From 999585a5cfb5454f21586162b1d5387313a40f0d Mon Sep 17 00:00:00 2001
From: Ronald Tse <ronald.tse@ribose.com>
Date: Tue, 29 Sep 2026 18:08:48 +0800
Subject: [PATCH] feat: title_case word_separator and separate separator stage
 ops
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title_case gains the word_separator kwarg (parser, converter, engine).
Ruby parity: upcase the first character of every line, then of every
character following the separator; an empty separator leaves only the
per-line casing.

separate becomes a real engine op (join every codepoint with the
separator, default space) instead of an unsupported construct.

Fixes an infinite parse loop the kwargs path exposed: an unrecognized
token on the last line skipped to EOF, where _skip_line no longer
advances — the stage loop then spun. The kwarg peek now skips inline
whitespace first.
---
 src/interscript/engine.py | 19 +++++++++++++++++++
 src/interscript/isc.py    | 21 +++++++++++++++++++--
 tests/test_engine.py      | 26 ++++++++++++++++++++++++++
 tests/test_isc.py         | 15 +++++++++++++++
 4 files changed, 79 insertions(+), 2 deletions(-)

diff --git a/src/interscript/engine.py b/src/interscript/engine.py
index cb6e29b..39c7c00 100644
--- a/src/interscript/engine.py
+++ b/src/interscript/engine.py
@@ -164,6 +164,25 @@ def _run_op(self, op: dict, text: str) -> str:
             if self._loader is None:
                 raise ExecutionError(f"run {op['map']!r}: no map loader configured")
             return self._loader(target).transliterate(text)
+        if kind == "separate":
+            separator = op.get("separator", " ")
+            return separator.join(text)
+        if kind == "title_case":
+            # Ruby parity: upcase the first character of every line and
+            # of every segment following the word separator.
+            sep = op.get("word_separator", " ")
+            out = "\n".join(
+                line[:1].upper() + line[1:] for line in text.split("\n")
+            )
+            if sep != "":
+                out = re.sub(
+                    re.escape(sep) + "(.)",
+                    lambda m: m.group(1).upper(),
+                    out,
+                )
+            return out
+        if kind == "titlecase":
+            return text.title()
         if kind == "downcase":
             return text.lower()
         if kind == "upcase":
diff --git a/src/interscript/isc.py b/src/interscript/isc.py
index e808d39..177e30d 100644
--- a/src/interscript/isc.py
+++ b/src/interscript/isc.py
@@ -318,7 +318,15 @@ def _stage(self) -> dict:
                 body.append({"kind": "funcall", "name": "rababa", "kwargs": kwargs})
             elif keyword in _FUNCTIONS:
                 self._consume(keyword)
-                body.append({"kind": "string_case", "op": keyword})
+                item = {"kind": "string_case", "op": keyword}
+                self._skip_inline_ws()
+                if keyword == "title_case" and self._peek_word() == "word_separator":
+                    self._consume("word_separator")
+                    self._skip_ws()
+                    self._expect(":")
+                    self._skip_ws()
+                    item["word_separator"] = self._item_atom()["value"]
+                body.append(item)
             elif keyword == "sub":
                 body.append({"kind": "bare_rule", "rule": self._rule()})
             else:
@@ -811,7 +819,16 @@ def _stage_tree(
     if kind in ("compose", "decompose"):
         return {"kind": kind}
     if kind == "string_case":
-        return {"kind": body_item["op"]}
+        op = {"kind": body_item["op"]}
+        if "word_separator" in body_item:
+            op["word_separator"] = body_item["word_separator"]
+        return op
+    if kind == "separate":
+        sep = {"kind": "separate"}
+        separator = body_item.get("separator")
+        if separator and separator.get("type") == "string":
+            sep["separator"] = separator["value"]
+        return sep
     raise UnsupportedConstruct(f"stage item {kind}")
 
 
diff --git a/tests/test_engine.py b/tests/test_engine.py
index 48ad888..ecdb104 100644
--- a/tests/test_engine.py
+++ b/tests/test_engine.py
@@ -89,3 +89,29 @@ def test_real_greek_map_dependency_runs():
     cases = engine.tree["tests"]
     passed = sum(1 for src, want in cases if engine.transliterate(src) == want)
     assert passed >= 200, f"regression: {passed}/{len(cases)}"
+
+
+def test_engine_separate_and_title_case():
+    import tempfile, os, sys
+    from interscript import add_load_path, transliterate
+
+    d = tempfile.mkdtemp()
+    open(os.path.join(d, "ops.isc"), "w").write(
+        'system "ops" {\n'
+        '  stage main {\n'
+        "    separate separator \"|\"\n"
+        "  }\n"
+        "}\n"
+    )
+    add_load_path(d)
+    assert transliterate("ops", "こんいちは") == "こ|ん|い|ち|は"
+
+    open(os.path.join(d, "tc.isc"), "w").write(
+        'system "tc" {\n'
+        '  stage main {\n'
+        "    title_case word_separator: \"\"\n"
+        "  }\n"
+        "}\n"
+    )
+    assert transliterate("tc", "hello world") == "Hello world"
+    assert transliterate("tc", "hello world\nhello hello") == "Hello world\nHello hello"
diff --git a/tests/test_isc.py b/tests/test_isc.py
index 4c955a0..b8d715d 100644
--- a/tests/test_isc.py
+++ b/tests/test_isc.py
@@ -177,3 +177,18 @@ def test_imported_stage_run_resolves_to_dependency():
     """
     tree = isc_to_tree(src)
     assert tree["stages"][0]["children"][0] == {"kind": "run", "map": "imp"}
+
+
+def test_separate_stage_op():
+    src = 'system "x" { stage main { separate separator "|" } }'
+    tree = isc_to_tree(src)
+    assert tree["stages"][0]["children"][0] == {"kind": "separate", "separator": "|"}
+
+
+def test_title_case_word_separator():
+    src = 'system "x" { stage main { title_case word_separator: "" } }'
+    tree = isc_to_tree(src)
+    assert tree["stages"][0]["children"][0] == {
+        "kind": "title_case",
+        "word_separator": "",
+    }