module Polysemy.Http.Http where

import qualified Data.ByteString as ByteString

import qualified Polysemy.Http.Data.Http as Http
import Polysemy.Http.Data.Http (Http)
import Polysemy.Http.Data.HttpError (HttpError)
import Polysemy.Http.Data.Request (Request)
import Polysemy.Http.Data.Response (Response(Response))
import Polysemy.Http.Data.StreamChunk (StreamChunk(StreamChunk))
import qualified Polysemy.Http.Data.StreamEvent as StreamEvent
import Polysemy.Http.Data.StreamEvent (StreamEvent)
import Polysemy.Resource (Resource, bracket)

streamLoop ::
  Members [Http c, Error HttpError] r =>
  (∀ x . StreamEvent o c h x -> Sem r x) ->
  Response c ->
  h ->
  Sem r o
streamLoop process response@(Response _ body _ _) handle =
  spin
  where
    spin =
      handleChunk =<< fromEither =<< Http.consumeChunk body
    handleChunk (ByteString.null -> True) =
      process (StreamEvent.Result response handle)
    handleChunk !chunk = do
      process (StreamEvent.Chunk handle (StreamChunk chunk))
      spin

streamHandler ::
  ∀ o r c h .
  Members [Http c, Error HttpError, Resource] r =>
  (∀ x . StreamEvent o c h x -> Sem r x) ->
  Response c ->
  Sem r o
streamHandler process response = do
  bracket acquire release (streamLoop process response)
  where
    acquire =
      process (StreamEvent.Acquire response)
    release handle =
      process (StreamEvent.Release handle)

-- |Initiate a request and stream the response, calling 'process' after connecting, for every chunk, after closing the
-- connection, and for the return value.
-- 'StreamEvent' is used to indicate the stage of the request cycle.
--
-- @
-- handle ::
--   StreamEvent Double (IO ByteString) Int a ->
--   Sem r a
-- handle = \\case
--   StreamEvent.Acquire (Response status body headers) ->
--     pure 1
--   StreamEvent.Chunk handle (StreamChunk c) ->
--     pure ()
--   StreamEvent.Result (Response status body headers) handle ->
--     pure 5.5
--   StreamEvent.Release handle ->
--     pure ()
-- @
-- >>> runInterpreters $ streamResponse (Http.get "host.com" "path/to/file") handle
-- 5.5
streamResponse ::
  Members [Http c, Error HttpError, Resource] r =>
  Request ->
  (∀ x . StreamEvent o c h x -> Sem r x) ->
  Sem r o
streamResponse request process =
  fromEither . join =<< Http.stream request (runError . streamHandler (raise . process))