"""TenantRegistry——进程内租户注册表(Phase 1 文件加载器)。

数据源:seed_profiles/<slug>/tenant.json(站点/品牌/引擎配置)+ 同目录
wall.json(并入 snapshot["wall"],compile_wall 编译期显性炸)。Phase 2 换
platform.db 时本模块的对外接口不变(spec §5.3:后台保存→原子替换条目,
进行中的会话下一条消息即用新配置)。

关键行为:
- resolve_site(host):host 小写去端口 → 域名索引 → (TenantRuntime, Site);
  未知 Host → UnknownTenantError(spec §4:404,不做兜底租户)。
  resolve(host) 只是它的便捷形式——双 API 一层实现,防两套解析漂移。
- 懒建:首次 resolve 才建 engine(WAL/pool=2)+ session_factory + ensure_schema,
  per-slug asyncio.Lock 串行,双检防并发双建;建库失败不留半开 engine。
- registry_reload(slug):重读磁盘→校验(坏 JSON/墙/域名冲突全在替换前抛,
  旧条目不动)→原子替换 _by_slug 条目并重建域名索引→dispose 旧 engine
  (Windows 下不关=库文件句柄泄漏)。

测试/teardown 纪律:凡建过 engine 的 Registry 用完必须 await dispose_all()
(Windows 文件锁,tmp 目录删不掉)。
"""
import asyncio
import json
import pathlib
from dataclasses import dataclass

from sqlalchemy import event
from sqlalchemy.ext.asyncio import (
    AsyncEngine,
    AsyncSession,
    async_sessionmaker,
    create_async_engine,
)

from app.engine.models import ensure_schema
from app.engine.wall_schema import CompiledWall, compile_wall
from app.platform.tenant_config import Site, TenantConfig


class UnknownTenantError(LookupError):
    """Host/域名无法映射到任何租户(调用方语义:聊天/公开端点 404)。"""


def make_tenant_engine(db_path: pathlib.Path) -> AsyncEngine:
    """每租户 SQLite engine:pool=2 无溢出(单租户低并发),忙等 30s
    (对齐 jc 现状:后台推送连接可能撞 SMTP 窗口写锁),打开即 WAL
    (spec §6.1 硬纪律:读写不互斥,优于靠 timeout 硬扛)。"""
    engine = create_async_engine(
        f"sqlite+aiosqlite:///{db_path.as_posix()}",
        pool_size=2, max_overflow=0,
        connect_args={"timeout": 30})

    @event.listens_for(engine.sync_engine, "connect")
    def _wal(dbapi_conn, _):                     # dbapi_conn = aiosqlite 同步适配层
        dbapi_conn.execute("PRAGMA journal_mode=WAL")

    return engine


def _normalize_host(host: str) -> str:
    """Host 头归一:去空白/小写/去端口/去 FQDN 尾点(真实请求 Host:8018、
    大写都可能出现);IPv6 字面量 [::1]:8018 取方括号内部分。"""
    host = (host or "").strip().lower().rstrip(".")
    if host.startswith("["):
        return host.split("]", 1)[0].lstrip("[")
    return host.split(":", 1)[0]


@dataclass
class TenantRuntime:
    """单租户运行时。config/db_path/compiled_wall 加载期就绪;engine/
    session_factory 由 Registry 首次 resolve 懒建;manager 由装配线注入
    (Task 5b),prompts 由 Task 6 注入——本任务不含。"""

    config: TenantConfig
    db_path: pathlib.Path
    compiled_wall: CompiledWall
    engine: AsyncEngine | None = None
    session_factory: async_sessionmaker | None = None

    def site_by_slug(self, slug: str) -> Site | None:
        """按 slug 取站点(空域名站点如 es 靠嵌入代码 data-site 接入)。"""
        for site in self.config.sites:
            if site.slug == slug:
                return site
        return None


class TenantRegistry:
    """tenant slug → TenantRuntime;域名 → (tenant_slug, site_slug) 索引。
    reload 重建索引而非增量维护——租户数是个位数,整建最简且无漂移。"""

    def __init__(self):
        self._seed_dir: pathlib.Path | None = None
        self._data_dir: pathlib.Path | None = None
        self._by_slug: dict[str, TenantRuntime] = {}
        self._domain_index: dict[str, tuple[str, str]] = {}
        self._locks: dict[str, asyncio.Lock] = {}

    # ---- 加载 -----------------------------------------------------------

    @classmethod
    def load_from_dir(cls, seed_dir, data_dir) -> "TenantRegistry":
        """seed_profiles/<slug>/tenant.json(+同目录 wall.json)→ Registry。

