{-# LANGUAGE TypeOperators #-}
{- |
@web-routes-boomerang@ makes it easy to use write custom
pretty-printers and parsers for your URL types. Instead of writing a
parser and a separate pretty-printer you can specify both at once by
using the @boomerang@ library:

<http://hackage.haskell.org/package/boomerang>

This demo will show the basics of getting started.

First we need to enable some language extensions:

@{\-\# LANGUAGE TemplateHaskell, TypeOperators, OverloadedStrings \#-\} @

> {-# LANGUAGE TemplateHaskell, TypeOperators, OverloadedStrings #-}
> module Main where

Note in the imports that we hide @(id, (.))@ from the "Prelude" and
use the versions from "Control.Category" instead.

> import Prelude              hiding (id, (.))
> import Control.Category     (Category(id, (.)))
> import Control.Monad.Trans  (MonadIO(liftIO))
> import Text.Boomerang.TH    (makeBoomerangs)
> import Web.Routes           (Site(..), RouteT(..), decodePathInfo, encodePathInfo, runSite, showURL)
> import Web.Routes.Boomerang (Router, (<>), (</>), int, parse1, boomerangSiteRouteT, anyString, parseStrings)

Next we define a data type that represents our sitemap.

> -- | the routes
> data Sitemap
>    = Home
>    | UserOverview
>    | UserDetail Int
>    | Article Int String
>    deriving (Eq, Show)


To use the 'Sitemap' type with @boomerang@ we need to call 'makeBoomerangs':

> $(makeBoomerangs ''Sitemap)

That will create new combinators corresponding to the constructors for
'Sitemap'. They will be named, @rHome@, @rUserOverview@, etc.

Now we can specify how the 'Sitemap' type is mapped to a url and back:

> sitemap :: Router Sitemap
> sitemap =
>     (  rHome
>     <> "users" . users
>     <> rArticle . ("article" </> int . "-" . anyString)
>     )
>   where
>     users  =  rUserOverview
>            <> rUserDetail </> int

The mapping looks like this:

@
 \/                       \<=\> Home
 \/users                  \<=\> UserOverview
 \/users\//<int>/            \<=\> UserDetail /<int>/
 \/article\//<int>/-/<string>/ \<=\> Article /<int>/ /<string>/
@

Next we have our function which maps a parsed route to the handler for
that route. (There is nothing @boomerang@ specific about this
function):

> handle :: Sitemap -> RouteT Sitemap IO ()
> handle url =
>     case url of
>       _ -> do liftIO $ print url
>               s <- showURL url
>               liftIO $ putStrLn s

Normally the @case@ statement would match on the different constructors and map them to different handlers. But in this case we use the same handler for all constructors. Also, instead of running in the IO monad, we would typically use a web framework monad like Happstack's 'ServerPartT'.

The handler does two things:

 1. prints the parsed url

 2. unparses the url and prints it

We now have two pieces:

 1. 'sitemap' - which converts urls to the 'Sitemap' type and back

 2. 'handle' - which maps 'Sitemap' to handlers

We tie these two pieces together use 'boomerangSiteRouteT':

> site :: Site Sitemap (IO ())
> site = boomerangSiteRouteT handle sitemap

This gives as a standard 'Site' value that we can use with 'runSite'
or with framework specific wrappers like @implSite@.

If we were not using 'RouteT' then we could use @boomerangSite@ instead.

Now we can create a simple test function that takes the path info part
of a url and runs our site:

> test :: ByteString -- ^ path info of incoming url
>      -> IO ()
> test path =
>     case runSite "" site (decodePathInfo path) of
>       (Left e)   -> putStrLn e
>       (Right io) -> io

We can use it like this:

@
ghci> test "users/1"
UserDetail 1
users/1
@

Here is a simple wrapper to call test interactively:

> -- | interactively call 'test'
> main :: IO ()
> main = mapM_ test =<< fmap lines getContents

Here are two more helper functions you can use to experiment interactively:

> -- | a little function to test rendering a url
> showurl :: Sitemap -> String
> showurl url =
>     let (ps, params) = formatPathSegments site url
>     in (encodePathInfo ps params)

> -- | a little function to test parsing a url
> testParse :: String -> Either String Sitemap
> testParse pathInfo =
>     case parsePathSegments site $ decodePathInfo pathInfo of
>       (Left e)  -> Left (show e)
>       (Right a) -> Right a

-}
module Web.Routes.Boomerang
    ( module Text.Boomerang
    , module Text.Boomerang.Texts
    , Router
    , boomerangSite
    , boomerangSiteRouteT
    , boomerangFromPathSegments
    , boomerangToPathSegments
    ) where

import Data.Function          (on)
import Data.List              (maximumBy)
import Data.Text              (Text, pack, unpack)
import qualified Data.Text    as T
import Text.Boomerang
import Text.Boomerang.Texts
import Text.ParserCombinators.Parsec.Prim (State(..), getParserState, setParserState)
import Text.Parsec.Pos        (sourceLine, sourceColumn, setSourceColumn, setSourceLine)
import Web.Routes             (RouteT(..), Site(..), PathInfo(..), URLParser)

