# This file is part of Wolne Lektury, licensed under GNU Affero GPLv3 or later.
# Copyright © Fundacja Wolne Lektury. See NOTICE for more information.
#
from datetime import date, datetime, timedelta
from decimal import Decimal
import paypalrestsdk
from django.contrib.sites.models import Site
from django.urls import reverse
from django.utils import timezone
from django.conf import settings
from .models import BillingPlan, BillingAgreement

paypalrestsdk.configure(settings.PAYPAL_CONFIG)


class PaypalError(Exception):
    pass


def absolute_url(url_name, kwargs=None):
    return "http://%s%s" % (Site.objects.get_current().domain, reverse(url_name, kwargs=kwargs))


def create_plan(amount):
    billing_plan = paypalrestsdk.BillingPlan({
        "name": "Cykliczna darowizna na Wolne Lektury: %s zł" % amount,
        "description": "Cykliczna darowizna na wsparcie Wolnych Lektur",
        "merchant_preferences": {
            "auto_bill_amount": "yes",
            "return_url": absolute_url('paypal_return', {'key': '-'}),
            "cancel_url": absolute_url('paypal_cancel'),
            # "initial_fail_amount_action": "continue",
            "max_fail_attempts": "3",
        },
        "payment_definitions": [
            {
                "amount": {
                    "currency": "PLN",
                    "value": str(amount),
                },
                "cycles": "0",
                "frequency": "MONTH",
                "frequency_interval": "1",
                "name": "Cykliczna darowizna",
                "type": "REGULAR",
            }
        ],
        "type": "INFINITE",
    })

    if not billing_plan.create():
        raise PaypalError(billing_plan.error)
    if not billing_plan.activate():
        raise PaypalError(billing_plan.error)
    plan, created = BillingPlan.objects.get_or_create(amount=amount, defaults={'plan_id': billing_plan.id})
    return plan.plan_id


def get_link(links, rel):
    for link in links:
        if link.rel == rel:
            return link.href


def create_agreement(amount, key, app=False):
    try:
        plan = BillingPlan.objects.get(amount=amount)
    except BillingPlan.DoesNotExist:
        plan_id = create_plan(amount)
    else:
        plan_id = plan.plan_id
    start = (timezone.now() + timedelta(0, 3600*24)).astimezone(timezone.utc).strftime('%Y-%m-%dT%H:%M:%SZ')
    billing_agreement = paypalrestsdk.BillingAgreement({
        "name": "Subskrypcja klubu WL",
        "description": "Stałe wsparcie Wolnych Lektur kwotą %s złotych" % amount,
        "start_date": start,
        "plan": {
            "id": plan_id,
        },
        "payer": {
            "payment_method": "paypal"
        },
    })
    if app:
        billing_agreement['override_merchant_preferences'] = {
            'return_url': absolute_url('paypal_app_return', {'key': key}),
        }
    else:
        billing_agreement['override_merchant_preferences'] = {
            'return_url': absolute_url('paypal_return', {'key': key}),
        }


    response = billing_agreement.create()
    if response:
        return billing_agreement
    else:
        raise PaypalError(billing_agreement.error)


def agreement_approval_url(amount, key, app=False):
    agreement = create_agreement(amount, key, app=app)
    return get_link(agreement.links, 'approval_url')


def get_agreement(agreement_id):
    try:
        return paypalrestsdk.BillingAgreement.find(agreement_id)
    except paypalrestsdk.ResourceNotFound:
        return None


def check_agreement(agreement_id):
    a = get_agreement(agreement_id)
    if a:
        return a.state == 'Active'


def execute_agreement(token):
    return paypalrestsdk.BillingAgreement.execute(token)


def get_donations(agreement_id, year):
    a = get_agreement(agreement_id)
    transactions = []
    for transaction in a.search_transactions(
            date(year - 1, 12, 31),
            date(year + 1, 1, 1))['agreement_transaction_list']:
        if transaction['status'] != 'Completed':
            continue
        dt = datetime.strptime(
            transaction['time_stamp'],
            '%Y-%m-%dT%H:%M:%S%z'
        ).astimezone()
        if dt.year != year:
            continue
        assert transaction['amount']['currency'] == 'PLN'
        transactions.append({
            'transaction_id': transaction['transaction_id'],
            'timestamp': dt,
            'amount': Decimal(transaction['amount']['value'])
        })
    return transactions
