Add option parsing utils and tests

src/utils.py

@@ -1,4 +1,5 @@
 import re
+from itertools import product
 
 
 def clean_prompt(text: str) -> str:
@@ -13,3 +14,66 @@ def clean_prompt(text: str) -> str:
     text = re.sub(r"^\s*,\s*", "", text, flags=re.MULTILINE)  # Leading comma
     text = re.sub(r"\n\s*\n", "\n", text)  # Empty lines
     return text.strip()
+
+
+def parse_options(raw: str) -> list[str]:
+    """
+    Parse the options field into a flat list of options.
+
+    Supports:
+    - Plain lines: direct options
+    - @combine / @end blocks: cartesian product of --- separated lists
+    - Empty lines: empty option (displayed as --)
+    - --- outside a block: treated as a literal option
+    """
+    lines = raw.split("\n")
+    result = []
+    in_combine = False
+    current_block: list[list[str]] = []
+    current_list: list[str] = []
+
+    for i, line in enumerate(lines, 1):
+        stripped = line.strip()
+
+        if stripped == "@combine":
+            if in_combine:
+                raise ValueError(
+                    f"parse_options: @combine at line {i} opened inside an unclosed @combine block."
+                )
+            in_combine = True
+            current_block = []
+            current_list = []
+
+        elif stripped == "@end":
+            if not in_combine:
+                raise ValueError(
+                    f"parse_options: @end at line {i} without matching @combine."
+                )
+            # Save last list
+            current_block.append(current_list)
+            current_list = []
+            in_combine = False
+
+            # Generate cartesian product
+            for combo in product(*current_block):
+                result.append(", ".join(combo))
+
+        elif stripped == "---":
+            if in_combine:
+                # Separator between lists in a combine block
+                current_block.append(current_list)
+                current_list = []
+            else:
+                # Outside a block, treat as literal option
+                result.append("---")
+
+        else:
+            if in_combine:
+                current_list.append(line)
+            else:
+                result.append(line)
+
+    if in_combine:
+        raise ValueError("parse_options: unclosed @combine block — missing @end.")
+
+    return result

tests/test_parse_options.py

@@ -0,0 +1,72 @@
+import pytest
+from src.utils import parse_options
+
+# --- Plain options ---
+
+
+def test_plain_options():
+    result = parse_options("from front\nfrom behind")
+    assert result == ["from front", "from behind"]
+
+
+def test_empty_line():
+    result = parse_options("from front\n\nfrom behind")
+    assert result == ["from front", "", "from behind"]
+
+
+def test_separator_outside_block():
+    result = parse_options("from front\n---\nfrom behind")
+    assert result == ["from front", "---", "from behind"]
+
+
+# --- Combine blocks ---
+
+
+def test_combine_two_lists():
+    raw = "before\n@combine\na\nb\n---\nc\nd\n@end\nafter"
+    result = parse_options(raw)
+    assert "before" in result
+    assert "after" in result
+    assert "a, c" in result
+    assert "a, d" in result
+    assert "b, c" in result
+    assert "b, d" in result
+    assert len(result) == 6  # before + 4 combos + after
+
+
+def test_combine_three_lists():
+    raw = "@combine\na\n---\nb\n---\nc\n@end"
+    result = parse_options(raw)
+    assert result == ["a, b, c"]
+
+
+def test_combine_empty_line_in_list():
+    raw = "@combine\na\n\n---\nb\n@end"
+    result = parse_options(raw)
+    assert ", b" in result  # empty + b
+    assert "a, b" in result
+
+
+def test_multiple_combine_blocks():
+    raw = "@combine\na\n---\nb\n@end\n@combine\nc\n---\nd\n@end"
+    result = parse_options(raw)
+    assert "a, b" in result
+    assert "c, d" in result
+
+
+# --- Validation errors ---
+
+
+def test_combine_without_end():
+    with pytest.raises(ValueError, match="unclosed @combine"):
+        parse_options("@combine\na\n---\nb")
+
+
+def test_end_without_combine():
+    with pytest.raises(ValueError, match="without matching @combine"):
+        parse_options("@end")
+
+
+def test_nested_combine():
+    with pytest.raises(ValueError, match="opened inside an unclosed"):
+        parse_options("@combine\na\n@combine\nb\n@end\n@end")