#!/usr/bin/env python3
"""
File monitoring and discovery for UPI files.
Scans SFTP directories for new files across multiple banks.

Filename convention handled:
    <LOCATION>_DDMMYYYY_<CODE>_UPI.txt.gz

Example:
    TUMLUK_31052026_8C_UPI.txt.gz
"""

import re
from typing import List, Tuple, Dict
from logging_config import get_logger
from config import get_config
from .sftp_client import SFTPClient

logger = get_logger(__name__)


class FileMonitor:
    """Monitors SFTP for new UPI files."""

    def __init__(self, sftp_client: SFTPClient = None):
        self.config = get_config()
        self.sftp_client = sftp_client or SFTPClient()

    def scan_for_new_files(self, processed_filenames: List[str]) -> List[Tuple[str, str, str]]:
        """
        Scan all bank directories for new UPI files.

        Returns:
            List of (filename, bankcode, full_remote_path)
        """
        new_files: List[Tuple[str, str, str]] = []

        for bank_code in self.config.bank_codes:
            remote_path = f"{self.config.sftp_base_path}/{bank_code}/UPI"

            #  Pattern for UPI files
            files = self.sftp_client.list_files(
                remote_path,
                pattern='*_UPI.txt.gz'
            )

            for filename in files:
                if filename not in processed_filenames:
                    full_path = f"{remote_path}/{filename}"
                    new_files.append((filename, bank_code, full_path))
                    logger.info(f"Found new UPI file: {filename} (bank: {bank_code})")
                else:
                    logger.debug(f"Skipping already processed UPI file: {filename}")

        logger.info(f"UPI scan complete: Found {len(new_files)} new files")
        return new_files

    @staticmethod
    def parse_filename(filename: str) -> Dict[str, str]:
        """
        Parse UPI filename.

        Expected format:
            <LOCATION>_DDMMYYYY_<CODE>_UPI.txt.gz

        Example:
            TUMLUK_31052026_8C_UPI.txt.gz
        """

        pattern = r'^([A-Z]+)_(\d{2})(\d{2})(\d{4})_([A-Z0-9]+)_UPI\.txt\.gz$'
        match = re.match(pattern, filename, flags=re.IGNORECASE)

        if not match:
            logger.warning(f"Could not parse UPI filename: {filename}")
            return {}

        location, day, month, year, code = match.groups()

        return {
            'filename': filename,
            'location': location,
            'day': day,
            'month': month,
            'year': year,
            'code': code,
            'timestamp': f"{day}/{month}/{year}"
        }

    def __enter__(self):
        if not self.sftp_client.sftp:
            self.sftp_client.connect()
        return self

    def __exit__(self, exc_type, exc_val, exc_tb):
        self.sftp_client.disconnect()