import json
import os
from pathlib import Path
from backend.nodes.roles import NodeRole


# Where node role overrides are persisted. Allow override via env var;
# otherwise default to a user-writable path under /var/lib/fester (or
# fall back to a tmp dir if neither is writable).
def _resolve_role_db() -> Path:
    env = os.environ.get("FESTER_ROLE_DB")
    if env:
        return Path(env)

    candidates = [
        Path("/etc/fester/node_roles.json"),
        Path("/var/lib/fester/node_roles.json"),
        Path.home() / ".fester" / "node_roles.json",
        Path("/tmp/fester_node_roles.json"),
    ]
    for c in candidates:
        try:
            c.parent.mkdir(parents=True, exist_ok=True)
            # touch to verify writability
            if not c.exists():
                c.write_text("{}")
            else:
                # verify we can write to it
                with open(c, "a"):
                    pass
            return c
        except (OSError, PermissionError):
            continue
    # Last resort: in-memory only (caller must handle None)
    return None


ROLE_DB = _resolve_role_db()

DEFAULT_ROLE = NodeRole(name="default")


def load_roles():
    if ROLE_DB is None or not ROLE_DB.exists():
        return {}

    try:
        raw = json.loads(ROLE_DB.read_text())
    except Exception:
        return {}

    roles = {}

    for node, cfg in raw.items():
        try:
            roles[node] = NodeRole(**cfg)
        except TypeError:
            # Schema drift — skip malformed entries
            continue

    return roles


def save_roles(roles):
    if ROLE_DB is None:
        return False
    raw = {
        node: role.__dict__
        for node, role in roles.items()
    }
    try:
        ROLE_DB.write_text(json.dumps(raw, indent=2))
        return True
    except (OSError, PermissionError):
        return False


def get_role(node_name, roles):
    return roles.get(node_name, DEFAULT_ROLE)