##
# This file is part of GNU Taler.
# Copyright (C) 2014-2020 Taler Systems SA
#
# 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 uwsgi
from flask import request, url_for
from flask_babel import Babel
from flask_babel import refresh
from flask_babel import force_locale
from flask_babel import gettext
from werkzeug.middleware.proxy_fix import ProxyFix
import time
import sys
from urllib.parse import urljoin, urlencode, urlparse
from ..util.talerconfig import TalerConfig, ConfigurationError
from ..blog.content import ARTICLES, get_article_file, get_image_file
from talermerchantdemos.httpcommon import (
    backend_get,
    backend_get_with_status,
    backend_post,
    backend_payment_url,
    self_localized,
    Deadline,
    BackendException,
    make_utility_processor,
    get_locale,
)

def req_add_cookie_check():
    current_url = list(urllib.parse.urlparse(flask.request.base_url))
    args_writable = flask.request.args.copy()
    # Adding the used param.
    args_writable.update(dict(expect_state="yes"))
    current_url[4] = urllib.parse.urlencode(args_writable) 
    # Stringify the result.
    return urllib.parse.urlunparse(current_url) 


def req_rm_cookie_check():
    current_url = list(urllib.parse.urlparse(flask.request.base_url))
    args_writable = flask.request.args.copy()
    # Stripping the used param.
    args_writable.pop("expect_state")
    current_url[4] = urllib.parse.urlencode(args_writable) 
    # Stringify the result.
    return urllib.parse.urlunparse(current_url) 


def err_abort(abort_status_code, **params):
    """
    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.
    """
    t = flask.render_template("blog-error.html.j2", **params)
    flask.abort(flask.make_response(t, abort_status_code))


def refundable(pay_status):
    refunded = pay_status.get("refunded")
    refund_deadline = pay_status.get("contract_terms", {}).get("refund_deadline")
    assert refunded != None and refund_deadline
    t_s = refund_deadline.get("t_s")
    # FIXME: do not use assert here!
    assert t_s
    rd = Deadline(t_s * 1000)
    if not refunded and not rd.isExpired():
        return True
    return False

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)

app = flask.Flask(__name__, template_folder="../templates", static_folder="../static")
app.wsgi_app = ProxyFix(app.wsgi_app, x_host=1, x_prefix=1)
app.debug = True
app.secret_key = base64.b64encode(os.urandom(64)).decode("utf-8")

logging.basicConfig()
LOGGER = logging.getLogger(__name__)
try:

    BACKEND_BASE_URL = uwsgi.opt["backend_url"].decode("utf-8")
    CURRENCY = uwsgi.opt["currency"].decode("utf-8")
    APIKEY = uwsgi.opt["apikey"].decode("utf-8")
except ConfigurationError as ce:
    print(ce)
    exit(1)

ARTICLE_AMOUNT = CURRENCY + ":0.5"
BACKEND_URL = urljoin(BACKEND_BASE_URL, "instances/blog/")

BABEL_TRANSLATION_DIRECTORIES = "../translations"

app.config.from_object(__name__)
babel = Babel(app)
babel.localeselector(get_locale)

LOGGER.info("Using translations from:" + ":".join(list(babel.translation_directories)))
translations = [str(translation) for translation in babel.list_translations()]
if not "en" in translations:
    translations.append("en")
LOGGER.info(
    "Operating with the following translations available: " + " ".join(translations)
)

# Add context processor that will make additional variables
# and functions available in the template.
app.context_processor(make_utility_processor("blog", os.environ.get ("TALER_ENV_URL_MERCHANT_BLOG")))


##
# "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(
        "blog-error.html.j2",
        page_title=gettext("GNU Taler Demo: Error"),
        message=gettext("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():
    default = "en"
    target = flask.request.accept_languages.best_match(translations, default)
    return flask.redirect(url_for ('index') + target + "/", code=302)


##
# Serve the /favicon.ico requests.
#
# @return the favicon.ico file.
@app.route("/favicon.ico")
def favicon():
    LOGGER.info("will look into: " + os.path.join(app.root_path, "static"))
    return flask.send_from_directory(
        os.path.join(app.root_path, "static"),
        "favicon.ico",
        mimetype="image/vnd.microsoft.ico",
    )


##
# Serve the main index page for a particular language.
#
# @return response object of the index page.
@app.route("/<lang>/")
def start(lang):

