from __future__ import annotations

import json
from datetime import datetime, timezone
from typing import Any

from database import get_db, init_db

BACKUP_VERSION = 1
TABLES = ("guest_links", "guest_claims", "traffic_grants")


def _now_iso() -> str:
    return datetime.now(timezone.utc).replace(microsecond=0).isoformat()


async def export_backup() -> dict[str, Any]:
    db = await get_db()
    try:
        payload: dict[str, Any] = {
            "format": "remna-site-backup",
            "version": BACKUP_VERSION,
            "exported_at": _now_iso(),
        }
        for table in TABLES:
            cursor = await db.execute(f"SELECT * FROM {table} ORDER BY id ASC")
            rows = await cursor.fetchall()
            payload[table] = [dict(row) for row in rows]
        return payload
    finally:
        await db.close()


def validate_backup(data: Any) -> dict[str, Any]:
    if not isinstance(data, dict):
        raise ValueError("Файл должен быть JSON-объектом")
    if data.get("format") != "remna-site-backup":
        raise ValueError("Неверный формат бэкапа (ожидается remna-site-backup)")
    version = data.get("version")
    if version != BACKUP_VERSION:
        raise ValueError(f"Неподдерживаемая версия бэкапа: {version}")
    for table in TABLES:
        if table not in data or not isinstance(data[table], list):
            raise ValueError(f"В бэкапе нет таблицы {table}")
    return data


async def import_backup(data: dict[str, Any]) -> dict[str, int]:
    validate_backup(data)
    await init_db()

    links = data["guest_links"]
    claims = data["guest_claims"]
    grants = data["traffic_grants"]

    db = await get_db()
    try:
        await db.execute("PRAGMA foreign_keys = OFF")
        await db.execute("BEGIN IMMEDIATE")
        await db.execute("DELETE FROM traffic_grants")
        await db.execute("DELETE FROM guest_claims")
        await db.execute("DELETE FROM guest_links")

        for row in links:
            cols = [
                "id",
                "token",
                "link_type",
                "title",
                "value",
                "max_uses",
                "used_count",
                "is_active",
                "expires_at",
                "created_at",
                "note",
                "duration_days",
                "plan_traffic_gb",
            ]
            values = [row.get(c) for c in cols]
            # defaults for older backups
            if values[cols.index("duration_days")] is None:
                values[cols.index("duration_days")] = 0
            if values[cols.index("plan_traffic_gb")] is None:
                values[cols.index("plan_traffic_gb")] = 0
            placeholders = ", ".join("?" for _ in cols)
            await db.execute(
                f"INSERT INTO guest_links ({', '.join(cols)}) VALUES ({placeholders})",
                values,
            )

        for row in claims:
            cols = ["id", "link_id", "username", "user_uuid", "detail", "claimed_at"]
            values = [row.get(c) for c in cols]
            placeholders = ", ".join("?" for _ in cols)
            await db.execute(
                f"INSERT INTO guest_claims ({', '.join(cols)}) VALUES ({placeholders})",
                values,
            )

        for row in grants:
            cols = [
                "id",
                "claim_id",
                "link_id",
                "user_uuid",
                "username",
                "bytes_added",
                "expires_at",
                "reverted_at",
                "status",
                "last_error",
                "created_at",
            ]
            values = [row.get(c) for c in cols]
            if values[cols.index("status")] is None:
                values[cols.index("status")] = "active"
            if values[cols.index("last_error")] is None:
                values[cols.index("last_error")] = ""
            if values[cols.index("username")] is None:
                values[cols.index("username")] = ""
            placeholders = ", ".join("?" for _ in cols)
            await db.execute(
                f"INSERT INTO traffic_grants ({', '.join(cols)}) VALUES ({placeholders})",
                values,
            )

        await db.commit()

        # восстановить autoincrement после вставки с явными id
        for table in TABLES:
            cursor = await db.execute(f"SELECT MAX(id) AS m FROM {table}")
            max_id = (await cursor.fetchone())["m"] or 0
            try:
                await db.execute("DELETE FROM sqlite_sequence WHERE name = ?", (table,))
                if max_id:
                    await db.execute(
                        "INSERT INTO sqlite_sequence(name, seq) VALUES (?, ?)",
                        (table, max_id),
                    )
            except Exception:
                # sqlite_sequence ещё нет — не критично
                pass
        await db.commit()
        await db.execute("PRAGMA foreign_keys = ON")
    except Exception:
        await db.execute("ROLLBACK")
        await db.execute("PRAGMA foreign_keys = ON")
        raise
    finally:
        await db.close()

    return {
        "guest_links": len(links),
        "guest_claims": len(claims),
        "traffic_grants": len(grants),
    }


def dumps_backup(payload: dict[str, Any]) -> bytes:
    return json.dumps(payload, ensure_ascii=False, indent=2).encode("utf-8")


def loads_backup(raw: bytes) -> dict[str, Any]:
    try:
        text = raw.decode("utf-8-sig")
    except UnicodeDecodeError as exc:
        raise ValueError("Файл должен быть в UTF-8") from exc
    try:
        data = json.loads(text)
    except json.JSONDecodeError as exc:
        raise ValueError(f"Некорректный JSON: {exc}") from exc
    return validate_backup(data)