Haskell HTTP basics

haskell_http.hs

-- Basic HTTP stuff

module Parser where

import System.Environment   
import Data.List 

import Data.Maybe
import Network.HTTP
import Network.URI

buildRequest :: String -> Request [Char]
buildRequest url = Request {
                    rqURI     = uri
                  , rqMethod  = GET
                  , rqHeaders = []
                  , rqBody    = ""
                  }
  where
    uri = fromJust $ parseURI url

-- Make a simple HTTP request 
makeRequest :: Request [Char] -> IO (Either [Char] [Char])
makeRequest request = do
  resp <- simpleHTTP request
  case resp of
    Left err -> return $ Left ("Error: " ++ show err)
    Right r -> 
      case rspCode r of 
        (2,_,_) -> return $ Right (rspBody r)
        (3,_,_) -> 
          case findHeader HdrLocation r of 
            Nothing  -> return $ Left (show r)
            Just url -> do
                        let secondRequest = buildRequest url
                        makeRequest secondRequest
        (4,_,_) -> return $ Left ("Not found")

-- Make a simple get request with no headers 
-- Example : httpGet "http://www.owainlewis.com"
httpGet :: String -> IO (Either [Char] [Char])
httpGet url = makeRequest $ buildRequest url

-- Main method (just does http get on the first param)
-- runhaskell parser.hs http://www.owainlewis.com
main = do   
  (url:_) <- getArgs 
  httpGet url