AliasClause.hs

module PostgresqlSyntax.Ast.AliasClause where

import qualified HeadedMegaparsec as Parser
import PostgresqlSyntax.Algebra
import PostgresqlSyntax.Ast.Ident
import PostgresqlSyntax.Ast.NameList
import qualified PostgresqlSyntax.Helpers.Parsers as Parsers
import qualified PostgresqlSyntax.Helpers.TextBuilders as TextBuilders
import qualified PostgresqlSyntax.KeywordSet as KeywordSet
import PostgresqlSyntax.Prelude
import qualified Test.QuickCheck as Qc

-- |
-- ==== References
-- @
-- alias_clause:
--   |  AS ColId '(' name_list ')'
--   |  AS ColId
--   |  ColId '(' name_list ')'
--   |  ColId
-- @
--
-- 'PostgresqlSyntax.Ast.ColId' is a bare alias to 'Ident', but its /parser/
-- (kept in "PostgresqlSyntax.Parsing" since @ColId@ itself isn't extracted
-- in this batch) is more permissive than plain 'Ident'. Since this module
-- sits below "PostgresqlSyntax.Parsing" (no import cycle allowed), that
-- ColId-flavored element parser is duplicated here (mirroring @colId@'s
-- definition), same as 'PostgresqlSyntax.Ast.NameList'.
data AliasClause = AliasClause Bool Ident (Maybe NameList)
  deriving (Show, Generic, Eq, Ord, Data)

instance IsAst AliasClause where
  toTextBuilder settings (AliasClause a b c) =
    TextBuilders.optLexemes
      [ if a then Just "AS" else Nothing,
        Just (toTextBuilder settings b),
        fmap (TextBuilders.renderInParens . toTextBuilder settings) c
      ]
  parser settings = do
    (as, alias) <- (True,) <$> (Parsers.keyword "as" *> Parsers.space1 *> Parser.endHead *> colIdLikeName) <|> (False,) <$> colIdLikeName
    columnAliases <- optional (Parsers.space1 *> Parsers.inParens (parser settings))
    return (AliasClause as alias columnAliases)
    where
      colIdLikeName =
        Parser.label "identifier" $
          parser settings
            <|> Parsers.keywordNameFromSet UnquotedIdent (KeywordSet.unreservedKeyword <> KeywordSet.colNameKeyword)

instance Qc.Arbitrary AliasClause where
  shrink = Qc.genericShrink
  arbitrary = AliasClause <$> arbitrary <*> arbitrary <*> arbitrary