from __future__ import annotations

import logging
import mimetypes
from pathlib import Path
from typing import List, Optional

from django.conf import settings
from django.contrib.auth import get_user_model
from django.db import IntegrityError
from django.db.models import Count, Prefetch, Q
from django.shortcuts import get_object_or_404
from django.utils import timezone
from ninja import File, Form, Query, Router, UploadedFile

from apps.blog.api.schemas import (
    AdminCategorySchema,
    AdminTagSchema,
    BlogBannerSchema,
    BlogFiltersSchema,
    BlogInteractionSchema,
    BlogProfileActivitySchema,
    CategorySchema,
    CategoryWriteSchema,
    CommentCreateSchema,
    CommentHideSchema,
    CommentSchema,
    CommentUpdateSchema,
    AuthorSchema,
    PostAssetCreateSchema,
    PostAssetSchema,
    PostCreateSchema,
    PostDetailSchema,
    PostListSchema,
    PostReviewSchema,
    TagSchema,
    TagWriteSchema,
)
from apps.blog.models import BlogBanner, Category, Comment, Like, Post, PostAsset, SavedPost, Tag
from apps.blog.permissions import (
    can_access_blog_admin,
    can_edit_post,
    can_manage_post_assets,
    can_moderate_blog_comments,
    can_review_blog_posts,
    can_write_blog_posts,
)
from apps.notifications.services import notify_user
from core.api.schemas import ErrorSchema, MessageSchema
from core.authentication import jwt_auth


blog_router = Router()
User = get_user_model()
logger = logging.getLogger(__name__)

IMAGE_EXTENSIONS = {".jpg", ".jpeg", ".png", ".gif", ".webp", ".bmp", ".tiff", ".svg"}
VIDEO_EXTENSIONS = {".mp4", ".webm", ".ogg", ".mov", ".mkv", ".avi"}
DOCUMENT_EXTENSIONS = {".pdf", ".doc", ".docx", ".xls", ".xlsx", ".ppt", ".pptx", ".txt", ".md", ".csv"}
ARCHIVE_EXTENSIONS = {".zip", ".rar", ".7z", ".tar", ".gz", ".bz2"}


def _post_queryset():
    return (
        Post.objects.select_related("author", "category", "reviewed_by", "published_by")
        .prefetch_related("tags", "writers", "assets__uploaded_by")
        .annotate(
            likes_count=Count("likes", distinct=True),
            saves_count=Count("saves", distinct=True),
            comments_count=Count(
                "comments",
                filter=Q(comments__is_approved=True, comments__is_hidden=False, comments__is_deleted=False),
                distinct=True,
            ),
        )
    )


def _published_queryset():
    return _post_queryset().filter(status=Post.StatusChoices.PUBLISHED)


def _optional_auth_user(request):
    auth_header = request.headers.get("Authorization", "")
    if not auth_header.lower().startswith("bearer "):
        return None
    token = auth_header.split(" ", 1)[1].strip()
    return jwt_auth.authenticate(request, token)


def _query_values(request, key: str, fallback: Optional[str] = None) -> list[str]:
    values = request.GET.getlist(key)
    if fallback and fallback not in values:
        values.append(fallback)

    cleaned: list[str] = []
    for value in values:
        for item in str(value).split(","):
            item = item.strip()
            if item and item not in cleaned:
                cleaned.append(item)
    return cleaned


def _category_and_descendant_ids(slug: str) -> list[int]:
    categories = list(Category.objects.values("id", "parent_id", "slug"))
    target = next((category for category in categories if category["slug"] == slug), None)
    if not target:
        return []

    children_by_parent: dict[int, list[int]] = {}
    for category in categories:
        parent_id = category["parent_id"]
        if parent_id:
            children_by_parent.setdefault(parent_id, []).append(category["id"])

    selected = [target["id"]]
    pending = [target["id"]]
    while pending:
        next_pending: list[int] = []
        for parent_id in pending:
            next_pending.extend(children_by_parent.get(parent_id, []))
        selected.extend(next_pending)
        pending = next_pending
    return selected


def _comment_visibility_filter(user=None) -> Q:
    if user and can_moderate_blog_comments(user):
        return Q(is_deleted=False) & (Q(is_approved=True, is_hidden=False) | Q(is_hidden=True))
    return Q(is_deleted=False, is_approved=True, is_hidden=False)


def _build_category_filter_tree():
    categories = list(
        Category.objects.annotate(
            post_count=Count(
                "posts",
                filter=Q(posts__status=Post.StatusChoices.PUBLISHED, posts__is_deleted=False),
                distinct=True,
            )
        ).order_by("name")
    )
    nodes = {
        category.id: {
            "id": category.id,
            "name": category.name,
            "slug": category.slug,
            "parent_id": category.parent_id,
            "post_count": category.post_count,
            "children": [],
        }
        for category in categories
    }
    roots = []
    for category in categories:
        node = nodes[category.id]
        if category.parent_id and category.parent_id in nodes:
            nodes[category.parent_id]["children"].append(node)
        else:
            roots.append(node)
    return roots


