110 lines
3.3 KiB
Haskell
110 lines
3.3 KiB
Haskell
{- Url downloading.
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-
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- Copyright 2011 Joey Hess <joey@kitenet.net>
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-
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- Licensed under the GNU GPL version 3 or higher.
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-}
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module Utility.Url (
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URLString,
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check,
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exists,
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canDownload,
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download,
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get
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) where
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import Common
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import qualified Network.Browser as Browser
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import Network.HTTP
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import Network.URI
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type URLString = String
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{- Checks that an url exists and could be successfully downloaded,
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- also checking that its size, if available, matches a specified size. -}
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check :: URLString -> Maybe Integer -> IO Bool
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check url expected_size = handle <$> exists url
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where
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handle (False, _) = False
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handle (True, Nothing) = True
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handle (True, s) = expected_size == s
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{- Checks that an url exists and could be successfully downloaded,
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- also returning its size if available. -}
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exists :: URLString -> IO (Bool, Maybe Integer)
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exists url =
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case parseURI url of
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Nothing -> return (False, Nothing)
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Just u -> do
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r <- request u HEAD
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case rspCode r of
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(2,_,_) -> return (True, size r)
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_ -> return (False, Nothing)
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where
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size = liftM Prelude.read . lookupHeader HdrContentLength . rspHeaders
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canDownload :: IO Bool
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canDownload = (||) <$> inPath "wget" <*> inPath "curl"
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{- Used to download large files, such as the contents of keys.
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-
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- Uses wget or curl program for its progress bar. (Wget has a better one,
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- so is preferred.) Which program to use is determined at run time; it
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- would not be appropriate to test at configure time and build support
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- for only one in.
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-}
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download :: URLString -> [CommandParam] -> FilePath -> IO Bool
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download url options file = ifM (inPath "wget") (wget , curl)
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where
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wget = go "wget" [Params "-c -O"]
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{- Uses the -# progress display, because the normal
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- one is very confusing when resuming, showing
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- the remainder to download as the whole file,
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- and not indicating how much percent was
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- downloaded before the resume. -}
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curl = go "curl" [Params "-L -C - -# -o"]
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go cmd opts = boolSystem cmd $
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options++opts++[File file, File url]
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{- Downloads a small file. -}
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get :: URLString -> IO String
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get url =
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case parseURI url of
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Nothing -> error "url parse error"
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Just u -> do
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r <- request u GET
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case rspCode r of
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(2,_,_) -> return $ rspBody r
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_ -> error $ rspReason r
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{- Makes a http request of an url. For example, HEAD can be used to
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- check if the url exists, or GET used to get the url content (best for
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- small urls).
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-
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- This does its own redirect following because Browser's is buggy for HEAD
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- requests.
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-}
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request :: URI -> RequestMethod -> IO (Response String)
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request url requesttype = go 5 url
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where
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go :: Int -> URI -> IO (Response String)
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go 0 _ = error "Too many redirects "
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go n u = do
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rsp <- Browser.browse $ do
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Browser.setErrHandler ignore
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Browser.setOutHandler ignore
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Browser.setAllowRedirects False
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snd <$> Browser.request (mkRequest requesttype u :: Request_String)
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case rspCode rsp of
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(3,0,x) | x /= 5 -> redir (n - 1) u rsp
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_ -> return rsp
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ignore = const $ return ()
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redir n u rsp = case retrieveHeaders HdrLocation rsp of
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[] -> return rsp
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(Header _ newu:_) ->
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case parseURIReference newu of
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Nothing -> return rsp
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Just newURI -> go n newURI_abs
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where
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newURI_abs = fromMaybe newURI (newURI `relativeTo` u)
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