96 lines
2.7 KiB
Haskell
96 lines
2.7 KiB
Haskell
{-# LANGUAGE TemplateHaskell #-}
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{-# LANGUAGE GeneralizedNewtypeDeriving #-}
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{-# LANGUAGE FlexibleInstances #-}
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{-# LANGUAGE CPP #-}
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{-# OPTIONS_GHC -fno-warn-missing-fields #-}
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-- | This module contains Shakespearean (see "Text.Shakespeare") templates
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-- for Elm. It introduces type-safe compile-time variable and URL
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-- interpolation. A typeclass @'ToElm'@ is provided for interpolated
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-- variables.
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--
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-- Further reading on Shakespearean templates:
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-- <http://www.yesodweb.com/book/templates>
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--
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-- Further reading on Elm: <http://elm-lang.org>
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module Language.Elm.Quasi
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( -- * Functions
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-- ** Template-Reading Functions
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-- |These QuasiQuoters return functions of the type @(t -> 'Elm')@
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-- where @t@ is the URL rendering function if type-safe URLs are used.
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--
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-- A usage example for both type-safe (Yesod) and standard path segment
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-- (Happstack) URLs is provided in the Examples folder in the Git
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-- repository.
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elm
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, elmFile
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, elmFileReload
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-- * Datatypes
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, Elm (..)
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-- * Typeclass for interpolated variables
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, ToElm (..)
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-- ** Rendering Functions
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, renderElm
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) where
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import Language.Haskell.TH.Quote (QuasiQuoter (..))
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import Language.Haskell.TH.Syntax
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import Data.Text.Lazy.Builder (Builder, fromText, toLazyText, fromLazyText)
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import Data.Monoid
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import qualified Data.Text as TS
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import qualified Data.Text.Lazy as TL
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import Text.Shakespeare
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-- | Render Elm to lazy Text.
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renderElm :: Elm -> TL.Text
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renderElm (Elm b) = toLazyText b
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-- | Newtype wrapper of 'Builder'.
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newtype Elm = Elm { unElm :: Builder }
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deriving Monoid
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-- | A typeclass for types that can be interpolated in Elm templates.
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class ToElm a where
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toElm :: a -> Builder
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instance ToElm [Char] where toElm = fromLazyText . TL.pack
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instance ToElm TS.Text where toElm = fromText
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instance ToElm TL.Text where toElm = fromLazyText
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elmSettings :: Q ShakespeareSettings
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elmSettings = do
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toJExp <- [|toElm|]
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wrapExp <- [|Elm|]
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unWrapExp <- [|unElm|]
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return $ defaultShakespeareSettings { toBuilder = toJExp
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, wrap = wrapExp
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, unwrap = unWrapExp
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}
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-- |QuasiQuoter for embedding Elm code inside of Haskell code.
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--
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-- Usage:
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-- @[elm|main = plaintext \"Some elm code\"|]@
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elm :: QuasiQuoter
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elm = QuasiQuoter { quoteExp = \s -> do
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rs <- elmSettings
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quoteExp (shakespeare rs) s
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}
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-- |A Template Haskell function for embedding Elm code from external
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-- .elm files.
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--
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-- Usage:
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-- @$(elmFile \"elm_source/index.elm\")@
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elmFile :: FilePath -> Q Exp
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elmFile fp = do
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rs <- elmSettings
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shakespeareFile rs fp
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elmFileReload :: FilePath -> Q Exp
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elmFileReload fp = do
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rs <- elmSettings
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shakespeareFileReload rs fp
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