-- | 'Router a b' is a simple type alias for 'Boomerang TextsError [Text] a b'
type Router a b = Boomerang TextsError [Text] a b

-- | function which creates a 'Site' from a 'Router' and a handler
boomerangSite :: ((url -> [(Text, Maybe Text)] -> Text) -> url -> a) -- ^ handler function
       -> Router () (url :- ()) -- ^ the router
       -> Site url a
boomerangSite :: forall url a.
((url -> [(Text, Maybe Text)] -> Text) -> url -> a)
-> Router () (url :- ()) -> Site url a
boomerangSite (url -> [(Text, Maybe Text)] -> Text) -> url -> a
handler r :: Router () (url :- ())
r@(Boomerang Parser TextsError [Text] (() -> url :- ())
pf (url :- ()) -> [([Text] -> [Text], ())]
sf) =
    Site { handleSite :: (url -> [(Text, Maybe Text)] -> Text) -> url -> a
handleSite = (url -> [(Text, Maybe Text)] -> Text) -> url -> a
handler
         , formatPathSegments :: url -> ([Text], [(Text, Maybe Text)])
formatPathSegments =  \url
url ->
             case forall e r. Boomerang e [Text] () (r :- ()) -> r -> Maybe [Text]
unparseTexts Router () (url :- ())
r url
url of
               Maybe [Text]
Nothing -> forall a. HasCallStack => [Char] -> a
error [Char]
"formatPathSegments failed to produce a url"
               (Just [Text]
ps) -> ([Text]
ps, [])
         , parsePathSegments :: [Text] -> Either [Char] url
parsePathSegments = \[Text]
paths -> forall {a} {b} {b}. (a -> b) -> Either a b -> Either b b
mapLeft (forall {a}. Show a => a -> TextsError -> [Char]
showErrors [Text]
paths) (forall r.
Boomerang TextsError [Text] () (r :- ())
-> [Text] -> Either TextsError r
parseTexts Router () (url :- ())
r [Text]
paths)
         }
    where
      mapLeft :: (a -> b) -> Either a b -> Either b b
mapLeft a -> b
f       = forall a c b. (a -> c) -> (b -> c) -> Either a b -> c
either (forall a b. a -> Either a b
Left forall b c a. (b -> c) -> (a -> b) -> a -> c
. a -> b
f) forall a b. b -> Either a b
Right
      showErrors :: a -> TextsError -> [Char]
showErrors a
paths TextsError
err = (forall pos. (pos -> [Char]) -> ParserError pos -> [Char]
showParserError MajorMinorPos -> [Char]
showPos TextsError
err) forall a. [a] -> [a] -> [a]
++ [Char]
" while parsing " forall a. [a] -> [a] -> [a]
++ forall a. Show a => a -> [Char]
show a
paths
      showPos :: MajorMinorPos -> [Char]
showPos (MajorMinorPos Integer
s Integer
c) = [Char]
"path segment " forall a. [a] -> [a] -> [a]
++ forall a. Show a => a -> [Char]
show (Integer
s forall a. Num a => a -> a -> a
+ Integer
1) forall a. [a] -> [a] -> [a]
++ [Char]
", character " forall a. [a] -> [a] -> [a]
++ forall a. Show a => a -> [Char]
show Integer
c

-- | function which creates a 'Site' from a 'Router' and a 'RouteT' handler
boomerangSiteRouteT :: (url -> RouteT url m a) -- ^ handler function
       -> Router () (url :- ()) -- ^ the router
       -> Site url (m a)
boomerangSiteRouteT :: forall url (m :: * -> *) a.
(url -> RouteT url m a) -> Router () (url :- ()) -> Site url (m a)
boomerangSiteRouteT url -> RouteT url m a
handler Router () (url :- ())
router = forall url a.
((url -> [(Text, Maybe Text)] -> Text) -> url -> a)
-> Router () (url :- ()) -> Site url a
boomerangSite (forall a b c. (a -> b -> c) -> b -> a -> c
flip forall a b. (a -> b) -> a -> b
$ forall url (m :: * -> *) a.
RouteT url m a -> (url -> [(Text, Maybe Text)] -> Text) -> m a
unRouteT forall b c a. (b -> c) -> (a -> b) -> a -> c
. url -> RouteT url m a
handler) Router () (url :- ())
router

