from __future__ import annotations

import os
from functools import lru_cache
from pathlib import Path
from typing import Any

import yaml
from fastapi import HTTPException
from pydantic import BaseModel, Field

_ROOT_DIR = Path(__file__).resolve().parents[1]
_MODELS_FILE = _ROOT_DIR / "config" / "models.yaml"


class ModelSpec(BaseModel):
    id: str
    label: str
    provider: str = "deepseek"
    api_model: str
    base_url: str
    api_key_env: str
    max_tokens: int = 4000
    # 直接并入请求体的模型专属参数，例如 thinking / reasoning_effort。
    params: dict[str, Any] = Field(default_factory=dict)


class ModelsFile(BaseModel):
    default: str
    models: list[ModelSpec] = Field(default_factory=list)


class ModelOption(BaseModel):
    id: str
    label: str


class ModelsListResponse(BaseModel):
    default: str
    models: list[ModelOption]


@lru_cache
def load_models_file() -> ModelsFile:
    if not _MODELS_FILE.is_file():
        raise RuntimeError(f"缺少模型配置文件：{_MODELS_FILE}")
    raw = yaml.safe_load(_MODELS_FILE.read_text(encoding="utf-8")) or {}
    data = ModelsFile.model_validate(raw)
    if not data.models:
        raise RuntimeError("models.yaml 中 models 不能为空")
    ids = {m.id for m in data.models}
    if data.default not in ids:
        raise RuntimeError(f"models.yaml 的 default「{data.default}」不在 models 列表中")
    return data


def list_model_options() -> ModelsListResponse:
    data = load_models_file()
    return ModelsListResponse(
        default=data.default,
        models=[ModelOption(id=m.id, label=m.label) for m in data.models],
    )


def get_model_spec(model_id: str | None = None) -> ModelSpec:
    data = load_models_file()
    chosen = (model_id or "").strip() or data.default
    for item in data.models:
        if item.id == chosen:
            return item
    raise HTTPException(
        status_code=400,
        detail=f"不支持的模型「{chosen}」，请从 /api/ai/models 列表中选择",
    )


def resolve_api_key(spec: ModelSpec) -> str:
    key = (os.getenv(spec.api_key_env) or "").strip()
    if not key:
        raise HTTPException(
            status_code=500,
            detail=f"未配置密钥环境变量：{spec.api_key_env}",
        )
    return key