import os
import requests

# ---------------------------------------------
# Load backend definition from .env
# ---------------------------------------------

def load_backend_config(name: str):
    """
    Given a backend name like 'PRIMARY' or 'OPENAI',
    load the matching provider / url / model from env.
    """

    prefix = f"LLM_{name.upper()}"

    provider = os.getenv(f"{prefix}_PROVIDER")
    url      = os.getenv(f"{prefix}_URL")
    model    = os.getenv(f"{prefix}_MODEL")

    if not provider or not url or not model:
        raise RuntimeError(
            f"Backend '{name}' is missing configuration. "
            f"Expected {prefix}_PROVIDER / URL / MODEL in .env"
        )

    return provider, url.rstrip("/"), model


# ---------------------------------------------
# Core call_llm() — fail hard, no fallback
# ---------------------------------------------

def call_llm(prompt: str, backend_env_var: str):
    """
    Example:
        call_llm(prompt, backend_env_var="CORTEX_LLM")

    backend_env_var should contain one of:
        PRIMARY, SECONDARY, OPENAI, FALLBACK, etc
    """

    backend_name = os.getenv(backend_env_var)
    if not backend_name:
        raise RuntimeError(f"{backend_env_var} is not set in .env")

    provider, base_url, model = load_backend_config(backend_name)

    # ---------------------------------------------
    # Provider-specific behavior
    # ---------------------------------------------

    if provider == "vllm":
        # vLLM OpenAI-compatible API
        response = requests.post(
            f"{base_url}/v1/completions",
            json={
                "model": model,
                "prompt": prompt,
                "max_tokens": 1024,
                "temperature": float(os.getenv("LLM_TEMPERATURE", "0.7"))
            },
            timeout=30
        )
        response.raise_for_status()
        data = response.json()
        return data["choices"][0]["text"]

    elif provider == "ollama":
        response = requests.post(
            f"{base_url}/api/chat",
            json={
                "model": model,
                "messages": [{"role": "user", "content": prompt}],
                "stream": False
            },
            timeout=30
        )
        response.raise_for_status()
        data = response.json()
        return data["message"]["content"]

    elif provider == "openai":
        api_key = os.getenv("OPENAI_API_KEY")
        if not api_key:
            raise RuntimeError("OPENAI_API_KEY missing but provider=openai was selected")

        response = requests.post(
            f"{base_url}/chat/completions",
            headers={"Authorization": f"Bearer {api_key}"},
            json={
                "model": model,
                "messages": [{"role": "user", "content": prompt}],
                "temperature": float(os.getenv("LLM_TEMPERATURE", "0.7"))
            },
            timeout=30
        )
        response.raise_for_status()
        data = response.json()
        return data["choices"][0]["message"]["content"]

    else:
        raise RuntimeError(f"Unknown LLM provider: {provider}")