"""Admin-side (write) page service.

The public site only has one editable page — "About" — so this
service is intentionally narrower than :class:`AdminPostsService`. The
slug is a fixed literal (``"about"``) and cannot be changed through
the admin. Only the title and body may be edited.

Every write:

- re-renders Markdown → sanitized HTML into ``body_html_cached`` so
  the public read path stays a single SELECT.
- bumps ``updated_at``.
- emits an ``AuditService`` ``page_updated`` event.
- invalidates the public :class:`PageService` (and, defensively, the
  :class:`PostService`) cache so the next request sees the new copy.
"""

from __future__ import annotations

from datetime import datetime, timezone
from typing import Optional

import structlog
from sqlalchemy import Engine, text

from app.models.entities import Page
from app.models.mappers import row_to_page
from app.services.audit import AuditService
from app.services.markdown import MarkdownService
from app.services.pages import PageService
from app.services.posts import PostService


_log = structlog.get_logger(__name__)


# The single editable page's slug. Hard-coded here (not injected) so
# the CLI contract is impossible to misuse — there is no way to point
# this service at a different slug.
ABOUT_SLUG: str = "about"


class AdminPagesService:
    """Write-side service for the About page."""

    def __init__(
        self,
        engine: Engine,
        markdown: MarkdownService,
        page_service: PageService,
        post_service: PostService,
        audit: AuditService,
    ) -> None:
        self._engine: Engine = engine
        self._markdown: MarkdownService = markdown
        self._page_service: PageService = page_service
        self._post_service: PostService = post_service
        self._audit: AuditService = audit

    # ------------------------------------------------------------------
    # Reads
    # ------------------------------------------------------------------
    def get_about(self) -> Optional[Page]:
        """Return the current About page row, or ``None`` if absent."""
        with self._engine.connect() as conn:
            row = conn.execute(
                text(
                    "SELECT id, slug, title, body_md, body_html_cached,"
                    " updated_at, published"
                    " FROM pages WHERE slug = :slug LIMIT 1"
                ),
                {"slug": ABOUT_SLUG},
            ).mappings().first()
        return row_to_page(row) if row is not None else None

    # ------------------------------------------------------------------
    # Writes
    # ------------------------------------------------------------------
    def update_about(
        self,
        *,
        title: str,
        body_md: str,
        actor_user_id: int,
    ) -> Optional[Page]:
        """Update the About page's title + body.

        Slug is immutable — the admin form does not expose it.
        """
        existing = self.get_about()
        if existing is None:
            return None

        clean_title = (title or "").strip()
        clean_body = body_md or ""
        body_html = self._markdown.render(clean_body)
        now_iso = datetime.now(timezone.utc).isoformat()

        with self._engine.begin() as conn:
            conn.execute(
                text(
                    "UPDATE pages"
                    " SET title = :title, body_md = :body_md,"
                    "     body_html_cached = :body_html,"
                    "     updated_at = :updated_at"
                    " WHERE slug = :slug"
                ),
                {
                    "title": clean_title,
                    "body_md": clean_body,
                    "body_html": body_html,
                    "updated_at": now_iso,
                    "slug": ABOUT_SLUG,
                },
            )

        self._audit.record(
            "page_updated",
            user_id=actor_user_id,
            detail={"slug": ABOUT_SLUG},
        )
        self._page_service.invalidate_all()
        self._post_service.invalidate_all()
        return self.get_about()