    --------------------------------------------------------------------------------
    -- | This module exposes a function which can relativize URL's on a webpage.
    --
    -- This means that one can deploy the resulting site on
    -- @http:\/\/example.com\/@, but also on @http:\/\/example.com\/some-folder\/@
    -- without having to change anything (simply copy over the files).
    --
    -- To use it, you should use absolute URL's from the site root everywhere. For
    -- example, use
    --
    -- > <img src="/images/lolcat.png" alt="Funny zomgroflcopter" />
    --
    -- in a blogpost. When running this through the relativize URL's module, this
    -- will result in (suppose your blogpost is located at @\/posts\/foo.html@:
    --
    -- > <img src="../images/lolcat.png" alt="Funny zomgroflcopter" />
    module Hakyll.Web.Html.RelativizeUrls
        ( relativizeUrls
        , relativizeUrlsWith
        ) where

    --------------------------------------------------------------------------------
    import           Data.List            (isPrefixOf)

    --------------------------------------------------------------------------------
    import           Hakyll.Core.Compiler
    import           Hakyll.Core.Item
    import           Hakyll.Web.Html

    --------------------------------------------------------------------------------
    -- | Compiler form of 'relativizeUrls' which automatically picks the right root
    -- path
    relativizeUrls :: Item String -> Compiler (Item String)
    relativizeUrls item = do
        route <- getRoute $ itemIdentifier item
        return $ case route of
            Nothing -> item
            Just r  -> fmap (relativizeUrlsWith $ toSiteRoot r) item

    --------------------------------------------------------------------------------
    -- | Relativize URL's in HTML
    relativizeUrlsWith :: String  -- ^ Path to the site root
                       -> String  -- ^ HTML to relativize
                       -> String  -- ^ Resulting HTML
    relativizeUrlsWith root = withUrls rel
      where
        isRel x = "/" `isPrefixOf` x && not ("//" `isPrefixOf` x)
        rel x   = if isRel x then root ++ x else x