import os
import configparser
from typing import Optional
from pathlib import Path


class Config:
    """从 config.ini 读取的应用配置"""

    _config = configparser.ConfigParser()
    _config_loaded = False
    DEFAULT_MODEL_SECTION = "gpt-4o"
    MAX_RETRIES = 3
    TIMEOUT = 30
    CONVERSATION_MAX_HISTORY_MESSAGES = 10
    CONVERSATION_ENABLE_MULTI_TURN = False
    CONVERSATION_ENABLE_COMPRESSION = False
    CONVERSATION_COMPRESSION_THRESHOLD = 8
    
    @classmethod
    def _get_config_path(cls) -> Path:
        """获取配置文件路径（支持环境变量覆盖）"""
        env_path = os.getenv("CONFIG_PATH")
        if env_path:
            return Path(env_path)
        
        project_root = Path(__file__).parent.parent
        return project_root / 'config' / 'config.ini'
    
    @classmethod
    def _load_config(cls):
        """懒加载配置"""
        if cls._config_loaded:
            return
        
        config_path = cls._get_config_path()
        
        if not config_path.exists():
            raise FileNotFoundError(
                f"Configuration file not found at: {config_path}. "
                "Please copy 'config/config.ini.example' to 'config/config.ini' and fill in your details."
            )
        
        with open(config_path, "r", encoding="utf-8") as f:
            cls._config.read_file(f)
        
        cls._config_loaded = True
    
    @classmethod
    def reload(cls):
        """重新加载配置（支持热重载）"""
        cls._config_loaded = False
        cls._load_config()
        _refresh_runtime_constants()
    
    @classmethod
    def get_model_config(cls, section: Optional[str] = None) -> dict:
        """
        获取指定模型配置段。
        若 section 为 None，则使用默认模型配置段。
        """
        if section is None:
            section = cls.DEFAULT_MODEL_SECTION

        if not cls._config.has_section(section):
            raise ValueError(f"Model section '{section}' not found in config.ini")

        config = dict(cls._config.items(section))

        # 确保必需的键存在
        if 'model_name' not in config or 'openai_api_key' not in config:
            raise ValueError(f"Model section '{section}' must contain 'model_name' and 'openai_api_key'")

        return {
            "model": config['model_name'],
            "api_key": config['openai_api_key'],
            "base_url": config.get('url') or config.get('base_url')
        }

    @classmethod
    def get_section(cls, section: str) -> dict:
        """获取指定配置段的键值对（键名会被转为小写）"""
        if not cls._config.has_section(section):
            return {}
        return dict(cls._config.items(section))

    @classmethod
    def validate_config(cls):
        """校验默认模型配置是否存在且有效"""
        try:
            default_config = cls.get_model_config()
            if not default_config.get("api_key") or 'your_openai_api_key_here' in default_config.get("api_key"):
                raise ValueError(f"API key for default model '{cls.DEFAULT_MODEL_SECTION}' is missing or a placeholder.")
        except (ValueError, configparser.Error) as e:
            raise ValueError(f"Configuration validation failed: {e}")


DEFAULT_MODEL_SECTION = Config.DEFAULT_MODEL_SECTION
MAX_RETRIES = Config.MAX_RETRIES
TIMEOUT = Config.TIMEOUT
CONVERSATION_MAX_HISTORY_MESSAGES = Config.CONVERSATION_MAX_HISTORY_MESSAGES
CONVERSATION_ENABLE_MULTI_TURN = Config.CONVERSATION_ENABLE_MULTI_TURN
CONVERSATION_ENABLE_COMPRESSION = Config.CONVERSATION_ENABLE_COMPRESSION
CONVERSATION_COMPRESSION_THRESHOLD = Config.CONVERSATION_COMPRESSION_THRESHOLD


def _refresh_runtime_constants() -> None:
    """同步模块级常量与 Config 类属性，兼容两种访问方式。"""
    global DEFAULT_MODEL_SECTION
    global MAX_RETRIES
    global TIMEOUT
    global CONVERSATION_MAX_HISTORY_MESSAGES
    global CONVERSATION_ENABLE_MULTI_TURN
    global CONVERSATION_ENABLE_COMPRESSION
    global CONVERSATION_COMPRESSION_THRESHOLD

    DEFAULT_MODEL_SECTION = Config._config.get('General', 'DEFAULT_MODEL_SECTION', fallback='gpt-4o')
    MAX_RETRIES = Config._config.getint('General', 'MAX_RETRIES', fallback=3)
    TIMEOUT = Config._config.getint('General', 'TIMEOUT', fallback=30)
    CONVERSATION_MAX_HISTORY_MESSAGES = Config._config.getint('conversation', 'max_history_messages', fallback=10)
    CONVERSATION_ENABLE_MULTI_TURN = Config._config.getboolean('conversation', 'enable_multi_turn', fallback=False)
    CONVERSATION_ENABLE_COMPRESSION = Config._config.getboolean('conversation', 'enable_memory_compression', fallback=False)
    CONVERSATION_COMPRESSION_THRESHOLD = Config._config.getint('conversation', 'compression_threshold', fallback=8)

    Config.DEFAULT_MODEL_SECTION = DEFAULT_MODEL_SECTION
    Config.MAX_RETRIES = MAX_RETRIES
    Config.TIMEOUT = TIMEOUT
    Config.CONVERSATION_MAX_HISTORY_MESSAGES = CONVERSATION_MAX_HISTORY_MESSAGES
    Config.CONVERSATION_ENABLE_MULTI_TURN = CONVERSATION_ENABLE_MULTI_TURN
    Config.CONVERSATION_ENABLE_COMPRESSION = CONVERSATION_ENABLE_COMPRESSION
    Config.CONVERSATION_COMPRESSION_THRESHOLD = CONVERSATION_COMPRESSION_THRESHOLD


# 在类定义完成后加载配置
Config._load_config()
_refresh_runtime_constants()


# 如有需要可在导入时做初始校验，
# 但已移到 main.py 以便更可控地执行。
# 如需在导入时校验，可在此调用 Config.validate_config()