bambuddy/backend/app/services/local_backup.py

"""Scheduled local backup service.

Creates ZIP snapshots of the full Bambuddy data (database + data directories)
on a configurable schedule with retention management.
"""

import asyncio
import logging
import os
from datetime import datetime, timedelta, timezone, tzinfo
from pathlib import Path
from zoneinfo import ZoneInfo, ZoneInfoNotFoundError

from sqlalchemy import select

from backend.app.core.config import settings as app_settings
from backend.app.core.database import async_session
from backend.app.models.settings import Settings

logger = logging.getLogger(__name__)


def _local_zone() -> tzinfo:
    """Resolve the local timezone for scheduled-backup HH:MM interpretation.

    Uses the container's ``TZ`` env var (the same value the support package
    surfaces); falls back to UTC when unset or unrecognised so a missing TZ
    keeps the legacy behaviour rather than crashing. See #1602 follow-up.

    On Windows the embedded Python in our installer doesn't carry an IANA
    tz database, so ``ZoneInfo(...)`` — including ``ZoneInfo("UTC")`` —
    raises ``ZoneInfoNotFoundError`` unless the ``tzdata`` PyPI package is
    installed. requirements.txt now pins ``tzdata`` on win32, but to keep
    this resilient on installs that haven't refreshed deps we fall through
    to the stdlib ``datetime.timezone.utc`` as a last resort; it satisfies
    every ``astimezone`` / ``str()`` call site without needing the IANA DB.
    """
    tz_name = os.environ.get("TZ", "").strip()
    if tz_name:
        try:
            return ZoneInfo(tz_name)
        except ZoneInfoNotFoundError:
            logger.warning("Unrecognised TZ env value %r, scheduling in UTC", tz_name)
    try:
        return ZoneInfo("UTC")
    except ZoneInfoNotFoundError:
        return timezone.utc


SCHEDULE_INTERVALS = {
    "hourly": 3600,
    "daily": 86400,
    "weekly": 604800,
}


def _default_backup_dir() -> Path:
    return app_settings.base_dir / "backups"


class LocalBackupService:
    """Manages scheduled local backup snapshots with retention."""

    def __init__(self):
        self._scheduler_task: asyncio.Task | None = None
        self._check_interval = 60
        self._running: bool = False
        self._last_backup_at: str | None = None
        self._last_status: str | None = None
        self._last_message: str | None = None
        self._next_run: datetime | None = None

    async def start_scheduler(self):
        """Start the background scheduler loop."""
        if self._scheduler_task is not None:
            return
        logger.info("Starting local backup scheduler")
        # Seed next_run from settings so the first check has a target
        await self._seed_next_run()
        self._scheduler_task = asyncio.create_task(self._scheduler_loop())

    def stop_scheduler(self):
        """Stop the scheduler."""
        if self._scheduler_task:
            self._scheduler_task.cancel()
            self._scheduler_task = None
            logger.info("Stopped local backup scheduler")

    async def _scheduler_loop(self):
        """Main scheduler loop — checks for due backups every minute."""
        while True:
            try:
                await asyncio.sleep(self._check_interval)
                await self._check_scheduled_backup()
            except asyncio.CancelledError:
                break
            except Exception as e:
                logger.error("Error in local backup scheduler: %s", e)
                await asyncio.sleep(60)

    async def _seed_next_run(self):
        """Load settings and calculate initial next_run."""
        try:
            settings = await self._load_settings()
            if settings.get("enabled"):
                self._next_run = self._calculate_next_run(
                    settings.get("schedule", "daily"),
                    settings.get("time", "03:00"),
                )
        except Exception as e:
            logger.debug("Could not seed local backup next_run: %s", e)

    async def _load_settings(self) -> dict:
        """Read local backup settings from the DB."""
        async with async_session() as db:
            keys = [
                "local_backup_enabled",
                "local_backup_schedule",
                "local_backup_time",
                "local_backup_retention",
                "local_backup_path",
            ]
            result = await db.execute(select(Settings).where(Settings.key.in_(keys)))
            rows = {r.key: r.value for r in result.scalars().all()}
        return {
            "enabled": rows.get("local_backup_enabled", "false").lower() == "true",
            "schedule": rows.get("local_backup_schedule", "daily"),
            "time": rows.get("local_backup_time", "03:00"),
            "retention": int(rows.get("local_backup_retention", "5")),
            "path": rows.get("local_backup_path", ""),
        }

    async def _check_scheduled_backup(self):
        """Check if a scheduled backup is due and run it."""
        settings = await self._load_settings()
        if not settings["enabled"]:
            self._next_run = None
            return

        now = datetime.now(timezone.utc)

        # If no next_run set, schedule one
        if self._next_run is None:
            self._next_run = self._calculate_next_run(settings["schedule"], settings["time"])
            return

        if self._next_run <= now:
            logger.info("Running scheduled local backup")
            await self.run_backup(settings)
            self._next_run = self._calculate_next_run(settings["schedule"], settings["time"])

    def _calculate_next_run(self, schedule_type: str, time_str: str = "03:00") -> datetime:
        """Calculate the next scheduled run time.

