import json
from pathlib import Path
from typing import Any


def load_runtime_config(path: str) -> tuple[dict[str, Any], str | None]:
    p = Path(path).expanduser()
    if not p.exists():
        return {}, None
    try:
        data = json.loads(p.read_text(encoding="utf-8"))
    except Exception as e:
        return {}, f"Failed to parse config '{p}': {e}"
    if not isinstance(data, dict):
        return {}, f"Config '{p}' must be a JSON object"
    return data, None


def save_runtime_config(path: str, config: dict[str, Any]) -> str | None:
    p = Path(path).expanduser()
    try:
        p.parent.mkdir(parents=True, exist_ok=True)
        p.write_text(json.dumps(config, indent=2, sort_keys=True), encoding="utf-8")
        return None
    except Exception as e:
        return f"Failed to save config '{p}': {e}"


def collect_cli_overrides(argv: list[str]) -> set[str]:
    """
    Collect option names explicitly passed on CLI, normalized to argparse dest form.
    Example: --focus-epics-enabled -> focus_epics_enabled
    """
    out: set[str] = set()
    for token in argv[1:]:
        if not token.startswith("--"):
            continue
        key = token[2:]
        if "=" in key:
            key = key.split("=", 1)[0]
        out.add(key.replace("-", "_"))
    return out