feat: add formatter module wrapping ruff and clang-format

formatter.py

@@ -0,0 +1,45 @@
+import subprocess
+
+TIMEOUT_SECONDS = 5
+
+CLANG_FORMAT_STYLE = "{BasedOnStyle: LLVM, IndentWidth: 4, BreakBeforeBraces: Allman}"
+
+
+class FormatError(Exception):
+    """代码格式化失败时抛出，message 为可展示给用户的错误信息"""
+
+
+def _run(cmd: list[str], code: str) -> str:
+    try:
+        result = subprocess.run(
+            cmd,
+            input=code,
+            capture_output=True,
+            text=True,
+            timeout=TIMEOUT_SECONDS,
+        )
+    except subprocess.TimeoutExpired:
+        raise FormatError("格式化超时")
+
+    if result.returncode != 0:
+        raise FormatError(result.stderr.strip() or "格式化失败")
+
+    return result.stdout
+
+
+def format_code(code: str, language: str) -> str:
+    if language in ("python", "turtle"):
+        return _run(["ruff", "format", "-", "--stdin-filename", "main.py"], code)
+
+    if language in ("c", "cpp"):
+        ext = "c" if language == "c" else "cpp"
+        return _run(
+            [
+                "clang-format",
+                f"-style={CLANG_FORMAT_STYLE}",
+                f"-assume-filename=main.{ext}",
+            ],
+            code,
+        )
+
+    raise FormatError(f"不支持的语言: {language}")

test_formatter.py

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+import pytest
+
+from formatter import FormatError, format_code
+
+
+def test_format_python_normalizes_spacing():
+    result = format_code("x=1\n", "python")
+    assert result == "x = 1\n"
+
+
+def test_format_turtle_uses_python_formatter():
+    result = format_code("t=1\n", "turtle")
+    assert result == "t = 1\n"
+
+
+def test_format_python_syntax_error_raises():
+    with pytest.raises(FormatError):
+        format_code("def foo(:\n", "python")
+
+
+def test_format_c_uses_allman_braces():
+    result = format_code("int main(){int x=1;return x;}", "c")
+    assert result.rstrip("\n") == "int main()\n{\n    int x = 1;\n    return x;\n}"
+
+
+def test_format_cpp_uses_allman_braces():
+    result = format_code("class Foo{};", "cpp")
+    assert result.rstrip("\n") == "class Foo\n{\n};"
+
+
+def test_format_unsupported_language_raises():
+    with pytest.raises(FormatError):
+        format_code("print(1)", "java")