-- | Abstracting over HTTP libraries
module Hackage.Security.Client.Repository.HttpLib (
    HttpLib(..)
  , HttpRequestHeader(..)
  , HttpResponseHeader(..)
  , HttpStatus(..)
  , ProxyConfig(..)
    -- ** Body reader
  , BodyReader
  , bodyReaderFromBS
  ) where

import Prelude
import Data.IORef
import Network.URI hiding (uriPath, path)
import qualified Data.ByteString      as BS
import qualified Data.ByteString.Lazy as BS.L

import Hackage.Security.Util.Checked
import Hackage.Security.Client.Repository (SomeRemoteError)

{-------------------------------------------------------------------------------
  Abstraction over HTTP clients (such as HTTP, http-conduit, etc.)
-------------------------------------------------------------------------------}

-- | Abstraction over HTTP clients
--
-- This avoids insisting on a particular implementation (such as the HTTP
-- package) and allows for other implementations (such as a conduit based one).
--
-- NOTE: Library-specific exceptions MUST be wrapped in 'SomeRemoteError'.
data HttpLib = HttpLib {
    -- | Download a file
    HttpLib
-> forall a.
   Throws SomeRemoteError =>
   [HttpRequestHeader]
   -> URI -> ([HttpResponseHeader] -> BodyReader -> IO a) -> IO a
httpGet :: forall a. Throws SomeRemoteError
            => [HttpRequestHeader]
            -> URI
            -> ([HttpResponseHeader] -> BodyReader -> IO a)
            -> IO a

    -- | Download a byte range
    --
    -- Range is starting and (exclusive) end offset in bytes.
    --
    -- HTTP servers are normally expected to respond to a range request with
    -- a "206 Partial Content" response. However, servers can respond with a
    -- "200 OK" response, sending the entire file instead (for instance, this
    -- may happen for servers that don't actually support range requests, but
    -- for which we optimistically assumed they did). Implementations of
    -- 'HttpLib' may accept such a response and inform the @hackage-security@
    -- library that the whole file is being returned; the security library can
    -- then decide to execute the 'BodyReader' anyway (downloading the entire
    -- file) or abort the request and try something else. For this reason
    -- the security library must be informed whether the server returned the
    -- full file or the requested range.
  , HttpLib
-> forall a.
   Throws SomeRemoteError =>
   [HttpRequestHeader]
   -> URI
   -> (Int, Int)
   -> (HttpStatus -> [HttpResponseHeader] -> BodyReader -> IO a)
   -> IO a
httpGetRange :: forall a. Throws SomeRemoteError
                 => [HttpRequestHeader]
                 -> URI
                 -> (Int, Int)
                 -> (HttpStatus -> [HttpResponseHeader] -> BodyReader -> IO a)
                 -> IO a
  }

-- | Additional request headers
--
-- Since different libraries represent headers differently, here we just
-- abstract over the few request headers that we might want to set
data HttpRequestHeader =
    -- | Set @Cache-Control: max-age=0@
    HttpRequestMaxAge0

