import copy
import json
import os

DEFAULT_CONFIG = {
    "api": {
        "api_key": None,
        "model": "deepseek-v4-flash",
        "base_url": "https://api.deepseek.com/chat/completions",
        "timeout": 120,
        "max_retries": 3,
        "max_tokens": 32768,
    }
}

ENV_OVERRIDES = {
    "api_key": "DEEPSEEK_API_KEY",
    "model": "DEEPSEEK_MODEL",
    "base_url": "DEEPSEEK_BASE_URL",
    "timeout": "DEEPSEEK_TIMEOUT",
    "max_retries": "DEEPSEEK_MAX_RETRIES",
    "max_tokens": "DEEPSEEK_MAX_TOKENS",
}

_INT_KEYS = {"timeout", "max_retries", "max_tokens"}


def _project_root() -> str:
    return os.path.dirname(os.path.dirname(os.path.abspath(__file__)))


def _default_config_path() -> str:
    return os.path.join(_project_root(), 'config.json')


def load_config(path: str = None) -> dict:
    config = copy.deepcopy(DEFAULT_CONFIG)

    if path is None:
        path = _default_config_path()

    if os.path.exists(path):
        with open(path, 'r', encoding='utf-8') as f:
            user_config = json.load(f)
        _deep_merge(config, user_config)

    for key, env_name in ENV_OVERRIDES.items():
        value = os.environ.get(env_name)
        if value is not None:
            if key in _INT_KEYS:
                value = int(value)
            config['api'][key] = value

    return config


def _deep_merge(base: dict, override: dict) -> None:
    for key, value in override.items():
        if isinstance(value, dict) and isinstance(base.get(key), dict):
            _deep_merge(base[key], value)
        else:
            base[key] = value