
      pDelimiter >> Fts (toS op) (toS <$> lang) <$> pSVal

    ops = M.filterWithKey (const . flip notElem ("in":"is":ftsOps)) operators
    ftsOps = M.keys ftsOperators

    -- case insensitive char and string
    ciChar :: Char -> GenParser Char state Char
    ciChar c = char c <|> char (toUpper c)
    ciString :: [Char] -> GenParser Char state [Char]
    ciString = traverse ciChar

pSingleVal :: Parser SingleVal
pSingleVal = toS <$> many anyChar

pListVal :: Parser ListVal
pListVal = lexeme (char '(') *> pListElement `sepBy1` char ',' <* lexeme (char ')')

pListElement :: Parser Text
pListElement = try (pQuotedValue <* notFollowedBy (noneOf ",)")) <|> (toS <$> many (noneOf ",)"))

pQuotedValue :: Parser Text
pQuotedValue = toS <$> (char '"' *> many pCharsOrSlashed <* char '"')
  where
    pCharsOrSlashed = noneOf "\\\"" <|> (char '\\' *> anyChar)

pDelimiter :: Parser Char
pDelimiter = char '.' <?> "delimiter (.)"

pOrder :: Parser [OrderTerm]
pOrder = lexeme pOrderTerm `sepBy1` char ','

pOrderTerm :: Parser OrderTerm
pOrderTerm = do
  fld <- pField
  dir <- optionMaybe $
         try (pDelimiter *> string "asc" $> OrderAsc) <|>
         try (pDelimiter *> string "desc" $> OrderDesc)
  nls <- optionMaybe pNulls <* pEnd <|>
         pEnd $> Nothing
  return $ OrderTerm fld dir nls
  where
    pNulls = try (pDelimiter *> string "nullsfirst" $> OrderNullsFirst) <|>
             try (pDelimiter *> string "nullslast"  $> OrderNullsLast)
    pEnd = try (void $ lookAhead (char ',')) <|>
           try eof

pLogicTree :: Parser LogicTree
pLogicTree = Stmnt <$> try pLogicFilter
             <|> Expr <$> pNot <*> pLogicOp <*> (lexeme (char '(') *> pLogicTree `sepBy1` lexeme (char ',') <* lexeme (char ')'))
  where
    pLogicFilter :: Parser Filter
    pLogicFilter = Filter <$> pField <* pDelimiter <*> pOpExpr pLogicSingleVal
    pNot :: Parser Bool
    pNot = try (string "not" *> pDelimiter $> True)
           <|> pure False
           <?> "negation operator (not)"
    pLogicOp :: Parser LogicOperator
    pLogicOp = try (string "and" $> And)
               <|> string "or" $> Or
               <?> "logic operator (and, or)"

pLogicSingleVal :: Parser SingleVal
pLogicSingleVal = try (pQuotedValue <* notFollowedBy (noneOf ",)")) <|> try pPgArray <|> (toS <$> many (noneOf ",)"))
  where
    pPgArray :: Parser Text
    pPgArray =  do
      a <- string "{"
      b <- many (noneOf "{}")
      c <- string "}"
      pure (toS $ a ++ b ++ c)

pLogicPath :: Parser (EmbedPath, Text)
pLogicPath = do
  path <- pFieldName `sepBy1` pDelimiter
  let op = last path
      notOp = "not." <> op
  return (filter (/= "not") (init path), if "not" `elem` path then notOp else op)

pColumns :: Parser [FieldName]
pColumns = pFieldName `sepBy1` lexeme (char ',')

mapError :: Either ParseError a -> Either ApiRequestError a
mapError = mapLeft translateError
  where
    translateError e =
      ParseRequestError message details
      where
        message = show $ errorPos e
        details = strip $ replace "\n" " " $ toS
           $ showErrorMessages "or" "unknown parse error" "expecting" "unexpected" "end of input" (errorMessages e)