certain/backend/app/routers/backup.py

"""Backup & Export: kompletter DB-Download (Admin), Datenexport je Nutzer und
das wiederherstellbare Voll-Backup als JSON (siehe ``services/backup_data``)."""

import csv
import io
import os
import sqlite3
import tempfile
from datetime import datetime, timezone
from pathlib import Path

from fastapi import APIRouter, Depends, File, Form, HTTPException, Response, UploadFile
from fastapi.responses import FileResponse
from sqlalchemy.orm import Session
from starlette.background import BackgroundTask

from ..config import get_settings
from ..database import get_db
from ..deps import get_current_user, require_admin
from ..models import (
    Account,
    AccountIdentifier,
    BudgetTemplateLine,
    Category,
    CategoryGroup,
    DashboardLayout,
    PlannedIncomeLine,
    Role,
    Transaction,
    User,
)
from ..services import backup_data, sessions

router = APIRouter(tags=["backup"])

# Ein Backup ist reiner Text; alles darüber ist mit Sicherheit keins mehr.
MAX_BACKUP_BYTES = 64 * 1024 * 1024


def _ts() -> str:
    return datetime.now(timezone.utc).strftime("%Y%m%d-%H%M%S")


def _sqlite_path() -> str | None:
    url = get_settings().effective_database_url
    return url.replace("sqlite:///", "", 1) if url.startswith("sqlite:///") else None


def _snapshot_before_restore() -> str | None:
    """Legt vor einem ersetzenden Restore eine Kopie der Datenbank ab.

    Dieselbe Absicherung, die ``deploy/update.sh`` vor einem Update macht: wer
    versehentlich das falsche Backup einspielt, hat noch einen Weg zurück."""
    db_path = _sqlite_path()
    if db_path is None or not os.path.exists(db_path):
        return None
    ziel_ordner = Path(get_settings().data_dir) / "backups"
    ziel_ordner.mkdir(parents=True, exist_ok=True)
    ziel = ziel_ordner / f"pre-restore-{_ts()}.db"
    src = sqlite3.connect(db_path)
    dst = sqlite3.connect(str(ziel))
    try:
        with dst:
            src.backup(dst)
    finally:
        dst.close()
        src.close()
    return str(ziel)


def _money(cents: int | None) -> str:
    return f"{(cents or 0) / 100:.2f}"


# --- Komplettes DB-Backup (nur Admin) --------------------------------------


@router.get("/backup/db")
def backup_db(_: User = Depends(require_admin)):
    db_path = _sqlite_path()
    if db_path is None:
        raise HTTPException(status_code=400, detail="DB-Backup ist nur für SQLite verfügbar.")
    tmp = tempfile.NamedTemporaryFile(prefix="cf-backup-", suffix=".db", delete=False)
    tmp.close()
    # Online-Backup-API: konsistente Kopie auch bei laufendem Betrieb.
    src = sqlite3.connect(db_path)
    dst = sqlite3.connect(tmp.name)
    try:
        with dst:
            src.backup(dst)
    finally:
        dst.close()
        src.close()
    return FileResponse(
        tmp.name,
        media_type="application/octet-stream",
        filename=f"certain-finance-{_ts()}.db",
        background=BackgroundTask(os.remove, tmp.name),
    )


# --- Transaktionsexport ----------------------------------------------------


def _maps(db: Session, user: User) -> tuple[dict[int, Account], dict[int, Category]]:
    accs = {a.id: a for a in db.query(Account).filter(Account.owner_id == user.id)}
    cats = {c.id: c for c in db.query(Category).filter(Category.owner_id == user.id)}
    return accs, cats


def _txns(db: Session, user: User) -> list[Transaction]:
    return (
        db.query(Transaction)
        .filter(Transaction.owner_id == user.id)
        .order_by(Transaction.date, Transaction.id)
        .all()
    )


@router.get("/export/transactions.csv")
def export_transactions_csv(db: Session = Depends(get_db), user: User = Depends(get_current_user)):
    accs, cats = _maps(db, user)
    buf = io.StringIO()
    w = csv.writer(buf, delimiter=";")
    w.writerow(["Datum", "Typ", "Konto", "Betrag", "Waehrung", "EUR-Wert",
                "Zielkonto", "Kategorie", "Empfaenger", "Verwendungszweck", "Notiz"])
    for t in _txns(db, user):
        acc = accs.get(t.account_id)
        w.writerow([
            t.date.isoformat(), t.type.value, acc.name if acc else "",
            _money(t.amount_cents), acc.currency if acc else "", _money(t.amount_eur_cents),
            accs[t.to_account_id].name if t.to_account_id and t.to_account_id in accs else "",
            cats[t.category_id].name if t.category_id and t.category_id in cats else "",
            t.payee or "", t.description or "", t.notes or "",
        ])
    return Response(
        content=buf.getvalue().encode("utf-8-sig"),
        media_type="text/csv",
        headers={"Content-Disposition": f'attachment; filename="transaktionen-{_ts()}.csv"'},
    )


