"""
ZFS Snapshot Monitoring Module.
Monitors the last sent ZFS snapshot timestamp and calculates age for alerting.
"""
from ..base import BaseExporter
from ..utils import safe_file_operation
import sys
import re
from datetime import datetime


class CustomExporter(BaseExporter):
    """
    Exporter for ZFS snapshot monitoring.
    Reads snapshot timestamp from /home/.zfs_last_sent_snapshot and exports metrics.
    """
    def metric_config(self):
        """Define metrics for ZFS snapshot monitoring"""
        return {
            "zfs_last_sent_snapshot_timestamp": {"type": "Gauge", "labels": []},
            "zfs_last_sent_snapshot_age_seconds": {"type": "Gauge", "labels": []},
        }

    def generate(self):
        """Generate ZFS snapshot metrics by reading and parsing the snapshot file"""
        snapshot_timestamp = self.metrics.get('zfs_last_sent_snapshot_timestamp')
        snapshot_age = self.metrics.get('zfs_last_sent_snapshot_age_seconds')

        with safe_file_operation(open, '/home/.zfs_last_sent_snapshot', 'r') as f:
            content = f.read().strip()

            match = re.match(r'LAST_SENT_SNAPSHOT=(.+?)_(\d{4}-\d{2}-\d{2}_\d{2}:\d{2}:\d{2})$', content)

            if match:
                timestamp_str = match.group(2)

                dt = datetime.strptime(timestamp_str, '%Y-%m-%d_%H:%M:%S')
                epoch_time = dt.timestamp()

                current_time = datetime.now().timestamp()
                age_seconds = current_time - epoch_time
                snapshot_timestamp.set(epoch_time)
                snapshot_age.set(age_seconds)
            else:
                print(f"Failed to parse snapshot format: {content}", file=sys.stderr)