"""多租户知识库管理模块。

用户 + 知识库 CRUD，持久化到 kb_data/ 目录。
每个 KB 拥有独立的 JSON 元数据文件和文件存储目录。
"""

import json
import os
import re
import uuid
import tempfile
import shutil
from datetime import datetime, timezone
from pathlib import Path
from typing import Optional

from dotenv import load_dotenv
from backend.logger import get_logger

load_dotenv()

_kb_log = get_logger("kb_manager")

KB_DATA_DIR = Path(os.getenv("KB_DATA_DIR", "./kb_data"))
_USERS_FILE = KB_DATA_DIR / "users.json"

_VALID_ID_RE = re.compile(r'^[a-fA-F0-9]{12,}$')


def _validate_id(id_str: str, label: str = "id") -> None:
    if not _VALID_ID_RE.match(id_str):
        raise ValueError(f"Invalid {label}: {id_str!r}")


def _now_iso() -> str:
    return datetime.now(timezone.utc).isoformat()


def _ensure_dir(path: Path) -> None:
    path.mkdir(parents=True, exist_ok=True)


def _read_json(fp: Path) -> dict:
    with open(fp, "r", encoding="utf-8") as f:
        return json.load(f)


def _write_json_atomic(fp: Path, data: dict) -> None:
    _ensure_dir(fp.parent)
    tmp = tempfile.NamedTemporaryFile(
        mode="w", suffix=".json", delete=False,
        dir=fp.parent, encoding="utf-8",
    )
    try:
        json.dump(data, tmp, ensure_ascii=False, indent=2)
        tmp.flush()
        os.fsync(tmp.fileno())
        tmp.close()
        os.replace(tmp.name, str(fp))
    except Exception:
        tmp.close()
        Path(tmp.name).unlink(missing_ok=True)
        raise


# ── User CRUD ──────────────────────────────────────────────────────────────

def _load_users() -> list[dict]:
    _ensure_dir(KB_DATA_DIR)
    if _USERS_FILE.exists():
        return _read_json(_USERS_FILE)
    return []


def _save_users(users: list[dict]) -> None:
    _write_json_atomic(_USERS_FILE, users)


def create_user(name: str, user_id: Optional[str] = None) -> dict:
    uid = user_id or uuid.uuid4().hex
    users = _load_users()
    if any(u["user_id"] == uid for u in users):
        raise ValueError(f"User {uid} already exists")
    user = {"user_id": uid, "name": name, "created_at": _now_iso()}
    users.append(user)
    _save_users(users)
    _ensure_dir(KB_DATA_DIR / uid)
    _write_json_atomic(KB_DATA_DIR / uid / "profile.json", user)
    _kb_log.info("创建用户", extra={"user_id": uid, "user_name": name})
    return user


def list_users() -> list[dict]:
    return _load_users()


def get_user(user_id: str) -> Optional[dict]:
    _validate_id(user_id, "user_id")
    for u in _load_users():
        if u["user_id"] == user_id:
            return u
    return None


def delete_user(user_id: str) -> bool:
    _validate_id(user_id, "user_id")
    users = _load_users()
    filtered = [u for u in users if u["user_id"] != user_id]
    if len(filtered) == len(users):
        return False
    _save_users(filtered)
    user_dir = KB_DATA_DIR / user_id
    if user_dir.exists():
        shutil.rmtree(user_dir)
    _kb_log.info("删除用户", extra={"user_id": user_id})
    return True


# ── KB CRUD ────────────────────────────────────────────────────────────────

def _kb_dir(kb_id: str) -> Optional[Path]:
    _validate_id(kb_id, "kb_id")
    for user_dir in KB_DATA_DIR.iterdir():
        if user_dir.is_dir() and not user_dir.name.startswith("."):
            candidate = user_dir / kb_id
            if candidate.is_dir():
                return candidate
    return None


def _ensure_user_dir(user_id: str) -> Path:
    _validate_id(user_id, "user_id")
    d = KB_DATA_DIR / user_id
    _ensure_dir(d)
    return d


def create_kb(user_id: str, name: str, description: str = "",
              kb_id: Optional[str] = None) -> dict:
    user_dir = _ensure_user_dir(user_id)
    kid = kb_id or uuid.uuid4().hex
    kb_dir = user_dir / kid
    _ensure_dir(kb_dir)
    _ensure_dir(kb_dir / "raw")

    now = _now_iso()
    meta = {
        "kb_id": kid, "user_id": user_id, "name": name,
        "description": description, "created_at": now, "updated_at": now,
        "fields": [], "templates": [], "file_count": 0,
        "chunk_count": 0, "parse_status": "empty",
    }
    _write_json_atomic(kb_dir / "meta.json", meta)
    _kb_log.info("创建知识库", extra={"kb_id": kid, "user_id": user_id, "kb_name": name})
    return meta


def list_kbs(user_id: str) -> list[dict]:
    user_dir = _ensure_user_dir(user_id)
    kbs = []
    for kb_dir in sorted(user_dir.iterdir(), key=os.path.getmtime, reverse=True):
        if kb_dir.is_dir() and not kb_dir.name.startswith("."):
            meta_path = kb_dir / "meta.json"
            if meta_path.exists():
                meta = _read_json(meta_path)
                kbs.append({
                    "kb_id": meta.get("kb_id", kb_dir.name),
                    "name": meta.get("name", kb_dir.name),
                    "description": meta.get("description", ""),
                    "created_at": meta.get("created_at", ""),
                    "updated_at": meta.get("updated_at", ""),
                    "field_count": len(meta.get("fields", [])),
                    "template_count": len(meta.get("templates", [])),
                    "file_count": meta.get("file_count", 0),
                    "chunk_count": meta.get("chunk_count", 0),
                    "parse_status": meta.get("parse_status", "empty"),
                })
    return kbs


def get_kb(kb_id: str) -> Optional[dict]:
    _validate_id(kb_id, "kb_id")
    kb_dir = _kb_dir(kb_id)
    if kb_dir is None:
        return None
    meta_path = kb_dir / "meta.json"
    return _read_json(meta_path) if meta_path.exists() else None


def update_kb_meta(kb_id: str, updates: dict) -> Optional[dict]:
    kb_dir = _kb_dir(kb_id)
    if kb_dir is None:
        return None
    meta_path = kb_dir / "meta.json"
    meta = _read_json(meta_path)
    meta.update(updates)
    meta["updated_at"] = _now_iso()
    _write_json_atomic(meta_path, meta)
    return meta


def delete_kb(kb_id: str) -> bool:
    kb_dir = _kb_dir(kb_id)
    if kb_dir is None:
        return False
    shutil.rmtree(kb_dir)
    _kb_log.info("删除知识库", extra={"kb_id": kb_id})
    return True


def get_kb_raw_dir(kb_id: str) -> Optional[Path]:
    kb_dir = _kb_dir(kb_id)
    return kb_dir / "raw" if kb_dir else None


def get_kb_chunks_path(kb_id: str) -> Optional[Path]:
    kb_dir = _kb_dir(kb_id)
    return kb_dir / "chunks.json" if kb_dir else None


def get_kb_chroma_path(kb_id: str) -> Optional[Path]:
    kb_dir = _kb_dir(kb_id)
    if kb_dir is None:
        return None
    chroma_dir = kb_dir / "chroma"
    _ensure_dir(chroma_dir)
    return chroma_dir