"""Health-Checks für Web und Worker (→ Betrieb).

live:  der Prozess antwortet (im Worker: die Schleife läuft). Bewusst ohne Datenbank,
       damit ein DB-Ausfall nicht zu Neustarts aller Prozesse führt.
ready: Datenbank erreichbar, Migrationen auf dem neuesten Stand, Upload-Verzeichnis
       beschreibbar, Master-Key gesetzt. Sonst 503: kein Traffic bzw. keine Runs.
"""

import logging
import tempfile
from dataclasses import dataclass, field
from functools import cache
from pathlib import Path

from alembic.script import ScriptDirectory
from sqlalchemy import text

from app.core.config import Settings
from app.core.database import Database

log = logging.getLogger(__name__)
MIGRATIONS = Path(__file__).resolve().parent.parent / "migrations"


@dataclass
class Report:
    checks: dict[str, str] = field(default_factory=dict)  # Name → "ok" oder Grund

    @property
    def ok(self) -> bool:
        return all(v == "ok" for v in self.checks.values())

    def body(self) -> dict:
        return {"status": "ok" if self.ok else "unavailable", "checks": self.checks}


@cache
def head_revision() -> str:
    from alembic.config import Config
    config = Config()
    config.set_main_option("script_location", str(MIGRATIONS))
    return ScriptDirectory.from_config(config).get_current_head()


def ready(db: Database, settings: Settings) -> Report:
    report = Report()
    try:
        with db.engine.connect() as connection:
            connection.execute(text("SELECT 1"))
            current = connection.execute(text("SELECT version_num FROM alembic_version")).scalar()
        report.checks["database"] = "ok"
        report.checks["migrations"] = "ok" if current == head_revision() else \
            f"Stand {current}, erwartet {head_revision()} (aiw migrate)"
    except Exception as e:
        report.checks["database"] = f"nicht erreichbar: {type(e).__name__}"
    report.checks["uploads"] = writable(Path(settings.upload_dir))
    report.checks["secret_key"] = "ok" if settings.secret_key else "AIW_SECRET_KEY fehlt"
    if not report.ok:
        log.warning("Nicht bereit", extra={"checks": report.checks})
    return report


def writable(directory: Path) -> str:
    try:
        directory.mkdir(parents=True, exist_ok=True)
        with tempfile.NamedTemporaryFile(dir=directory, prefix=".ready-", delete=True):
            pass
        return "ok"
    except OSError as e:
        return f"nicht beschreibbar: {e.strerror or type(e).__name__}"