"""SSM-backed state for tracking chart freshness across invocations."""
import json

import boto3
from botocore.exceptions import ClientError

import config

logger = config.logger
_ssm = boto3.client('ssm')

# Shape: {"pending_date": "2026-06-29", "detected_at": "2026-06-30T10:00:00+00:00", "alerted": false}  # noqa: E501
# Empty dict means no new Spotify date is pending.


def load() -> dict:
    """Return current state from SSM, or {} if none exists."""
    try:
        resp = _ssm.get_parameter(Name=config.SSM_STATE_PARAM)
        try:
            value = json.loads(resp['Parameter']['Value'])
        except json.JSONDecodeError:
            logger.warning('SSM state contains invalid JSON; returning empty state')
            return {}
        if not isinstance(value, dict):
            logger.warning(
                f'SSM state is not a JSON object (got {type(value).__name__}); '
                'returning empty state'
            )
            return {}
        return value
    except ClientError as e:
        if e.response['Error']['Code'] == 'ParameterNotFound':
            return {}
        raise


def save(state: dict) -> None:
    """Persist state to SSM."""
    _ssm.put_parameter(
        Name=config.SSM_STATE_PARAM,
        Value=json.dumps(state),
        Type='String',
        Overwrite=True,
    )
    logger.info(f'State saved: {state}')


def clear() -> None:
    """Clear state — called when charts are back in sync."""
    save({})