Extract shared mail routing and IMAP folder helpers

Prompt since previous commit: execute step 1

Centralized route targets, source-folder policy, and modified UTF-7 mailbox quoting. Verification: py_compile, route/folder consistency, and git diff --check passed.

kopieer_naar_backup.py

@@ -24,6 +24,7 @@ import time
 import config
 from pathlib import Path
 from datetime import datetime, timezone
+from imap_utils import list_folders, quote_mailbox
 
 LOG_FILE    = Path(__file__).parent / "backup_log.json"
 
@@ -33,13 +34,6 @@ SKIP_MAPPEN = {"INBOX.Trash", "INBOX.Spam"}
 
 # ── helpers ───────────────────────────────────────────────────────────────────
 
-def parse_folder_name(raw: bytes) -> str | None:
-    decoded = raw.decode("utf-8", errors="replace")
-    m = re.match(r'\(.*?\)\s+".*?"\s+(.*)', decoded)
-    if m:
-        return m.group(1).strip().strip('"')
-    return None
-
 
 def parse_flags(flag_str: str) -> list[str]:
     """Haal standaard IMAP-vlaggen op uit fetch-response."""
@@ -60,7 +54,7 @@ def parse_internaldate(response: bytes) -> str | None:
 
 def haal_bestaande_message_ids(mail: imaplib.IMAP4_SSL, folder: str) -> set[str]:
     """Geef alle Message-IDs terug die al in een doelmap staan."""
-    status, data = mail.select(f'"{folder}"', readonly=True)
+    status, data = mail.select(quote_mailbox(folder), readonly=True)
     if status != "OK" or int(data[0]) == 0:
         return set()
 
@@ -100,7 +94,7 @@ def kopieer_map(
     Geeft (gekopieerd, overgeslagen) terug.
     """
     # Selecteer bronmap
-    status, data = bron.select(f'"{folder}"', readonly=True)
+    status, data = bron.select(quote_mailbox(folder), readonly=True)
     if status != "OK":
         print(f"  Kan bronmap niet openen: {folder}")
         return 0, 0
@@ -116,7 +110,7 @@ def kopieer_map(
     ids = data[0].split()
 
     # Zorg dat doelmap bestaat
-    doel.create(f'"{folder}"')   # negeer fout als al bestaat
+    doel.create(quote_mailbox(folder))   # negeer fout als al bestaat
 
     # Welke Message-IDs staan al in de doelmap?
     bestaande = haal_bestaande_message_ids(doel, folder)
@@ -166,7 +160,7 @@ def kopieer_map(
         # Schrijf naar doelmap
         flag_str = "(" + " ".join(flags) + ")" if flags else "()"
         status, _ = doel.append(
-            f'"{folder}"',
+            quote_mailbox(folder),
             flag_str,
             internaldate,
             raw_message,
@@ -242,9 +236,7 @@ def run():
         sys.exit(1)
 
     # Mappenlijst van bron
-    status, raw_folders = bron.list()
-    alle_mappen = [parse_folder_name(f) for f in raw_folders if f]
-    alle_mappen = [f for f in alle_mappen if f and f not in SKIP_MAPPEN]
+    alle_mappen = [folder for folder in list_folders(bron) if folder not in SKIP_MAPPEN]
     alle_mappen.sort()
 
     log = load_log()