browse-0.5.0.0: Browse.hs

{-|

This module provides simple utility functions useful to present web
content to the user via their default browser. Use `browse` in
order to simply show some markup (HTML) to the user, and use
`browseLinked` with an array of `Asset` in order to show a page
linking to multiple files, for example a page linking to a local style
file and a local Javascript file

-}
module Browse (
  browse,
  Asset(..),
  browseLinked,
  ) where

import Control.Exception
import Web.Browser (openBrowser)
import System.IO
import System.Directory (createDirectory)
import System.FilePath
import qualified Data.Text as T
import qualified Data.Text.IO as T

-- | Writes its argument to a file and opens the user's browser 
-- to show that file
browse content = do
  let path = "browse.html"
  writeContentToTempFile content path
  openBrowser path
  pure ()

writeContentToTempFile content fileName = do
  handle <- openFile fileName ReadWriteMode
  hPutStr handle content
  hFlush handle

-- | Use this to create resources that are linking to
-- each other, and you want to show to the user all together. For
-- example one resource could contain some HTML linking to another
-- resource containing Javascript or other. 
data Asset = Asset {
  location :: FilePath, -- ^ 'location' should contain a relative URL where the resource will be placed. For example this could be @"script.js"@ for a Javascript file
  content :: T.Text
}

writeAsset (Asset loc con) = T.writeFile loc con

-- | Present multiple files via the user's browser, so that they can
-- reference each other. A directory is created, the files
-- are written there, and the browser is opened on the first resource
-- passed as an argument to this function
browseLinked :: [Asset] -> IO ()
browseLinked resources = do
  let containing = "browse"
  try $ createDirectory containing :: IO (Either SomeException ())
  mapM_ writeAsset (combined containing)
  (openBrowser . location . head) (combined containing)
  pure ()
  where
    combined dir = map (applyLocation (combine dir)) resources
    applyLocation f (Asset a b) = Asset (f a) b