def _asset_file_type(file: UploadedFile) -> str:
    suffix = Path(file.name).suffix.lower()
    content_type = (file.content_type or mimetypes.guess_type(file.name)[0] or "").lower()
    if content_type.startswith("image/") or suffix in IMAGE_EXTENSIONS:
        return PostAsset.FileType.IMAGE
    if content_type.startswith("video/") or suffix in VIDEO_EXTENSIONS:
        return PostAsset.FileType.VIDEO
    if suffix in DOCUMENT_EXTENSIONS:
        return PostAsset.FileType.DOCUMENT
    if suffix in ARCHIVE_EXTENSIONS:
        return PostAsset.FileType.ARCHIVE
    return PostAsset.FileType.OTHER


def _validate_asset_file(file: UploadedFile) -> str | None:
    file_type = _asset_file_type(file)
    suffix = Path(file.name).suffix.lower()
    if file_type == PostAsset.FileType.OTHER:
        return "Unsupported file type."

    max_size_mb = getattr(settings, "BLOG_ASSET_MAX_SIZE_MB", 50)
    image_max_size_mb = getattr(settings, "BLOG_IMAGE_ASSET_MAX_SIZE_MB", 10)
    limit_mb = image_max_size_mb if file_type == PostAsset.FileType.IMAGE else max_size_mb
    if file.size > limit_mb * 1024 * 1024:
        return f"File size must be less than {limit_mb}MB."

    allowed = IMAGE_EXTENSIONS | VIDEO_EXTENSIONS | DOCUMENT_EXTENSIONS | ARCHIVE_EXTENSIONS
    if suffix and suffix not in allowed:
        return "Unsupported file extension."
    return None


def _validate_featured_image(file: UploadedFile) -> str | None:
    suffix = Path(file.name).suffix.lower()
    content_type = (file.content_type or mimetypes.guess_type(file.name)[0] or "").lower()
    if not content_type.startswith("image/") and suffix not in IMAGE_EXTENSIONS:
        return "Featured image must be an image file."

    image_max_size_mb = getattr(settings, "BLOG_IMAGE_ASSET_MAX_SIZE_MB", 10)
    if file.size > image_max_size_mb * 1024 * 1024:
        return f"Featured image size must be less than {image_max_size_mb}MB."
    return None


def _apply_post_payload(post: Post, data: PostCreateSchema, *, user, allow_status: bool = False) -> Post:
    payload = data.dict(exclude_unset=True)
    tag_ids = payload.pop("tag_ids", None)
    writer_ids = payload.pop("writer_ids", None)
    category_id = payload.pop("category_id", None)
    requested_status = payload.pop("status", None)

    if category_id is not None:
        post.category = Category.objects.filter(id=category_id, is_deleted=False).first() if category_id else None

    if requested_status and allow_status:
        post.status = requested_status
        if requested_status == Post.StatusChoices.PUBLISHED:
            post.published_by = user

    for field, value in payload.items():
        setattr(post, field, value if value is not None else "")

    post.save()
    if tag_ids is not None:
        post.tags.set(tag_ids)
    if writer_ids is not None:
        if user.is_superuser or user.is_staff or can_review_blog_posts(user):
            writers = list(post.writers.model.objects.filter(id__in=writer_ids, is_active=True))
            post.writers.set(writers or [post.author])
        else:
            post.writers.set([user])
    elif not post.writers.exists():
        post.writers.set([post.author])
    return post


def _interaction_payload(post: Post, user) -> BlogInteractionSchema:
    return BlogInteractionSchema(
        liked=Like.objects.filter(post=post, user=user).exists(),
        saved=SavedPost.objects.filter(post=post, user=user).exists(),
        likes_count=post.likes.count(),
        saves_count=post.saves.count(),
        comments_count=post.comments.filter(is_approved=True, is_hidden=False, is_deleted=False).count(),
    )


def _frontend_blog_url(post: Post) -> str:
    root = getattr(settings, "FRONTEND_ROOT", "/") or "/"
    if not root.endswith("/"):
        root = f"{root}/"
    return f"{root}blog/{post.slug}"


def _blog_moderator_ids() -> set[int]:
    return set(
        User.objects.filter(is_active=True)
        .filter(
            Q(is_staff=True)
            | Q(is_superuser=True)
            | Q(groups__permissions__content_type__app_label="blog", groups__permissions__codename="moderate_blog_comment")
            | Q(user_permissions__content_type__app_label="blog", user_permissions__codename="moderate_blog_comment")
        )
        .distinct()
        .values_list("id", flat=True)
    )


def _post_author_ids(post: Post) -> set[int]:
    author_ids = set(post.writers.values_list("id", flat=True))
    if post.author_id:
        author_ids.add(post.author_id)
    return author_ids


def _notify_blog_comment(comment: Comment) -> None:
    post = comment.post
    actor_id = comment.author_id
    action_url = _frontend_blog_url(post)
    excluded_ids = {actor_id}

    if comment.parent_id and comment.parent.author_id != actor_id:
        notify_user(
            comment.parent.author_id,
            {
                "type": "blog_reply",
                "title": "پاسخ جدید",
                "message": f"به کامنت شما در «{post.title}» پاسخ داده شد.",
                "level": "info",
                "action_url": action_url,
                "entity_type": "blog_comment",
                "entity_id": comment.id,
                "meta": {"post_id": post.id, "post_slug": post.slug, "parent_id": comment.parent_id},
            },
        )
        excluded_ids.add(comment.parent.author_id)

