import flask
import requests
from urllib.parse import urljoin, urlencode
import taler.util.amount
import base64
import os
import logging
import json
from random import randint
from datetime import datetime


app = flask.Flask(__name__)
app.secret_key = base64.b64encode(os.urandom(64)).decode('utf-8')
logger = logging.getLogger(__name__)

CURRENCY = "TESTKUDOS"
BACKEND_URL = "http://backend.test.taler.net/"

def make_url(page, *query_params):
    """
    Return a URL to a page in the current Flask application with the given
    query parameters (sequence of key/value pairs).
    """
    query = urlencode(query_params)
    if page.startswith("/"):
        root = flask.request.url_root
        page = page.lstrip("/")
    else:
        root = flask.request.base_url
    url = urljoin(root, "%s?%s" % (page, query))
    # urlencode is overly eager with quoting, the wallet right now
    # needs some characters unquoted.
    return url.replace("%24", "$").replace("%7B", "{").replace("%7D", "}")

@app.route("/")
def index():
    return flask.render_template("index.html")


@app.route("/donate")
def donate():
   response = flask.Response(status=402)
   response.headers["X-Taler-Contract-Url"] = "/generate-proposal"
   return response


@app.route("/generate-proposal")
def generate_proposal():
    DONATION = amount.string_to_amount("0.1:%s" % CURRENCY)
    MAX_FEE = amount.string_to_amount("0.05:%s" % CURRENCY)
    ORDER_ID = "tutorial-%X-%s" % (randint(0, 0xFFFFFFFF), datetime.today().strftime("%H_%M_%S"))
    order = dict(
        order_id=ORDER_ID,
        nonce=flask.request.args.get("nonce"),
        amount=DONATION,
        max_fee=MAX_FEE,
        products=[
            dict(
                description="Donation",
                quantity=1,
                product_id=0,
                price=DONATION,
            ),
        ],
        fulfillment_url=make_url("/fulfillment", ("order_id", ORDER_ID)),
        pay_url=make_url("/pay"),
        merchant=dict(
            instance="tutorial",
            address="nowhere",
            name="Donation tutorial",
            jurisdiction="none",
        ),
    )

    url = urljoin(BACKEND_URL, "proposal")

    r = requests.post(url, json=dict(order=order))
    if r.status_code != 200:
        logger.error("failed to POST to '%s'", url)
        return r.text, r.status_code
    proposal_resp = r.json()
    return flask.jsonify(**proposal_resp)


@app.route("/fulfillment")
def fulfillment():
    paid = flask.session.get("paid", False)
    if paid:
        return "Thank you! Your order id is: <b>%s</b>." % flask.session["order_id"]

    response = flask.Response(status=402)
    response.headers["X-Taler-Contract-Url"] = make_url("/generate-contract")
    response.headers["X-Taler-Contract-Query"] = "fulfillment_url"
    response.headers["X-Taler-Offer-Url"] = make_url("/donate")

    return response


@app.route("/pay", methods=["POST"])
def pay():
    deposit_permission = flask.request.get_json()
    if deposit_permission is None:
        e = flask.jsonify(error="no json in body")
        return e, 400
    r = requests.post(urljoin(BACKEND_URL, 'pay'), json=deposit_permission)
    if 200 != r.status_code:
        logger.error("Backend said, status code: %d, object: %s" % (r.status_code, r.text))
        return r.text, r.status_code
    contract_terms = r.json()["contract_terms"]
    flask.session["paid"] = True
    flask.session["order_id"] = contract_terms["order_id"]
    return flask.jsonify(r.json()), 200