"""配置加载器 —— 读取 TOML 文件并注入 os.environ。

加载顺序（后覆盖前）：
1. app.toml           — 基础配置
2. app.{APP_ENV}.toml — 环境差异
3. app.ai.toml        — AI 专用（最高 TOML 优先级）
4. 已有环境变量        — 不覆盖（最高优先级）
"""

from __future__ import annotations

import os
import sys
from pathlib import Path

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


def _find_project_root() -> Path:
    """查找项目根目录（包含 app.toml 的目录）。"""
    return _ROOT


def _load_toml(path: Path) -> dict:
    """读取 TOML 文件并展平 [SECTION].KEY → SECTION_KEY。"""
    try:
        import tomllib
    except ImportError:
        import tomli as tomllib

    with open(path, "rb") as fh:
        data = tomllib.load(fh)

    flat: dict[str, str] = {}
    for section, values in data.items():
        if not isinstance(values, dict):
            continue
        for key, val in values.items():
            env_key = f"{section.upper()}_{key.upper()}"
            if isinstance(val, list):
                flat[env_key] = ",".join(str(v) for v in val)
            elif isinstance(val, bool):
                flat[env_key] = str(val).lower()
            elif val is not None:
                flat[env_key] = str(val)
    return flat


def load_config() -> None:
    """加载所有 TOML 配置到 os.environ（不覆盖已有环境变量）。"""
    root = _find_project_root()

    env = os.getenv("APP_ENV", "development")
    toml_files = [
        root / "app.toml",
        root / f"app.{env}.toml",
        root / "app.ai.toml",
    ]

    for toml_path in toml_files:
        if not toml_path.exists():
            continue
        for key, value in _load_toml(toml_path).items():
            os.environ.setdefault(key, value)

    # 确保项目根在 sys.path 中
    if str(root) not in sys.path:
        sys.path.insert(0, str(root))