"""Config file backup/restore before writes (simplified from sh2 config_governance.py)."""

from __future__ import annotations

import errno
import shutil
from datetime import datetime
from pathlib import Path
from typing import Any

MAX_BACKUPS_PER_FILE = 24


def _now_stamp() -> str:
    return datetime.now().strftime("%Y-%m-%d_%H-%M-%S")


def _backup_root(base_dir: Path) -> Path:
    return base_dir / "backup_config" / "__web__"


def _history_dir(base_dir: Path, rel_name: str) -> Path:
    rel = Path(rel_name.replace("\\", "/").lstrip("/"))
    return _backup_root(base_dir) / rel.parent / f"{rel.name}.history"


def backup_config_file(config_dir: Path, rel_name: str, *, reason: str = "save") -> dict[str, Any] | None:
    """Copy current config to history before overwrite. rel_name e.g. youtube.ini or relay_pro/foo.ini"""
    config_dir = Path(config_dir)
    target = config_dir / rel_name.replace("\\", "/").lstrip("/")
    if not target.is_file():
        return None
    hist_dir = _history_dir(config_dir, rel_name)
    try:
        hist_dir.mkdir(parents=True, exist_ok=True)
    except OSError:
        return None
    suffix = target.suffix or ".bak"
    backup_name = f"{_now_stamp()}__{reason}{suffix}"
    backup_path = hist_dir / backup_name
    try:
        shutil.copy2(target, backup_path)
    except OSError:
        return None
    files = sorted(
        (p for p in hist_dir.iterdir() if p.is_file()),
        key=lambda p: p.stat().st_mtime,
        reverse=True,
    )
    for old in files[MAX_BACKUPS_PER_FILE:]:
        try:
            old.unlink(missing_ok=True)
        except OSError:
            pass
    stat = backup_path.stat()
    return {
        "id": backup_name,
        "reason": reason,
        "label": backup_name,
        "created_at": datetime.fromtimestamp(stat.st_mtime).isoformat(timespec="seconds"),
        "size": stat.st_size,
    }


def list_config_backups(config_dir: Path, rel_name: str) -> list[dict[str, Any]]:
    hist_dir = _history_dir(config_dir, rel_name)
    if not hist_dir.is_dir():
        return []
    out: list[dict[str, Any]] = []
    for item in sorted(hist_dir.iterdir(), key=lambda p: p.stat().st_mtime, reverse=True):
        if not item.is_file():
            continue
        stat = item.stat()
        stem = item.stem
        reason = "snapshot"
        if "__" in stem:
            _, _, reason = stem.partition("__")
        out.append(
            {
                "id": item.name,
                "reason": reason or "snapshot",
                "label": item.name,
                "created_at": datetime.fromtimestamp(stat.st_mtime).isoformat(timespec="seconds"),
                "size": stat.st_size,
            }
        )
    return out


def restore_config_backup(config_dir: Path, rel_name: str, backup_id: str) -> tuple[bool, str]:
    config_dir = Path(config_dir)
    rel = rel_name.replace("\\", "/").lstrip("/")
    target = config_dir / rel
    hist_dir = _history_dir(config_dir, rel_name)
    backup_path = hist_dir / Path(backup_id).name
    if not backup_path.is_file() or backup_path.parent != hist_dir:
        return False, "备份不存在"
    try:
        target.parent.mkdir(parents=True, exist_ok=True)
        if target.is_file():
            backup_config_file(config_dir, rel_name, reason="pre_restore")
        shutil.copy2(backup_path, target)
        return True, "已恢复配置"
    except OSError as exc:
        if exc.errno in {errno.EACCES, errno.EPERM}:
            return False, f"无写入权限: {target}"
        return False, str(exc)


def write_config_text(config_dir: Path, rel_name: str, content: str, *, reason: str = "save") -> Path:
    config_dir = Path(config_dir)
    rel = rel_name.replace("\\", "/").lstrip("/")
    target = config_dir / rel
    backup_config_file(config_dir, rel_name, reason=reason)
    target.parent.mkdir(parents=True, exist_ok=True)
    target.write_text(content, encoding="utf-8")
    return target