from enum import Enum
from typing import Any, Dict, Optional, Union

from django.contrib.contenttypes.fields import GenericForeignKey
from django.contrib.contenttypes.models import ContentType
from django.db import models
from django.db.models import CASCADE, Q
from typing_extensions import override

from zerver.models import Realm, UserProfile
from zilencer.models import RemoteRealm, RemoteZulipServer


class Customer(models.Model):
    """
    This model primarily serves to connect a Realm with
    the corresponding Stripe customer object for payment purposes
    and the active plan, if any.
    """

    # The actual model object that this customer is associated
    # with. Exactly one of the following will be non-null.
    realm = models.OneToOneField(Realm, on_delete=CASCADE, null=True)
    remote_realm = models.OneToOneField(RemoteRealm, on_delete=CASCADE, null=True)
    remote_server = models.OneToOneField(RemoteZulipServer, on_delete=CASCADE, null=True)

    stripe_customer_id = models.CharField(max_length=255, null=True, unique=True)
    sponsorship_pending = models.BooleanField(default=False)
    # A percentage, like 85.
    default_discount = models.DecimalField(decimal_places=4, max_digits=7, null=True)
    # Some non-profit organizations on manual license management pay
    # only for their paid employees.  We don't prevent these
    # organizations from adding more users than the number of licenses
    # they purchased.
    exempt_from_license_number_check = models.BooleanField(default=False)

    class Meta:
        # Enforce that at least one of these is set.
        constraints = [
            models.CheckConstraint(
                check=Q(realm__isnull=False)
                | Q(remote_server__isnull=False)
                | Q(remote_realm__isnull=False),
                name="has_associated_model_object",
            )
        ]

    @override
    def __str__(self) -> str:
        if self.realm is not None:
            return f"{self.realm!r} (with stripe_customer_id: {self.stripe_customer_id})"
        else:
            return f"{self.remote_server!r} (with stripe_customer_id: {self.stripe_customer_id})"


def get_customer_by_realm(realm: Realm) -> Optional[Customer]:
    return Customer.objects.filter(realm=realm).first()


def get_customer_by_remote_server(remote_server: RemoteZulipServer) -> Optional[Customer]:
    return Customer.objects.filter(remote_server=remote_server).first()


def get_customer_by_remote_realm(remote_realm: RemoteRealm) -> Optional[Customer]:  # nocoverage
    return Customer.objects.filter(remote_realm=remote_realm).first()


class Event(models.Model):
    stripe_event_id = models.CharField(max_length=255)

    type = models.CharField(max_length=255)

    RECEIVED = 1
    EVENT_HANDLER_STARTED = 30
    EVENT_HANDLER_FAILED = 40
    EVENT_HANDLER_SUCCEEDED = 50
    status = models.SmallIntegerField(default=RECEIVED)

    content_type = models.ForeignKey(ContentType, on_delete=models.CASCADE)
    object_id = models.PositiveIntegerField(db_index=True)
    content_object = GenericForeignKey("content_type", "object_id")

    handler_error = models.JSONField(default=None, null=True)

    def get_event_handler_details_as_dict(self) -> Dict[str, Any]:
        details_dict = {}
        details_dict["status"] = {
            Event.RECEIVED: "not_started",
            Event.EVENT_HANDLER_STARTED: "started",
            Event.EVENT_HANDLER_FAILED: "failed",
            Event.EVENT_HANDLER_SUCCEEDED: "succeeded",
        }[self.status]
        if self.handler_error:
            details_dict["error"] = self.handler_error
        return details_dict


def get_last_associated_event_by_type(
    content_object: Union["PaymentIntent", "Session"], event_type: str
) -> Optional[Event]:
    content_type = ContentType.objects.get_for_model(type(content_object))
    return Event.objects.filter(
        content_type=content_type, object_id=content_object.id, type=event_type
    ).last()


class Session(models.Model):
    customer = models.ForeignKey(Customer, on_delete=CASCADE)
    stripe_session_id = models.CharField(max_length=255, unique=True)

    CARD_UPDATE_FROM_BILLING_PAGE = 40
    CARD_UPDATE_FROM_UPGRADE_PAGE = 50
    type = models.SmallIntegerField()

    CREATED = 1
    COMPLETED = 10
    status = models.SmallIntegerField(default=CREATED)