    recipient_ids = (_blog_moderator_ids() | _post_author_ids(post)) - excluded_ids
    for user_id in recipient_ids:
        notify_user(
            user_id,
            {
                "type": "blog_comment",
                "title": "کامنت جدید",
                "message": f"برای «{post.title}» کامنت جدید ثبت شد.",
                "level": "info",
                "action_url": action_url,
                "entity_type": "blog_post",
                "entity_id": post.id,
                "meta": {"post_id": post.id, "post_slug": post.slug, "comment_id": comment.id},
            },
        )


def _can_manage_blog_taxonomy(user) -> bool:
    return bool(
        user
        and getattr(user, "is_authenticated", False)
        and (
            user.is_superuser
            or user.is_staff
            or user.has_perm("blog.add_category")
            or user.has_perm("blog.change_category")
            or user.has_perm("blog.add_tag")
            or user.has_perm("blog.change_tag")
        )
    )


def _category_queryset_with_counts():
    return Category.objects.annotate(post_count=Count("posts", filter=Q(posts__is_deleted=False), distinct=True))


def _tag_queryset_with_counts():
    return Tag.objects.annotate(post_count=Count("posts", filter=Q(posts__is_deleted=False), distinct=True))


def _validate_category_parent(category_id: int | None, parent_id: int | None) -> tuple[Category | None, str | None]:
    if not parent_id:
        return None, None
    if category_id and parent_id == category_id:
        return None, "A category cannot be its own parent."
    if category_id and Category.objects.filter(parent_id=category_id).exists():
        return None, "A category with child categories must remain a root category."

    parent = Category.objects.filter(id=parent_id).first()
    if not parent:
        return None, "Parent category not found."
    if parent.parent_id:
        return None, "Only root categories can be selected as a parent."

    current = parent
    seen: set[int] = set()
    while current:
        if current.id in seen:
            return None, "Invalid category hierarchy."
        seen.add(current.id)
        if category_id and current.id == category_id:
            return None, "Category parent would create a cycle."
        current = current.parent
    return parent, None


def _apply_category_payload(category: Category, data: CategoryWriteSchema) -> tuple[Category | None, str | None]:
    name = (data.name or "").strip()
    if not name:
        return None, "Category name is required."

    parent, error = _validate_category_parent(category.id, data.parent_id)
    if error:
        return None, error

    category.name = name
    if data.slug is not None:
        category.slug = data.slug.strip()
    category.description = data.description or ""
    category.parent = parent
    return category, None


def _apply_tag_payload(tag: Tag, data: TagWriteSchema) -> tuple[Tag | None, str | None]:
    name = (data.name or "").strip()
    if not name:
        return None, "Tag name is required."

    tag.name = name
    if data.slug is not None:
        tag.slug = data.slug.strip()
    return tag, None


@blog_router.get("/admin/writers", response={200: List[AuthorSchema], 403: ErrorSchema}, auth=jwt_auth)
def list_blog_writers(request):
    if not (request.auth.is_superuser or request.auth.is_staff or can_review_blog_posts(request.auth)):
        return 403, {"error": "Permission denied"}
    return (
        User.objects.filter(is_active=True)
        .filter(
            Q(is_staff=True)
            | Q(is_superuser=True)
            | Q(groups__permissions__content_type__app_label="blog", groups__permissions__codename__in=["add_post", "change_post"])
            | Q(user_permissions__content_type__app_label="blog", user_permissions__codename__in=["add_post", "change_post"])
        )
        .distinct()
        .order_by("first_name", "last_name", "username")
    )


@blog_router.get("/admin/posts", response={200: List[PostListSchema], 403: ErrorSchema}, auth=jwt_auth)
def list_admin_posts(
    request,
    status: Optional[str] = Query(None),
    search: Optional[str] = Query(None),
    mine: bool = Query(False),
    limit: int = Query(50, ge=1, le=200),
    offset: int = Query(0, ge=0),
):
    user = request.auth
    if not can_access_blog_admin(user):
        return 403, {"error": "Permission denied"}

    queryset = _post_queryset().order_by("-updated_at", "-created_at")
    if not (user.is_superuser or user.is_staff or can_review_blog_posts(user)) or mine:
        queryset = queryset.filter(author=user)
    if status:
        queryset = queryset.filter(status=status)
    if search:
        queryset = queryset.filter(Q(title__icontains=search) | Q(content__icontains=search) | Q(excerpt__icontains=search))
    return list(queryset[offset : offset + limit])


