{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE CPP #-}

module Text.Heterocephalus
  (
  -- * Core functions
    compileText
  , compileTextFile
  , compileHtml
  , compileHtmlFile

  -- * low-level
  , HeterocephalusSetting(escapeExp)
  , compile
  , compileFile
  , compileFromString
  ) where

import Data.Char (isDigit)
import qualified Data.Foldable as F
import Data.List (intercalate)
import Data.Text (Text, pack)
import qualified Data.Text.Lazy as TL
import Language.Haskell.TH.Quote
#if MIN_VERSION_template_haskell(2,9,0)
import Language.Haskell.TH.Syntax hiding (Module)
#else
import Language.Haskell.TH.Syntax
#endif
import Text.Blaze (preEscapedToMarkup)
import Text.Blaze.Html (toHtml)
import Text.Blaze.Internal (preEscapedText)
import Text.Hamlet
import Text.Hamlet.Parse
import Text.Shakespeare.Base

import Text.Heterocephalus.Parse (Doc(..), Content(..), parseDoc)

{- $setup
  >>> :set -XTemplateHaskell -XQuasiQuotes
  >>> import Text.Blaze.Renderer.String
-}

{-| Heterocephalus quasi-quoter.
  This function DOES NOT escape template variables.
  To render the compiled file, use @Text.Blaze.Renderer.*.renderMarkup@.

  >>> renderMarkup (let as = ["<a>", "b"] in [compileText|sample %{ forall a <- as }key: #{a}, %{ endforall }|])
  "sample key: <a>, key: b, "

  >>> renderMarkup (let num=2 in [compileText|#{num} is %{ if even num }even number.%{ else }odd number.%{ endif }|])
  "2 is even number."
 -}
compileText :: QuasiQuoter
compileText = compile textSetting

{-| Heterocephalus quasi-quoter for Html.
  Same as 'compileText' but this function do escape template variables for Html.

  >>> renderMarkup (let as = ["<a>", "b"] in [compileHtml|sample %{ forall a <- as }key: #{a}, %{ endforall }|])
  "sample key: &lt;a&gt;, key: b, "
 -}
compileHtml :: QuasiQuoter
compileHtml = compile htmlSetting

{-| Heterocephalus quasi-quoter.
  Same as 'compileText' but this function read template literal from an external file.

  >>> putStr $ renderMarkup (let as = ["<a>", "b"] in $(compileTextFile "templates/sample.txt"))
  sample
  key: <a>,
  key: b,
 -}
compileTextFile :: FilePath -> Q Exp
compileTextFile = compileFile textSetting

{-| Heterocephalus quasi-quoter.
  Same as 'compileTextFile' but escapes template variables for Html.

  >>> putStr $ renderMarkup (let as = ["<a>", "b"] in $(compileHtmlFile "templates/sample.txt"))
  sample
  key: &lt;a&gt;,
  key: b,
 -}
compileHtmlFile :: FilePath -> Q Exp
compileHtmlFile = compileFile htmlSetting

compile :: HeterocephalusSetting -> QuasiQuoter
compile set =
  QuasiQuoter
  { quoteExp = compileFromString set
  , quotePat = error "not used"
  , quoteType = error "not used"
  , quoteDec = error "not used"
  }

{-| Compile a template file.
-}
compileFile :: HeterocephalusSetting -> FilePath -> Q Exp
compileFile set fp = do
#ifdef GHC_7_4
  qAddDependentFile fp
#endif
  contents <- fmap TL.unpack $ qRunIO $ readUtf8File fp
  compileFromString set contents

compileFromString :: HeterocephalusSetting -> String -> Q Exp
compileFromString set s =
  docsToExp set [] $ docFromString s

docFromString :: String -> [Doc]
docFromString s =
  case parseDoc s of
    Error s' -> error s'
    Ok d -> d

data HeterocephalusSetting = HeterocephalusSetting
  { escapeExp :: Q Exp
  }

{-| A setting that escapes template variables for Html
 -}
htmlSetting :: HeterocephalusSetting
htmlSetting = HeterocephalusSetting
  { escapeExp = [|toHtml|]
  }

{-| A setting that DOES NOT escape template variables
 -}
textSetting :: HeterocephalusSetting
textSetting = HeterocephalusSetting
  { escapeExp = [|preEscapedToMarkup|]
  }

-- ==============================================
--  Helper functions
-- ==============================================

docsToExp :: HeterocephalusSetting -> Scope -> [Doc] -> Q Exp
docsToExp set scope docs = do
  exps <- mapM (docToExp set scope) docs
  case exps of
    [] -> [|return ()|]
    [x] -> return x
    _ -> return $ DoE $ map NoBindS exps