        加载期显性失败(不流入运行期):目录无任何 tenant.json(seed_dir
        路径拼错→静默空注册表→全量 404,必须炸)、slug 与目录名不一致、
        零站点、wall 编译错误、域名重复绑定。
        """
        reg = cls()
        reg._seed_dir = pathlib.Path(seed_dir)
        reg._data_dir = pathlib.Path(data_dir)
        tenant_jsons = sorted(reg._seed_dir.glob("*/tenant.json"))
        if not tenant_jsons:
            raise ValueError(f"{reg._seed_dir} 下没有任何 <slug>/tenant.json")
        for tenant_json in tenant_jsons:
            rt = reg._load_tenant(tenant_json.parent)
            if rt.config.slug in reg._by_slug:
                raise ValueError(f"租户 slug 重复: {rt.config.slug}")
            reg._by_slug[rt.config.slug] = rt
        reg._domain_index = reg._build_domain_index(reg._by_slug)
        return reg

    def _load_tenant(self, tenant_dir: pathlib.Path) -> TenantRuntime:
        slug = tenant_dir.name
        tenant_json = json.loads(
            (tenant_dir / "tenant.json").read_text(encoding="utf-8"))
        if tenant_json.get("slug") != slug:
            raise ValueError(
                f"{tenant_dir / 'tenant.json'}: slug 字段 "
                f"{tenant_json.get('slug')!r} 与目录名 {slug!r} 不一致")
        sites = tenant_json.get("sites") or []
        if not sites:
            raise ValueError(f"{slug}: 每租户至少一个站点(sites 为空)")
        # wall 并入 snapshot["wall"]:data["wall"] 保留原始词表(后台编辑/
        # 回滚用),编译产物挂 runtime.compiled_wall(引擎消费,单一编译)
        wall_cfg = json.loads(
            (tenant_dir / "wall.json").read_text(encoding="utf-8"))
        snapshot = dict(tenant_json.get("config") or {})
        snapshot["wall"] = wall_cfg
        config = TenantConfig.from_snapshot(
            slug, tenant_json.get("name", slug), snapshot,
            sites=sites, status=tenant_json.get("status", "active"))
        return TenantRuntime(
            config=config,
            db_path=self._data_dir / f"{slug}.db",
            compiled_wall=compile_wall(wall_cfg))

    def _build_domain_index(
            self, by_slug: dict[str, TenantRuntime]
    ) -> dict[str, tuple[str, str]]:
        index: dict[str, tuple[str, str]] = {}
        for slug, rt in by_slug.items():
            for site in rt.config.sites:
                for domain in site.domains:
                    key = _normalize_host(domain)
                    if not key:
                        continue
                    if index.get(key, (slug, site.slug)) != (slug, site.slug):
                        raise ValueError(
                            f"域名 {key} 同时绑定 {index[key][0]} 与 "
                            f"{slug} 的站点(域名不可重复绑定)")
                    index[key] = (slug, site.slug)
        return index

    # ---- 解析(对外 API)--------------------------------------------------

    async def resolve_site(self, host: str) -> tuple[TenantRuntime, Site]:
        """host → (TenantRuntime, Site)。首次 resolve 懒建该租户 engine。"""
        mapped = self._domain_index.get(_normalize_host(host))
        if mapped is None:
            raise UnknownTenantError(f"未知 Host: {host!r}")
        tenant_slug, site_slug = mapped
        rt = self._by_slug[tenant_slug]
        await self._ensure_ready(rt)
        site = rt.site_by_slug(site_slug)
        if site is None:        # 防御:索引与配置同源重建,正常不可达
            raise UnknownTenantError(
                f"站点 {site_slug!r} 不存在于租户 {tenant_slug!r}")
        return rt, site

    async def resolve(self, host: str) -> TenantRuntime:
        """resolve_site 的便捷形式(双 API 一层实现)。"""
        return (await self.resolve_site(host))[0]

    # ---- 懒建 / 热加载 / 释放 ---------------------------------------------

    async def _ensure_ready(self, rt: TenantRuntime) -> TenantRuntime:
        """懒建 engine + session_factory + ensure_schema,per-slug Lock 串行。

        双检:抢到锁后重看 engine——等锁期间前一个协程可能已建好。
        建库失败 dispose 半开 engine 并保持未就绪,下次 resolve 重试。
        """
        if rt.engine is not None:
            return rt
        lock = self._locks.setdefault(rt.config.slug, asyncio.Lock())
        async with lock:
            if rt.engine is not None:
                return rt
            self._data_dir.mkdir(parents=True, exist_ok=True)
            engine = make_tenant_engine(rt.db_path)
            try:
                await ensure_schema(engine)
            except Exception:
                await engine.dispose()
                raise
            rt.engine = engine
            rt.session_factory = async_sessionmaker(
                engine, class_=AsyncSession, expire_on_commit=False)
        return rt

    async def registry_reload(self, slug: str) -> None:
        """重读磁盘,原子替换条目;旧 runtime 若已建 engine,dispose 掉。

        先全量校验(重读 tenant.json/wall.json + 候选域名索引)再替换——
        坏配置抛异常时旧条目原样服务,不留半更新状态。
        """
        if slug not in self._by_slug:
            raise UnknownTenantError(f"租户不存在: {slug!r}")
        old = self._by_slug[slug]
        rt = self._load_tenant(self._seed_dir / slug)
        candidate = dict(self._by_slug)
        candidate[slug] = rt
        new_index = self._build_domain_index(candidate)
        self._by_slug[slug] = rt                 # 原子替换(单事件循环内无 await)
        self._domain_index = new_index
        if old.engine is not None:
            await old.engine.dispose()
            old.engine = old.session_factory = None

    async def dispose_all(self) -> None:
        """关闭全部 engine 并复位为未就绪(测试 teardown 用——Windows 文件锁;
        复位后若再 resolve 会重新懒建,可安全复用)。"""
        for rt in self._by_slug.values():
            if rt.engine is not None:
                await rt.engine.dispose()
                rt.engine = rt.session_factory = None