from django.db import models
from django.contrib.contenttypes.fields import GenericForeignKey
from django.contrib.contenttypes.models import ContentType
from django.contrib.postgres.fields import ArrayField
from django_choices_field import TextChoicesField

from core.models.base import BaseModel
from core.models.enums import (
    EventTypeChoices,
    NotificationChannelChoices,
    NotificationStatusChoices,
    DeliveryStatusChoices,
    RoleChoices
)


class Event(BaseModel):
    """
    Event model to track system events that may trigger notifications.
    Provides audit trail and basis for notification system.
    """
    event_type = TextChoicesField(
        choices_enum=EventTypeChoices,
        help_text="Type of event that occurred"
    )
    entity_type = models.CharField(
        max_length=100,
        help_text="Type of entity (e.g., 'Project', 'Report', 'Invoice')"
    )
    entity_id = models.UUIDField(
        help_text="UUID of the entity that triggered this event"
    )
    metadata = models.JSONField(
        default=dict,
        blank=True,
        help_text="Additional event metadata (e.g., old_status, new_status, changed_fields)"
    )
    # Generic foreign key to support both TeamProfile and CustomerProfile
    triggered_by_content_type = models.ForeignKey(
        ContentType,
        on_delete=models.SET_NULL,
        null=True,
        blank=True,
        related_name='triggered_events'
    )
    triggered_by_object_id = models.UUIDField(
        null=True,
        blank=True
    )
    triggered_by = GenericForeignKey('triggered_by_content_type', 'triggered_by_object_id')

    class Meta:
        db_table = 'events'
        ordering = ['-created_at']
        indexes = [
            models.Index(fields=['event_type', 'created_at']),
            models.Index(fields=['entity_type', 'entity_id']),
            models.Index(fields=['created_at']),
        ]

    def __str__(self):
        return f"{self.event_type} - {self.entity_type}:{self.entity_id} at {self.created_at}"


class NotificationRule(BaseModel):
    """
    Admin-defined rules for generating notifications based on events.
    """
    name = models.CharField(
        max_length=200,
        help_text="Descriptive name for this notification rule"
    )
    description = models.TextField(
        blank=True,
        help_text="Description of when and how this rule applies"
    )
    event_types = ArrayField(
        TextChoicesField(choices_enum=EventTypeChoices),
        help_text="List of event types that trigger this rule"
    )
    channels = ArrayField(
        TextChoicesField(choices_enum=NotificationChannelChoices),
        help_text="Delivery channels for notifications (IN_APP, EMAIL, SMS)"
    )
    target_roles = ArrayField(
        TextChoicesField(choices_enum=RoleChoices),
        blank=True,
        default=list,
        help_text="Roles that should receive notifications (empty = all authenticated users)"
    )
    target_team_profiles = models.ManyToManyField(
        'TeamProfile',
        blank=True,
        related_name='notification_rules',
        help_text="Specific team profiles to notify"
    )
    target_customer_profiles = models.ManyToManyField(
        'CustomerProfile',
        blank=True,
        related_name='notification_rules',
        help_text="Specific customer profiles to notify"
    )
    is_active = models.BooleanField(
        default=True,
        help_text="Whether this rule is currently active"
    )
    template_subject = models.CharField(
        max_length=500,
        blank=True,
        help_text="Template for notification subject (supports variables)"
    )
    template_body = models.TextField(
        blank=True,
        help_text="Template for notification body (supports variables)"
    )
    conditions = models.JSONField(
        default=dict,
        blank=True,
        help_text="Additional conditions for when this rule applies (e.g., {'status': 'COMPLETED'})"
    )

    class Meta:
        db_table = 'notification_rules'
        ordering = ['name']

    def __str__(self):
        return f"{self.name} ({', '.join(self.event_types)})"