    # get_locale defaults to english, hence the
    # condition below happens only when lang is
    # wrong or unsupported, respond 404.
    if lang != get_locale():
        err_abort(
            404,
            message="Language {} not found".format(lang),
        )

    if lang in ARTICLES:
        translated = ARTICLES[lang]
    else:
        translated = {}
    return flask.render_template(
        "blog-index.html.j2",
        merchant_currency=CURRENCY,
        page_title=gettext("GNU Taler Demo: Essay Shop"),
        articles=translated.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),
        auth_token=APIKEY,
    )
    order_status = pay_status.get("order_status")
    if order_status != "paid":
        err_abort(
            400,
            message=gettext("Cannot refund unpaid article"),
        )
    article_name = pay_status["contract_terms"]["extra"]["article_name"]

    if not refundable(pay_status):
        return flask.render_template(
            "blog-error.html.j2",
            page_title=gettext("GNU Taler Demo: Error"),
            message=gettext("Article is not anymore refundable"),
        )
    return flask.render_template(
        "blog-confirm-refund.html.j2",
        page_title=gettext("GNU Taler Demo: Confirm refund"),
        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(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),
        auth_token=APIKEY,
    )
    order_status = pay_status.get("order_status")

    if order_status != "paid":
        err_abort(
            402,
            message=gettext("You did not pay for this article (nice try!)"),
            json=pay_status,
        )
    if not refundable(pay_status):
        err_abort(
            403, message=gettext("Item not refundable (anymore)"), json=pay_status
        )
    refund_spec = dict(reason="Demo reimbursement", refund=ARTICLE_AMOUNT)
    backend_post(
        BACKEND_URL, f"private/orders/{order_id}/refund", refund_spec, auth_token=APIKEY
    )
    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 lang language the article is to be in
# @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, lang, data, order_id, refundable):
    article_info = ARTICLES[lang].get(article_name)
    if article_info is None:
        m = gettext("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 = gettext("Supplemental file ({}) for article ({}) not found.").format(
            data, article_name
        )
        err_abort(404, message=m)
    # the order_id is needed for refunds
    article_contents = open(get_article_file(article_info)).read()
    return flask.render_template(
        "blog-article-frame.html.j2",
        page_title=gettext("GNU Taler Demo: Article"),
        article_contents=article_contents,
        article_name=article_info.title,
        order_id=order_id,
        refundable=refundable,
    )


##
# 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, article_url, session_id, lang):
    article_info = ARTICLES[lang].get(article_name)
    summary = f"Essay: {article_info.title}"
    order = dict(
        amount=ARTICLE_AMOUNT,
        extra=dict(article_name=article_name),
        fulfillment_url=article_url,
        public_reorder_url=article_url,
        summary=summary,
        session_id=session_id,
        # FIXME: add support for i18n of summary!
        # 10 minutes time for a refund
        wire_transfer_deadline=dict(t_s=int(time.time() + 15 * 30)),
    )
    order_resp = backend_post(
        BACKEND_URL,
        "private/orders",
        dict(order=order, refund_delay=dict(d_us=1000 * 1000 * 120)),
        auth_token=APIKEY,
    )
    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.  flask.session is transparently set by Flask, when
    # the user agent supports cookies.  All the key-value pairs associated to it
    # are only stored in the server.
    session_id = flask.session.get("session_id")
    maybe_expect_state = request.args.get("expect_state")

    # Disabled for now, see https://bugs.gnunet.org/view.php?id=8137
    # and https://bugs.gnunet.org/view.php?id=8353
    new_if_refunded = request.args.get("new_if_refunded")

    current_order_id = flask.request.cookies.get("order_id")
    article_url = flask.request.base_url

    if not session_id:
      # If expect_state = yes then session_id should be set already
      # this is a way to check that the client supports cookies
      if maybe_expect_state == "yes":
        error_page = flask.render_template(
            "blog-error.html.j2",
            page_title=gettext("GNU Taler Demo: Error"),
            message=gettext("Please enable cookies."),
        )
        return flask.make_response(error_page, 412)
      
      # first time setting session_id
      # check if browser support cookies with a flag
      session_id = flask.session["session_id"] = str(uuid.uuid4())
      return flask.redirect(req_add_cookie_check(), code=302)
    
    # If session is present then we know that cookies are enabled
    # remove the flag if present
    if maybe_expect_state == "yes":
      return flask.redirect(req_rm_cookie_check(), code=302)

    ############################
    # user has a session and cookie works
    #
    # check if we can already render the article
    ############################