    # Did the user opt to manually manage licenses before clicking on update button?
    is_manual_license_management_upgrade_session = models.BooleanField(default=False)

    def get_status_as_string(self) -> str:
        return {Session.CREATED: "created", Session.COMPLETED: "completed"}[self.status]

    def get_type_as_string(self) -> str:
        return {
            Session.CARD_UPDATE_FROM_BILLING_PAGE: "card_update_from_billing_page",
            Session.CARD_UPDATE_FROM_UPGRADE_PAGE: "card_update_from_upgrade_page",
        }[self.type]

    def to_dict(self) -> Dict[str, Any]:
        session_dict: Dict[str, Any] = {}

        session_dict["status"] = self.get_status_as_string()
        session_dict["type"] = self.get_type_as_string()
        session_dict[
            "is_manual_license_management_upgrade_session"
        ] = self.is_manual_license_management_upgrade_session
        event = self.get_last_associated_event()
        if event is not None:
            session_dict["event_handler"] = event.get_event_handler_details_as_dict()
        return session_dict

    def get_last_associated_event(self) -> Optional[Event]:
        if self.status == Session.CREATED:
            return None
        return get_last_associated_event_by_type(self, "checkout.session.completed")


class PaymentIntent(models.Model):
    customer = models.ForeignKey(Customer, on_delete=CASCADE)
    stripe_payment_intent_id = models.CharField(max_length=255, unique=True)

    REQUIRES_PAYMENT_METHOD = 1
    REQUIRES_CONFIRMATION = 20
    REQUIRES_ACTION = 30
    PROCESSING = 40
    REQUIRES_CAPTURE = 50
    CANCELLED = 60
    SUCCEEDED = 70

    status = models.SmallIntegerField()
    last_payment_error = models.JSONField(default=None, null=True)

    @classmethod
    def get_status_integer_from_status_text(cls, status_text: str) -> int:
        return getattr(cls, status_text.upper())

    def get_status_as_string(self) -> str:
        return {
            PaymentIntent.REQUIRES_PAYMENT_METHOD: "requires_payment_method",
            PaymentIntent.REQUIRES_CONFIRMATION: "requires_confirmation",
            PaymentIntent.REQUIRES_ACTION: "requires_action",
            PaymentIntent.PROCESSING: "processing",
            PaymentIntent.REQUIRES_CAPTURE: "requires_capture",
            PaymentIntent.CANCELLED: "cancelled",
            PaymentIntent.SUCCEEDED: "succeeded",
        }[self.status]

    def get_last_associated_event(self) -> Optional[Event]:
        if self.status == PaymentIntent.SUCCEEDED:
            event_type = "payment_intent.succeeded"
        # TODO: Add test for this case. Not sure how to trigger naturally.
        else:  # nocoverage
            return None  # nocoverage
        return get_last_associated_event_by_type(self, event_type)

    def to_dict(self) -> Dict[str, Any]:
        payment_intent_dict: Dict[str, Any] = {}
        payment_intent_dict["status"] = self.get_status_as_string()
        event = self.get_last_associated_event()
        if event is not None:
            payment_intent_dict["event_handler"] = event.get_event_handler_details_as_dict()
        return payment_intent_dict


class CustomerPlan(models.Model):
    """
    This is for storing most of the fiddly details
    of the customer's plan.
    """

    # A customer can only have one ACTIVE plan, but old, inactive plans
    # are preserved to allow auditing - so there can be multiple
    # CustomerPlan objects pointing to one Customer.
    customer = models.ForeignKey(Customer, on_delete=CASCADE)

    automanage_licenses = models.BooleanField(default=False)
    charge_automatically = models.BooleanField(default=False)

    # Both of these are in cents. Exactly one of price_per_license or
    # fixed_price should be set. fixed_price is only for manual deals, and
    # can't be set via the self-serve billing system.
    price_per_license = models.IntegerField(null=True)
    fixed_price = models.IntegerField(null=True)

    # Discount that was applied. For display purposes only.
    discount = models.DecimalField(decimal_places=4, max_digits=6, null=True)

    # Initialized with the time of plan creation. Used for calculating
    # start of next billing cycle, next invoice date etc. This value
    # should never be modified. The only exception is when we change
    # the status of the plan from free trial to active and reset the
    # billing_cycle_anchor.
    billing_cycle_anchor = models.DateTimeField()

