RateLimit.hs

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-- Rate Limiting Middleware for WAI                                           --
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-- This source code is licensed under the MIT license found in the LICENSE    --
-- file in the root directory of this source tree.                            --
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{-# LANGUAGE AllowAmbiguousTypes #-}

-- | Implements WAI 'Middleware' for rate limiting. 
module Network.Wai.RateLimit (
    rateLimiting
) where 

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import Control.Monad

import Network.HTTP.Types
import Network.Wai
import Network.Wai.RateLimit.Strategy
import Network.Wai.RateLimit.Backend

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-- | 'rateLimiting' @strategy@ is a WAI 'Middleware' which limits requests
-- according to the configuration represented by @strategy@.
rateLimiting :: Strategy -> Middleware
rateLimiting MkStrategy{..} app req sendResponse = do
    -- check that the client has not exceeded 
    allowRequest <- strategyOnRequest req

    if allowRequest
    -- if not: process the request normally
    then app req sendResponse
    -- otherwise: return a 429 response with an appropriate message
    else sendResponse $ responseLBS status429 [] "Rate limit exceeded" 

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