def _txn_dict(t: Transaction, accs: dict[int, Account], cats: dict[int, Category]) -> dict:
    acc = accs.get(t.account_id)
    return {
        "date": t.date.isoformat(),
        "type": t.type.value,
        "account": acc.name if acc else None,
        "currency": acc.currency if acc else None,
        "amount_cents": t.amount_cents,
        "amount_eur_cents": t.amount_eur_cents,
        "to_account": accs[t.to_account_id].name if t.to_account_id in accs else None,
        "to_amount_cents": t.to_amount_cents,
        "category": cats[t.category_id].name if t.category_id in cats else None,
        "payee": t.payee,
        "description": t.description,
        "notes": t.notes,
    }


@router.get("/export/transactions.json")
def export_transactions_json(db: Session = Depends(get_db), user: User = Depends(get_current_user)):
    accs, cats = _maps(db, user)
    data = [_txn_dict(t, accs, cats) for t in _txns(db, user)]
    return Response(
        content=_json_bytes(data),
        media_type="application/json",
        headers={"Content-Disposition": f'attachment; filename="transaktionen-{_ts()}.json"'},
    )


# --- Gesamt-Export (alle eigenen Daten als JSON) ---------------------------


def _json_bytes(obj) -> bytes:
    import json

    return json.dumps(obj, ensure_ascii=False, indent=2).encode("utf-8")


@router.get("/export/all.json")
def export_all_json(db: Session = Depends(get_db), user: User = Depends(get_current_user)):
    accs, cats = _maps(db, user)
    idents: dict[int, list] = {}
    for i in db.query(AccountIdentifier).join(Account).filter(Account.owner_id == user.id):
        idents.setdefault(i.account_id, []).append({"kind": i.kind.value, "value": i.value})

    accounts = [{
        "name": a.name, "type": a.type.value, "currency": a.currency,
        "opening_balance_cents": a.opening_balance_cents,
        "opening_date": a.opening_date.isoformat() if a.opening_date else None,
        "icon": a.icon, "color": a.color, "archived": a.is_archived,
        "identifiers": idents.get(a.id, []),
    } for a in accs.values()]

    groups = []
    for g in db.query(CategoryGroup).filter(CategoryGroup.owner_id == user.id).order_by(CategoryGroup.position):
        groups.append({
            "name": g.name, "kind": g.kind.value, "icon": g.icon, "color": g.color,
            "categories": [
                {"name": c.name, "icon": c.icon, "color": c.color}
                for c in sorted(g.categories, key=lambda x: x.position)
            ],
        })

    budget_template = [
        {"category": cats[l.category_id].name if l.category_id in cats else None, "planned_cents": l.planned_cents}
        for l in db.query(BudgetTemplateLine).filter(BudgetTemplateLine.owner_id == user.id)
    ]
    planned_income = [
        {"label": l.label, "planned_cents": l.planned_cents,
         "category": cats[l.category_id].name if l.category_id in cats else None,
         "target_account": accs[l.target_account_id].name if l.target_account_id in accs else None}
        for l in db.query(PlannedIncomeLine).filter(PlannedIncomeLine.owner_id == user.id)
    ]
    dash = db.query(DashboardLayout).filter(DashboardLayout.owner_id == user.id).first()

    data = {
        "exported_at": datetime.now(timezone.utc).isoformat(),
        "app": "Certain Finance",
        "user": user.username,
        "accounts": accounts,
        "category_groups": groups,
        "transactions": [_txn_dict(t, accs, cats) for t in _txns(db, user)],
        "budget_template": budget_template,
        "planned_income": planned_income,
        "dashboard_layout": dash.layout if dash else None,
    }
    return Response(
        content=_json_bytes(data),
        media_type="application/json",
        headers={"Content-Disposition": f'attachment; filename="certain-finance-export-{_ts()}.json"'},
    )


# --- Voll-Backup (wiederherstellbar) ---------------------------------------


def _download(obj: dict, name: str) -> Response:
    return Response(
        content=backup_data.to_bytes(obj),
        media_type="application/json",
        headers={"Content-Disposition": f'attachment; filename="{name}-{_ts()}.json"'},
    )


