##
# This file is part of GNU taler.
# Copyright (C) 2014-2017 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
# @brief Implementation of a Taler-compatible blog.

import urllib.parse
import logging
import os
import traceback
import uuid
import base64
import flask
import time
import sys
from urllib.parse import urljoin, urlencode, urlparse
from taler.util.talerconfig import TalerConfig, ConfigurationError
from ..blog.content import ARTICLES, get_article_file, get_image_file
from talermerchantdemos.httpcommon import backend_get, backend_post

if not sys.version_info.major == 3 and sys.version_info.minor >= 6:
    print("Python 3.6 or higher is required.")
    print("You are using Python {}.{}.".format(sys.version_info.major, sys.version_info.minor))
    sys.exit(1)


BASE_DIR = os.path.dirname(os.path.abspath(__file__))
app = flask.Flask(__name__, template_folder=BASE_DIR, static_folder=BASE_DIR + '/../static/')
app.secret_key = base64.b64encode(os.urandom(64)).decode("utf-8")

LOGGER = logging.getLogger(__name__)
TC = TalerConfig.from_env()
try:
    BACKEND_BASE_URL = TC["frontends"]["backend"].value_string(required=True)
    CURRENCY = TC["taler"]["currency"].value_string(required=True)
    APIKEY = TC["frontends"]["backend_apikey"].value_string(required=True)
except ConfigurationError as ce:
    print(ce)
    exit(1)
ARTICLE_AMOUNT = CURRENCY + ":0.5"
BACKEND_URL = urljoin(BACKEND_BASE_URL, "instances/blog/")

app.config.from_object(__name__)


##
# Extends the templating language with a function (@c env)
# that fetches values from the environment.
#
# @return a @a dict containing the extension.
@app.context_processor
def utility_processor():
    # These helpers will be available in templates
    def env(name, default=None):
        return os.environ.get(name, default)

    return dict(env=env)


##
# Return a error response to the client.
#
# @param abort_status_code status code to return along the response.
# @param params _kw_ arguments to passed verbatim to the templating engine.
def err_abort(abort_status_code, **params):
    t = flask.render_template("templates/error.html", **params)
    flask.abort(flask.make_response(t, abort_status_code))


##
# "Fallback" exception handler to capture all the unmanaged errors.
#
# @param e the Exception object, currently unused.
# @return flask-native response object carrying the error message
#         (and execution stack!).
@app.errorhandler(Exception)
def internal_error(e):
    return flask.render_template(
        "templates/error.html", message="Internal error", stack=traceback.format_exc()
    )


##
# Serve the main index page, redirecting to /<lang>/
#
# @return response object of the index page.
@app.route("/")
def index():
    supported = ['en', 'de' ]
    default = 'en'
    target = flask.request.accept_languages.best_match(supported, default)
    return flask.redirect("/" + target + "/", code=302)

##
# Serve the main index page for a particular language.
#
# @return response object of the index page.
@app.route("/<lang>/")
def start(lang):
    return flask.render_template(
        "templates/index.html", lang=lang, merchant_currency=CURRENCY, articles=ARTICLES.values()
    )


@app.route("/<lang>/confirm-refund/<order_id>", methods=["GET"])
def confirm_refund(lang, order_id):
    session_id = flask.session.get("session_id", "")
    pay_status = backend_get(
        BACKEND_URL, f"private/orders/{order_id}", params=dict(session_id=session_id)
    )
    order_status = pay_status.get("order_status")
    if order_status != "paid":
        err_abort(
            400, message="Cannot refund unpaid article",
        )
    article_name = pay_status["contract_terms"]["extra"]["article_name"]
    return flask.render_template(
        "templates/confirm_refund.html", article_name=article_name, order_id=order_id
    )


##
# Triggers the refund by serving /refund/test?order_id=XY.
# Will be triggered by a "refund button".
#
# @param order_id the order ID of the transaction to refund.
# @return the following errors (named by HTTP response code):
#         - 400: order unknown
#         - 402: the refund was asked on an unpaid article.
#         - 302: in the successful case, a redirection to the
#           "refund URL" is returned; then the wallet will run
#           the refund protocol in a transparent way.
@app.route("/refund/<order_id>", methods=["POST"])
def refund(lang, order_id):
    if not order_id:
        return flask.jsonify(dict(error="Aborting refund: order unknown")), 400
    session_id = flask.session.get("session_id", "")
    pay_status = backend_get(
        BACKEND_URL, f"private/orders/{order_id}", params=dict(session_id=session_id)
    )
    order_status = pay_status.get("order_status")
    if order_status != "paid":
        err_abort(
            402, message="You did not pay for this article (nice try!)", json=pay_status
        )
    refund_spec = dict(reason="Demo reimbursement", refund=ARTICLE_AMOUNT)
    resp = backend_post(BACKEND_URL, f"private/orders/{order_id}/refund", refund_spec)
    return flask.redirect(pay_status["order_status_url"])


