"""
Verifies the rules/ module boundary: nothing inside activity_core/rules/
may import from temporalio, sqlalchemy, fastapi, or any activity_core.*
module outside rules/.
"""

import ast
import os
from pathlib import Path

_RULES_DIR = Path(__file__).parent.parent.parent / "src" / "activity_core" / "rules"

_FORBIDDEN_MODULES = {
    "temporalio",
    "sqlalchemy",
    "fastapi",
}


def _get_imports(filepath: Path) -> list[str]:
    """Return all top-level imported module names from a Python file."""
    tree = ast.parse(filepath.read_text())
    imports = []
    for node in ast.walk(tree):
        if isinstance(node, ast.Import):
            for alias in node.names:
                imports.append(alias.name.split(".")[0])
        elif isinstance(node, ast.ImportFrom):
            if node.module:
                root = node.module.split(".")[0]
                imports.append(root)
                # Detect cross-boundary activity_core imports
                if node.module.startswith("activity_core.") and not node.module.startswith(
                    "activity_core.rules"
                ):
                    imports.append(f"_cross_boundary:{node.module}")
    return imports


def test_rules_module_boundary() -> None:
    """No file in rules/ may import forbidden modules or cross the boundary."""
    violations: list[str] = []

    for py_file in sorted(_RULES_DIR.glob("*.py")):
        imports = _get_imports(py_file)
        for imp in imports:
            if imp in _FORBIDDEN_MODULES:
                violations.append(f"{py_file.name}: imports {imp!r}")
            if imp.startswith("_cross_boundary:"):
                module = imp[len("_cross_boundary:"):]
                violations.append(
                    f"{py_file.name}: cross-boundary import from {module!r}"
                )

    assert not violations, (
        "rules/ boundary violations:\n" + "\n".join(violations)
    )