146 lines
4.2 KiB
Haskell
146 lines
4.2 KiB
Haskell
-- | Efficient generation of JSON documents, with HTML-entity encoding handled via types.
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{-# LANGUAGE GeneralizedNewtypeDeriving #-}
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{-# LANGUAGE CPP #-}
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module Yesod.Json
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( -- * Monad
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Json
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, jsonToContent
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, jsonToRepJson
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-- * Generate Json output
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, jsonScalar
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, jsonList
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, jsonList'
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, jsonMap
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, jsonMap'
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#if TEST
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, testSuite
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#endif
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)
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where
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import Text.Hamlet.Monad
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import Control.Applicative
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import Data.Text (pack)
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import qualified Data.Text as T
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import Data.Char (isControl)
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import Yesod.Hamlet
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import Control.Monad (when)
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import Yesod.Handler
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import Web.Routes.Quasi (Routes)
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import Numeric (showHex)
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#if TEST
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import Test.Framework (testGroup, Test)
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import Test.Framework.Providers.HUnit
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import Test.HUnit hiding (Test)
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import Data.Text.Lazy (unpack)
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import Yesod.Content hiding (testSuite)
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#else
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import Yesod.Content
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#endif
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-- | A monad for generating Json output. In truth, it is just a newtype wrapper
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-- around 'Hamlet'; we thereby get the benefits of Hamlet (interleaving IO and
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-- enumerator output) without accidently mixing non-JSON content.
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--
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-- This is an opaque type to avoid any possible insertion of non-JSON content.
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-- Due to the limited nature of the JSON format, you can create any valid JSON
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-- document you wish using only 'jsonScalar', 'jsonList' and 'jsonMap'.
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newtype Json url a = Json { unJson :: Hamlet url IO a }
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deriving (Functor, Applicative, Monad)
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-- | Extract the final result from the given 'Json' value.
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--
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-- See also: applyLayoutJson in "Yesod.Yesod".
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jsonToContent :: Json (Routes master) () -> GHandler sub master Content
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jsonToContent = hamletToContent . unJson
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-- | Wraps the 'Content' generated by 'jsonToContent' in a 'RepJson'.
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jsonToRepJson :: Json (Routes master) () -> GHandler sub master RepJson
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jsonToRepJson = fmap RepJson . jsonToContent
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-- | Outputs a single scalar. This function essentially:
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--
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-- * Performs HTML entity escaping as necesary.
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--
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-- * Performs JSON encoding.
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--
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-- * Wraps the resulting string in quotes.
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jsonScalar :: HtmlContent -> Json url ()
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jsonScalar s = Json $ do
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outputString "\""
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output $ encodeJson $ htmlContentToText s
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outputString "\""
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where
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encodeJson = T.concatMap (T.pack . encodeJsonChar)
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encodeJsonChar '\b' = "\\b"
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encodeJsonChar '\f' = "\\f"
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encodeJsonChar '\n' = "\\n"
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encodeJsonChar '\r' = "\\r"
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encodeJsonChar '\t' = "\\t"
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encodeJsonChar '"' = "\\\""
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encodeJsonChar '\\' = "\\\\"
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encodeJsonChar c
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| not $ isControl c = [c]
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| c < '\x10' = '\\' : 'u' : '0' : '0' : '0' : hexxs
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| c < '\x100' = '\\' : 'u' : '0' : '0' : hexxs
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| c < '\x1000' = '\\' : 'u' : '0' : hexxs
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where hexxs = showHex (fromEnum c) "" -- FIXME
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encodeJsonChar c = [c]
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-- | Outputs a JSON list, eg [\"foo\",\"bar\",\"baz\"].
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jsonList :: [Json url ()] -> Json url ()
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jsonList = jsonList' . fromList
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-- | Same as 'jsonList', but uses an 'Enumerator' for input.
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jsonList' :: Enumerator (Json url ()) (Json url) -> Json url ()
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jsonList' (Enumerator enum) = do
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Json $ outputString "["
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_ <- enum go False
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Json $ outputString "]"
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where
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go putComma j = do
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when putComma $ Json $ outputString ","
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() <- j
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return $ Right True
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-- | Outputs a JSON map, eg {\"foo\":\"bar\",\"baz\":\"bin\"}.
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jsonMap :: [(String, Json url ())] -> Json url ()
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jsonMap = jsonMap' . fromList
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-- | Same as 'jsonMap', but uses an 'Enumerator' for input.
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jsonMap' :: Enumerator (String, Json url ()) (Json url) -> Json url ()
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jsonMap' (Enumerator enum) = do
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Json $ outputString "{"
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_ <- enum go False
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Json $ outputString "}"
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where
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go putComma (k, v) = do
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when putComma $ Json $ outputString ","
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jsonScalar $ Unencoded $ pack k
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Json $ outputString ":"
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() <- v
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return $ Right True
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#if TEST
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testSuite :: Test
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testSuite = testGroup "Yesod.Json"
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[ testCase "simple output" caseSimpleOutput
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]
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caseSimpleOutput :: Assertion
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caseSimpleOutput = do
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let j = do
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jsonMap
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[ ("foo" , jsonList
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[ jsonScalar $ Encoded $ pack "bar"
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, jsonScalar $ Encoded $ pack "baz"
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])
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]
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t <- hamletToText id $ unJson j
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"{\"foo\":[\"bar\",\"baz\"]}" @=? unpack t
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#endif
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