##
# Render the article after a successful purchase.
#
# @param article_name _slugged_ (= spaces converted to underscores) article title.
# @param data image filename to return along the article.
# @param order_id the ID of the order where this article got purchased.
#        (Will be put in the refund-request form action, since any article
#         will also have a "refund button" aside.)
# @return the following errors (named by HTTP return code):
#         - 500: file for article not found.
#         - 404: supplemental @a data not found.
#         In the successful case, a response object carrying the
#         article in it will be returned.
def render_article(article_name, data, order_id):
    article_info = ARTICLES.get(article_name)
    if article_info is None:
        m = "Internal error: Files for article ({}) not found.".format(article_name)
        err_abort(500, message=m)
    if data is not None:
        if data in article_info.extra_files:
            return flask.send_file(get_image_file(data))
        m = "Supplemental file ({}) for article ({}) not found.".format(
            data, article_name
        )
        err_abort(404, message=m)
    # the order_id is needed for refunds
    return flask.render_template(
        "templates/article_frame.html",
        article_file=get_article_file(article_info),
        article_name=article_name,
        order_id=order_id,
    )

##
# Setup a fresh order with the backend.
#
# @param article_name which article the order is for
# @param lang which language to use
#
def post_order(article_name,lang):
    order = dict(
        amount=ARTICLE_AMOUNT,
        extra=dict(article_name=article_name,lang=lang),
        fulfillment_url=flask.request.base_url,
        summary="Essay: " + article_name.replace("_", " "),
        # 10 minutes time for a refund
        refund_deadline=dict(t_ms=1000 * int(time.time() + 10 * 30)),
        wire_transfer_deadline=dict(t_ms=1000 * int(time.time() + 15 * 30)),
    )
    order_resp = backend_post(BACKEND_URL, "private/orders", dict(order=order))
    return order_resp


##
# Trigger a article purchase.  The logic follows the main steps:
#
# 1. Always check if the article was paid already, via the
#    "/private/orders/$ORDER_ID" API from the backend.
# 2. If so, return the article.
# 3. If not, redirect the browser to a page where the
#    wallet will initiate the payment protocol.
#
# @param article_name (slugged) article title.
# @param data filename of a supplement data (image/sound/..)
# @return the following errors might occur (named by HTTP response code):
#         - 402: @a article_name does not correspond to the @a order_id
#                of a PAYED article.
#         - 500: neither the article was paid, nor a payment was triggered.
#         - 400: a invalid order_id was passed along the GET parameters.
#         In the successful case, either the article is returned, or
#         the browser gets redirected to a page where the wallet can
#         send the payment.
@app.route("/<lang>/essay/<article_name>")
@app.route("/<lang>/essay/<article_name>/data/<data>")
@app.route("/essay/<article_name>/data/<data>")
def article(article_name, lang=None, data=None):
    # We use an explicit session ID so that each payment (or payment replay) is
    # bound to a browser.  This forces re-play and prevents sharing the article
    # by just sharing the URL.
    session_id = flask.session.get("session_id")
    order_id = flask.request.cookies.get("order_id")

    if not session_id:
        session_id = flask.session["session_id"] = str(uuid.uuid4())
        order_id = None
    ##
    # First-timer; generate order first.
    if not order_id:
        if not lang:
            err_abort(403, message="Direct access forbidden")
        order_resp = post_order(article_name,lang)
        order_id = order_resp["order_id"]

    # Ask the backend for the status of the payment
    pay_status = backend_get(
        BACKEND_URL, f"private/orders/{order_id}", params=dict(session_id=session_id)
    )

    order_status = pay_status.get("order_status")
    if order_status == "claimed":
        if not lang:
            err_abort(403, message="Direct access forbidden")
        # Order already claimed, must setup fresh order
        order_resp = post_order(article_name,lang)
        order_id = order_resp["order_id"]
        pay_status = backend_get(
            BACKEND_URL, f"private/orders/{order_id}", params=dict(session_id=session_id)
        )
        order_status = pay_status.get("order_status")
        # This really must be 'unpaid' now...

    if order_status == "paid":
        refunded = pay_status["refunded"]
         if refunded:
             return flask.render_template(
                "templates/article_refunded.html",
                article_name=article_name,
                order_id=order_id,
            )
        else:
            response = render_article(article_name, data, order_id)
            response.set_cookie("order_id", order_id, path=urllib.parse.quote(f"/essay/{article_name}"))
            response.set_cookie("order_id", order_id, path=urllib.parse.quote(f"/{lang}/essay/{article_name}"))
            return response
    else:
        # Check if the customer came on this page via the
        # re-purchase detection mechanism
        ai = pay_status.get("already_paid_order_id")
        au = pay_status.get("already_paid_fulfillment_url")
        if ai is not None and au is not None:
            response = flask.redirect(au)
            response.set_cookie("order_id", ai, path=urllib.parse.quote(f"/essay/{article_name}"))
            return response

    # Redirect the browser to a page where the wallet can
    # run the payment protocol.
    response = flask.redirect(pay_status["order_status_url"])
    response.set_cookie("order_id", order_id, path=urllib.parse.quote(f"/essay/{article_name}"))
    response.set_cookie("order_id", order_id, path=urllib.parse.quote(f"/{lang}/essay/{article_name}"))
    return response