backend/core/models.py

import os
from typing import Optional, Union, Any, List
from langchain_google_genai import ChatGoogleGenerativeAI
from langchain_openai import ChatOpenAI
from langchain_anthropic import ChatAnthropic
from langchain_core.messages import BaseMessage, HumanMessage, SystemMessage, AIMessage

def get_llm(
    provider: str,
    model: str,
    api_key: str,
    temperature: float = 0.7,
    streaming: bool = True
):
    """
    Factory function to get a unified LLM instance based on provider.
    Supports DEV_MODE if api_key is missing.
    """
    dev_mode = os.getenv("DEV_MODE", "false").lower() == "true"
    
    # Fallback to server key if user key is missing (Prod & Dev)
    target_api_key = api_key
    if not api_key:
        if provider == "google":
            target_api_key = os.getenv("GOOGLE_API_KEY")
        elif provider == "openai":
            target_api_key = os.getenv("OPENAI_API_KEY")
        elif provider == "anthropic":
            target_api_key = os.getenv("ANTHROPIC_API_KEY")
        elif provider == "nvidia":
            target_api_key = os.getenv("NVIDIA_API_KEY")

    if not target_api_key:
        raise ValueError(f"Missing API Key for {provider}. Please ensure server secrets are set or provide a key in settings.")

    if provider == "google":
        return ChatGoogleGenerativeAI(
            model=model,
            google_api_key=target_api_key,
            temperature=temperature,
            streaming=streaming,
            # Suppress common safety filters using the dictionary format
            safety_settings={
                "HARM_CATEGORY_HARASSMENT": "BLOCK_NONE",
                "HARM_CATEGORY_HATE_SPEECH": "BLOCK_NONE",
                "HARM_CATEGORY_SEXUALLY_EXPLICIT": "BLOCK_NONE",
                "HARM_CATEGORY_DANGEROUS_CONTENT": "BLOCK_NONE",
            }
        )
    elif provider == "openai":
        return ChatOpenAI(
            model=model,
            api_key=target_api_key,
            temperature=temperature,
            streaming=streaming
        )
    elif provider == "anthropic":
        return ChatAnthropic(
            model=model,
            api_key=target_api_key,
            temperature=temperature,
            streaming=streaming
        )
    elif provider == "nvidia":
        return ChatOpenAI(
            model=model,
            api_key=target_api_key,
            base_url=os.getenv("NVIDIA_BASE_URL", "https://integrate.api.nvidia.com/v1"),
            temperature=temperature,
            streaming=streaming
        )
    else:
        raise ValueError(f"Unsupported provider: {provider}")

def convert_history_to_langchain(history: List[dict]):
    """Convert standard role/content dicts to LangChain message objects."""
    messages = []
    for msg in history:
        role = msg.get("role", "user")
        content = msg.get("content", "")
        if role == "user":
            messages.append(HumanMessage(content=content))
        elif role == "assistant":
            messages.append(AIMessage(content=content))
        elif role == "system":
            messages.append(SystemMessage(content=content))
    return messages