"""Check Spotify provider API for the latest available daily chart date."""
import base64
from datetime import date, timedelta

import boto3
import requests

import config

logger = config.logger
_secrets = boto3.client('secretsmanager')

# How many days back to probe (today, yesterday, day before)
_PROBE_DAYS = 3
# Statuses that mean "no chart yet for this date" — try an earlier date
_NOT_FOUND_STATUSES = {403, 404}


def get_latest_chart_date() -> str | None:
    """Return the most recent date (YYYY-MM-DD) for which Spotify has daily chart data.

    Probes today → yesterday → 2 days ago. Returns the first hit, or None
    if the Spotify API is unreachable / returning errors (so we don't
    misattribute a Spotify outage as a Chartmetric lag).
    """
    try:
        token = _get_oauth_token()
    except Exception:
        logger.exception('Failed to obtain Spotify OAuth token')
        return None

    today = date.today()
    for days_back in range(_PROBE_DAYS):
        candidate = today - timedelta(days=days_back)
        status = _probe(token, candidate)
        if status == 200:
            logger.info(f'Spotify chart available for {candidate}')
            return candidate.isoformat()
        elif status is None:
            # Network error — treat as Spotify API down
            logger.warning(f'Network error probing Spotify chart for {candidate}')
            return None
        elif status not in _NOT_FOUND_STATUSES:
            # 401 / 429 / 5xx — real API error, not a missing date
            logger.error(
                f'Spotify API returned unexpected status {status} for {candidate}'
            )
            return None
        # 404 / 403 = not yet available for this date, try earlier

    logger.warning(f'No daily chart found in last {_PROBE_DAYS} days')
    return None


def _probe(token: str, chart_date: date) -> int | None:
    """GET the chart URL with stream=True (no body downloaded).

    Returns HTTP status code, or None on network error.
    """
    url = config.SPOTIFY_CHART_URL.format(
        year=chart_date.year,
        month=f'{chart_date.month:02d}',
        day=f'{chart_date.day:02d}',
    )
    try:
        # stream=True + immediate close avoids downloading the full chart file
        resp = requests.get(
            url,
            headers={'Authorization': f'Bearer {token}'},
            stream=True,
            timeout=10,
        )
        resp.close()
        return resp.status_code
    except requests.RequestException as e:
        logger.warning(f'Request error for {chart_date}: {e}')
        return None


def _get_oauth_token() -> str:
    client_id = _get_secret('SPOTIFY_API_CLIENT_ID')
    client_secret = _get_secret('SPOTIFY_API_CLIENT_SECRET')
    credentials = base64.b64encode(f'{client_id}:{client_secret}'.encode()).decode()
    resp = requests.post(
        config.SPOTIFY_OAUTH_URL,
        data={'grant_type': 'client_credentials'},
        headers={'Authorization': f'Basic {credentials}'},
        timeout=10,
    )
    resp.raise_for_status()
    return resp.json()['access_token']


def _get_secret(key: str) -> str:
    resp = _secrets.get_secret_value(SecretId=f'{config.SPOTIFY_SECRETS_PATH}/{key}')
    return resp['SecretString']