import logging
from decimal import Decimal
import stripe
from typing import Any, Dict, cast, Optional, Union

from django.core import signing
from django.http import HttpRequest, HttpResponse, HttpResponseRedirect
from django.utils.timezone import now as timezone_now
from django.utils.translation import ugettext as _
from django.shortcuts import render
from django.urls import reverse
from django.conf import settings

from zerver.decorator import zulip_login_required, require_billing_access
from zerver.lib.request import REQ, has_request_variables
from zerver.lib.response import json_error, json_success
from zerver.lib.validator import check_string, check_int
from zerver.models import UserProfile
from corporate.lib.stripe import STRIPE_PUBLISHABLE_KEY, \
    stripe_get_customer, get_latest_seat_count, \
    process_initial_upgrade, sign_string, \
    unsign_string, BillingError, do_change_plan_status, do_replace_payment_source, \
    MIN_INVOICED_LICENSES, DEFAULT_INVOICE_DAYS_UNTIL_DUE, \
    start_of_next_billing_cycle, renewal_amount, \
    make_end_of_cycle_updates_if_needed
from corporate.models import CustomerPlan, get_current_plan_by_customer, \
    get_customer_by_realm, get_current_plan_by_realm

billing_logger = logging.getLogger('corporate.stripe')

def unsign_seat_count(signed_seat_count: str, salt: str) -> int:
    try:
        return int(unsign_string(signed_seat_count, salt))
    except signing.BadSignature:
        raise BillingError('tampered seat count')

def check_upgrade_parameters(
        billing_modality: str, schedule: str, license_management: Optional[str], licenses: Optional[int],
        has_stripe_token: bool, seat_count: int) -> None:
    if billing_modality not in ['send_invoice', 'charge_automatically']:
        raise BillingError('unknown billing_modality')
    if schedule not in ['annual', 'monthly']:
        raise BillingError('unknown schedule')
    if license_management not in ['automatic', 'manual']:
        raise BillingError('unknown license_management')

    if billing_modality == 'charge_automatically':
        if not has_stripe_token:
            raise BillingError('autopay with no card')

    min_licenses = seat_count
    if billing_modality == 'send_invoice':
        min_licenses = max(seat_count, MIN_INVOICED_LICENSES)
    if licenses is None or licenses < min_licenses:
        raise BillingError('not enough licenses',
                           _("You must invoice for at least {} users.").format(min_licenses))

# Should only be called if the customer is being charged automatically
def payment_method_string(stripe_customer: stripe.Customer) -> str:
    stripe_source: Optional[Union[stripe.Card, stripe.Source]] = stripe_customer.default_source
    # In case of e.g. an expired card
    if stripe_source is None:  # nocoverage
        return _("No payment method on file")
    if stripe_source.object == "card":
        return _("%(brand)s ending in %(last4)s") % {
            'brand': cast(stripe.Card, stripe_source).brand,
            'last4': cast(stripe.Card, stripe_source).last4}
    # There might be one-off stuff we do for a particular customer that
    # would land them here. E.g. by default we don't support ACH for
    # automatic payments, but in theory we could add it for a customer via
    # the Stripe dashboard.
    return _("Unknown payment method. Please contact %s.") % (settings.ZULIP_ADMINISTRATOR,)  # nocoverage

@has_request_variables
def upgrade(request: HttpRequest, user: UserProfile,
            billing_modality: str=REQ(validator=check_string),
            schedule: str=REQ(validator=check_string),
            license_management: Optional[str]=REQ(validator=check_string, default=None),
            licenses: Optional[int]=REQ(validator=check_int, default=None),
            stripe_token: Optional[str]=REQ(validator=check_string, default=None),
            signed_seat_count: str=REQ(validator=check_string),
            salt: str=REQ(validator=check_string)) -> HttpResponse:
    try:
        seat_count = unsign_seat_count(signed_seat_count, salt)
        if billing_modality == 'charge_automatically' and license_management == 'automatic':
            licenses = seat_count
        if billing_modality == 'send_invoice':
            schedule = 'annual'
            license_management = 'manual'
        check_upgrade_parameters(
            billing_modality, schedule, license_management, licenses,
            stripe_token is not None, seat_count)
        assert licenses is not None
        automanage_licenses = license_management == 'automatic'

        billing_schedule = {'annual': CustomerPlan.ANNUAL,
                            'monthly': CustomerPlan.MONTHLY}[schedule]
        process_initial_upgrade(user, licenses, automanage_licenses, billing_schedule, stripe_token)
    except BillingError as e:
        if not settings.TEST_SUITE:  # nocoverage
            billing_logger.warning(
                ("BillingError during upgrade: %s. user=%s, realm=%s (%s), billing_modality=%s, "
                 "schedule=%s, license_management=%s, licenses=%s, has stripe_token: %s")
                % (e.description, user.id, user.realm.id, user.realm.string_id, billing_modality,
                   schedule, license_management, licenses, stripe_token is not None))
        return json_error(e.message, data={'error_description': e.description})
    except Exception as e:
        billing_logger.exception("Uncaught exception in billing: %s" % (e,))
        error_message = BillingError.CONTACT_SUPPORT
        error_description = "uncaught exception during upgrade"
        return json_error(error_message, data={'error_description': error_description})
    else:
        return json_success()

