"""SQLite 引擎、Session、Base、get_db 依赖。

自包含：无需外部 MySQL，容器内单文件 SQLite 即可。对齐 server/database.py 的接口形态，
但用 SQLite（本项目独立运行、无并发写入压力）。
"""

from __future__ import annotations

from pathlib import Path
from typing import Generator

from sqlalchemy import create_engine
from sqlalchemy.orm import DeclarativeBase, Session, sessionmaker

from .config import get_settings

_engine = None
_SessionLocal = None


def _db_path() -> Path:
    """SQLite 文件落在 work_dir 下，跟数据一起走 volume。"""
    s = get_settings()
    p = s.work_dir() / "audio2text.db"
    p.parent.mkdir(parents=True, exist_ok=True)
    return p


def get_engine():
    global _engine, _SessionLocal
    if _engine is None:
        url = f"sqlite:///{_db_path()}"
        _engine = create_engine(
            url,
            # 后台 reaper / 缓存清理线程与请求线程并发写同一库；busy_timeout 让等待方
            # 在拿锁时阻塞 5s 而非立即报 database is locked。
            connect_args={"check_same_thread": False, "timeout": 30},
            future=True,
        )
        _SessionLocal = sessionmaker(bind=_engine, autoflush=False, expire_on_commit=False)
    return _engine


def get_session_local():
    get_engine()
    return _SessionLocal


class Base(DeclarativeBase):
    pass


def init_db_schema() -> None:
    """建表（幂等）+ 旧库迁移（给 task 表补新字段）。

    SQLAlchemy 的 create_all 只建新表不改旧表。对已存在的 task 表，
    需手动 ALTER TABLE ADD COLUMN 补 wav_path / segments_json（nullable）。
    """
    from .models.task import Task  # noqa: F401
    from .models.upload_session import UploadSession  # noqa: F401
    from .models.setting import Setting  # noqa: F401

    engine = get_engine()
    Base.metadata.create_all(engine)
    _migrate_task_columns(engine)


def _migrate_task_columns(engine) -> None:
    """检测 task 表缺失的列并 ALTER TABLE 补上（nullable，向后兼容）。"""
    from sqlalchemy import inspect, text

    insp = inspect(engine)
    if "task" not in insp.get_table_names():
        return  # 新库，create_all 已建好完整表
    existing = {c["name"] for c in insp.get_columns("task")}
    # 新增字段：(列名, 列定义)
    additions = [
        ("wav_path", "VARCHAR(1024)"),
        ("segments_json", "TEXT"),
    ]
    with engine.begin() as conn:
        for col, coltype in additions:
            if col not in existing:
                conn.execute(text(f"ALTER TABLE task ADD COLUMN {col} {coltype}"))


def get_db() -> Generator[Session, None, None]:
    """FastAPI 依赖：每请求一个 Session，结束自动关闭。"""
    db = get_session_local()()
    try:
        yield db
    finally:
        db.close()