    BILLING_SCHEDULE_ANNUAL = 1
    BILLING_SCHEDULE_MONTHLY = 2
    BILLING_SCHEDULES = {
        BILLING_SCHEDULE_ANNUAL: "Annual",
        BILLING_SCHEDULE_MONTHLY: "Monthly",
    }
    billing_schedule = models.SmallIntegerField()

    # The next date the billing system should go through ledger
    # entries and create invoices for additional users or plan
    # renewal. Since we use a daily cron job for invoicing, the
    # invoice will be generated the first time the cron job runs after
    # next_invoice_date.
    next_invoice_date = models.DateTimeField(db_index=True, null=True)

    # On next_invoice_date, we go through ledger entries that were
    # created after invoiced_through and process them by generating
    # invoices for any additional users and/or plan renewal. Once the
    # invoice is generated, we update the value of invoiced_through
    # and set it to the last ledger entry we processed.
    invoiced_through = models.ForeignKey(
        "LicenseLedger", null=True, on_delete=CASCADE, related_name="+"
    )
    end_date = models.DateTimeField(null=True)

    INVOICING_STATUS_DONE = 1
    INVOICING_STATUS_STARTED = 2
    INVOICING_STATUS_INITIAL_INVOICE_TO_BE_SENT = 3
    # This status field helps ensure any errors encountered during the
    # invoicing process do not leave our invoicing system in a broken
    # state.
    invoicing_status = models.SmallIntegerField(default=INVOICING_STATUS_DONE)

    TIER_CLOUD_STANDARD = 1
    TIER_CLOUD_PLUS = 2
    # Reserved tier IDs for future use
    TIER_CLOUD_COMMUNITY = 3
    TIER_CLOUD_ENTERPRISE = 4

    TIER_SELF_HOSTED_BASE = 100
    TIER_SELF_HOSTED_LEGACY = 101
    TIER_SELF_HOSTED_COMMUNITY = 102
    TIER_SELF_HOSTED_BUSINESS = 103
    TIER_SELF_HOSTED_PLUS = 104
    TIER_SELF_HOSTED_ENTERPRISE = 105
    tier = models.SmallIntegerField()

    ACTIVE = 1
    DOWNGRADE_AT_END_OF_CYCLE = 2
    FREE_TRIAL = 3
    SWITCH_TO_ANNUAL_AT_END_OF_CYCLE = 4
    SWITCH_PLAN_TIER_NOW = 5
    SWITCH_TO_MONTHLY_AT_END_OF_CYCLE = 6
    DOWNGRADE_AT_END_OF_FREE_TRIAL = 7
    SWITCH_PLAN_TIER_AT_PLAN_END = 8
    # "Live" plans should have a value < LIVE_STATUS_THRESHOLD.
    # There should be at most one live plan per customer.
    LIVE_STATUS_THRESHOLD = 10
    ENDED = 11
    NEVER_STARTED = 12
    status = models.SmallIntegerField(default=ACTIVE)

    # TODO maybe override setattr to ensure billing_cycle_anchor, etc
    # are immutable.

    @override
    def __str__(self) -> str:
        return f"{self.name} (status: {self.get_plan_status_as_text()})"

    @staticmethod
    def name_from_tier(tier: int) -> str:
        # NOTE: Check `statement_descriptor` values after updating this.
        # Stripe has a 22 character limit on the statement descriptor length.
        # https://stripe.com/docs/payments/account/statement-descriptors
        return {
            CustomerPlan.TIER_CLOUD_STANDARD: "Zulip Cloud Standard",
            CustomerPlan.TIER_CLOUD_PLUS: "Zulip Cloud Plus",
            CustomerPlan.TIER_CLOUD_ENTERPRISE: "Zulip Enterprise",
            CustomerPlan.TIER_SELF_HOSTED_LEGACY: "Self-managed (legacy plan)",
            CustomerPlan.TIER_SELF_HOSTED_BUSINESS: "Zulip Business",
            CustomerPlan.TIER_SELF_HOSTED_COMMUNITY: "Community",
        }[tier]

