# ============================================================
# 数据库引擎与会话（moduleId: db-database, 可重生 ✅）
# SQLite 单文件：server/data/master.db（APS_DB_PATH 可覆盖）
# ============================================================
from __future__ import annotations

import os
import threading

from sqlalchemy import create_engine
from sqlalchemy.engine import Engine
from sqlalchemy.orm import Session, sessionmaker

_PATH_ENV = "APS_DB_PATH"
_URL_ENV = "APS_DATABASE_URL"
_APPROVAL_SQLITE_TEST_ENV = "APS_APPROVAL_DATABASE_ALLOW_SQLITE"
_MIGRATION_MANAGED_TABLES = frozenset({
    "aps_approval_requests",
    "aps_approval_grants",
    "aps_approval_events",
})


def _default_db_path() -> str:
    try:
        from server.aps_home import default_db_path
        return default_db_path()
    except Exception:
        return "server/data/master.db"


_DEFAULT_PATH = "server/data/master.db"


_lock = threading.Lock()
_engine: Engine | None = None
_engine_path: str | None = None
_SessionLocal: sessionmaker | None = None


def _db_path() -> str:
    return os.environ.get(_PATH_ENV) or _default_db_path()


def _database_url() -> str:
    configured = (os.environ.get(_URL_ENV) or "").strip()
    if configured:
        return configured
    return f"sqlite:///{_db_path()}"


def get_engine() -> Engine:
    """懒加载引擎；APS_DB_PATH 变化时自动重建（测试隔离用）。"""
    global _engine, _engine_path, _SessionLocal
    url = _database_url()
    with _lock:
        if _engine is None or _engine_path != url:
            kwargs = {"pool_pre_ping": True}
            if url.startswith("sqlite:///"):
                path = url.removeprefix("sqlite:///")
                os.makedirs(os.path.dirname(path) or ".", exist_ok=True)
                kwargs["connect_args"] = {"check_same_thread": False}
            _engine = create_engine(url, **kwargs)
            _engine_path = url
            _SessionLocal = sessionmaker(bind=_engine, expire_on_commit=False)
            init_db(_engine)
        return _engine


def reset_engine() -> None:
    """丢弃当前引擎（测试切换 APS_DB_PATH 后调用）。"""
    global _engine, _engine_path, _SessionLocal
    with _lock:
        if _engine is not None:
            _engine.dispose()
        _engine = None
        _engine_path = None
        _SessionLocal = None


def get_session() -> Session:
    get_engine()
    assert _SessionLocal is not None
    return _SessionLocal()


def init_db(engine: Engine | None = None) -> None:
    """建表（幂等）。"""
    from server.db.models import Base
    target = engine or get_engine()
    if target.dialect.name == "sqlite":
        _migrate_legacy_sqlite(target)
    allow_sqlite_approval_ddl = (
        target.dialect.name == "sqlite"
        and os.environ.get(_APPROVAL_SQLITE_TEST_ENV) == "1"
    )
    runtime_tables = None
    if not allow_sqlite_approval_ddl:
        runtime_tables = [
            table
            for table in Base.metadata.sorted_tables
            if table.name not in _MIGRATION_MANAGED_TABLES
        ]
    Base.metadata.create_all(target, tables=runtime_tables)


def _migrate_legacy_sqlite(engine: Engine) -> None:
    """Small compatibility migration for databases created before tenant columns existed."""
    from sqlalchemy import inspect, text

    inspector = inspect(engine)
    additions = {
        "projects": {
            "tenant_uuid": "VARCHAR(32) NOT NULL DEFAULT 'platform'",
            "creator_id": "BIGINT",
            "updater_id": "BIGINT",
            "updated_at": "VARCHAR(32) NOT NULL DEFAULT ''",
            "deleted": "BIGINT NOT NULL DEFAULT 0",
            "owner_user_id": "BIGINT",
            "data_version": "INTEGER NOT NULL DEFAULT 0",
        },
        "master_records": {
            "tenant_uuid": "VARCHAR(32) NOT NULL DEFAULT 'platform'",
            "creator_id": "BIGINT",
            "updater_id": "BIGINT",
            "updated_at": "VARCHAR(32) NOT NULL DEFAULT ''",
            "deleted": "BIGINT NOT NULL DEFAULT 0",
        },
        "project_settings": {
            "tenant_uuid": "VARCHAR(32) NOT NULL DEFAULT 'platform'",
            "creator_id": "BIGINT",
            "updater_id": "BIGINT",
            "updated_at": "VARCHAR(32) NOT NULL DEFAULT ''",
            "deleted": "BIGINT NOT NULL DEFAULT 0",
        },
        "routing_templates": {
            "tenant_uuid": "VARCHAR(32) NOT NULL DEFAULT 'platform'",
            "creator_id": "BIGINT",
            "updater_id": "BIGINT",
            "updated_at": "VARCHAR(32) NOT NULL DEFAULT ''",
            "deleted": "BIGINT NOT NULL DEFAULT 0",
        },
        "routing_template_steps": {
            "tenant_uuid": "VARCHAR(32) NOT NULL DEFAULT 'platform'",
            "creator_id": "BIGINT",
            "updater_id": "BIGINT",
            "updated_at": "VARCHAR(32) NOT NULL DEFAULT ''",
            "deleted": "BIGINT NOT NULL DEFAULT 0",
        },
    }
    tables = set(inspector.get_table_names())
    with engine.begin() as connection:
        for table, columns in additions.items():
            if table not in tables:
                continue
            existing = {col["name"] for col in inspector.get_columns(table)}
            for name, ddl in columns.items():
                if name not in existing:
                    connection.execute(text(f"ALTER TABLE {table} ADD COLUMN {name} {ddl}"))