Price tracker - Use a more memory efficient price scraper, use subprocess on linux for cleaner memory management. (#3864)

changedetectionio/processors/restock_diff/pure_python_extractor.py

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+"""
+Pure Python metadata extractor - no lxml, no memory leaks.
+
+This module provides a fast, memory-efficient alternative to extruct for common
+e-commerce metadata extraction. It handles:
+- JSON-LD (covers 80%+ of modern sites)
+- OpenGraph meta tags
+- Basic microdata attributes
+
+Uses Python's built-in html.parser instead of lxml/libxml2, avoiding C-level
+memory allocation issues. For edge cases, the main processor can fall back to
+extruct (with subprocess isolation on Linux).
+"""
+
+from html.parser import HTMLParser
+import json
+import re
+from loguru import logger
+
+
+class JSONLDExtractor(HTMLParser):
+    """
+    Extract JSON-LD structured data from HTML.
+
+    Finds all <script type="application/ld+json"> tags and parses their content.
+    Handles multiple JSON-LD blocks on the same page.
+    """
+
+    def __init__(self):
+        super().__init__()
+        self.in_jsonld = False
+        self.data = []  # List of all parsed JSON-LD objects
+        self.current_script = []
+
+    def handle_starttag(self, tag, attrs):
+        if tag == 'script':
+            # Check if this is a JSON-LD script tag
+            for attr, value in attrs:
+                if attr == 'type' and value == 'application/ld+json':
+                    self.in_jsonld = True
+                    self.current_script = []
+                    break
+
+    def handle_data(self, data):
+        if self.in_jsonld:
+            self.current_script.append(data)
+
+    def handle_endtag(self, tag):
+        if tag == 'script' and self.in_jsonld:
+            # Parse the accumulated script content
+            script_content = ''.join(self.current_script)
+            if script_content.strip():
+                try:
+                    # Parse JSON (handles both objects and arrays)
+                    parsed = json.loads(script_content)
+                    if isinstance(parsed, list):
+                        self.data.extend(parsed)
+                    else:
+                        self.data.append(parsed)
+                except json.JSONDecodeError as e:
+                    logger.debug(f"Failed to parse JSON-LD: {e}")
+                    pass
+
+            self.in_jsonld = False
+            self.current_script = []
+
+
+class OpenGraphExtractor(HTMLParser):
+    """
+    Extract OpenGraph meta tags from HTML.
+
+    Finds <meta property="og:*"> tags commonly used for social media sharing.
+    """
+
+    def __init__(self):
+        super().__init__()
+        self.og_data = {}
+
+    def handle_starttag(self, tag, attrs):
+        if tag == 'meta':
+            attrs_dict = dict(attrs)
+            prop = attrs_dict.get('property', '')
+
+            # Extract OpenGraph properties
+            if prop.startswith('og:'):
+                content = attrs_dict.get('content', '')
+                if content:
+                    self.og_data[prop] = content
+
+
+class MicrodataExtractor(HTMLParser):
+    """
+    Extract basic microdata attributes from HTML.
+
+    Finds elements with itemprop attributes. This is a simplified extractor
+    that doesn't handle nested itemscope/itemtype hierarchies - for complex
+    cases, use extruct as fallback.
+    """
+
+    def __init__(self):
+        super().__init__()
+        self.microdata = {}
+        self.current_itemprop = None
+
+    def handle_starttag(self, tag, attrs):
+        attrs_dict = dict(attrs)
+
+        if 'itemprop' in attrs_dict:
+            itemprop = attrs_dict['itemprop']
+
+            # Price/currency/availability can be in content/href attributes
+            if itemprop == 'price':
+                if 'content' in attrs_dict:
+                    self.microdata['price'] = attrs_dict['content']
+                else:
+                    self.current_itemprop = 'price'
+
+            elif itemprop == 'priceCurrency':
+                if 'content' in attrs_dict:
+                    self.microdata['currency'] = attrs_dict['content']
+                else:
+                    self.current_itemprop = 'priceCurrency'
+
+            elif itemprop == 'availability':
+                # Can be in href (link) or content (meta)
+                if 'href' in attrs_dict:
+                    self.microdata['availability'] = attrs_dict['href']
+                elif 'content' in attrs_dict:
+                    self.microdata['availability'] = attrs_dict['content']
+                else:
+                    self.current_itemprop = 'availability'
+
+    def handle_data(self, data):
+        # Capture text content for itemprop elements
+        if self.current_itemprop == 'price':
+            # Try to extract numeric price from text
+            try:
+                price_text = re.sub(r'[^\d.]', '', data.strip())
+                if price_text:
+                    self.microdata['price'] = float(price_text)
+            except ValueError:
+                pass
+        elif self.current_itemprop == 'priceCurrency':
+            currency = data.strip()
+            if currency:
+                self.microdata['currency'] = currency
+        elif self.current_itemprop == 'availability':
+            availability = data.strip()
+            if availability:
+                self.microdata['availability'] = availability
+
+    def handle_endtag(self, tag):
+        # Reset current itemprop after closing tag
+        self.current_itemprop = None
+
+
+def extract_metadata_pure_python(html_content):
+    """
+    Extract structured metadata from HTML using pure Python parsers.
