Network.HTTP.Query

A small library for querying a Web API.

import Data.Text.IO as T
import Network.HTTP.Query

main = do
  let api = "http://www.example.com/api/1"
      endpoint = api +/+ "search"
  res <- webAPIQuery endpoint $ makeKey "q" "needle"
  T.putStrLn $
    case lookupKey "results" res of
      Nothing ->
        fromMaybe "search failed" $ lookupKey "error" res
      Just results ->
        lookupKey' "location" results

Queries

withURLQuery :: String -> Query -> (Request -> a) -> a

Sets up an API request for some action

webAPIQuery

Arguments

:: (MonadIO m, FromJSON a)

=> String

URL of endpoint

-> Query

query options

-> m a

returned JSON

Low-level web api query

apiQueryURI

Arguments

:: String

URL of endpoint

-> Query

query options

-> URI

Get the URI for a web query

(+/+) :: String -> String -> String infixr 5

Combine two path segments with a slash

"abc" +/+ "def" == "abc/def"
"abc/" +/+ "def" == "abc/def"
"abc" +/+ "/def" == "abc/def"

Query parameters

type Query = [QueryItem]

Query.

General form: a=b&c=d, but if the value is Nothing, it becomes a&c=d.

type QueryItem = (ByteString, Maybe ByteString)

Query item

maybeKey :: String -> Maybe String -> Query

Maybe create a query key

makeKey :: String -> String -> Query

Make a singleton key-value Query

makeItem :: String -> String -> QueryItem

Make a key-value QueryItem

Lookup fields

lookupKey :: FromJSON a => Text -> Object -> Maybe a

Look up key in object

lookupKeyEither :: FromJSON a => Text -> Object -> Either String a

Like lookupKey but returns error message if not found

lookupKey' :: FromJSON a => Text -> Object -> a

Like lookupKey but raises an error if no key found