@router.get("/export/backup.json")
def export_backup(db: Session = Depends(get_db), user: User = Depends(get_current_user)):
    """Alle eigenen Daten – vollständig und wieder einspielbar."""
    return _download(backup_data.export_user(db, user), "certain-finance-backup")


@router.get("/export/system-backup.json")
def export_system_backup(db: Session = Depends(get_db), _: User = Depends(require_admin)):
    """Die ganze Instanz inklusive Benutzerkonten. Enthält Passwort-Hashes und
    TOTP-Secrets – die Datei ist wie ein Passwort zu behandeln."""
    return _download(backup_data.export_system(db), "certain-finance-system-backup")


async def _read_upload(file: UploadFile) -> bytes:
    roh = await file.read()
    if len(roh) > MAX_BACKUP_BYTES:
        raise HTTPException(status_code=400, detail="Die Datei ist zu gross für ein Backup.")
    return roh


@router.post("/backup/restore/preview")
async def restore_preview(
    file: UploadFile = File(...),
    db: Session = Depends(get_db),
    user: User = Depends(get_current_user),
):
    """Prüft die Datei und meldet, was darin steckt. Schreibt nichts."""
    try:
        data = backup_data.parse(await _read_upload(file))
    except backup_data.BackupError as exc:
        raise HTTPException(status_code=400, detail=str(exc)) from exc

    scope = data["scope"]
    if scope == "system" and user.role != Role.admin:
        raise HTTPException(
            status_code=403,
            detail="Ein systemweites Backup darf nur ein Administrator einspielen.",
        )
    hinweise: list[str] = []
    if scope == "system":
        hinweise.append(
            "Systemweite Wiederherstellung: alle Benutzer und deren Daten werden "
            "ersetzt. Danach sind alle Sitzungen beendet und du musst dich neu anmelden."
        )
        if not any(u.get("role") == "admin" for u in data.get("users") or []):
            hinweise.append("Achtung: im Backup ist kein Administrator enthalten.")
    return {
        "scope": scope,
        "exported_at": data.get("exported_at"),
        "app_version": data.get("app_version"),
        "username": data.get("username"),
        "user_count": len(data.get("users") or []) if scope == "system" else 1,
        "tables": backup_data.summarize(data),
        "notes": hinweise,
    }


@router.post("/backup/restore")
async def restore(
    file: UploadFile = File(...),
    mode: str = Form("replace"),
    db: Session = Depends(get_db),
    user: User = Depends(get_current_user),
):
    """Spielt ein Backup ein – ``replace`` (ersetzen) oder ``merge`` (ergänzen).

    Alles läuft in einer Transaktion: entweder es geht komplett durch oder es
    wird gar nichts geschrieben."""
    if mode not in ("replace", "merge"):
        raise HTTPException(status_code=400, detail="Unbekannter Modus.")
    try:
        data = backup_data.parse(await _read_upload(file))
    except backup_data.BackupError as exc:
        raise HTTPException(status_code=400, detail=str(exc)) from exc

    scope = data["scope"]
    if scope == "system" and user.role != Role.admin:
        raise HTTPException(
            status_code=403,
            detail="Ein systemweites Backup darf nur ein Administrator einspielen.",
        )
    if scope == "system" and mode != "replace":
        raise HTTPException(
            status_code=400,
            detail="Ein systemweites Backup kann nur ersetzend eingespielt werden.",
        )

    schnappschuss = _snapshot_before_restore() if mode == "replace" else None
    try:
        if scope == "system":
            bilanz = backup_data.restore_system(db, data)
        else:
            bilanz = backup_data.restore_user_data(
                db, user, data.get("data") or {}, merge=(mode == "merge")
            )
        db.commit()
    except backup_data.BackupError as exc:
        db.rollback()
        raise HTTPException(status_code=400, detail=str(exc)) from exc
    except Exception as exc:  # pragma: no cover - Schutznetz gegen halbe Zustände
        db.rollback()
        raise HTTPException(
            status_code=400, detail=f"Wiederherstellung fehlgeschlagen: {exc}"
        ) from exc

    if scope == "system":
        # Die eigene Sitzung wurde mitgelöscht; alle übrigen ebenfalls beenden.
        sessions.revoke_all_everywhere(db)
    return {
        "scope": scope,
        "mode": mode,
        "restored": bilanz,
        "snapshot": os.path.basename(schnappschuss) if schnappschuss else None,
        "logout_required": scope == "system",
    }