@blog_router.post("/admin/posts", response={201: PostDetailSchema, 400: ErrorSchema, 403: ErrorSchema}, auth=jwt_auth)
def create_admin_post(request, data: PostCreateSchema):
    user = request.auth
    if not can_write_blog_posts(user):
        return 403, {"error": "Permission denied"}

    try:
        post = Post(author=user)
        _apply_post_payload(post, data, user=user, allow_status=can_review_blog_posts(user))
        if not can_review_blog_posts(user) and post.status == Post.StatusChoices.PUBLISHED:
            post.status = Post.StatusChoices.DRAFT
            post.published_at = None
            post.published_by = None
            post.save(update_fields=["status", "published_at", "published_by", "updated_at"])
        return 201, _post_queryset().get(pk=post.pk)
    except Exception as exc:
        return 400, {"error": "Failed to create post", "details": str(exc)}


@blog_router.get("/admin/posts/{post_id}", response={200: PostDetailSchema, 403: ErrorSchema, 404: ErrorSchema}, auth=jwt_auth)
def get_admin_post(request, post_id: int):
    post = get_object_or_404(_post_queryset(), id=post_id)
    if not can_edit_post(request.auth, post):
        return 403, {"error": "Permission denied"}
    return 200, post


@blog_router.put("/admin/posts/{post_id}", response={200: PostDetailSchema, 400: ErrorSchema, 403: ErrorSchema}, auth=jwt_auth)
def update_admin_post(request, post_id: int, data: PostCreateSchema):
    post = get_object_or_404(Post, id=post_id)
    if not can_edit_post(request.auth, post):
        return 403, {"error": "Permission denied"}

    try:
        _apply_post_payload(post, data, user=request.auth, allow_status=can_review_blog_posts(request.auth))
        return 200, _post_queryset().get(pk=post.pk)
    except Exception as exc:
        return 400, {"error": "Failed to update post", "details": str(exc)}


@blog_router.post("/admin/posts/{post_id}/featured-image", response={200: PostDetailSchema, 400: ErrorSchema, 403: ErrorSchema}, auth=jwt_auth)
def upload_post_featured_image(request, post_id: int, file: UploadedFile = File(...)):
    post = get_object_or_404(Post, id=post_id)
    if not can_edit_post(request.auth, post):
        return 403, {"error": "Permission denied"}

    error = _validate_featured_image(file)
    if error:
        return 400, {"error": error}

    post.featured_image = file
    post.save(update_fields=["featured_image", "updated_at"])
    return 200, _post_queryset().get(pk=post.pk)


@blog_router.delete("/admin/posts/{post_id}/featured-image", response={200: PostDetailSchema, 403: ErrorSchema}, auth=jwt_auth)
def delete_post_featured_image(request, post_id: int):
    post = get_object_or_404(Post, id=post_id)
    if not can_edit_post(request.auth, post):
        return 403, {"error": "Permission denied"}

    post.featured_image = None
    post.save(update_fields=["featured_image", "updated_at"])
    return 200, _post_queryset().get(pk=post.pk)


@blog_router.post("/admin/posts/{post_id}/submit", response={200: PostDetailSchema, 403: ErrorSchema}, auth=jwt_auth)
def submit_post_for_review(request, post_id: int):
    post = get_object_or_404(Post, id=post_id)
    if not can_edit_post(request.auth, post):
        return 403, {"error": "Permission denied"}
    post.status = Post.StatusChoices.SUBMITTED
    post.submitted_at = timezone.now()
    post.review_note = ""
    post.save(update_fields=["status", "submitted_at", "review_note", "updated_at"])
    return 200, _post_queryset().get(pk=post.pk)


@blog_router.post("/admin/posts/{post_id}/review", response={200: PostDetailSchema, 400: ErrorSchema, 403: ErrorSchema}, auth=jwt_auth)
def review_post(request, post_id: int, data: PostReviewSchema):
    user = request.auth
    if not can_review_blog_posts(user):
        return 403, {"error": "Permission denied"}

    post = get_object_or_404(Post, id=post_id)
    action = data.action.strip().lower()
    if action in {"publish", "approve"}:
        post.status = Post.StatusChoices.PUBLISHED
        post.published_at = post.published_at or timezone.now()
        post.published_by = user
    elif action in {"request_changes", "changes_requested"}:
        post.status = Post.StatusChoices.CHANGES_REQUESTED
    elif action == "archive":
        post.status = Post.StatusChoices.ARCHIVED
    else:
        return 400, {"error": "Unsupported review action"}

    post.reviewed_by = user
    post.reviewed_at = timezone.now()
    post.review_note = data.note or ""
    post.save()
    return 200, _post_queryset().get(pk=post.pk)


@blog_router.get("/admin/posts/{post_id}/assets", response={200: List[PostAssetSchema], 403: ErrorSchema}, auth=jwt_auth)
def list_post_assets(request, post_id: int):
    post = get_object_or_404(Post, id=post_id)
    if not can_edit_post(request.auth, post):
        return 403, {"error": "Permission denied"}
    return list(post.assets.select_related("uploaded_by"))


