"""Ownership rules for config-file entities (hosts, channels, threshold configs).

Rule: an entry whose config dict has a non-empty ``owner`` is private to that
owner — visible, usable, and editable only by the owner (and admins).  An
entry with no ``owner`` is global: usable by everyone, editable by admins only.

The scoped-merge helpers implement the non-admin save path for
``POST /api/0/config``: the caller's visible subset of a section is replaced
by the submitted payload; everything else is preserved untouched.
"""

from typing import Any, Dict


class ScopedMergeError(Exception):
    """A non-admin payload violated an ownership rule; message names the entry."""


def is_global(cfg: Any) -> bool:
    """True when *cfg* has no owner (usable by everyone)."""
    return not (isinstance(cfg, dict) and cfg.get("owner"))


def user_can_use(cfg: Any, username: str) -> bool:
    """True when *username* may use/see this entry (global or own)."""
    return is_global(cfg) or cfg.get("owner") == username


def _as_list(value: Any) -> list:
    if value is None:
        return []
    if isinstance(value, str):
        return [value]
    return list(value)


def user_hosts(hosts_cfg: Any, username: str) -> Dict[str, Any]:
    """Subset of *hosts_cfg* where *username* is owner or manager."""
    result = {}
    for name, cfg in (hosts_cfg or {}).items():
        if not isinstance(cfg, dict):
            continue
        if cfg.get("owner") == username or username in _as_list(cfg.get("managers")):
            result[name] = cfg
    return result


def user_channels(channels_cfg: Any, username: str) -> Dict[str, Any]:
    """Subset of channels usable by *username*: global + own."""
    return {
        name: cfg for name, cfg in (channels_cfg or {}).items()
        if isinstance(cfg, dict) and user_can_use(cfg, username)
    }


def user_threshold_configs(threshold_cfgs: Any, username: str) -> Dict[str, Any]:
    """Subset of threshold configs usable by *username*: global + own."""
    return {
        name: cfg for name, cfg in (threshold_cfgs or {}).items()
        if isinstance(cfg, dict) and user_can_use(cfg, username)
    }