from django.db import models
from django.conf import settings
from django.contrib.contenttypes.fields import GenericForeignKey
from django.contrib.contenttypes.models import ContentType
from .managers import CommentThreadManager, ThreadedModelManager

class CommentThread(models.Model):
    """
    A thread of comments that can be attached to any model instance,
    including historical versions.
    """
    content_type = models.ForeignKey(ContentType, on_delete=models.CASCADE)
    object_id = models.PositiveIntegerField()
    content_object = GenericForeignKey('content_type', 'object_id')
    
    title = models.CharField(max_length=255, blank=True)
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)
    created_by = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.SET_NULL,
        null=True,
        related_name='created_comment_threads'
    )
    is_locked = models.BooleanField(default=False)
    is_hidden = models.BooleanField(default=False)

    objects = CommentThreadManager()

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

    def __str__(self):
        return f"Comment Thread on {self.content_object} - {self.title}"

class CommentThreads:
    """
    Helper class to manage comment threads for a model instance.
    This is used instead of direct inheritance to avoid historical model issues.
    """
    def __init__(self, instance):
        self.instance = instance
        self._info = {}

    def get_info(self):
        """Get or compute comment thread information."""
        if not self._info:
            ct = ContentType.objects.get_for_model(self.instance.__class__)
            self._info = {
                'count': CommentThread.objects.filter(
                    content_type=ct,
                    object_id=self.instance.pk
                ).count(),
                'content_type': ct,
                'object_id': self.instance.pk
            }
        return self._info

    def get_threads(self):
        """Get comment threads for this instance."""
        info = self.get_info()
        return CommentThread.objects.filter(
            content_type=info['content_type'],
            object_id=info['object_id']
        )

    def add_thread(self, title='', created_by=None):
        """Create a new comment thread for this instance."""
        info = self.get_info()
        thread = CommentThread.objects.create(
            content_type=info['content_type'],
            object_id=info['object_id'],
            title=title,
            created_by=created_by
        )
        self._info = {}  # Clear cache
        return thread

def get_comment_threads(instance):
    """Get or create a CommentThreads helper for a model instance."""
    if not hasattr(instance, '_comment_threads'):
        instance._comment_threads = CommentThreads(instance)
    return instance._comment_threads

class Comment(models.Model):
    """Individual comment within a thread."""
    thread = models.ForeignKey(
        CommentThread,
        on_delete=models.CASCADE,
        related_name='comments'
    )
    author = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.SET_NULL,
        null=True,
        related_name='comments'
    )
    content = models.TextField()
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)
    is_edited = models.BooleanField(default=False)
    is_hidden = models.BooleanField(default=False)
    parent = models.ForeignKey(
        'self',
        on_delete=models.CASCADE,
        null=True,
        blank=True,
        related_name='replies'
    )

    class Meta:
        ordering = ['created_at']

    def __str__(self):
        return f"Comment by {self.author} on {self.created_at}"