    -- | Set @Cache-Control: no-transform@
  | HttpRequestNoTransform
  deriving (HttpRequestHeader -> HttpRequestHeader -> Bool
(HttpRequestHeader -> HttpRequestHeader -> Bool)
-> (HttpRequestHeader -> HttpRequestHeader -> Bool)
-> Eq HttpRequestHeader
forall a. (a -> a -> Bool) -> (a -> a -> Bool) -> Eq a
$c== :: HttpRequestHeader -> HttpRequestHeader -> Bool
== :: HttpRequestHeader -> HttpRequestHeader -> Bool
$c/= :: HttpRequestHeader -> HttpRequestHeader -> Bool
/= :: HttpRequestHeader -> HttpRequestHeader -> Bool
Eq, Eq HttpRequestHeader
Eq HttpRequestHeader =>
(HttpRequestHeader -> HttpRequestHeader -> Ordering)
-> (HttpRequestHeader -> HttpRequestHeader -> Bool)
-> (HttpRequestHeader -> HttpRequestHeader -> Bool)
-> (HttpRequestHeader -> HttpRequestHeader -> Bool)
-> (HttpRequestHeader -> HttpRequestHeader -> Bool)
-> (HttpRequestHeader -> HttpRequestHeader -> HttpRequestHeader)
-> (HttpRequestHeader -> HttpRequestHeader -> HttpRequestHeader)
-> Ord HttpRequestHeader
HttpRequestHeader -> HttpRequestHeader -> Bool
HttpRequestHeader -> HttpRequestHeader -> Ordering
HttpRequestHeader -> HttpRequestHeader -> HttpRequestHeader
forall a.
Eq a =>
(a -> a -> Ordering)
-> (a -> a -> Bool)
-> (a -> a -> Bool)
-> (a -> a -> Bool)
-> (a -> a -> Bool)
-> (a -> a -> a)
-> (a -> a -> a)
-> Ord a
$ccompare :: HttpRequestHeader -> HttpRequestHeader -> Ordering
compare :: HttpRequestHeader -> HttpRequestHeader -> Ordering
$c< :: HttpRequestHeader -> HttpRequestHeader -> Bool
< :: HttpRequestHeader -> HttpRequestHeader -> Bool
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>= :: HttpRequestHeader -> HttpRequestHeader -> Bool
$cmax :: HttpRequestHeader -> HttpRequestHeader -> HttpRequestHeader
max :: HttpRequestHeader -> HttpRequestHeader -> HttpRequestHeader
$cmin :: HttpRequestHeader -> HttpRequestHeader -> HttpRequestHeader
min :: HttpRequestHeader -> HttpRequestHeader -> HttpRequestHeader
Ord, Int -> HttpRequestHeader -> ShowS
[HttpRequestHeader] -> ShowS
HttpRequestHeader -> String
(Int -> HttpRequestHeader -> ShowS)
-> (HttpRequestHeader -> String)
-> ([HttpRequestHeader] -> ShowS)
-> Show HttpRequestHeader
forall a.
(Int -> a -> ShowS) -> (a -> String) -> ([a] -> ShowS) -> Show a
$cshowsPrec :: Int -> HttpRequestHeader -> ShowS
showsPrec :: Int -> HttpRequestHeader -> ShowS
$cshow :: HttpRequestHeader -> String
show :: HttpRequestHeader -> String
$cshowList :: [HttpRequestHeader] -> ShowS
showList :: [HttpRequestHeader] -> ShowS
Show)

-- | HTTP status code
data HttpStatus =
     -- | 200 OK
     HttpStatus200OK

     -- | 206 Partial Content
   | HttpStatus206PartialContent

-- | Response headers
--
-- Since different libraries represent headers differently, here we just
-- abstract over the few response headers that we might want to know about.
data HttpResponseHeader =
    -- | Server accepts byte-range requests (@Accept-Ranges: bytes@)
    HttpResponseAcceptRangesBytes
  deriving (HttpResponseHeader -> HttpResponseHeader -> Bool
(HttpResponseHeader -> HttpResponseHeader -> Bool)
-> (HttpResponseHeader -> HttpResponseHeader -> Bool)
-> Eq HttpResponseHeader
forall a. (a -> a -> Bool) -> (a -> a -> Bool) -> Eq a
$c== :: HttpResponseHeader -> HttpResponseHeader -> Bool
== :: HttpResponseHeader -> HttpResponseHeader -> Bool
$c/= :: HttpResponseHeader -> HttpResponseHeader -> Bool
/= :: HttpResponseHeader -> HttpResponseHeader -> Bool
Eq, Eq HttpResponseHeader
Eq HttpResponseHeader =>
(HttpResponseHeader -> HttpResponseHeader -> Ordering)
-> (HttpResponseHeader -> HttpResponseHeader -> Bool)
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(a -> a -> Ordering)
-> (a -> a -> Bool)
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-> (a -> a -> a)
-> Ord a
$ccompare :: HttpResponseHeader -> HttpResponseHeader -> Ordering
compare :: HttpResponseHeader -> HttpResponseHeader -> Ordering
$c< :: HttpResponseHeader -> HttpResponseHeader -> Bool
< :: HttpResponseHeader -> HttpResponseHeader -> Bool
$c<= :: HttpResponseHeader -> HttpResponseHeader -> Bool
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$c> :: HttpResponseHeader -> HttpResponseHeader -> Bool
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>= :: HttpResponseHeader -> HttpResponseHeader -> Bool
$cmax :: HttpResponseHeader -> HttpResponseHeader -> HttpResponseHeader
max :: HttpResponseHeader -> HttpResponseHeader -> HttpResponseHeader
$cmin :: HttpResponseHeader -> HttpResponseHeader -> HttpResponseHeader
min :: HttpResponseHeader -> HttpResponseHeader -> HttpResponseHeader
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forall a.
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$cshowsPrec :: Int -> HttpResponseHeader -> ShowS
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showList :: [HttpResponseHeader] -> ShowS
Show)