    @property
    def name(self) -> str:
        return self.name_from_tier(self.tier)

    def get_plan_status_as_text(self) -> str:
        return {
            self.ACTIVE: "Active",
            self.DOWNGRADE_AT_END_OF_CYCLE: "Scheduled for downgrade at end of cycle",
            self.FREE_TRIAL: "Free trial",
            self.SWITCH_TO_ANNUAL_AT_END_OF_CYCLE: "Scheduled for switch to annual at end of cycle",
            self.SWITCH_TO_MONTHLY_AT_END_OF_CYCLE: "Scheduled for switch to monthly at end of cycle",
            self.DOWNGRADE_AT_END_OF_FREE_TRIAL: "Scheduled for downgrade at end of free trial",
            self.SWITCH_PLAN_TIER_AT_PLAN_END: "Scheduled for switch to new plan at the end of plan",
            self.ENDED: "Ended",
            self.NEVER_STARTED: "Never started",
        }[self.status]

    def licenses(self) -> int:
        ledger_entry = LicenseLedger.objects.filter(plan=self).order_by("id").last()
        assert ledger_entry is not None
        return ledger_entry.licenses

    def licenses_at_next_renewal(self) -> Optional[int]:
        if self.status in (
            CustomerPlan.DOWNGRADE_AT_END_OF_CYCLE,
            CustomerPlan.DOWNGRADE_AT_END_OF_FREE_TRIAL,
        ):
            return None
        ledger_entry = LicenseLedger.objects.filter(plan=self).order_by("id").last()
        assert ledger_entry is not None
        return ledger_entry.licenses_at_next_renewal

    def is_free_trial(self) -> bool:
        return self.status == CustomerPlan.FREE_TRIAL


def get_current_plan_by_customer(customer: Customer) -> Optional[CustomerPlan]:
    return CustomerPlan.objects.filter(
        customer=customer, status__lt=CustomerPlan.LIVE_STATUS_THRESHOLD
    ).first()


def get_current_plan_by_realm(realm: Realm) -> Optional[CustomerPlan]:
    customer = get_customer_by_realm(realm)
    if customer is None:
        return None
    return get_current_plan_by_customer(customer)


class LicenseLedger(models.Model):
    """
    This table's purpose is to store the current, and historical,
    count of "seats" purchased by the organization.

    Because we want to keep historical data, when the purchased
    seat count changes, a new LicenseLedger object is created,
    instead of updating the old one. This lets us preserve
    the entire history of how the seat count changes, which is
    important for analytics as well as auditing and debugging
    in case of issues.
    """

    plan = models.ForeignKey(CustomerPlan, on_delete=CASCADE)

    # Also True for the initial upgrade.
    is_renewal = models.BooleanField(default=False)

    event_time = models.DateTimeField()

    # The number of licenses ("seats") purchased by the the organization at the time of ledger
    # entry creation. Normally, to add a user the organization needs at least one spare license.
    # Once a license is purchased, it is valid till the end of the billing period, irrespective
    # of whether the license is used or not. So the value of licenses will never decrease for
    # subsequent LicenseLedger entries in the same billing period.
    licenses = models.IntegerField()

    # The number of licenses the organization needs in the next billing cycle. The value of
    # licenses_at_next_renewal can increase or decrease for subsequent LicenseLedger entries in
    # the same billing period. For plans on automatic license management this value is usually
    # equal to the number of activated users in the organization.
    licenses_at_next_renewal = models.IntegerField(null=True)


class SponsoredPlanTypes(Enum):
    # unspecified used for cloud sponsorship requests
    UNSPECIFIED = ""
    COMMUNITY = "Community"
    BUSINESS = "Business"


class ZulipSponsorshipRequest(models.Model):
    customer = models.ForeignKey(Customer, on_delete=CASCADE)
    requested_by = models.ForeignKey(UserProfile, on_delete=CASCADE, null=True, blank=True)

    org_type = models.PositiveSmallIntegerField(
        default=Realm.ORG_TYPES["unspecified"]["id"],
        choices=[(t["id"], t["name"]) for t in Realm.ORG_TYPES.values()],
    )

    MAX_ORG_URL_LENGTH: int = 200
    org_website = models.URLField(max_length=MAX_ORG_URL_LENGTH, blank=True, null=True)

    org_description = models.TextField(default="")
    expected_total_users = models.TextField(default="")
    paid_users_count = models.TextField(default="")
    paid_users_description = models.TextField(default="")

    requested_plan = models.CharField(
        max_length=50,
        choices=[(plan.value, plan.name) for plan in SponsoredPlanTypes],
        default=SponsoredPlanTypes.UNSPECIFIED.value,
    )