class Notification(BaseModel):
    """
    Individual notification instance sent to a specific recipient.
    """
    event = models.ForeignKey(
        Event,
        on_delete=models.CASCADE,
        related_name='notifications',
        help_text="Event that triggered this notification"
    )
    rule = models.ForeignKey(
        NotificationRule,
        on_delete=models.SET_NULL,
        null=True,
        blank=True,
        related_name='notifications',
        help_text="Rule that generated this notification"
    )
    # Generic foreign key to support both TeamProfile and CustomerProfile
    recipient_content_type = models.ForeignKey(
        ContentType,
        on_delete=models.CASCADE,
        related_name='notifications'
    )
    recipient_object_id = models.UUIDField()
    recipient = GenericForeignKey('recipient_content_type', 'recipient_object_id')
    status = TextChoicesField(
        choices_enum=NotificationStatusChoices,
        default=NotificationStatusChoices.PENDING,
        help_text="Current status of the notification"
    )
    subject = models.CharField(
        max_length=500,
        help_text="Notification subject line"
    )
    body = models.TextField(
        help_text="Notification body content"
    )
    action_url = models.URLField(
        blank=True,
        max_length=500,
        help_text="Optional URL for action button (e.g., link to project detail)"
    )
    read_at = models.DateTimeField(
        null=True,
        blank=True,
        help_text="Timestamp when notification was marked as read"
    )
    metadata = models.JSONField(
        default=dict,
        blank=True,
        help_text="Additional notification metadata"
    )

    class Meta:
        db_table = 'notifications'
        ordering = ['-created_at']
        indexes = [
            models.Index(fields=['recipient_content_type', 'recipient_object_id', 'status', 'created_at']),
            models.Index(fields=['recipient_content_type', 'recipient_object_id', 'read_at']),
            models.Index(fields=['event']),
        ]

    def __str__(self):
        return f"Notification for {self.recipient} - {self.subject}"

    def mark_as_read(self):
        """Mark notification as read"""
        if not self.read_at:
            from django.utils import timezone
            self.read_at = timezone.now()
            self.status = NotificationStatusChoices.READ
            self.save(update_fields=['read_at', 'status', 'updated_at'])


class NotificationDelivery(BaseModel):
    """
    Track delivery attempts for a notification via specific channels.
    """
    notification = models.ForeignKey(
        Notification,
        on_delete=models.CASCADE,
        related_name='deliveries',
        help_text="Notification being delivered"
    )
    channel = TextChoicesField(
        choices_enum=NotificationChannelChoices,
        help_text="Delivery channel (IN_APP, EMAIL, SMS)"
    )
    status = TextChoicesField(
        choices_enum=DeliveryStatusChoices,
        default=DeliveryStatusChoices.PENDING,
        help_text="Current delivery status"
    )
    attempts = models.PositiveIntegerField(
        default=0,
        help_text="Number of delivery attempts"
    )
    last_attempt_at = models.DateTimeField(
        null=True,
        blank=True,
        help_text="Timestamp of last delivery attempt"
    )
    sent_at = models.DateTimeField(
        null=True,
        blank=True,
        help_text="Timestamp when successfully sent"
    )
    delivered_at = models.DateTimeField(
        null=True,
        blank=True,
        help_text="Timestamp when delivery was confirmed (if supported by channel)"
    )
    error_message = models.TextField(
        blank=True,
        help_text="Error message from failed delivery attempts"
    )
    external_id = models.CharField(
        max_length=200,
        blank=True,
        help_text="External service ID (e.g., Twilio message SID, email message ID)"
    )
    metadata = models.JSONField(
        default=dict,
        blank=True,
        help_text="Additional delivery metadata"
    )

    class Meta:
        db_table = 'notification_deliveries'
        ordering = ['-created_at']
        indexes = [
            models.Index(fields=['notification', 'channel']),
            models.Index(fields=['status', 'last_attempt_at']),
            models.Index(fields=['channel', 'status']),
        ]
        unique_together = [['notification', 'channel']]

    def __str__(self):
        return f"{self.channel} delivery for notification {self.notification_id} - {self.status}"