"""Artifact storage module — per-session CRUD operations on the filesystem."""

from pathlib import Path

ARTIFACTS_DIR = Path("/app/artifacts")


def list_artifacts(session_id: str) -> list[dict]:
    """Return sorted list of artifact dicts for a session.

    Each dict contains: name, session_id, size.
    Returns [] if the session directory does not exist or if session_id
    would resolve outside ARTIFACTS_DIR (path traversal guard).
    """
    session_dir = (ARTIFACTS_DIR / session_id).resolve()
    if not session_dir.is_relative_to(ARTIFACTS_DIR.resolve()):
        return []
    if not session_dir.exists():
        return []
    return sorted(
        [
            {
                "name": f.name,
                "session_id": session_id,
                "size": f.stat().st_size,
            }
            for f in session_dir.iterdir()
            if f.is_file()
        ],
        key=lambda d: d["name"],
    )


def get_artifact(session_id: str, name: str) -> str | None:
    """Return file content (utf-8) or None if artifact does not exist.

    Returns None (silently) if the resolved path would escape ARTIFACTS_DIR
    (path traversal guard).
    """
    artifact_path = (ARTIFACTS_DIR / session_id / name).resolve()
    if not artifact_path.is_relative_to(ARTIFACTS_DIR.resolve()):
        return None
    if not artifact_path.is_file():
        return None
    return artifact_path.read_text(encoding="utf-8")


def save_artifact(session_id: str, name: str, content: str) -> Path:
    """Write content to the artifact file, creating parent dirs as needed.

    Returns the Path of the written file.
    Raises ValueError if the resolved path would escape ARTIFACTS_DIR
    (path traversal guard).
    """
    session_dir = ARTIFACTS_DIR / session_id
    artifact_path = (session_dir / name).resolve()
    if not artifact_path.is_relative_to(ARTIFACTS_DIR.resolve()):
        raise ValueError(f"Path traversal detected in artifact name: {name!r}")
    session_dir.mkdir(parents=True, exist_ok=True)
    artifact_path.write_text(content, encoding="utf-8")
    return artifact_path