# This file is part of GNU TALER.
# Copyright (C) 2014-2016 INRIA
#
# TALER is free software; you can redistribute it and/or modify it under the
# terms of the GNU Lesser General Public License as published by the Free Software
# Foundation; either version 2.1, or (at your option) any later version.
#
# TALER is distributed in the hope that it will be useful, but WITHOUT ANY
# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
# A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public License along with
# GNU TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
#
# @author Florian Dold
# @author Marcello Stanisci

from urllib.parse import urljoin, parse_qsl
import logging
import os
import uuid
import base64
import random
import requests
import flask
import traceback
from ..talerconfig import TalerConfig

LOGGER = logging.getLogger(__name__)

BASE_DIR = os.path.dirname(os.path.abspath(__file__))

app = flask.Flask(__name__, template_folder=BASE_DIR)
app.debug = True
app.secret_key = base64.b64encode(os.urandom(64)).decode('utf-8')

TC = TalerConfig.from_env()
BACKEND_URL = TC["frontends"]["backend"].value_string(required=True)
CURRENCY = TC["taler"]["currency"].value_string(required=True)

app.config.from_object(__name__)

@app.context_processor
def utility_processor():
    def env(name, default=None):
        return os.environ.get(name, default)
    return dict(env=env)


def err_abort(abort_status_code, **params):
    t = flask.render_template("templates/error.html", **params)
    flask.abort(flask.make_response(t, abort_status_code))


def backend_get(endpoint, params):
    try:
        resp = requests.get(urljoin(BACKEND_URL, endpoint), params=params)
    except requests.ConnectionError:
        err_abort(500, message="Could not establish connection to backend")
    try:
        response_json = resp.json()
    except ValueError:
        err_abort(500, message="Could not parse response from backend")
    if resp.status_code != 200:
        err_abort(500, message="Backend returned error status",
                  json=response_json, status_code=resp.status_code)
    return response_json


def backend_post(endpoint, json):
    try:
        resp = requests.post(urljoin(BACKEND_URL, endpoint), json=json)
    except requests.ConnectionError:
        err_abort(500, message="Could not establish connection to backend")
    try:
        response_json = resp.json()
    except ValueError:
        err_abort(500, message="Could not parse response from backend",
                  status_code=resp.status_code)
    if resp.status_code != 200:
        err_abort(500, message="Backend returned error status",
                  json=response_json, status_code=resp.status_code)
    return response_json


def expect_parameter(name):
    val = flask.request.args.get(name)
    if not val:
        return err_abort(400, "parameter '{}' required".format(name))
    return val


@app.errorhandler(Exception)
def internal_error(e):
    return flask.render_template("templates/error.html",
                                 message="Internal error",
                                 stack=traceback.format_exc())


@app.route("/")
def index():
    return flask.render_template("templates/index.html", merchant_currency=CURRENCY)

@app.route("/javascript")
def javascript_licensing():
    return flask.render_template("templates/javascript.html")


@app.route("/checkout", methods=["GET"])
def checkout():
    amount = expect_parameter("donation_amount")
    donation_receiver = expect_parameter("donation_receiver")
    donation_donor = expect_parameter("donation_donor")
    return flask.render_template(
        "templates/checkout.html",
        donation_amount=amount,
        donation_receiver=donation_receiver,
        donation_donor=donation_donor,
        merchant_currency=CURRENCY)


@app.route("/provider-not-supported")
def provider_not_supported():
    return flask.render_template( "templates/provider-not-supported.html")


@app.route("/donate")
def donate():
    donation_receiver = expect_parameter("donation_receiver")
    donation_amount = expect_parameter("donation_amount")
    donation_donor = expect_parameter("donation_donor")
    payment_system = expect_parameter("payment_system")
    if payment_system != "taler":
        return flask.redirect(flask.url_for("provider_not_supported"))
    fulfillment_url = flask.url_for("fulfillment", receiver=donation_receiver, _external=True)
    order = dict(
        amount=donation_amount,
        extra=dict(donor=donation_donor, receiver=donation_receiver, amount=donation_amount),
        fulfillment_url=fulfillment_url,
        instance=donation_receiver,
        summary="Donation to {}".format(donation_receiver),
    )
    proposal_resp = backend_post("proposal", dict(order=order))
    order_id = proposal_resp["order_id"]
    return flask.redirect(flask.url_for("fulfillment", receiver=donation_receiver, order_id=order_id))


@app.route("/donation/<receiver>")
def fulfillment(receiver):
    order_id = expect_parameter("order_id")
    pay_params = dict(
        instance=receiver,
        order_id=order_id,
    )

    pay_status = backend_get("check-payment", pay_params)

    if pay_status.get("payment_redirect_url"):
        return flask.redirect(pay_status["payment_redirect_url"])

    if pay_status.get("paid"):
        extra = pay_status["contract_terms"]["extra"]
        return flask.render_template(
            "templates/fulfillment.html",
            donation_receiver=extra["receiver"],
            donation_amount=extra["amount"],
            donation_donor=extra["donor"],
            order_id=order_id,
            currency=CURRENCY)

    # no pay_redirect but article not paid, this should never happen!
    err_abort(500, message="Internal error, invariant failed", json=pay_status)