@blog_router.post("/admin/posts/{post_id}/assets", response={201: PostAssetSchema, 400: ErrorSchema, 403: ErrorSchema}, auth=jwt_auth)
def upload_post_asset(
    request,
    post_id: int,
    file: UploadedFile = File(...),
    data: PostAssetCreateSchema = Form(...),
):
    post = get_object_or_404(Post, id=post_id)
    if not can_manage_post_assets(request.auth, post):
        return 403, {"error": "Permission denied"}

    error = _validate_asset_file(file)
    if error:
        return 400, {"error": error}

    try:
        asset = PostAsset.objects.create(
            post=post,
            file=file,
            file_type=_asset_file_type(file),
            title=(data.title if data else "") or file.name,
            alt_text=data.alt_text if data else "",
            caption=data.caption if data else "",
            size=file.size,
            mime_type=file.content_type or mimetypes.guess_type(file.name)[0] or "",
            uploaded_by=request.auth,
        )
        return 201, asset
    except Exception as exc:
        return 400, {"error": "Failed to upload asset", "details": str(exc)}


@blog_router.delete("/admin/posts/{post_id}/assets/{asset_id}", response={200: MessageSchema, 403: ErrorSchema}, auth=jwt_auth)
def delete_post_asset(request, post_id: int, asset_id: int):
    post = get_object_or_404(Post, id=post_id)
    asset = get_object_or_404(PostAsset, id=asset_id, post=post)
    if not can_manage_post_assets(request.auth, post):
        return 403, {"error": "Permission denied"}
    asset.delete()
    return 200, {"message": "Asset deleted successfully"}


@blog_router.get("/me/activity", response=BlogProfileActivitySchema, auth=jwt_auth)
def my_blog_activity(request):
    comments = (
        Comment.objects.filter(
            author=request.auth,
            is_approved=True,
            is_hidden=False,
            is_deleted=False,
            post__status=Post.StatusChoices.PUBLISHED,
            post__is_deleted=False,
        )
        .select_related("author", "post")
        .order_by("-created_at")[:20]
    )
    return {
        "liked_posts": list(_published_queryset().filter(likes__user=request.auth)[:20]),
        "saved_posts": list(_published_queryset().filter(saves__user=request.auth)[:20]),
        "comments": [comment for comment in comments if comment.parent_id is None],
        "replies": [comment for comment in comments if comment.parent_id is not None],
    }


@blog_router.get("/banners", response=List[BlogBannerSchema])
def list_banners(request):
    return BlogBanner.objects.filter(is_active=True, is_deleted=False).order_by("sort_order", "-created_at")


@blog_router.get("/filters", response=BlogFiltersSchema)
def blog_filters(request):
    tag_rows = (
        Tag.objects.annotate(
            post_count=Count(
                "posts",
                filter=Q(posts__status=Post.StatusChoices.PUBLISHED, posts__is_deleted=False),
                distinct=True,
            )
        )
        .filter(post_count__gt=0)
        .order_by("name")
    )

    author_post_ids: dict[int, set[int]] = {}
    published_posts = Post.objects.filter(status=Post.StatusChoices.PUBLISHED, is_deleted=False)
    for row in published_posts.values("id", "author_id"):
        author_post_ids.setdefault(row["author_id"], set()).add(row["id"])
    for row in Post.writers.through.objects.filter(post__status=Post.StatusChoices.PUBLISHED, post__is_deleted=False).values("post_id", "user_id"):
        author_post_ids.setdefault(row["user_id"], set()).add(row["post_id"])

    users = User.objects.filter(id__in=author_post_ids.keys(), is_active=True).order_by("first_name", "last_name", "username")
    authors = [
        {
            "id": user.id,
            "username": user.username,
            "first_name": user.first_name,
            "last_name": user.last_name,
            "post_count": len(author_post_ids.get(user.id, set())),
        }
        for user in users
    ]

    return {
        "categories": _build_category_filter_tree(),
        "tags": [
            {"id": tag.id, "name": tag.name, "slug": tag.slug, "post_count": tag.post_count}
            for tag in tag_rows
        ],
        "authors": authors,
    }


@blog_router.get("/posts", response=List[PostListSchema])
def list_posts(
    request,
    page: int = Query(1, ge=1),
    limit: int = Query(10, ge=1, le=50),
    category: Optional[str] = None,
    tag: Optional[str] = None,
    search: Optional[str] = None,
    featured: Optional[bool] = None,
    author: Optional[str] = None,
):
    queryset = _published_queryset()
    if category:
        category_ids = _category_and_descendant_ids(category)
        queryset = queryset.filter(category_id__in=category_ids) if category_ids else queryset.none()
    tags = _query_values(request, "tag", tag)
    if tags:
        queryset = queryset.filter(tags__slug__in=tags)
    if search:
        queryset = queryset.filter(Q(title__icontains=search) | Q(content__icontains=search) | Q(excerpt__icontains=search))
    if featured is not None:
        queryset = queryset.filter(is_featured=featured)
    authors = _query_values(request, "author", author)
    if authors:
        queryset = queryset.filter(Q(author__username__in=authors) | Q(writers__username__in=authors))
    offset = (page - 1) * limit
    return list(queryset.distinct()[offset : offset + limit])


