"""数据库引擎与会话管理"""

import os
from pathlib import Path
from urllib.parse import quote_plus

from sqlalchemy import create_engine, event
from sqlalchemy.orm import sessionmaker, declarative_base

PROJECT_ROOT = Path(__file__).resolve().parents[2]


def _env_int(name: str, default: int) -> int:
    """读取正整数环境变量，非法值回退到默认值。"""
    try:
        value = int(os.getenv(name, str(default)))
    except ValueError:
        return default
    return value if value > 0 else default


def _get_database_url() -> str:
    """优先使用完整连接串，否则按 DB_* 环境变量构造 MySQL 连接。"""
    database_url = os.getenv("DATABASE_URL", "").strip()
    if database_url:
        return database_url

    db_host = os.getenv("DB_HOST", "").strip()
    if db_host:
        db_port = _env_int("DB_PORT", 3306)
        db_name = os.getenv("DB_NAME", "douyu_login").strip()
        db_user = os.getenv("DB_USER", "douyu_login").strip()
        db_password = os.getenv("DB_PASSWORD", "")
        if not db_name or not db_user or not db_password:
            raise RuntimeError("使用 DB_HOST 时必须同时设置 DB_NAME、DB_USER 和 DB_PASSWORD")
        return (
            f"mysql+pymysql://{quote_plus(db_user)}:{quote_plus(db_password)}"
            f"@{db_host}:{db_port}/{db_name}?charset=utf8mb4"
        )

    raise RuntimeError(
        "未配置数据库连接。请设置 DATABASE_URL=mysql+pymysql://...，"
        "或设置 DB_HOST、DB_NAME、DB_USER、DB_PASSWORD"
    )


DATABASE_URL = _get_database_url()

connect_args = (
    {"check_same_thread": False, "timeout": 30}
    if DATABASE_URL.startswith("sqlite")
    else {}
)

engine_options = {
    "connect_args": connect_args,
    "echo": False,
}
if not DATABASE_URL.startswith("sqlite"):
    engine_options.update(
        pool_pre_ping=True,
        pool_size=_env_int("DB_POOL_SIZE", 20),
        max_overflow=_env_int("DB_MAX_OVERFLOW", 20),
        pool_timeout=_env_int("DB_POOL_TIMEOUT", 30),
        pool_recycle=_env_int("DB_POOL_RECYCLE", 1800),
    )

engine = create_engine(DATABASE_URL, **engine_options)


if DATABASE_URL.startswith("sqlite"):
    @event.listens_for(engine, "connect")
    def _set_sqlite_pragmas(dbapi_connection, connection_record):
        """提升 SQLite 并发写入稳定性。"""
        cursor = dbapi_connection.cursor()
        cursor.execute("PRAGMA journal_mode=WAL")
        cursor.execute("PRAGMA busy_timeout=30000")
        cursor.execute("PRAGMA foreign_keys=ON")
        cursor.close()

SessionLocal = sessionmaker(bind=engine, autocommit=False, autoflush=False)
Base = declarative_base()


def get_db():
    """FastAPI 依赖：提供数据库会话，请求结束自动关闭。"""
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()


def init_db():
    """执行数据库迁移 + 写入初始数据。"""
    run_migrations()
    _seed()
    _encrypt_existing_sensitive_data()


def run_migrations():
    """运行 Alembic 迁移到最新版本。"""
    from alembic import command
    from alembic.config import Config

    config = Config(str(PROJECT_ROOT / "alembic.ini"))
    config.set_main_option("script_location", str(PROJECT_ROOT / "web" / "backend" / "migrations"))
    config.set_main_option("sqlalchemy.url", DATABASE_URL)
    # 标记为应用内嵌调用，env.py 据此跳过 fileConfig，避免覆盖 uvicorn 日志配置。
    os.environ["ALEMBIC_EMBEDDED"] = "1"
    try:
        command.upgrade(config, "head")
    finally:
        os.environ.pop("ALEMBIC_EMBEDDED", None)


def _seed():
    """写入默认超管账号和角色（账号密码通过环境变量配置）。"""
    from .models import User
    from .security import hash_password

    admin_username = os.getenv("ADMIN_USERNAME", "admin")
    admin_password = os.getenv("ADMIN_PASSWORD", "admin123")

    db = SessionLocal()
    try:
        if not db.query(User).first():
            admin = User(
                username=admin_username,
                password_hash=hash_password(admin_password),
                role="super_admin",
                is_active=True,
                remark="默认超级管理员",
            )
            db.add(admin)
            db.commit()
    finally:
        db.close()


def _encrypt_existing_sensitive_data():
    """启动时把历史明文敏感数据迁移为密文。"""
    from loguru import logger
    from .crypto_storage import encrypt_existing_sensitive_data

    changed = encrypt_existing_sensitive_data(engine)
    if changed:
        logger.info(f"已加密历史敏感字段: {changed} 个值")