Clean up search engine

Notable changes:
1. Prevent excessive engine module imports.
2. Replace trivial usage of `join()`.
3. Keep the output text sorted whenever possible.
4. Close handles properly.
5. Print error to stderr, not stdout.
6. Report search job exit code.
7. Print exception message to stderr if exception was thrown when
   running a search job.
8. Utilize XML library to build XML data
   And use 2 spaces as indentation.

PR #21098.

src/searchengine/nova3/helpers.py

@@ -1,4 +1,4 @@
-#VERSION: 1.47
+#VERSION: 1.48
 
 # Author:
 #  Christophe DUMEZ (chris@qbittorrent.org)
@@ -35,12 +35,12 @@ import os
 import re
 import socket
 import socks
+import sys
 import tempfile
 import urllib.error
-import urllib.parse
 import urllib.request
 from collections.abc import Mapping
-from typing import Any, Dict, Optional
+from typing import Any, Optional
 
 
 def getBrowserUserAgent() -> str:
@@ -59,7 +59,7 @@ def getBrowserUserAgent() -> str:
     return f"Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:{nowVersion}.0) Gecko/20100101 Firefox/{nowVersion}.0"
 
 
-headers: Dict[str, Any] = {'User-Agent': getBrowserUserAgent()}
+headers: dict[str, Any] = {'User-Agent': getBrowserUserAgent()}
 
 # SOCKS5 Proxy support
 if "sock_proxy" in os.environ and len(os.environ["sock_proxy"].strip()) > 0:
@@ -91,51 +91,52 @@ def htmlentitydecode(s: str) -> str:
 
 def retrieve_url(url: str, custom_headers: Mapping[str, Any] = {}) -> str:
     """ Return the content of the url page as a string """
-    req = urllib.request.Request(url, headers={**headers, **custom_headers})
+
+    request = urllib.request.Request(url, headers={**headers, **custom_headers})
     try:
-        response = urllib.request.urlopen(req)
+        response = urllib.request.urlopen(request)
     except urllib.error.URLError as errno:
-        print(" ".join(("Connection error:", str(errno.reason))))
+        print(f"Connection error: {errno.reason}", file=sys.stderr)
         return ""
-    dat: bytes = response.read()
+    data: bytes = response.read()
+
     # Check if it is gzipped
-    if dat[:2] == b'\x1f\x8b':
+    if data[:2] == b'\x1f\x8b':
         # Data is gzip encoded, decode it
-        compressedstream = io.BytesIO(dat)
-        gzipper = gzip.GzipFile(fileobj=compressedstream)
-        extracted_data = gzipper.read()
-        dat = extracted_data
-    info = response.info()
+        with io.BytesIO(data) as compressedStream, gzip.GzipFile(fileobj=compressedStream) as gzipper:
+            data = gzipper.read()
+
     charset = 'utf-8'
     try:
-        ignore, charset = info['Content-Type'].split('charset=')
-    except Exception:
+        charset = response.getheader('Content-Type', '').split('charset=', 1)[1]
+    except IndexError:
         pass
-    datStr = dat.decode(charset, 'replace')
-    datStr = htmlentitydecode(datStr)
-    return datStr
+
+    dataStr = data.decode(charset, 'replace')
+    dataStr = htmlentitydecode(dataStr)
+    return dataStr
 
 
 def download_file(url: str, referer: Optional[str] = None) -> str:
     """ Download file at url and write it to a file, return the path to the file and the url """
-    fileHandle, path = tempfile.mkstemp()
-    file = os.fdopen(fileHandle, "wb")
+
     # Download url
-    req = urllib.request.Request(url, headers=headers)
+    request = urllib.request.Request(url, headers=headers)
     if referer is not None:
-        req.add_header('referer', referer)
-    response = urllib.request.urlopen(req)
-    dat = response.read()
+        request.add_header('referer', referer)
+    response = urllib.request.urlopen(request)
+    data = response.read()
+
     # Check if it is gzipped
-    if dat[:2] == b'\x1f\x8b':
+    if data[:2] == b'\x1f\x8b':
         # Data is gzip encoded, decode it
-        compressedstream = io.BytesIO(dat)
-        gzipper = gzip.GzipFile(fileobj=compressedstream)
-        extracted_data = gzipper.read()
-        dat = extracted_data
+        with io.BytesIO(data) as compressedStream, gzip.GzipFile(fileobj=compressedStream) as gzipper:
+            data = gzipper.read()
 
     # Write it to a file
-    file.write(dat)
-    file.close()
+    fileHandle, path = tempfile.mkstemp()
+    with os.fdopen(fileHandle, "wb") as file:
+        file.write(data)
+
     # return file path
-    return (path + " " + url)
+    return f"{path} {url}"