from __future__ import annotations

import json
import os
from dataclasses import asdict, dataclass
from pathlib import Path


@dataclass
class AgentPersistentState:
    inventory_sequence: int = 0
    telemetry_sequence: int = 0


class AgentStateStore:
    def __init__(self, state_file: Path, credential_file: Path) -> None:
        self.state_file = state_file
        self.credential_file = credential_file

    def load(self) -> AgentPersistentState:
        try:
            payload = json.loads(self.state_file.read_text(encoding="utf-8"))
            return AgentPersistentState(
                inventory_sequence=int(payload.get("inventory_sequence", 0)),
                telemetry_sequence=int(payload.get("telemetry_sequence", 0)),
            )
        except (OSError, ValueError, TypeError, json.JSONDecodeError):
            return AgentPersistentState()

    def save(self, state: AgentPersistentState) -> None:
        self.state_file.parent.mkdir(parents=True, exist_ok=True)
        temporary = self.state_file.with_suffix(".tmp")
        temporary.write_text(json.dumps(asdict(state), sort_keys=True), encoding="utf-8")
        os.replace(temporary, self.state_file)

    def credential(self) -> str | None:
        try:
            value = self.credential_file.read_text(encoding="utf-8").strip()
            return value or None
        except OSError:
            return None

    def save_credential(self, credential: str) -> None:
        self.credential_file.parent.mkdir(parents=True, exist_ok=True)
        self.credential_file.write_text(credential, encoding="utf-8")
        os.chmod(self.credential_file, 0o600)