"""LLM provider factory with prompt caching support."""

from __future__ import annotations

from typing import TYPE_CHECKING

if TYPE_CHECKING:
    from langchain_core.language_models import BaseChatModel

    from app.config import Settings


def create_llm(settings: Settings) -> BaseChatModel:
    """Create an LLM instance based on the configured provider."""
    provider = settings.llm_provider
    model = settings.llm_model

    if provider == "anthropic":
        from langchain_anthropic import ChatAnthropic

        return ChatAnthropic(
            model=model,
            api_key=settings.anthropic_api_key,
        )

    if provider == "openai":
        from langchain_openai import ChatOpenAI

        return ChatOpenAI(
            model=model,
            api_key=settings.openai_api_key,
        )

    if provider == "google":
        from langchain_google_genai import ChatGoogleGenerativeAI

        return ChatGoogleGenerativeAI(
            model=model,
            google_api_key=settings.google_api_key,
        )

    raise ValueError(f"Unknown LLM provider: '{provider}'. Use 'anthropic', 'openai', or 'google'.")