changedetection.io/changedetectionio/processors/restock_diff.py

from . import difference_detection_processor
from loguru import logger
import hashlib
import urllib3

urllib3.disable_warnings(urllib3.exceptions.InsecureRequestWarning)

name = 'Re-stock detection for single product pages'
description = 'Detects if the product goes back to in-stock'

class UnableToExtractRestockData(Exception):
    def __init__(self, status_code):
        # Set this so we can use it in other parts of the app
        self.status_code = status_code
        return

class perform_site_check(difference_detection_processor):
    screenshot = None
    xpath_data = None

    def run_changedetection(self, watch, skip_when_checksum_same=True):

        if not watch:
            raise Exception("Watch no longer exists.")

        # Unset any existing notification error
        update_obj = {'last_notification_error': False, 'last_error': False}

        self.screenshot = self.fetcher.screenshot
        self.xpath_data = self.fetcher.xpath_data

        # Track the content type
        update_obj['content_type'] = self.fetcher.headers.get('Content-Type', '')
        update_obj["last_check_status"] = self.fetcher.get_last_status_code()

        # Main detection method
        fetched_md5 = None
        if self.fetcher.instock_data:
            fetched_md5 = hashlib.md5(self.fetcher.instock_data.encode('utf-8')).hexdigest()
            # 'Possibly in stock' comes from stock-not-in-stock.js when no string found above the fold.
            update_obj["in_stock"] = True if self.fetcher.instock_data == 'Possibly in stock' else False
            logger.debug(f"Watch UUID {watch.get('uuid')} restock check returned '{self.fetcher.instock_data}' from JS scraper.")
        else:
            raise UnableToExtractRestockData(status_code=self.fetcher.status_code)

        # The main thing that all this at the moment comes down to :)
        changed_detected = False
        logger.debug(f"Watch UUID {watch.get('uuid')} restock check - Previous MD5: {watch.get('previous_md5')}, Fetched MD5 {fetched_md5}")

        if watch.get('previous_md5') and watch.get('previous_md5') != fetched_md5:
            # Yes if we only care about it going to instock, AND we are in stock
            if watch.get('in_stock_only') and update_obj["in_stock"]:
                changed_detected = True

            if not watch.get('in_stock_only'):
                # All cases
                changed_detected = True

        # Always record the new checksum
        update_obj["previous_md5"] = fetched_md5
        return changed_detected, update_obj, self.fetcher.instock_data.encode('utf-8').strip()