refactor: centralize slugify in utils (#30)

Add utils.slugify.slugify (ASCII-safe, matches former export_api).
Remove duplicate implementations from api/export_api.py and
scripts/export.py; add regression tests.
Closes #30

Author: clean6378-max-it

api/export_api.py

@@ -14,6 +14,7 @@
 from utils.md_exporter import session_to_markdown
 from utils.json_exporter import session_to_json
 from utils.exclusion_rules import is_session_excluded
+from utils.slugify import slugify
 
 export_bp = Blueprint("export", __name__)
 
@@ -49,13 +50,6 @@ def get_export_state():
     })
 
 
-def _slugify(text: str) -> str:
-    import re
-    text = text.lower()
-    text = re.sub(r"[^a-z0-9]+", "-", text)
-    return text.strip("-")
-
-
 @export_bp.route("/api/export", methods=["POST"])
 def bulk_export():
     body = request.get_json(silent=True) or {}
@@ -97,9 +91,9 @@ def bulk_export():
 
                     stats = compute_stats(session)
                     md = session_to_markdown(session, stats)
-                    title_slug = _slugify(session["title"]) or "session"
+                    title_slug = slugify(session["title"]) or "session"
                     short_id = sid[:8]
-                    proj_slug = _slugify(project["name"])
+                    proj_slug = slugify(project["name"])
                     ts = session["metadata"].get("first_timestamp", "")
                     ts_file = ts[:19].replace(":", "-") if ts else "0000-00-00T00-00-00"
                     rel_path = f"{proj_slug}/{ts_file}__{title_slug}__{short_id}.md"
@@ -155,7 +149,7 @@ def export_session(project_name, session_id):
     if is_session_excluded(rules, session, project_name):
         return jsonify({"error": "Session not found"}), 404
     stats = compute_stats(session)
-    title_slug = _slugify(session["title"]) or "session"
+    title_slug = slugify(session["title"]) or "session"
 
     if fmt == "json":
         content = session_to_json(session, stats)

scripts/export.py

@@ -33,6 +33,7 @@
     load_rules,
     is_session_excluded,
 )
+from utils.slugify import slugify
 
 
 STATE_DIR = os.path.join(os.path.expanduser("~"), ".claude-code-chat-browser")
@@ -366,9 +367,9 @@ def cmd_export(args):
                 meta["first_timestamp"] = ts
             date_str = ts[:10]
             ts_file = ts[:19].replace(":", "-")   # 2026-02-10T01-46-15
-            title_slug = _slugify(session["title"])
+            title_slug = slugify(session["title"])
             short_id = sid[:8]
-            project_slug = _slugify(project["name"])
+            project_slug = slugify(project["name"])
 
             if fmt in ("md", "both"):
                 md = session_to_markdown(session, stats)
@@ -444,7 +445,7 @@ def cmd_export(args):
 
 def _export_single(session: dict, stats: dict, fmt: str, out_dir: str):
     """Write one session to disk as md, json, or both."""
-    title_slug = _slugify(session["title"])
+    title_slug = slugify(session["title"])
     short_id = session["session_id"][:8]
     ts = session["metadata"].get("first_timestamp", "")
     ts_file = ts[:19].replace(":", "-") if ts else "0000-00-00T00-00-00"
@@ -609,18 +610,6 @@ def _save_state(sessions: dict, count: int, out_dir: str):
         json.dump(state, f, indent=2)
 
 
-def _slugify(text: str) -> str:
-    slug = ""
-    for c in text.lower():
-        if c.isalnum():
-            slug += c
-        elif c in " -_/.":
-            slug += "-"
-    while "--" in slug:
-        slug = slug.replace("--", "-")
-    return slug.strip("-")
-
-
 def _die(msg: str):
     print(f"Error: {msg}", file=sys.stderr)
     sys.exit(1)

tests/test_slugify.py

@@ -0,0 +1,30 @@
+"""Regression tests for utils.slugify (Issue #30 / CCC8).
+
+Historically ``scripts/export.py`` used ``isalnum()`` (Unicode letters preserved)
+while ``api/export_api.py`` used ASCII-only ``[^a-z0-9]+``. The canonical
+implementation matches the API for portable zip / download filenames.
+"""
+
+from utils.slugify import slugify
+
+
+def test_ascii_words_hyphenated():
+    assert slugify("Hello World") == "hello-world"
+
+
+def test_punctuation_collapses_to_single_hyphen():
+    assert slugify("foo__bar") == "foo-bar"
+    assert slugify("a.b.c") == "a-b-c"
+
+
+def test_unicode_letters_become_ascii_safe():
+    """Old CLI kept Latin-1 letters (e.g. é); canonical slug strips to ASCII."""
+    assert slugify("Café noir") == "caf-noir"
+
+
+def test_empty_after_strip():
+    assert slugify("!!!") == ""
+
+
+def test_digits_preserved():
+    assert slugify("Issue 42 Fix") == "issue-42-fix"

utils/slugify.py

@@ -0,0 +1,18 @@
+"""Filesystem- and URL-safe slugs for export paths and download names.
+
+Uses ASCII letters and digits only; other characters (including Unicode
+letters and punctuation) become hyphen runs, then trimmed. Matches the
+historical behavior of ``api/export_api.py`` and avoids platform-specific
+issues with non-ASCII paths inside zip archives.
+"""
+
+from __future__ import annotations
+
+import re
+
+
+def slugify(text: str) -> str:
+    """Lowercase *text* and replace each run of non-[a-z0-9] with a single hyphen."""
+    text = text.lower()
+    text = re.sub(r"[^a-z0-9]+", "-", text)
+    return text.strip("-")