@blog_router.get("/posts/{slug}/recommended", response=List[PostListSchema])
def recommended_posts(request, slug: str, limit: int = Query(3, ge=1, le=12)):
    post = get_object_or_404(
        Post.objects.select_related("category").prefetch_related("tags"),
        slug=slug,
        status=Post.StatusChoices.PUBLISHED,
    )
    tag_ids = list(post.tags.values_list("id", flat=True))
    selected = []
    seen_ids = {post.id}

    def append_posts(queryset):
        remaining = limit - len(selected)
        if remaining <= 0:
            return
        for candidate in queryset.exclude(id__in=seen_ids)[:remaining]:
            selected.append(candidate)
            seen_ids.add(candidate.id)

    if tag_ids:
        append_posts(
            _published_queryset()
            .filter(tags__id__in=tag_ids)
            .annotate(shared_tags=Count("tags", filter=Q(tags__id__in=tag_ids), distinct=True))
            .order_by("-shared_tags", "-published_at", "-created_at")
            .distinct()
        )

    if len(selected) < limit and post.category_id:
        append_posts(
            _published_queryset()
            .filter(category_id=post.category_id)
            .order_by("-published_at", "-created_at")
        )

    if len(selected) < limit:
        append_posts(_published_queryset().order_by("-published_at", "-created_at"))

    return selected


@blog_router.get("/posts/{slug}", response=PostDetailSchema)
def get_post(request, slug: str):
    return get_object_or_404(_published_queryset(), slug=slug)


@blog_router.post("/posts", response={201: PostDetailSchema, 400: ErrorSchema, 403: ErrorSchema}, auth=jwt_auth)
def create_post_compat(request, data: PostCreateSchema):
    return create_admin_post(request, data)


@blog_router.put("/posts/{slug}", response={200: PostDetailSchema, 400: ErrorSchema, 403: ErrorSchema}, auth=jwt_auth)
def update_post_compat(request, slug: str, data: PostCreateSchema):
    post = get_object_or_404(Post, slug=slug)
    return update_admin_post(request, post.id, data)


@blog_router.delete("/posts/{slug}", response={200: MessageSchema, 403: ErrorSchema}, auth=jwt_auth)
def delete_post(request, slug: str):
    if not request.auth.is_superuser:
        return 403, {"error": "Only superusers can delete posts"}
    post = get_object_or_404(Post, slug=slug)
    post.delete()
    return 200, {"message": "Post deleted successfully"}


@blog_router.get("/posts/{slug}/comments", response=List[CommentSchema])
def list_comments(request, slug: str):
    post = get_object_or_404(Post, slug=slug, status=Post.StatusChoices.PUBLISHED)
    user = _optional_auth_user(request)
    visibility = _comment_visibility_filter(user)
    replies = (
        Comment.objects.filter(visibility)
        .select_related("author", "post")
        .prefetch_related(Prefetch("replies", queryset=Comment.objects.filter(visibility).select_related("author", "post").order_by("-created_at")))
        .order_by("-created_at")
    )
    comments = (
        Comment.objects.filter(visibility, post=post, parent=None)
        .select_related("author", "post")
        .prefetch_related(Prefetch("replies", queryset=replies))
        .order_by("-created_at")
    )
    return list(comments)


@blog_router.post("/posts/{slug}/comments", response={201: CommentSchema, 400: ErrorSchema}, auth=jwt_auth)
def create_comment(request, slug: str, data: CommentCreateSchema):
    post = get_object_or_404(Post, slug=slug, status=Post.StatusChoices.PUBLISHED)
    parent = None
    if data.parent_id:
        parent = get_object_or_404(Comment, id=data.parent_id, post=post, is_approved=True, is_hidden=False, is_deleted=False)
    comment = Comment.objects.create(post=post, author=request.auth, content=data.content, parent=parent)
    try:
        _notify_blog_comment(comment)
    except Exception:
        logger.exception("Failed to send blog comment notifications for comment=%s", comment.id)
    return 201, comment


@blog_router.post("/comments/{comment_id}/hide", response={200: MessageSchema, 403: ErrorSchema}, auth=jwt_auth)
def hide_comment(request, comment_id: int, data: CommentHideSchema):
    if not can_moderate_blog_comments(request.auth):
        return 403, {"error": "Permission denied"}
    comment = get_object_or_404(Comment, id=comment_id)
    comment.hide(request.auth, data.note or "")
    return 200, {"message": "Comment hidden successfully"}


@blog_router.post("/comments/{comment_id}/unhide", response={200: MessageSchema, 403: ErrorSchema}, auth=jwt_auth)
def unhide_comment(request, comment_id: int):
    if not can_moderate_blog_comments(request.auth):
        return 403, {"error": "Permission denied"}
    comment = get_object_or_404(Comment, id=comment_id)
    comment.unhide()
    return 200, {"message": "Comment restored successfully"}


@blog_router.post("/comments/{comment_id}/delete", response={200: MessageSchema, 403: ErrorSchema}, auth=jwt_auth)
def soft_delete_comment_tree(request, comment_id: int, data: CommentHideSchema):
    if not can_moderate_blog_comments(request.auth):
        return 403, {"error": "Permission denied"}
    comment = get_object_or_404(Comment.all_objects, id=comment_id, is_deleted=False)
    deleted_count = 1 + len(comment.descendant_ids())
    comment.soft_delete_tree(request.auth, data.note or "")
    return 200, {"message": f"{deleted_count} comment(s) deleted successfully"}