@zulip_login_required
def initial_upgrade(request: HttpRequest) -> HttpResponse:
    if not settings.BILLING_ENABLED:
        return render(request, "404.html")

    user = request.user
    customer = get_customer_by_realm(user.realm)
    if customer is not None and get_current_plan_by_customer(customer) is not None:
        return HttpResponseRedirect(reverse('corporate.views.billing_home'))

    percent_off = Decimal(0)
    if customer is not None and customer.default_discount is not None:
        percent_off = customer.default_discount

    seat_count = get_latest_seat_count(user.realm)
    signed_seat_count, salt = sign_string(str(seat_count))
    context: Dict[str, Any] = {
        'publishable_key': STRIPE_PUBLISHABLE_KEY,
        'email': user.delivery_email,
        'seat_count': seat_count,
        'signed_seat_count': signed_seat_count,
        'salt': salt,
        'min_invoiced_licenses': max(seat_count, MIN_INVOICED_LICENSES),
        'default_invoice_days_until_due': DEFAULT_INVOICE_DAYS_UNTIL_DUE,
        'plan': "Zulip Standard",
        'page_params': {
            'seat_count': seat_count,
            'annual_price': 8000,
            'monthly_price': 800,
            'percent_off': float(percent_off),
        },
    }
    response = render(request, 'corporate/upgrade.html', context=context)
    return response

@zulip_login_required
def billing_home(request: HttpRequest) -> HttpResponse:
    user = request.user
    customer = get_customer_by_realm(user.realm)
    if customer is None:
        return HttpResponseRedirect(reverse('corporate.views.initial_upgrade'))
    if not CustomerPlan.objects.filter(customer=customer).exists():
        return HttpResponseRedirect(reverse('corporate.views.initial_upgrade'))

    if not user.is_realm_admin and not user.is_billing_admin:
        context: Dict[str, Any] = {'admin_access': False}
        return render(request, 'corporate/billing.html', context=context)

    context = {
        'admin_access': True,
        'has_active_plan': False,
    }

    plan = get_current_plan_by_customer(customer)
    if plan is not None:
        now = timezone_now()
        last_ledger_entry = make_end_of_cycle_updates_if_needed(plan, now)
        if last_ledger_entry is not None:
            plan_name = {
                CustomerPlan.STANDARD: 'Zulip Standard',
                CustomerPlan.PLUS: 'Zulip Plus',
            }[plan.tier]
            licenses = last_ledger_entry.licenses
            licenses_used = get_latest_seat_count(user.realm)
            # Should do this in javascript, using the user's timezone
            renewal_date = '{dt:%B} {dt.day}, {dt.year}'.format(dt=start_of_next_billing_cycle(plan, now))
            renewal_cents = renewal_amount(plan, now)
            charge_automatically = plan.charge_automatically
            stripe_customer = stripe_get_customer(customer.stripe_customer_id)
            if charge_automatically:
                payment_method = payment_method_string(stripe_customer)
            else:
                payment_method = 'Billed by invoice'

            context.update({
                'plan_name': plan_name,
                'has_active_plan': True,
                'licenses': licenses,
                'licenses_used': licenses_used,
                'renewal_date': renewal_date,
                'renewal_amount': '{:,.2f}'.format(renewal_cents / 100.),
                'payment_method': payment_method,
                'charge_automatically': charge_automatically,
                'publishable_key': STRIPE_PUBLISHABLE_KEY,
                'stripe_email': stripe_customer.email,
            })

    return render(request, 'corporate/billing.html', context=context)

@require_billing_access
@has_request_variables
def change_plan_at_end_of_cycle(request: HttpRequest, user: UserProfile,
                                status: int=REQ("status", validator=check_int)) -> HttpResponse:
    assert(status in [CustomerPlan.ACTIVE, CustomerPlan.DOWNGRADE_AT_END_OF_CYCLE])
    plan = get_current_plan_by_realm(user.realm)
    assert(plan is not None)  # for mypy
    do_change_plan_status(plan, status)
    return json_success()

@require_billing_access
@has_request_variables
def replace_payment_source(request: HttpRequest, user: UserProfile,
                           stripe_token: str=REQ("stripe_token", validator=check_string)) -> HttpResponse:
    try:
        do_replace_payment_source(user, stripe_token, pay_invoices=True)
    except BillingError as e:
        return json_error(e.message, data={'error_description': e.description})
    return json_success()