        For hourly: next full hour (timezone-agnostic).
        For daily/weekly: next occurrence of the configured HH:MM, interpreted
        in the container's local timezone (TZ env var, UTC fallback). Returns
        a UTC-aware datetime for storage / comparison against ``now``.
        """
        now_utc = datetime.now(timezone.utc)

        if schedule_type == "hourly":
            # Next full hour
            next_run = now_utc.replace(minute=0, second=0, microsecond=0) + timedelta(hours=1)
            return next_run

        # Parse HH:MM time
        try:
            parts = time_str.strip().split(":")
            hour = int(parts[0])
            minute = int(parts[1]) if len(parts) > 1 else 0
        except (ValueError, IndexError):
            hour, minute = 3, 0

        local_tz = _local_zone()
        now_local = now_utc.astimezone(local_tz)
        # Next occurrence of HH:MM local time, today or tomorrow.
        # ``fold=0`` resolves the ambiguous wall-clock window at DST fall-back
        # to the earlier instance (consistent with cron's behaviour). On the
        # spring-forward gap the synthesized local time will normalise to the
        # next valid instant when converted to UTC.
        next_local = now_local.replace(hour=hour, minute=minute, second=0, microsecond=0, fold=0)
        if next_local <= now_local:
            next_local += timedelta(days=1)

        if schedule_type == "weekly":
            next_local += timedelta(weeks=1)

        return next_local.astimezone(timezone.utc)

    def _resolve_backup_dir(self, path_setting: str) -> Path:
        """Resolve the backup output directory from settings."""
        if path_setting.strip():
            return Path(path_setting.strip())
        return _default_backup_dir()

    async def run_backup(self, settings: dict | None = None) -> dict:
        """Run a backup now. Returns {success, message, filename}."""
        if self._running:
            return {"success": False, "message": "Backup already in progress"}

        self._running = True
        try:
            if settings is None:
                settings = await self._load_settings()

            backup_dir = self._resolve_backup_dir(settings["path"])
            backup_dir.mkdir(parents=True, exist_ok=True)

            from backend.app.api.routes.settings import create_backup_zip

            zip_path, filename = await create_backup_zip(output_path=backup_dir)

            # Prune old backups
            retention = max(1, settings["retention"])
            self._prune_backups(backup_dir, retention)

            self._last_backup_at = datetime.now(timezone.utc).isoformat()
            self._last_status = "success"
            self._last_message = filename
            logger.info("Local backup created: %s", zip_path)
            return {"success": True, "message": "Backup created", "filename": filename}

        except Exception as e:
            self._last_backup_at = datetime.now(timezone.utc).isoformat()
            self._last_status = "failed"
            self._last_message = str(e)
            logger.error("Local backup failed: %s", e, exc_info=True)
            return {"success": False, "message": f"Backup failed: {e}"}
        finally:
            self._running = False

    def _prune_backups(self, backup_dir: Path, retention: int):
        """Delete oldest backups exceeding the retention count."""
        backups = sorted(
            backup_dir.glob("bambuddy-backup-*.zip"),
            key=lambda p: p.stat().st_mtime,
            reverse=True,
        )
        for old_backup in backups[retention:]:
            try:
                old_backup.unlink()
                logger.info("Pruned old backup: %s", old_backup.name)
            except OSError as e:
                logger.warning("Could not delete old backup %s: %s", old_backup.name, e)

    def get_status(self) -> dict:
        """Return current scheduler status."""
        return {
            "is_running": self._running,
            "last_backup_at": self._last_backup_at,
            "last_status": self._last_status,
            "last_message": self._last_message,
            "next_run": self._next_run.isoformat() if self._next_run else None,
        }

    def resolve_backup_file(self, path_setting: str, filename: str) -> Path | None:
        """Resolve a backup filename to a full path, with safety checks."""
        if "/" in filename or "\\" in filename or ".." in filename:
            return None
        if not filename.startswith("bambuddy-backup-") or not filename.endswith(".zip"):
            return None
        backup_dir = self._resolve_backup_dir(path_setting)
        target = (
            backup_dir / filename
        )  # SEC-PATH-OK: filename rejected above on /, \\, .., plus startswith "bambuddy-backup-" + endswith ".zip" gate
        if not target.exists():
            return None
        return target

    def list_backups(self, path_setting: str) -> list[dict]:
        """List backup ZIP files in the backup directory."""
        backup_dir = self._resolve_backup_dir(path_setting)
        if not backup_dir.exists():
            return []

        backups = []
        for f in sorted(backup_dir.glob("bambuddy-backup-*.zip"), key=lambda p: p.stat().st_mtime, reverse=True):
            stat = f.stat()
            backups.append(
                {
                    "filename": f.name,
                    "size": stat.st_size,
                    "created_at": datetime.fromtimestamp(stat.st_mtime, tz=timezone.utc).isoformat(),
                }
            )
        return backups

    def delete_backup(self, path_setting: str, filename: str) -> dict:
        """Delete a specific backup file. Returns {success, message}."""
        # Path traversal protection
        if "/" in filename or "\\" in filename or ".." in filename:
            return {"success": False, "message": "Invalid filename"}

        backup_dir = self._resolve_backup_dir(path_setting)
        target = (
            backup_dir / filename
        )  # SEC-PATH-OK: filename rejected above on /, \\, .., plus startswith "bambuddy-backup-" + endswith ".zip" gate below

        if not target.exists():
            return {"success": False, "message": "Backup not found"}
        if not target.name.startswith("bambuddy-backup-") or not target.name.endswith(".zip"):
            return {"success": False, "message": "Invalid backup file"}

        try:
            target.unlink()
            return {"success": True, "message": "Backup deleted"}
        except OSError as e:
            return {"success": False, "message": f"Could not delete: {e}"}


local_backup_service = LocalBackupService()