taggy-lens

Lenses for the taggy html/xml parser.

Lenses, folds, traversals and prisms for taggy.

This greatly simplifies your life when dealing with the ugly world of Real Life HTML. Here's an example. It lists the date, author and package name of all the recent package uploads entries from the hackage page of the same name. Note that it uses wreq to fetch the Hackage page.

module Main (main) where

import Control.Lens (to, only,(^?),ix, toListOf)
import Data.ByteString.Lazy (ByteString)
import Data.Text (Text)
import Data.Text.Encoding.Error (lenientDecode)
import Data.Text.Lazy.Encoding (decodeUtf8With)
import Network.HTTP.Client (Response)
import Network.Wreq (responseBody, get)
import Text.Taggy (Node)
import Text.Taggy.Lens (html, elements, children, contents,allNamed)

data Upload =
  Upload Text -- ^ date
         Text -- ^ author
         Text -- ^ package name
  deriving (Show)

table :: [Node] -> Maybe Upload
table row = do
  date    <- row ^? ix 0 . contents
  author  <- row ^? ix 1 . contents
  package <- row ^? ix 2 . elements . contents
  return $ Upload date author package

recentPackages :: Response ByteString -> [Maybe Upload]
recentPackages = toListOf
               $ responseBody . to (decodeUtf8With lenientDecode)
               . html . allNamed (only "tr") . children . to table

main :: IO ()
main = get "https://hackage.haskell.org/packages/recent" >>= print `fmap` recentPackages

Report any problem on our issues page on github.