"""核心配置层：加载根目录 config.yaml + .env，向全应用提供 Settings。

加载优先级：环境变量 > 根目录 .env > 根目录 config.yaml > 代码默认值。
密钥只存在于 .env（config.yaml 经 *_env 字段引用变量名）。
"""

from __future__ import annotations

import os
from dataclasses import dataclass
from functools import lru_cache
from pathlib import Path

import yaml

# 项目根：<root>/backend/app/core/config.py → parents[3]
PROJECT_ROOT = Path(__file__).resolve().parents[3]
BACKEND_ROOT = PROJECT_ROOT / "backend"
CONFIG_PATH = PROJECT_ROOT / "config.yaml"
ENV_PATH = PROJECT_ROOT / ".env"

_SQLITE_PREFIX = "sqlite:///"


def _load_env_file(path: Path) -> None:
    """把 .env 读入 os.environ（不覆盖已存在的环境变量）。"""
    if not path.exists():
        return
    for raw in path.read_text(encoding="utf-8").splitlines():
        line = raw.strip()
        if not line or line.startswith("#") or "=" not in line:
            continue
        key, _, value = line.partition("=")
        key = key.strip()
        if key and key not in os.environ:
            os.environ[key] = value.strip().strip("\"'")


def _load_config_yaml(path: Path) -> dict:
    if not path.exists():
        return {}
    with path.open(encoding="utf-8") as fh:
        data = yaml.safe_load(fh)
    return data if isinstance(data, dict) else {}


def _deep(cfg: dict, dotted: str) -> object:
    node: object = cfg
    for part in dotted.split("."):
        if not isinstance(node, dict) or part not in node:
            return None
        node = node[part]
    return node


@dataclass(frozen=True)
class Settings:
    """应用全局配置（已解析、不可变）。"""

    app_name: str
    app_version: str
    debug: bool
    secret_key: str
    api_prefix: str
    database_url: str
    sqlalchemy_echo: bool
    migrations_dir: Path
    data_source_primary: str
    data_source_fallback: str
    tushare_token: str
    llm_api_key: str
    llm_base_url: str | None
    llm_model: str
    storage: dict[str, Path]
    job_mode: str
    job_memory_limit_gb: int
    job_max_concurrent: int
    config_path: Path = CONFIG_PATH
    env_path: Path = ENV_PATH
    project_root: Path = PROJECT_ROOT


def _resolve_storage_dirs(cfg: dict) -> dict[str, Path]:
    storage_cfg = _deep(cfg, "storage") or {}
    return {
        key: PROJECT_ROOT / str(value)
        for key, value in storage_cfg.items()
        if isinstance(value, str)
    }


def _normalize_sqlite_url(url: str) -> str:
    """把相对路径的 sqlite URL 解析为项目根下的绝对路径。"""
    if not url.startswith(_SQLITE_PREFIX):
        return url
    rest = url[len(_SQLITE_PREFIX) :]
    if rest.startswith("/"):  # 已是绝对路径（sqlite:////abs/path）
        return url
    return f"{_SQLITE_PREFIX}{(PROJECT_ROOT / rest).resolve()}"


@lru_cache
def get_settings() -> Settings:
    """加载并缓存 Settings。config / env 路径可通过参数覆盖以便测试。"""
    _load_env_file(ENV_PATH)
    cfg = _load_config_yaml(CONFIG_PATH)

    secret_env = _deep(cfg, "app.secret_key_env") or "APP_SECRET_KEY"
    url_env = _deep(cfg, "database.url_env") or "DATABASE_URL"
    token_env = _deep(cfg, "data_source.tushare_token_env") or "TUSHARE_TOKEN"
    # Agent LLM：URL/模型名在 config.yaml 明文，api_key 只从 .env 读（env 可覆盖 url/model）
    agent_llm = _deep(cfg, "agent.llm") or {}
    llm_key_env = agent_llm.get("api_key_env") or "LLM_API_KEY"
    llm_url_env = agent_llm.get("base_url_env") or "LLM_BASE_URL"
    llm_model_env = agent_llm.get("model_env") or "LLM_MODEL"

    default_url = "sqlite:///./data/quant.db"
    database_url = os.environ.get(url_env) or default_url

    migrations_rel = _deep(cfg, "database.migrations_dir") or (
        "app/infrastructure/persistence/migrations"
    )

    # Job 执行：环境变量 JOB_MODE / QLIB_JOB_MEM_LIMIT_GB 可覆盖 config.yaml（测试用）
    job_cfg = _deep(cfg, "job") or {}
    try:
        job_memory_limit_gb = int(
            os.environ.get("QLIB_JOB_MEM_LIMIT_GB") or job_cfg.get("max_memory_gb") or 6
        )
    except (TypeError, ValueError):
        job_memory_limit_gb = 6
    try:
        job_max_concurrent = int(
            os.environ.get("QLIB_JOB_MAX_CONCURRENT") or job_cfg.get("max_concurrent_jobs") or 2
        )
    except (TypeError, ValueError):
        job_max_concurrent = 2

    return Settings(
        app_name=str(_deep(cfg, "app.name") or "qlib-platform"),
        app_version=str(_deep(cfg, "app.version") or "0.1.0"),
        debug=bool(_deep(cfg, "app.debug") or False),
        secret_key=os.environ.get(secret_env, "dev-insecure-key"),
        api_prefix=str(_deep(cfg, "api.prefix") or "/api"),
        database_url=_normalize_sqlite_url(database_url),
        sqlalchemy_echo=bool(_deep(cfg, "database.echo") or False),
        migrations_dir=BACKEND_ROOT / str(migrations_rel),
        data_source_primary=str(_deep(cfg, "data_source.primary") or "tushare"),
        data_source_fallback=str(_deep(cfg, "data_source.fallback") or "sina"),
        tushare_token=os.environ.get(token_env, ""),
        llm_api_key=os.environ.get(llm_key_env, ""),
        llm_base_url=os.environ.get(llm_url_env) or (agent_llm.get("base_url") or None),
        llm_model=os.environ.get(llm_model_env) or agent_llm.get("model") or "qwen-plus",
        storage=_resolve_storage_dirs(cfg),
        job_mode=os.environ.get("JOB_MODE") or job_cfg.get("mode") or "subprocess",
        job_memory_limit_gb=job_memory_limit_gb,
        job_max_concurrent=job_max_concurrent,
    )