@blog_router.put("/comments/{comment_id}", response={200: CommentSchema, 400: ErrorSchema, 403: ErrorSchema}, auth=jwt_auth)
def update_comment(request, comment_id: int, data: CommentUpdateSchema):
    comment = get_object_or_404(Comment.objects.select_related("author", "post"), id=comment_id)
    if comment.author_id != request.auth.id:
        return 403, {"error": "Permission denied"}
    if comment.is_deleted or comment.is_hidden or not comment.is_approved or comment.hidden_at:
        return 403, {"error": "Hidden comments cannot be edited"}

    content = data.content.strip()
    if not content:
        return 400, {"error": "Comment content is required"}

    comment.content = content
    comment.save(update_fields=["content", "updated_at"])
    return 200, comment


@blog_router.post("/posts/{slug}/like", response={200: BlogInteractionSchema}, auth=jwt_auth)
def toggle_like(request, slug: str):
    post = get_object_or_404(Post, slug=slug, status=Post.StatusChoices.PUBLISHED)
    like, created = Like.objects.get_or_create(post=post, user=request.auth)
    if not created:
        like.delete()
    return 200, _interaction_payload(post, request.auth)


@blog_router.get("/posts/{slug}/likes", response={200: MessageSchema})
def get_likes_count(request, slug: str):
    post = get_object_or_404(Post, slug=slug, status=Post.StatusChoices.PUBLISHED)
    return 200, {"message": str(post.likes.count())}


@blog_router.post("/posts/{slug}/save", response={200: BlogInteractionSchema}, auth=jwt_auth)
def toggle_save(request, slug: str):
    post = get_object_or_404(Post, slug=slug, status=Post.StatusChoices.PUBLISHED)
    saved, created = SavedPost.objects.get_or_create(post=post, user=request.auth)
    if not created:
        saved.delete()
    return 200, _interaction_payload(post, request.auth)


@blog_router.get("/posts/{slug}/interaction", response={200: BlogInteractionSchema}, auth=jwt_auth)
def get_interaction(request, slug: str):
    post = get_object_or_404(Post, slug=slug, status=Post.StatusChoices.PUBLISHED)
    return 200, _interaction_payload(post, request.auth)


@blog_router.get("/deleted/posts", response={200: List[PostListSchema], 403: ErrorSchema}, auth=jwt_auth)
def list_deleted_posts(request):
    if not request.auth.is_superuser:
        return 403, {"error": "Permission denied"}
    return 200, Post.deleted_objects.all().select_related("author", "category").prefetch_related("tags")


@blog_router.post("/deleted/posts/{post_id}/restore", response={200: MessageSchema, 403: ErrorSchema, 400: ErrorSchema}, auth=jwt_auth)
def restore_post(request, post_id: int):
    if not request.auth.is_superuser:
        return 403, {"error": "Permission denied"}
    try:
        post = Post.deleted_objects.get(id=post_id)
        post.restore()
        return 200, {"message": f"Post '{post.title}' restored successfully."}
    except Post.DoesNotExist:
        return 400, {"error": "Post not found or not soft-deleted."}


@blog_router.get("/deleted/comments", response={200: List[CommentSchema], 403: ErrorSchema}, auth=jwt_auth)
def list_deleted_comments(request):
    if not can_moderate_blog_comments(request.auth):
        return 403, {"error": "Permission denied"}
    return 200, Comment.deleted_objects.all().select_related("author", "post")


@blog_router.post("/deleted/comments/{comment_id}/restore", response={200: MessageSchema, 403: ErrorSchema, 400: ErrorSchema}, auth=jwt_auth)
def restore_comment(request, comment_id: int):
    if not can_moderate_blog_comments(request.auth):
        return 403, {"error": "Permission denied"}
    try:
        comment = Comment.deleted_objects.get(id=comment_id)
        comment.restore()
        return 200, {"message": f"Comment by {comment.author.username} restored successfully."}
    except Comment.DoesNotExist:
        return 400, {"error": "Comment not found or not soft-deleted."}


@blog_router.get("/admin/categories", response={200: List[AdminCategorySchema], 403: ErrorSchema}, auth=jwt_auth)
def list_admin_categories(request):
    if not _can_manage_blog_taxonomy(request.auth):
        return 403, {"error": "Permission denied"}
    return 200, _category_queryset_with_counts().order_by("name")


@blog_router.post("/admin/categories", response={201: AdminCategorySchema, 400: ErrorSchema, 403: ErrorSchema}, auth=jwt_auth)
def create_admin_category(request, data: CategoryWriteSchema):
    if not _can_manage_blog_taxonomy(request.auth):
        return 403, {"error": "Permission denied"}
    category, error = _apply_category_payload(Category(), data)
    if error:
        return 400, {"error": error}
    try:
        category.save()
    except IntegrityError:
        return 400, {"error": "Category name or slug already exists."}
    return 201, _category_queryset_with_counts().get(id=category.id)