-- | Proxy configuration
--
-- Although actually setting the proxy is the purview of the initialization
-- function for individual 'HttpLib' implementations and therefore outside
-- the scope of this module, we offer this 'ProxyConfiguration' type here as a
-- way to uniformly configure proxies across all 'HttpLib's.
data ProxyConfig a =
    -- | Don't use a proxy
    ProxyConfigNone

    -- | Use this specific proxy
    --
    -- Individual HTTP backends use their own types for specifying proxies.
  | ProxyConfigUse a

    -- | Use automatic proxy settings
    --
    -- What precisely automatic means is 'HttpLib' specific, though
    -- typically it will involve looking at the @HTTP_PROXY@ environment
    -- variable or the (Windows) registry.
  | ProxyConfigAuto

{-------------------------------------------------------------------------------
  Body readers
-------------------------------------------------------------------------------}

-- | An @IO@ action that represents an incoming response body coming from the
-- server.
--
-- The action gets a single chunk of data from the response body, or an empty
-- bytestring if no more data is available.
--
-- This definition is copied from the @http-client@ package.
type BodyReader = IO BS.ByteString

-- | Construct a 'Body' reader from a lazy bytestring
--
-- This is appropriate if the lazy bytestring is constructed, say, by calling
-- 'hGetContents' on a network socket, and the chunks of the bytestring
-- correspond to the chunks as they are returned from the OS network layer.
--
-- If the lazy bytestring needs to be re-chunked this function is NOT suitable.
bodyReaderFromBS :: BS.L.ByteString -> IO BodyReader
bodyReaderFromBS :: ByteString -> IO BodyReader
bodyReaderFromBS ByteString
lazyBS = do
    IORef [ByteString]
chunks <- [ByteString] -> IO (IORef [ByteString])
forall a. a -> IO (IORef a)
newIORef ([ByteString] -> IO (IORef [ByteString]))
-> [ByteString] -> IO (IORef [ByteString])
forall a b. (a -> b) -> a -> b
$ ByteString -> [ByteString]
BS.L.toChunks ByteString
lazyBS
    -- NOTE: Lazy bytestrings invariant: no empty chunks
    let br :: BodyReader
br = do [ByteString]
bss <- IORef [ByteString] -> IO [ByteString]
forall a. IORef a -> IO a
readIORef IORef [ByteString]
chunks
                case [ByteString]
bss of
                  []        -> ByteString -> BodyReader
forall a. a -> IO a
forall (m :: * -> *) a. Monad m => a -> m a
return ByteString
BS.empty
                  (ByteString
bs:[ByteString]
bss') -> IORef [ByteString] -> [ByteString] -> IO ()
forall a. IORef a -> a -> IO ()
writeIORef IORef [ByteString]
chunks [ByteString]
bss' IO () -> BodyReader -> BodyReader
forall a b. IO a -> IO b -> IO b
forall (m :: * -> *) a b. Monad m => m a -> m b -> m b
>> ByteString -> BodyReader
forall a. a -> IO a
forall (m :: * -> *) a. Monad m => a -> m a
return ByteString
bs
    BodyReader -> IO BodyReader
forall a. a -> IO a
forall (m :: * -> *) a. Monad m => a -> m a
return BodyReader
br