"""YAML round-trip read/write for .hb.yaml, with backup and atomic writes."""

import glob
import os
import threading
from datetime import datetime

from ruamel.yaml import YAML

_write_lock = threading.Lock()


def _make_yaml() -> YAML:
    y = YAML()
    y.preserve_quotes = True
    return y

# Top-level keys managed by the 'server' logical section
_SERVER_KEYS = [
    "hbd_port", "hbd_host", "ws_port", "wss_port", "hb_port",
    "interval", "grace", "base_url", "threshold_renotify_interval",
    "logfile", "pidfile", "pickfile", "journal_enabled", "journal_dir",
    "journal_max_size", "journal_max_backups", "default_owner",
    "default_threshold_config",
]

# Top-level keys managed by the 'dns' logical section
_DNS_KEYS = ["nsupdate_bin", "dyndomains", "dyndnshosts", "drophosts"]


def read_roundtrip(path: str):
    """Load .hb.yaml with ruamel.yaml, preserving comments and ordering."""
    with open(path, "r", encoding="utf-8") as f:
        return _make_yaml().load(f)


def write_config(path: str, data) -> None:
    """Backup current file then atomically write data.

    Backup naming: {path}.bak.YYYYMMDD-HHMMSS
    Rotation: keep the 10 most recent backups, delete older ones.
    Atomic write: write to {path}.tmp then os.replace({path}.tmp, path).
    Acquires _write_lock for the full backup+write sequence.
    """
    with _write_lock:
        ts = datetime.now().strftime("%Y%m%d-%H%M%S")
        backup_path = f"{path}.bak.{ts}"
        n = 0
        while os.path.exists(backup_path):
            n += 1
            backup_path = f"{path}.bak.{ts}-{n}"
        orig_mode = None
        if os.path.exists(path):
            orig_mode = os.stat(path).st_mode
            with open(path, "rb") as src, open(backup_path, "wb") as dst:
                dst.write(src.read())
            os.chmod(backup_path, orig_mode)
        backups = sorted(glob.glob(f"{path}.bak.*"), reverse=True)
        for old in backups[10:]:
            os.unlink(old)
        tmp = f"{path}.tmp"
        try:
            with open(tmp, "w", encoding="utf-8") as f:
                _make_yaml().dump(data, f)
            if orig_mode is not None:
                os.chmod(tmp, orig_mode)
            os.replace(tmp, path)
        except Exception:
            try:
                os.unlink(tmp)
            except OSError:
                pass
            raise


def list_backups(path: str) -> list:
    """Return backup paths sorted newest-first."""
    return sorted(glob.glob(f"{path}.bak.*"), reverse=True)


def apply_structured_section(data, section: str, values: dict) -> None:
    """Merge a dict of scalar/list values into data for the named logical section.

    For 'server': updates each known key individually, preserving comments on
    unchanged keys. For 'users': replaces the entire users dict.
    """
    if section == "server":
        for key in _SERVER_KEYS:
            if key in values:
                data[key] = values[key]
    elif section == "users":
        data["users"] = values
    elif section == "hosts":
        data["hosts"] = values
    else:
        raise ValueError(f"Unknown structured section: {section!r}")


def apply_channel(data, name: str, channel_cfg: dict) -> None:
    """Insert or replace a single notification channel entry, preserving others."""
    if not data.get("notification_channels"):
        data["notification_channels"] = {}
    data["notification_channels"][name] = channel_cfg


def delete_channel(data, name: str) -> None:
    """Remove a notification channel by name. No-op if not found."""
    nc = data.get("notification_channels") or {}
    nc.pop(name, None)


def apply_yaml_section(data, section: str, yaml_text: str) -> None:
    """Replace the named logical section by parsing yaml_text."""
    parsed = _make_yaml().load(yaml_text)
    if section == "notification_channels":
        data["notification_channels"] = parsed
    elif section == "thresholds":
        data["threshold_configs"] = parsed
    elif section == "hosts":
        data["hosts"] = parsed
    elif section == "dns":
        if parsed:
            for key in _DNS_KEYS:
                if key in parsed:
                    data[key] = parsed[key]
        else:
            for key in _DNS_KEYS:
                data.pop(key, None)
    else:
        raise ValueError(f"Unknown YAML section: {section!r}")