-- | convert to a 'URLParser' so we can create a 'PathInfo' instance
boomerangFromPathSegments :: Boomerang TextsError [Text] () (url :- ()) -> URLParser url
boomerangFromPathSegments :: forall url.
Boomerang TextsError [Text] () (url :- ()) -> URLParser url
boomerangFromPathSegments (Boomerang Parser TextsError [Text] (() -> url :- ())
prs (url :- ()) -> [([Text] -> [Text], ())]
_) =
    do State [Text] ()
st <- forall (m :: * -> *) s u. Monad m => ParsecT s u m (State s u)
getParserState
       let results :: [Either TextsError ((() -> url :- (), [Text]), Pos TextsError)]
results = forall e tok a.
Parser e tok a -> tok -> Pos e -> [Either e ((a, tok), Pos e)]
runParser Parser TextsError [Text] (() -> url :- ())
prs (forall s u. State s u -> s
stateInput State [Text] ()
st) (Integer -> Integer -> MajorMinorPos
MajorMinorPos (forall a b. (Integral a, Num b) => a -> b
fromIntegral forall a b. (a -> b) -> a -> b
$ SourcePos -> Line
sourceLine (forall s u. State s u -> SourcePos
statePos State [Text] ()
st)) (forall a b. (Integral a, Num b) => a -> b
fromIntegral forall a b. (a -> b) -> a -> b
$ SourcePos -> Line
sourceColumn (forall s u. State s u -> SourcePos
statePos State [Text] ()
st)))
           successes :: [((url :- (), [Text]), MajorMinorPos)]
successes = [ ((() -> url :- ()
f (), [Text]
tok), MajorMinorPos
pos) | (Right ((() -> url :- ()
f, [Text]
tok), MajorMinorPos
pos)) <- [Either TextsError ((() -> url :- (), [Text]), MajorMinorPos)]
results]
       case [((url :- (), [Text]), MajorMinorPos)]
successes of
         [] -> forall (m :: * -> *) a. MonadFail m => [Char] -> m a
fail (forall pos. (pos -> [Char]) -> ParserError pos -> [Char]
showParserError (forall a b. a -> b -> a
const [Char]
"") forall a b. (a -> b) -> a -> b
$ forall a. [a] -> a
head forall a b. (a -> b) -> a -> b
$ forall e. (ErrorPosition e, Ord (Pos e)) => [e] -> [e]
bestErrors  [TextsError
e | Left TextsError
e <- [Either TextsError ((() -> url :- (), [Text]), MajorMinorPos)]
results])
         [((url :- (), [Text]), MajorMinorPos)]
_ -> case (forall (t :: * -> *) a.
Foldable t =>
(a -> a -> Ordering) -> t a -> a
maximumBy (forall a. Ord a => a -> a -> Ordering
compare forall b c a. (b -> b -> c) -> (a -> b) -> a -> a -> c
`on` forall a b. (a, b) -> b
snd) [((url :- (), [Text]), MajorMinorPos)]
successes) of
                (((url
u :- ()), [Text]
tok), MajorMinorPos
pos) ->
                    do let st' :: State [Text] ()
st' = State [Text] ()
st { statePos :: SourcePos
statePos   = SourcePos -> Line -> SourcePos
setSourceColumn (SourcePos -> Line -> SourcePos
setSourceLine (forall s u. State s u -> SourcePos
statePos State [Text] ()
st) (forall a b. (Integral a, Num b) => a -> b
fromIntegral forall a b. (a -> b) -> a -> b
$ MajorMinorPos -> Integer
major MajorMinorPos
pos)) (forall a b. (Integral a, Num b) => a -> b
fromIntegral forall a b. (a -> b) -> a -> b
$ MajorMinorPos -> Integer
minor MajorMinorPos
pos)
                                    , stateInput :: [Text]
stateInput = [Text] -> [Text]
trim [Text]
tok
                                    }
                       forall (m :: * -> *) s u.
Monad m =>
State s u -> ParsecT s u m (State s u)
setParserState State [Text] ()
st'
                       forall (m :: * -> *) a. Monad m => a -> m a
return url
u
    where
      trim :: [Text] -> [Text]
trim []     = []
      trim (Text
t:[Text]
ts) = if Text -> Bool
T.null Text
t then [Text]
ts else (Text
tforall a. a -> [a] -> [a]
:[Text]
ts)

-- | convert to the type expected by 'toPathSegments' from 'PathInfo'
boomerangToPathSegments :: Boomerang TextsError [Text] () (url :- ()) -> (url -> [Text])
boomerangToPathSegments :: forall url.
Boomerang TextsError [Text] () (url :- ()) -> url -> [Text]
boomerangToPathSegments Boomerang TextsError [Text] () (url :- ())
pp =
    \url
url -> case forall tok e a.
tok -> Boomerang e tok () (a :- ()) -> a -> Maybe tok
unparse1 [] Boomerang TextsError [Text] () (url :- ())
pp url
url of
              Maybe [Text]
Nothing -> forall a. HasCallStack => [Char] -> a
error forall a b. (a -> b) -> a -> b
$ [Char]
"boomerangToPathSegments: could not convert url to [Text]"
              (Just [Text]
txts) -> [Text]
txts