"""Persistence helpers for provider/model configuration and cached Excel context."""

import json
import os

from .config import PROVIDERS_BY_NAME, STATE_FILE


def find_env_api_key(env_names: tuple[str, ...]) -> str | None:
	"""Return the first non-empty API key found in the provided env var names."""
	for env_name in env_names:
		value = os.getenv(env_name)
		if value:
			return value
	return None


def load_state() -> dict[str, str] | None:
	"""Load and validate persisted provider state from disk.

	Returns None when the file is missing, malformed, or missing required keys.
	"""
	if not STATE_FILE.exists():
		return None
	try:
		data = json.loads(STATE_FILE.read_text(encoding="utf-8"))
	except (OSError, json.JSONDecodeError):
		return None

	provider_name = data.get("provider")
	api_key = data.get("api_key")
	model = data.get("model")
	# Guard against stale or corrupted state payloads.
	if not isinstance(provider_name, str) or provider_name not in PROVIDERS_BY_NAME:
		return None
	if not isinstance(api_key, str) or not api_key:
		return None
	if not isinstance(model, str) or not model:
		return None
	state: dict[str, str] = {"provider": provider_name, "api_key": api_key, "model": model}

	excel_dir = data.get("excel_dir")
	excel_signature = data.get("excel_signature")
	excel_info = data.get("excel_info")
	excel_info_format_version = data.get("excel_info_format_version")
	if isinstance(excel_dir, str) and excel_dir:
		state["excel_dir"] = excel_dir
	if isinstance(excel_signature, str) and excel_signature:
		state["excel_signature"] = excel_signature
	if isinstance(excel_info, str) and excel_info:
		state["excel_info"] = excel_info
	if isinstance(excel_info_format_version, str) and excel_info_format_version:
		state["excel_info_format_version"] = excel_info_format_version

	return state


def save_state(
	provider_name: str,
	api_key: str,
	model: str,
	*,
	excel_dir: str | None = None,
	excel_signature: str | None = None,
	excel_info: str | None = None,
	excel_info_format_version: str | None = None,
) -> None:
	"""Persist provider/model state and optional Excel metadata cache fields."""
	payload: dict[str, str] = {"provider": provider_name, "api_key": api_key, "model": model}
	if excel_dir:
		payload["excel_dir"] = excel_dir
	if excel_signature:
		payload["excel_signature"] = excel_signature
	if excel_info:
		payload["excel_info"] = excel_info
	if excel_info_format_version:
		payload["excel_info_format_version"] = excel_info_format_version
	STATE_FILE.write_text(json.dumps(payload, indent=2), encoding="utf-8")
	try:
		# Restrict file permissions because API keys are stored in this file.
		os.chmod(STATE_FILE, 0o600)
	except OSError:
		# Best effort; some filesystems may not support chmod.
		pass