+
+    Returns a dict with three keys:
+    - 'json-ld': List of parsed JSON-LD objects
+    - 'opengraph': Dict of OpenGraph properties
+    - 'microdata': Dict of microdata properties
+
+    Args:
+        html_content: HTML string to parse
+
+    Returns:
+        dict: Extracted metadata in three formats
+    """
+    result = {
+        'json-ld': [],
+        'opengraph': {},
+        'microdata': {}
+    }
+
+    # Extract JSON-LD
+    try:
+        jsonld_extractor = JSONLDExtractor()
+        jsonld_extractor.feed(html_content)
+        result['json-ld'] = jsonld_extractor.data
+        logger.trace(f"Pure Python: Found {len(jsonld_extractor.data)} JSON-LD blocks")
+    except Exception as e:
+        logger.debug(f"JSON-LD extraction failed: {e}")
+
+    # Extract OpenGraph
+    try:
+        og_extractor = OpenGraphExtractor()
+        og_extractor.feed(html_content)
+        result['opengraph'] = og_extractor.og_data
+        if result['opengraph']:
+            logger.trace(f"Pure Python: Found {len(og_extractor.og_data)} OpenGraph tags")
+    except Exception as e:
+        logger.debug(f"OpenGraph extraction failed: {e}")
+
+    # Extract Microdata
+    try:
+        microdata_extractor = MicrodataExtractor()
+        microdata_extractor.feed(html_content)
+        result['microdata'] = microdata_extractor.microdata
+        if result['microdata']:
+            logger.trace(f"Pure Python: Found microdata: {result['microdata']}")
+    except Exception as e:
+        logger.debug(f"Microdata extraction failed: {e}")
+
+    return result
+
+
+def query_price_availability(extracted_data):
+    """
+    Query extracted metadata for price and availability information.
+
+    Uses jsonpath_ng to query JSON-LD data (same approach as extruct).
+    Falls back to OpenGraph and microdata if JSON-LD doesn't have the data.
+
+    Args:
+        extracted_data: Dict from extract_metadata_pure_python()
+
+    Returns:
+        dict: {'price': float, 'currency': str, 'availability': str}
+    """
+    from jsonpath_ng import parse
+
+    result = {}
+
+    # 1. Try JSON-LD first (most reliable and common)
+    for data in extracted_data.get('json-ld', []):
+        try:
+            # Use jsonpath to find price/availability anywhere in the structure
+            price_parse = parse('$..(price|Price)')
+            availability_parse = parse('$..(availability|Availability)')
+            currency_parse = parse('$..(priceCurrency|currency|priceCurrency)')
+
+            price_results = [m.value for m in price_parse.find(data)]
+            if price_results and not result.get('price'):
+                # Handle various price formats
+                price_val = price_results[0]
+                if isinstance(price_val, (int, float)):
+                    result['price'] = float(price_val)
+                elif isinstance(price_val, str):
+                    # Extract numeric value from string
+                    try:
+                        result['price'] = float(re.sub(r'[^\d.]', '', price_val))
+                    except ValueError:
+                        pass
+
+            avail_results = [m.value for m in availability_parse.find(data)]
+            if avail_results and not result.get('availability'):
+                result['availability'] = str(avail_results[0])
+
+            curr_results = [m.value for m in currency_parse.find(data)]
+            if curr_results and not result.get('currency'):
+                result['currency'] = str(curr_results[0])
+
+            # If we found price, this JSON-LD block is good
+            if result.get('price'):
+                logger.debug(f"Pure Python: Found price data in JSON-LD: {result}")
+                break
+
+        except Exception as e:
+            logger.debug(f"Error querying JSON-LD: {e}")
+            continue
+
+    # 2. Try OpenGraph if JSON-LD didn't provide everything
+    og_data = extracted_data.get('opengraph', {})
+    if not result.get('price') and 'og:price:amount' in og_data:
+        try:
+            result['price'] = float(og_data['og:price:amount'])
+        except ValueError:
+            pass
+    if not result.get('currency') and 'og:price:currency' in og_data:
+        result['currency'] = og_data['og:price:currency']
+    if not result.get('availability') and 'og:availability' in og_data:
+        result['availability'] = og_data['og:availability']
+
+    # 3. Use microdata as last resort
+    microdata = extracted_data.get('microdata', {})
+    if not result.get('price') and 'price' in microdata:
+        result['price'] = microdata['price']
+    if not result.get('currency') and 'currency' in microdata:
+        result['currency'] = microdata['currency']
+    if not result.get('availability') and 'availability' in microdata:
+        result['availability'] = microdata['availability']
+
+    return result