from django.db import models
from django.contrib.contenttypes.models import ContentType
from django.contrib.contenttypes.fields import GenericForeignKey
from django.contrib.auth import get_user_model
from simple_history.models import HistoricalRecords
from .mixins import HistoricalChangeMixin
from typing import Any, Type, TypeVar, cast, Optional
from django.db.models import QuerySet
from django.core.exceptions import ValidationError
from django.utils import timezone

T = TypeVar('T', bound=models.Model)

User = get_user_model()

class HistoricalModel(models.Model):
    """Abstract base class for models with history tracking"""
    id = models.BigAutoField(primary_key=True)
    history: HistoricalRecords = HistoricalRecords(
        inherit=True,
        bases=(HistoricalChangeMixin,)
    )

    class Meta:
        abstract = True

    @property
    def _history_model(self) -> Type[T]:
        """Get the history model class"""
        return cast(Type[T], self.history.model)  # type: ignore

    def get_history(self) -> QuerySet:
        """Get all history records for this instance"""
        model = self._history_model
        return model.objects.filter(id=self.pk).order_by('-history_date')

class HistoricalSlug(models.Model):
    """Track historical slugs for models"""
    content_type = models.ForeignKey(ContentType, on_delete=models.CASCADE)
    object_id = models.PositiveIntegerField()
    content_object = GenericForeignKey('content_type', 'object_id')
    slug = models.SlugField(max_length=255)
    created_at = models.DateTimeField(auto_now_add=True)

    class Meta:
        unique_together = ('content_type', 'slug')
        indexes = [
            models.Index(fields=['content_type', 'object_id']),
            models.Index(fields=['slug']),
        ]

    def __str__(self) -> str:
        return f"{self.content_type} - {self.object_id} - {self.slug}"

class VersionBranch(models.Model):
    """Represents a version control branch for tracking parallel development"""
    name = models.CharField(max_length=255, unique=True)
    parent = models.ForeignKey('self', null=True, blank=True, on_delete=models.CASCADE, related_name='children')
    created_at = models.DateTimeField(auto_now_add=True)
    created_by = models.ForeignKey(User, on_delete=models.SET_NULL, null=True)
    metadata = models.JSONField(default=dict, blank=True)
    is_active = models.BooleanField(default=True)

    class Meta:
        ordering = ['-created_at']
        indexes = [
            models.Index(fields=['name']),
            models.Index(fields=['parent']),
            models.Index(fields=['created_at']),
        ]

    def __str__(self) -> str:
        return f"{self.name} ({'active' if self.is_active else 'inactive'})"

    def clean(self) -> None:
        # Prevent circular references
        if self.parent and self.pk:
            branch = self.parent
            while branch:
                if branch.pk == self.pk:
                    raise ValidationError("Circular branch reference detected")
                branch = branch.parent

class VersionTag(models.Model):
    """Tags specific versions for reference (releases, milestones, etc)"""
    name = models.CharField(max_length=255, unique=True)
    branch = models.ForeignKey(VersionBranch, on_delete=models.CASCADE, related_name='tags')
    content_type = models.ForeignKey(ContentType, on_delete=models.CASCADE)
    object_id = models.PositiveIntegerField()
    historical_instance = GenericForeignKey('content_type', 'object_id')
    created_at = models.DateTimeField(auto_now_add=True)
    created_by = models.ForeignKey(User, on_delete=models.SET_NULL, null=True)
    metadata = models.JSONField(default=dict, blank=True)

    class Meta:
        ordering = ['-created_at']
        indexes = [
            models.Index(fields=['name']),
            models.Index(fields=['branch']),
            models.Index(fields=['created_at']),
            models.Index(fields=['content_type', 'object_id']),
        ]

    def __str__(self) -> str:
        return f"{self.name} ({self.branch.name})"

class ChangeSet(models.Model):
    """Groups related changes together for atomic version control operations"""
    branch = models.ForeignKey(VersionBranch, on_delete=models.CASCADE, related_name='changesets')
    created_at = models.DateTimeField(auto_now_add=True)
    created_by = models.ForeignKey(User, on_delete=models.SET_NULL, null=True)
    description = models.TextField(blank=True)
    metadata = models.JSONField(default=dict, blank=True)
    dependencies = models.JSONField(default=dict, blank=True)
    status = models.CharField(
        max_length=20,
        choices=[
            ('pending', 'Pending'),
            ('applied', 'Applied'),
            ('failed', 'Failed'),
            ('reverted', 'Reverted')
        ],
        default='pending'
    )

    # Instead of directly relating to HistoricalRecord, use GenericForeignKey
    content_type = models.ForeignKey(ContentType, on_delete=models.CASCADE)
    object_id = models.PositiveIntegerField()
    historical_instance = GenericForeignKey('content_type', 'object_id')

    class Meta:
        ordering = ['-created_at']
        indexes = [
            models.Index(fields=['branch']),
            models.Index(fields=['created_at']),
            models.Index(fields=['status']),
            models.Index(fields=['content_type', 'object_id']),
        ]

    def __str__(self) -> str:
        return f"ChangeSet {self.pk} ({self.branch.name} - {self.status})"

    def apply(self) -> None:
        """Apply the changeset to the target branch"""
        if self.status != 'pending':
            raise ValidationError(f"Cannot apply changeset with status: {self.status}")

        try:
            # Apply changes through the historical instance
            if self.historical_instance:
                instance = self.historical_instance.instance
                if instance:
                    instance.save()
            self.status = 'applied'
        except Exception as e:
            self.status = 'failed'
            self.metadata['error'] = str(e)
        self.save()

    def revert(self) -> None:
        """Revert the changes in this changeset"""
        if self.status != 'applied':
            raise ValidationError(f"Cannot revert changeset with status: {self.status}")

        try:
            # Revert changes through the historical instance
            if self.historical_instance:
                instance = self.historical_instance.instance
                if instance:
                    instance.save()
            self.status = 'reverted'
        except Exception as e:
            self.metadata['revert_error'] = str(e)
        self.save()