feat(fusion_accounting_bank_rec): memo_tokenizer for Canadian bank memo formats

Made-with: Cursor

fusion_accounting_bank_rec/services/__init__.py

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+from . import memo_tokenizer

fusion_accounting_bank_rec/services/memo_tokenizer.py

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+"""Extract searchable tokens from Canadian bank statement memos.
+
+Handles common memo formats from RBC, TD, Scotia, BMO, plus generic
+cheque-number and reference-number patterns. Output is normalized
+(uppercase, alphanumeric) for case-insensitive matching.
+"""
+
+import re
+
+REF_PATTERNS = [
+    (re.compile(r'\b(REF|REFERENCE)\s*#?\s*(\d+)\b', re.I), r'REF\2'),
+    (re.compile(r'\b(CHQ|CHEQUE|CHECK)\s*#?\s*(\d+)\b', re.I), r'CHEQUE\2'),
+    (re.compile(r'\b(INV|INVOICE)\s*#?\s*(\d+)\b', re.I), r'INV\2'),
+]
+
+MIN_TOKEN_LENGTH = 2
+
+
+def tokenize_memo(memo: str | None) -> list[str]:
+    """Return list of normalized tokens from a bank memo.
+
+    Empty/None input returns []. Order preserved (first occurrence wins
+    for de-duplication)."""
+    if not memo:
+        return []
+
+    text = memo.upper()
+    for pattern, replacement in REF_PATTERNS:
+        text = pattern.sub(replacement, text)
+
+    text = re.sub(r'[^A-Z0-9]+', ' ', text)
+    raw_tokens = text.split()
+
+    seen = set()
+    tokens = []
+    for tok in raw_tokens:
+        if len(tok) < MIN_TOKEN_LENGTH:
+            continue
+        if tok in seen:
+            continue
+        seen.add(tok)
+        tokens.append(tok)
+
+    return tokens