@blog_router.put("/admin/categories/{category_id}", response={200: AdminCategorySchema, 400: ErrorSchema, 403: ErrorSchema}, auth=jwt_auth)
def update_admin_category(request, category_id: int, data: CategoryWriteSchema):
    if not _can_manage_blog_taxonomy(request.auth):
        return 403, {"error": "Permission denied"}
    category = get_object_or_404(Category, id=category_id)
    category, error = _apply_category_payload(category, data)
    if error:
        return 400, {"error": error}
    try:
        category.save()
    except IntegrityError:
        return 400, {"error": "Category name or slug already exists."}
    return 200, _category_queryset_with_counts().get(id=category.id)


@blog_router.delete("/admin/categories/{category_id}", response={200: MessageSchema, 403: ErrorSchema}, auth=jwt_auth)
def delete_admin_category(request, category_id: int):
    if not request.auth.is_superuser:
        return 403, {"error": "Permission denied"}
    category = get_object_or_404(Category, id=category_id)
    category.delete()
    return 200, {"message": f"Category '{category.name}' deleted successfully."}


@blog_router.get("/admin/tags", response={200: List[AdminTagSchema], 403: ErrorSchema}, auth=jwt_auth)
def list_admin_tags(request):
    if not _can_manage_blog_taxonomy(request.auth):
        return 403, {"error": "Permission denied"}
    return 200, _tag_queryset_with_counts().order_by("name")


@blog_router.post("/admin/tags", response={201: AdminTagSchema, 400: ErrorSchema, 403: ErrorSchema}, auth=jwt_auth)
def create_admin_tag(request, data: TagWriteSchema):
    if not _can_manage_blog_taxonomy(request.auth):
        return 403, {"error": "Permission denied"}
    tag, error = _apply_tag_payload(Tag(), data)
    if error:
        return 400, {"error": error}
    try:
        tag.save()
    except IntegrityError:
        return 400, {"error": "Tag name or slug already exists."}
    return 201, _tag_queryset_with_counts().get(id=tag.id)


@blog_router.put("/admin/tags/{tag_id}", response={200: AdminTagSchema, 400: ErrorSchema, 403: ErrorSchema}, auth=jwt_auth)
def update_admin_tag(request, tag_id: int, data: TagWriteSchema):
    if not _can_manage_blog_taxonomy(request.auth):
        return 403, {"error": "Permission denied"}
    tag = get_object_or_404(Tag, id=tag_id)
    tag, error = _apply_tag_payload(tag, data)
    if error:
        return 400, {"error": error}
    try:
        tag.save()
    except IntegrityError:
        return 400, {"error": "Tag name or slug already exists."}
    return 200, _tag_queryset_with_counts().get(id=tag.id)


@blog_router.delete("/admin/tags/{tag_id}", response={200: MessageSchema, 403: ErrorSchema}, auth=jwt_auth)
def delete_admin_tag(request, tag_id: int):
    if not request.auth.is_superuser:
        return 403, {"error": "Permission denied"}
    tag = get_object_or_404(Tag, id=tag_id)
    tag.delete()
    return 200, {"message": f"Tag '{tag.name}' deleted successfully."}


@blog_router.get("/categories", response=List[CategorySchema])
def list_categories(request):
    return Category.objects.all()


@blog_router.get("/categories/{slug}", response=CategorySchema)
def get_category(request, slug: str):
    return get_object_or_404(Category, slug=slug)


@blog_router.get("/deleted/categories", response={200: List[CategorySchema], 403: ErrorSchema}, auth=jwt_auth)
def list_deleted_categories(request):
    if not request.auth.is_superuser:
        return 403, {"error": "Permission denied"}
    return 200, Category.deleted_objects.all()


@blog_router.post("/deleted/categories/{category_id}/restore", response={200: MessageSchema, 403: ErrorSchema, 400: ErrorSchema}, auth=jwt_auth)
def restore_category(request, category_id: int):
    if not request.auth.is_superuser:
        return 403, {"error": "Permission denied"}
    try:
        category = Category.deleted_objects.get(id=category_id)
        category.restore()
        return 200, {"message": f"Category '{category.name}' restored successfully."}
    except Category.DoesNotExist:
        return 400, {"error": "Category not found or not soft-deleted."}


@blog_router.get("/tags", response=List[TagSchema])
def list_tags(request):
    return Tag.objects.all()


@blog_router.get("/tags/{slug}", response=TagSchema)
def get_tag(request, slug: str):
    return get_object_or_404(Tag, slug=slug)


@blog_router.get("/deleted/tags", response={200: List[TagSchema], 403: ErrorSchema}, auth=jwt_auth)
def list_deleted_tags(request):
    if not request.auth.is_superuser:
        return 403, {"error": "Permission denied"}
    return 200, Tag.deleted_objects.all()


@blog_router.post("/deleted/tags/{tag_id}/restore", response={200: MessageSchema, 403: ErrorSchema, 400: ErrorSchema}, auth=jwt_auth)
def restore_tag(request, tag_id: int):
    if not request.auth.is_superuser:
        return 403, {"error": "Permission denied"}
    try:
        tag = Tag.deleted_objects.get(id=tag_id)
        tag.restore()
        return 200, {"message": f"Tag '{tag.name}' restored successfully."}
    except Tag.DoesNotExist:
        return 400, {"error": "Tag not found or not soft-deleted."}