Re: [Haskell-beginners] Getting warp and blaze to like each other

10 Jul 2013

      Hi Michael,

Seeing as you thought my puzzle would be useful to the community, I thought
that by the same logic you might want to update that sample you posted with
the next thing I had to bust my brain over. parseRequestBody gave me a bit
of a headache cos the only sample I could find was out of date and used
something called lbsSink. I'm sure you'd want to tidy it up first...

I'm also a bit worried about those (toHtml.show)s near the bottom.

{-# LANGUAGE OverloadedStrings #-}

module Main where

import Network.Wai
import Network.HTTP.Types
import Network.HTTP.Types.Header (hContentType, hContentLength,
hConnection)
import Network.Wai.Handler.Warp (run)
import Blaze.ByteString.Builder (fromByteString, fromLazyByteString)
import qualified Data.ByteString.Char8 as BS
import Data.Text

import qualified Text.Blaze.Html5 as H (form)
--import qualified Text.Blaze.Html5.Attributes as A
import Text.Blaze.Html5
import Text.Blaze.Html5.Attributes
import Text.Blaze.Html.Renderer.Utf8

import qualified Data.ByteString.Lazy as LB
import System.Environment (getEnv)
import Network.Wai.Parse (parseRequestBody, lbsBackEnd)

application:: Application
application req =
    parseRequestBody lbsBackEnd req >>= \(b,_) ->
    let (code, html) = app ((requestMethod req),(pathInfo req),(queryString
req),b) in
    return $ ResponseBuilder
               code
               [ (hContentType, "text/html"),
                 (hConnection, "keep-alive")]
               $ renderHtmlBuilder html

app x = case x of
  ("GET", url, [], _) -> (status200, aform url)
  ("GET", url, qs, _) -> (status200, gform qs)
  ("POST", url, _, hsm) -> (status200, pform hsm)

aform :: [Text] -> Html
aform url = docTypeHtml $ do
    body $ do
      h3 "GETting form"
      H.form ! name "fooform" ! method "get" ! action "/in" $
        ( mapM_ (\n -> (toHtml n) >> input ! name (toValue n) ! type_
"text" >> br )  url )
        >> input ! type_ "submit" ! value "Submit"
      h3 "POSTting form"
      H.form ! name "fooform" ! method "post" ! action "/in" $
        ( mapM_ (\n -> (toHtml n) >> input ! name (toValue n) ! type_
"text" >> br )  url )
        >> input ! type_ "submit" ! value "Submit"

gform :: [QueryItem] -> Html
gform qs = docTypeHtml $
    body $ do
      h3 "GETted form"
      mapM_ (\(n,mv) -> "The " >> ((toHtml.show) n) >> " is " >> maybe ""
(toHtml.show) mv >> br) qs

pform :: [(BS.ByteString, BS.ByteString)] -> Html
pform hs = docTypeHtml $
    body $ do
      h3 "POSTed form"
      mapM_ (\(n,v) -> "The " >> ((toHtml.show) n) >> " is " >>
(toHtml.show) v >> br) hs

main:: IO ()
main = getEnv "PORT" >>= flip run application . read

Adrian.

On 9 July 2013 21:16, Adrian May <adrian.alexander.may@gmail.com> wrote:
...
Thanks! That's fantastic. Now I try to master that <*> trick to get
something out of a post and then see if HaskellDB wants to eat it.
Adrian.
On 9 July 2013 18:03, Michael Snoyman <michael@snoyman.com> wrote:
...
I've put together a more efficient version on School of Haskell:
https://www.fpcomplete.com/user/snoyberg/random-code-snippets/wai-blaze-html
The differences from yours are:
- Instead of turning your H.Html into a lazy ByteString and then into
   a Builder, this code goes directly to a Builder via renderHtmlBuilder.
   - No content-length header is included in the output, since that
   would require rendering the builder to a lazy bytestring, which would be an
   unnecessary buffer copy.
   - Doesn't use BS.pack, since OverloadedStrings makes it unnecessary.
On Tue, Jul 9, 2013 at 11:44 AM, Adrian May <
adrian.alexander.may@gmail.com> wrote:
...
Hi All,
I just cobbled together the code below from a couple of samples, but got
the types matched up by trial and error. I don't really understand when
things are getting converted between lazy, strict, utf8, ascii, etc. I
don't want ascii in the served page at all. Is it optimal?
TIA,
Adrian
{-# LANGUAGE OverloadedStrings #-}
module Main where
import Network.Wai (Application, Response (ResponseBuilder))
import Network.HTTP.Types (status200)
import Network.HTTP.Types.Header (hContentType, hContentLength,
hConnection)
import Network.Wai.Handler.Warp (run)
import Blaze.ByteString.Builder (fromByteString, fromLazyByteString)
import qualified Data.ByteString.Char8 as BS (pack, length)
import qualified Text.Blaze.Html5 as H
import qualified Text.Blaze.Html5.Attributes as A
import Text.Blaze.Html.Renderer.Utf8
import qualified Data.ByteString.Lazy as LB
application:: Application
application _ = return $
    ResponseBuilder status200 [(hContentType, BS.pack "text/html"),
                               (hContentLength, BS.pack bodyLen),
                               (hConnection, BS.pack "keep-alive")]
                    $ fromLazyByteString body
    where body = root
          bodyLen = show. LB.length $ body
root = renderHtml rooth
rooth :: H.Html
rooth = H.docTypeHtml $ do
    H.body $ do
        H.h1 "Hello"
main:: IO ()
main = run 8080 application
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