-- TODO What's scope?
docToExp :: HeterocephalusSetting -> Scope -> Doc -> Q Exp
docToExp set scope (DocForall list idents inside) = do
  let list' = derefToExp scope list
  (pat, extraScope) <- bindingPattern idents
  let scope' = extraScope ++ scope
  mh <- [|F.mapM_|]
  inside' <- docsToExp set scope' inside
  let lam = LamE [pat] inside'
  return $ mh `AppE` lam `AppE` list'
docToExp set scope (DocCond conds final) = do
  conds' <- mapM go conds
  final' <-
    case final of
      Nothing -> [|Nothing|]
      Just f -> do
        f' <- docsToExp set scope f
        j <- [|Just|]
        return $ j `AppE` f'
  ch <- [|condH|]
  return $ ch `AppE` ListE conds' `AppE` final'
  where
    go :: (Deref, [Doc]) -> Q Exp
    go (d, docs) = do
      let d' = derefToExp ((specialOrIdent, VarE 'or) : scope) d
      docs' <- docsToExp set scope docs
      return $ TupE [d', docs']
docToExp set v (DocContent c) = contentToExp set v c

contentToExp :: HeterocephalusSetting -> Scope -> Content -> Q Exp
contentToExp _ _ (ContentRaw s) = do
  os <- [|preEscapedText . pack|]
  let s' = LitE $ StringL s
  return $ os `AppE` s'
contentToExp set scope (ContentVar d) = do
  str <- escapeExp set
  return $ str `AppE` derefToExp scope d

-- ==============================================
-- Codes from Text.Hamlet that is not exposed
-- ==============================================

unIdent :: Ident -> String
unIdent (Ident s) = s

bindingPattern :: Binding -> Q (Pat, [(Ident, Exp)])
bindingPattern (BindAs i@(Ident s) b) = do
  name <- newName s
  (pattern, scope) <- bindingPattern b
  return (AsP name pattern, (i, VarE name) : scope)
bindingPattern (BindVar i@(Ident s))
  | s == "_" = return (WildP, [])
  | all isDigit s = do return (LitP $ IntegerL $ read s, [])
  | otherwise = do
    name <- newName s
    return (VarP name, [(i, VarE name)])
bindingPattern (BindTuple is) = do
  (patterns, scopes) <- fmap unzip $ mapM bindingPattern is
  return (TupP patterns, concat scopes)
bindingPattern (BindList is) = do
  (patterns, scopes) <- fmap unzip $ mapM bindingPattern is
  return (ListP patterns, concat scopes)
bindingPattern (BindConstr con is) = do
  (patterns, scopes) <- fmap unzip $ mapM bindingPattern is
  return (ConP (mkConName con) patterns, concat scopes)
bindingPattern (BindRecord con fields wild) = do
  let f (Ident field, b) = do
        (p, s) <- bindingPattern b
        return ((mkName field, p), s)
  (patterns, scopes) <- fmap unzip $ mapM f fields
  (patterns1, scopes1) <-
    if wild
      then bindWildFields con $ map fst fields
      else return ([], [])
  return
    (RecP (mkConName con) (patterns ++ patterns1), concat scopes ++ scopes1)

mkConName :: DataConstr -> Name
mkConName = mkName . conToStr

conToStr :: DataConstr -> String
conToStr (DCUnqualified (Ident x)) = x
conToStr (DCQualified (Module xs) (Ident x)) = intercalate "." $ xs ++ [x]

-- Wildcards bind all of the unbound fields to variables whose name
-- matches the field name.
--
-- For example: data R = C { f1, f2 :: Int }
-- C {..}           is equivalent to   C {f1=f1, f2=f2}
-- C {f1 = a, ..}   is equivalent to   C {f1=a,  f2=f2}
-- C {f2 = a, ..}   is equivalent to   C {f1=f1, f2=a}
bindWildFields :: DataConstr -> [Ident] -> Q ([(Name, Pat)], [(Ident, Exp)])
bindWildFields conName fields = do
  fieldNames <- recordToFieldNames conName
  let available n = nameBase n `notElem` map unIdent fields
  let remainingFields = filter available fieldNames
  let mkPat n = do
        e <- newName (nameBase n)
        return ((n, VarP e), (Ident (nameBase n), VarE e))
  fmap unzip $ mapM mkPat remainingFields

-- Important note! reify will fail if the record type is defined in the
-- same module as the reify is used. This means quasi-quoted Hamlet
-- literals will not be able to use wildcards to match record types
-- defined in the same module.
recordToFieldNames :: DataConstr -> Q [Name]
recordToFieldNames conStr
  -- use 'lookupValueName' instead of just using 'mkName' so we reify the
  -- data constructor and not the type constructor if their names match.
 = do
  Just conName <- lookupValueName $ conToStr conStr
#if MIN_VERSION_template_haskell(2,11,0)
  DataConI _ _ typeName         <- reify conName
  TyConI (DataD _ _ _ _ cons _) <- reify typeName
#else
  DataConI _ _ typeName _     <- reify conName
  TyConI (DataD _ _ _ cons _) <- reify typeName
#endif
  [fields] <- return [fields | RecC name fields <- cons, name == conName]
  return [fieldName | (fieldName, _, _) <- fields]

type QueryParameters = [(Text, Text)]

data VarExp msg url
  = EPlain Html
  | EUrl url
  | EUrlParam (url, QueryParameters)
  | EMixin (HtmlUrl url)
  | EMixinI18n (HtmlUrlI18n msg url)
  | EMsg msg

instance Show (VarExp msg url) where
  show (EPlain _) = "EPlain"
  show (EUrl _) = "EUrl"
  show (EUrlParam _) = "EUrlParam"
  show (EMixin _) = "EMixin"
  show (EMixinI18n _) = "EMixinI18n"
  show (EMsg _) = "EMsg"