"""Client SQLite 数据库的路径、连接和初始化函数。"""

import sqlite3
import sys
from pathlib import Path
from typing import Optional, Union

from .db_schema import MIGRATIONS, SCHEMA_VERSION


PathValue = Union[str, Path]


class DatabaseVersionError(RuntimeError):
    """数据库版本比当前程序支持的版本新。"""


def data_dir() -> Path:
    """返回可写数据目录；目录不存在时自动创建。"""

    if getattr(sys, "frozen", False):
        executable_directory = Path(sys.executable).resolve().parent
        # 发布包结构是 Launcher.exe + app/CMAutoBuy.exe。主程序位于 app
        # 目录时，data 必须放在上一层，升级替换 app 才不会覆盖本地数据库。
        install_root = (
            executable_directory.parent
            if executable_directory.name.casefold() == "app"
            else executable_directory
        )
        directory = install_root / "data"
    else:
        directory = Path(__file__).resolve().parents[1] / "data"
    directory.mkdir(parents=True, exist_ok=True)
    return directory


def app_dir() -> Path:
    """返回只读资源根目录；源码和打包运行使用同一相对结构。"""

    if getattr(sys, "frozen", False):
        return Path(sys._MEIPASS).resolve()
    return Path(__file__).resolve().parents[1]


def default_database_path() -> Path:
    """返回默认数据库文件路径。"""

    return data_dir() / "client.db"


def open_database(db_path: Optional[PathValue] = None) -> sqlite3.Connection:
    """打开一个独立连接，并启用项目要求的 SQLite 参数。

    调用者用完后必须关闭连接。不同线程不能共享同一个连接。
    """

    path = Path(db_path) if db_path is not None else default_database_path()
    path.parent.mkdir(parents=True, exist_ok=True)

    connection = sqlite3.connect(str(path), timeout=5.0)
    connection.row_factory = sqlite3.Row
    connection.execute("PRAGMA foreign_keys = ON")
    connection.execute("PRAGMA journal_mode = WAL")
    connection.execute("PRAGMA busy_timeout = 5000")
    return connection


def migrate_database(connection: sqlite3.Connection) -> None:
    """把数据库从当前版本依次迁移到最新版本。"""

    current_version = int(connection.execute("PRAGMA user_version").fetchone()[0])
    if current_version > SCHEMA_VERSION:
        raise DatabaseVersionError(
            f"数据库版本 {current_version} 高于程序支持版本 {SCHEMA_VERSION}"
        )

    for version in range(current_version + 1, SCHEMA_VERSION + 1):
        statements = MIGRATIONS.get(version)
        if statements is None:
            raise RuntimeError(f"缺少数据库迁移版本 {version}")

        try:
            connection.execute("BEGIN IMMEDIATE")
            for statement in statements:
                connection.execute(statement)
            connection.execute(f"PRAGMA user_version = {version}")
            connection.commit()
        except Exception:
            connection.rollback()
            raise


def initialize_database(db_path: Optional[PathValue] = None) -> Path:
    """创建或升级数据库，完成后返回数据库文件路径。"""

    path = Path(db_path) if db_path is not None else default_database_path()
    connection = open_database(path)
    try:
        migrate_database(connection)
    finally:
        connection.close()
    return path