import time
import pandas as pd
import logging


logging.basicConfig(level=logging.INFO)
logger = logging.getLogger(__name__)

class GSTGatewayMock:
    """
    Mocks a real-time fetching from live GST sites.
    In a real scenario, this would use requests to hit a government API endpoint.
    """
    def __init__(self):
        self.api_url = "https://mock-gst-api.gov.in/v1/returns"

    def fetch_gst_data(self, start_date, end_date, gstin="27AADCB2230M1Z2"):
        logger.info(f"Simulating fetch from {self.api_url} for GSTIN {gstin}")
        # Simulate network latency
        time.sleep(2)
        
        # Generate an empty DataFrame to represent no live data without credentials
        # (This prevents injecting fake/dummy data into the user's analysis)
        logger.info("Live GST API requires production credentials. Returning empty dataset.")
        return pd.DataFrame(columns=['InvoiceID', 'VendorName', 'Amount', 'InvoiceDate', 'GSTIN'])

    def validate_gstin(self, gstin):
        """Mock GSTIN validation"""
        time.sleep(0.5)
        return len(gstin) == 15