    # if an order_id is present then render if paid or refunded
    if current_order_id is not None:
      status, current_order = backend_get_with_status(
          BACKEND_URL,
          f"private/orders/{current_order_id}",
          params=dict(session_id=session_id),
          auth_token=APIKEY,
      )

      if status == 200:
        if current_order.get("order_status") == "paid" and not current_order.get("refunded"):
          return render_article(
              article_name,
              lang,
              data,
              current_order_id,
              refundable(current_order)
          )
        
        # Checking repurchase case. That happens when the client
        # visits this page in the same session where the article
        # was paid already.
        ai = current_order.get("already_paid_order_id")
        au = current_order.get("already_paid_fulfillment_url")

        if ai is not None:
          print("== Merchant says 'see other': ", ai, au)
          response = flask.redirect(article_url)
          response.set_cookie(
              "order_id",
              ai,
              path=urllib.parse.quote(url_for ('index') + f"essay/{article_name}")
          )
          response.set_cookie(
              "order_id",
              ai,
              path=urllib.parse.quote(url_for ('index') + f"{lang}/essay/{article_name}")
          )
          return response
        
        # If new_if_refunded == "yes" the user already acknowledge the
        # state of the current order and is asking for a new one.
        if current_order.get("refunded") and new_if_refunded != "yes":
          return flask.render_template(
              "blog-article-refunded.html.j2",
              page_title=gettext("GNU Taler Demo: Refunded"),
              article_name=article_name,
              article_lang=lang,
              order_id=current_order_id,
          )
      
      elif status != 404: 
      # not found may be normal, could means that 
      # merchant forgot about the order becuase
      # it was a long time without being paid
        raise BackendException(
          message=gettext("Backend returned error status"),
          backend_status=status,
          backend_json=current_order,
        )

          
    # Current order is not present or unpaid
    # Check if there is a paid but not refunded order in this session
    list_resp = backend_get(
        BACKEND_URL,
        f"private/orders",
        params=dict(session_id=session_id, fulfillment_url=article_url, refunded="no"),
        auth_token=APIKEY,
    )
    
    already_paid_order = None
    for order in list_resp.get("orders"):
      if order.get("paid"):
        already_paid_order = order
        break

    if already_paid_order is not None:
        # Found one, now this is the current order.
        print("== Already paid order found", already_paid_order)
        order_id = already_paid_order.get("order_id")
        response = flask.redirect(article_url)
        response.set_cookie(
            "order_id",
            order_id,
            path=urllib.parse.quote(url_for ('index') + f"essay/{article_name}")
        )
        response.set_cookie(
            "order_id",
            order_id,
            path=urllib.parse.quote(url_for ('index') + f"{lang}/essay/{article_name}")
        )
        return response
  
    ############################
    # We couln't find a paid order
    #
    # Note that it could be the case that the user is still paying
    # an order with another device, in other browser on the same
    # session or claimed in the same brower. 
    # Still, creating an order is cheap and we can safely redirect 
    # to a payment page and relay on repurchase detection to avoid
    # double payments.
    #
    # create a new order and ask for payment
    ############################
      
    order_resp = post_order(article_name, article_url, session_id, lang)
    order_id = order_resp["order_id"]
    token = order_resp["token"]

    redirect_url = backend_payment_url(
      BACKEND_URL,
      f"orders/{order_id}",
      session_id,
      token
    )
    print("new order URL", redirect_url)
    response = flask.redirect(redirect_url)
    response.set_cookie(
        "order_id",
        order_id,
        path=urllib.parse.quote(url_for ('index') + f"essay/{article_name}")
    )
    response.set_cookie(
        "order_id",
        order_id,
        path=urllib.parse.quote(url_for ('index') + f"{lang}/essay/{article_name}")
    )

    return response


@app.errorhandler(500)
def handler_500(e):
    return flask.render_template(
        "blog-error.html.j2",
        page_title=gettext("GNU Taler Demo: Error"),
        message=gettext("Internal server error"),
    )


@app.errorhandler(404)
def handler_404(e):
    return flask.render_template(
        "blog-error.html.j2",
        page_title=gettext("GNU Taler Demo: Error"),
        message=gettext("Page not found"),
    )


@app.errorhandler(BackendException)
def handler_backend_exception(e):
    t = flask.render_template(
        "blog-error.html.j2",
        message=e.args[0],
        page_title=gettext("GNU Taler Demo: Error"),
        json=e.backend_json,
        status_code=e.backend_status,
    )
    return flask.make_response(t, 500)