from pathlib import Path
from typing import Annotated, Literal

import yaml
from pydantic import BaseModel, Field


class CodexConfig(BaseModel):
    provider: Literal["codex"]
    model: str = "gpt-5.6-luna"

    credential_path: Path | None = None


class OpenAiConfig(BaseModel):
    provider: Literal["openai"]
    model: str

    api_key_env: str = "API_KEY"
    base_url_env: str = "BASE_URL"


LLMConfig = Annotated[
    CodexConfig | OpenAiConfig,
    Field(discriminator="provider")
]


class AppConfig(BaseModel):
    llm: LLMConfig


def load_config(path: str | Path = "config.yaml") -> AppConfig:
    path = Path(path)

    with path.open("r", encoding="utf-8") as file:
        data = yaml.safe_load(file)

    return AppConfig.model_validate(data)