{-# LANGUAGE OverloadedStrings #-}
module Yesod.Core.Class.Breadcrumbs where

import Yesod.Core.Handler
import Yesod.Routes.Class
import Data.Text (Text)

-- | A type-safe, concise method of creating breadcrumbs for pages. For each
-- resource, you declare the title of the page and the parent resource (if
-- present).
class YesodBreadcrumbs site where
    -- | Returns the title and the parent resource, if available. If you return
    -- a 'Nothing', then this is considered a top-level page.
    breadcrumb :: Route site -> HandlerFor site (Text , Maybe (Route site))

-- | Gets the title of the current page and the hierarchy of parent pages,
-- along with their respective titles.
breadcrumbs :: YesodBreadcrumbs site => HandlerFor site (Text, [(Route site, Text)])
breadcrumbs :: HandlerFor site (Text, [(Route site, Text)])
breadcrumbs = do
    Maybe (Route site)
x <- HandlerFor site (Maybe (Route site))
forall (m :: * -> *).
MonadHandler m =>
m (Maybe (Route (HandlerSite m)))
getCurrentRoute
    case Maybe (Route site)
x of
        Maybe (Route site)
Nothing -> (Text, [(Route site, Text)])
-> HandlerFor site (Text, [(Route site, Text)])
forall (m :: * -> *) a. Monad m => a -> m a
return (Text
"Not found", [])
        Just Route site
y -> do
            (Text
title, Maybe (Route site)
next) <- Route site -> HandlerFor site (Text, Maybe (Route site))
forall site.
YesodBreadcrumbs site =>
Route site -> HandlerFor site (Text, Maybe (Route site))
breadcrumb Route site
y
            [(Route site, Text)]
z <- [(Route site, Text)]
-> Maybe (Route site) -> HandlerFor site [(Route site, Text)]
forall site.
YesodBreadcrumbs site =>
[(Route site, Text)]
-> Maybe (Route site) -> HandlerFor site [(Route site, Text)]
go [] Maybe (Route site)
next
            (Text, [(Route site, Text)])
-> HandlerFor site (Text, [(Route site, Text)])
forall (m :: * -> *) a. Monad m => a -> m a
return (Text
title, [(Route site, Text)]
z)
  where
    go :: [(Route site, Text)]
-> Maybe (Route site) -> HandlerFor site [(Route site, Text)]
go [(Route site, Text)]
back Maybe (Route site)
Nothing = [(Route site, Text)] -> HandlerFor site [(Route site, Text)]
forall (m :: * -> *) a. Monad m => a -> m a
return [(Route site, Text)]
back
    go [(Route site, Text)]
back (Just Route site
this) = do
        (Text
title, Maybe (Route site)
next) <- Route site -> HandlerFor site (Text, Maybe (Route site))
forall site.
YesodBreadcrumbs site =>
Route site -> HandlerFor site (Text, Maybe (Route site))
breadcrumb Route site
this
        [(Route site, Text)]
-> Maybe (Route site) -> HandlerFor site [(Route site, Text)]
go ((Route site
this, Text
title) (Route site, Text) -> [(Route site, Text)] -> [(Route site, Text)]
forall a. a -> [a] -> [a]
: [(Route site, Text)]
back) Maybe (Route site)
next