"""Persistencia del estado de migración (migration-state.json).

El estado permite reanudar una migración interrumpida y evitar volver a
copiar mensajes ya migrados. Nunca se almacenan contraseñas aquí.
"""

import json
import os
import tempfile
import threading
from datetime import datetime, timezone

STATE_VERSION = 1


class MigrationState:
    def __init__(self, path: str, account: str):
        self.path = path
        self.account = account
        self._lock = threading.Lock()
        self._data = self._load()

    def _load(self) -> dict:
        if os.path.exists(self.path):
            with open(self.path, "r", encoding="utf-8") as f:
                data = json.load(f)
            data.setdefault("folders", {})
            return data
        return {
            "version": STATE_VERSION,
            "account": self.account,
            "created_at": datetime.now(timezone.utc).isoformat(),
            "folders": {},
        }

    def save(self) -> None:
        with self._lock:
            self._data["updated_at"] = datetime.now(timezone.utc).isoformat()
            target_dir = os.path.dirname(os.path.abspath(self.path)) or "."
            os.makedirs(target_dir, exist_ok=True)
            fd, tmp_path = tempfile.mkstemp(prefix=".migration-state-", dir=target_dir)
            try:
                with os.fdopen(fd, "w", encoding="utf-8") as f:
                    json.dump(self._data, f, indent=2, ensure_ascii=False)
                os.replace(tmp_path, self.path)
            finally:
                if os.path.exists(tmp_path):
                    try:
                        os.remove(tmp_path)
                    except OSError:
                        pass

    def _folder(self, folder: str) -> dict:
        return self._data["folders"].setdefault(
            folder,
            {"fingerprints": {}, "last_scanned_a_uid": 0, "a_uidvalidity": None},
        )

    def get_uidvalidity(self, folder: str):
        return self._folder(folder).get("a_uidvalidity")

    def set_uidvalidity(self, folder: str, value) -> None:
        f = self._folder(folder)
        if f.get("a_uidvalidity") != value:
            f["a_uidvalidity"] = value
            f["last_scanned_a_uid"] = 0

    def get_last_scanned_uid(self, folder: str) -> int:
        return self._folder(folder).get("last_scanned_a_uid", 0)

    def set_last_scanned_uid(self, folder: str, uid: int) -> None:
        f = self._folder(folder)
        f["last_scanned_a_uid"] = max(f.get("last_scanned_a_uid", 0), uid)

    def has_fingerprint(self, folder: str, fingerprint: str) -> bool:
        return fingerprint in self._folder(folder)["fingerprints"]

    def mark_migrated(self, folder: str, fingerprint: str, a_uid: int, b_uid, size: int) -> None:
        self._folder(folder)["fingerprints"][fingerprint] = {
            "a_uid": a_uid,
            "b_uid": b_uid,
            "size": size,
            "migrated_at": datetime.now(timezone.utc).isoformat(),
        }

    def folders_seen(self) -> list[str]:
        return list(self._data["folders"].keys())