39 lines
1.4 KiB
Haskell
39 lines
1.4 KiB
Haskell
{- This Source Code Form is subject to the terms of the Mozilla Public License,
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v. 2.0. If a copy of the MPL was not distributed with this file, You can
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obtain one at https://mozilla.org/MPL/2.0/. -}
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-- | Template Haskell helpers.
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module Language.GraphQL.TH
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( gql
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) where
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import Language.Haskell.TH.Quote (QuasiQuoter(..))
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import Language.Haskell.TH (Exp(..), Lit(..))
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stripIndentation :: String -> String
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stripIndentation code = reverse
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$ dropNewlines
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$ reverse
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$ unlines
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$ indent spaces <$> lines withoutLeadingNewlines
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where
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indent 0 xs = xs
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indent count (' ' : xs) = indent (count - 1) xs
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indent _ xs = xs
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withoutLeadingNewlines = dropNewlines code
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dropNewlines = dropWhile $ flip any ['\n', '\r'] . (==)
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spaces = length $ takeWhile (== ' ') withoutLeadingNewlines
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-- | Removes leading and trailing newlines. Indentation of the first line is
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-- removed from each line of the string.
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gql :: QuasiQuoter
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gql = QuasiQuoter
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{ quoteExp = pure . LitE . StringL . stripIndentation
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, quotePat = const
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$ fail "Illegal gql QuasiQuote (allowed as expression only, used as a pattern)"
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, quoteType = const
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$ fail "Illegal gql QuasiQuote (allowed as expression only, used as a type)"
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, quoteDec = const
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$ fail "Illegal gql QuasiQuote (allowed as expression only, used as a declaration)"
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}
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