class OpenAI::Stream

def call(chunk, _bytes, env = nil)
  handle_http_error(chunk: chunk, env: env) if env && env.status != 200
  parser.feed(chunk) do |event, data|
    next if data == DONE
    args = [JSON.parse(data), event].first(user_proc_arity)
    user_proc.call(*args)
  end
end

def handle_http_error(chunk:, env:)
  raise_error = Faraday::Response::RaiseError.new
  raise_error.on_complete(env.merge(body: try_parse_json(chunk)))
end

def initialize(user_proc:, parser: EventStreamParser::Parser.new)
  @user_proc = user_proc
  @parser = parser
  # To be backwards compatible, we need to check how many arguments the user_proc takes.
  @user_proc_arity =
    case user_proc
    when Proc
      user_proc.arity.abs
    else
      user_proc.method(:call).arity.abs
    end
end

def to_proc
  method(:call).to_proc
end

def try_parse_json(maybe_json)
  JSON.parse(maybe_json)
rescue JSON::ParserError
  maybe_json
end