"""M22 (item 12) — AST-based one-directional import lint.

Enforces guardrail 8: the renderer-agnostic / substrate-agnostic core modules must
never depend on the extraction layer. Concretely, none of::

    loosecanvas.contracts
    loosecanvas.context_packer
    loosecanvas.validator
    loosecanvas.reducer
    loosecanvas.graph_repository
    loosecanvas.response_format

may import anything from ``loosecanvas.extractors`` (any submodule). The dependency
flows one way only: extractors -> core, never core -> extractors.

Run as a CLI (exit 0 clean, 1 on violations)::

    .venv\\Scripts\\python.exe scripts\\lint_import_dependencies.py
"""

from __future__ import annotations

import ast
import sys
from pathlib import Path

# Core modules that must stay free of any extraction-layer dependency.
_CORE_MODULES = (
    "contracts",
    "context_packer",
    "validator",
    "reducer",
    "graph_repository",
    "response_format",
)

_FORBIDDEN_PREFIX = "loosecanvas.extractors"


def _src_root(explicit: Path | None = None) -> Path:
    """Resolve ``src/loosecanvas`` from an explicit root or this file's location."""
    if explicit is not None:
        return explicit
    repo_root = Path(__file__).resolve().parents[1]
    return repo_root / "src" / "loosecanvas"


def _imports_extractors(tree: ast.AST) -> list[str]:
    """Return the forbidden ``loosecanvas.extractors`` import targets found in ``tree``."""
    hits: list[str] = []
    for node in ast.walk(tree):
        if isinstance(node, ast.Import):
            for alias in node.names:
                if alias.name == _FORBIDDEN_PREFIX or alias.name.startswith(
                    f"{_FORBIDDEN_PREFIX}."
                ):
                    hits.append(alias.name)
        elif isinstance(node, ast.ImportFrom):
            module = node.module or ""
            if module == _FORBIDDEN_PREFIX or module.startswith(
                f"{_FORBIDDEN_PREFIX}."
            ):
                hits.append(module)
    return hits


def find_forbidden_imports(src_root: Path | None = None) -> list[str]:
    """Scan the core modules and return one violation string per forbidden import.

    A violation reads ``"<module> imports <forbidden_target>"``. An empty list means the
    one-directional dependency holds. Missing core files are reported as violations so the
    check fails loudly rather than silently passing.
    """
    root = _src_root(src_root)
    violations: list[str] = []
    for module in _CORE_MODULES:
        path = root / f"{module}.py"
        if not path.is_file():
            violations.append(f"{module}: source file not found at {path}")
            continue
        tree = ast.parse(path.read_text(encoding="utf-8"))
        for target in _imports_extractors(tree):
            violations.append(f"loosecanvas.{module} imports {target}")
    return violations


def main() -> int:
    """Print any violations and return a process exit code (0 clean, 1 on violations)."""
    violations = find_forbidden_imports()
    if violations:
        print("Import-dependency lint FAILED (core must not import extractors):")
        for line in violations:
            print(f"  - {line}")
        return 1
    print("Import-dependency lint passed: core modules import no extractors.")
    return 0


if __name__ == "__main__":
    sys.exit(main())