import logging
import traceback
from itertools import chain

from flask import Flask, jsonify, request

logger = logging.getLogger()


class Nothing:
    pass


def has_next(peekable_iter):
    return peekable_iter.peek(Nothing) == Nothing


def set_up_processing_server(process_fn):
    app = Flask(__name__)
    response_payload_iter = []

    @app.route("/ready", methods=["GET"])
    def ready():
        resp = jsonify("OK")
        resp.status_code = 200
        return resp

    @app.route("/process", methods=["POST", "PATCH"])
    def process():
        response_payload = process_fn(request, final=request.method == "POST")
        return jsonify(response_payload)

    @app.route("/submit", methods=["POST"])
    def submit():
        nonlocal response_payload_iter
        response_payload_iter = chain(response_payload_iter, process_fn(request, final=True))
        return jsonify({"pickup_endpoint": "pickup"})

    @app.route("/pickup", methods=["GET"])
    def pickup():

        try:
            resp = jsonify(next(response_payload_iter))
            resp.status_code = 206

        except StopIteration:
            resp = jsonify("No more items left")
            resp.status_code = 204

        except:
            logger.error(traceback.format_exc())
            raise

        return resp

    return app