import base64
import hashlib
import json

from cryptography.fernet import Fernet, InvalidToken

from .config import get_settings
from .llm import DeepSeekClient
from .models import AppSetting


def _cipher():
    secret = get_settings().wisegrade_secret_key
    if len(secret) < 32 or secret == "replace-with-a-random-32-character-secret":
        raise ValueError("请设置至少32位随机WISEGRADE_SECRET_KEY后保存模型配置")
    return Fernet(base64.urlsafe_b64encode(hashlib.sha256(secret.encode()).digest()))


def _get(db, key):
    item = db.get(AppSetting, key)
    if not item:
        return None
    try:
        return _cipher().decrypt(item.encrypted_value).decode()
    except InvalidToken as exc:
        raise ValueError("已保存的模型设置无法解密，请恢复原WISEGRADE_SECRET_KEY") from exc


def _set(db, key, value):
    item = db.get(AppSetting, key)
    if not item:
        item = AppSetting(key=key, encrypted_value=b"")
        db.add(item)
    item.encrypted_value = _cipher().encrypt(value.encode())


def model_config(db):
    settings = get_settings()
    base = {"base_url": settings.deepseek_base_url, "model": settings.deepseek_model,
            "timeout_seconds": settings.model_timeout_seconds, "concurrency": settings.model_concurrency,
            "retries": settings.model_retries}
    stored = _get(db, "model_config") if db.get(AppSetting, "model_config") else None
    return {**base, **(json.loads(stored) if stored else {})}


def key_configured(db):
    return bool(get_settings().deepseek_api_key or db.get(AppSetting, "api_key"))


def save_model_config(db, data: dict):
    config = model_config(db)
    config.update({key: data[key] for key in config if key in data})
    if "api_key" in data and data["api_key"]:
        _set(db, "api_key", data["api_key"])
    _set(db, "model_config", json.dumps(config))
    db.commit()
    return {**config, "api_key_configured": key_configured(db)}


def client_for_batch(db, batch):
    stored_key = _get(db, "api_key") if db.get(AppSetting, "api_key") else None
    config = batch.model_config_snapshot
    return DeepSeekClient(base_url=config["base_url"], model=config["model"],
                          api_key=stored_key or get_settings().deepseek_api_key,
                          timeout=config["timeout_seconds"], retries=config["retries"])


def client_for_chat(db):
    stored_key = _get(db, "api_key") if db.get(AppSetting, "api_key") else None
    config = model_config(db)
    return DeepSeekClient(base_url=config["base_url"], model=config["model"],
                          api_key=stored_key or get_settings().deepseek_api_key,
                          timeout=config["timeout_seconds"], retries=config["retries"])