#!/usr/bin/env python3
"""
Per-user Box.com OAuth token storage.

Box rotates refresh tokens on every refresh — every successful refresh returns
a NEW refresh token and invalidates the previous one. Always write back the
new pair via save_tokens() after a refresh, or the user will be silently
disconnected the next time around.

File: backend/box_tokens.json (gitignored — holds long-lived refresh tokens
that grant access to the user's Box account).
"""

import json
import os
from datetime import datetime, timedelta, timezone
from threading import Lock

_TOKENS_PATH = os.path.join(os.path.dirname(os.path.abspath(__file__)), 'box_tokens.json')
_lock = Lock()


def _default():
    return {'version': 1, 'users': {}}


def _load():
    if not os.path.exists(_TOKENS_PATH):
        return _default()
    try:
        with open(_TOKENS_PATH, 'r') as f:
            data = json.load(f)
        if 'users' not in data:
            data = _default()
        return data
    except (json.JSONDecodeError, OSError):
        return _default()


def _save(data):
    tmp = _TOKENS_PATH + '.tmp'
    with open(tmp, 'w') as f:
        json.dump(data, f, indent=2)
    os.replace(tmp, _TOKENS_PATH)


def _normalize(email):
    return (email or '').strip().lower()


def get_tokens(email):
    """Return the stored token record for `email`, or None."""
    email = _normalize(email)
    if not email:
        return None
    with _lock:
        return _load().get('users', {}).get(email)


def save_tokens(email, token_response, box_user=None):
    """
    Persist a Box token response for `email`.

    Args:
        email: Oliver-side user email (the QC tool identity, not the Box login)
        token_response: dict with at least access_token, refresh_token, expires_in (seconds)
        box_user: optional dict with Box user info {id, login, name}
    """
    email = _normalize(email)
    if not email:
        raise ValueError('email is required')
    if not token_response.get('access_token') or not token_response.get('refresh_token'):
        raise ValueError('token_response must include access_token and refresh_token')

    expires_in = int(token_response.get('expires_in', 3600))
    # Subtract a small skew so we refresh slightly before actual expiry.
    expires_at = datetime.now(timezone.utc) + timedelta(seconds=max(expires_in - 60, 60))

    with _lock:
        data = _load()
        prior = data.get('users', {}).get(email, {})
        record = {
            'access_token': token_response['access_token'],
            'refresh_token': token_response['refresh_token'],
            'access_token_expires_at': expires_at.isoformat().replace('+00:00', 'Z'),
            'connected_at': prior.get('connected_at') or datetime.now(timezone.utc).isoformat().replace('+00:00', 'Z'),
            'updated_at': datetime.now(timezone.utc).isoformat().replace('+00:00', 'Z'),
        }
        if box_user:
            record['box_user_id'] = box_user.get('id') or prior.get('box_user_id')
            record['box_user_login'] = box_user.get('login') or prior.get('box_user_login')
            record['box_user_name'] = box_user.get('name') or prior.get('box_user_name')
        else:
            for k in ('box_user_id', 'box_user_login', 'box_user_name'):
                if prior.get(k):
                    record[k] = prior[k]
        data.setdefault('users', {})[email] = record
        _save(data)
        return record


def delete_tokens(email):
    """Forget the Box connection for `email` (user clicks Disconnect)."""
    email = _normalize(email)
    with _lock:
        data = _load()
        if email in data.get('users', {}):
            del data['users'][email]
            _save(data)
            return True
        return False


def is_connected(email):
    return get_tokens(email) is not None


def access_token_is_expired(record):
    """True if the stored access token is past its expiry."""
    expires_at_str = (record or {}).get('access_token_expires_at')
    if not expires_at_str:
        return True
    try:
        expires_at = datetime.fromisoformat(expires_at_str.replace('Z', '+00:00'))
    except ValueError:
        return True
    return datetime.now(timezone.utc) >= expires_at