"""Model loading with mock/real switching based on environment.

Supports two loading modes:
- MOCK_MODELS=true: Loads mock models (fast, for local dev on RTX 4090)
- MOCK_MODELS=false: Loads all real models at startup (~38-43GB total)

Memory Strategy (Simultaneous Loading for 4xL4 GPUs with 88GB total):
- Vision 30B-A3B FP8 via vLLM: ~30-35GB
- Embedding 2B: ~4GB
- Reranker 2B: ~4GB
- Total: ~38-43GB, leaving ~45GB+ headroom
"""

import logging
import time
from typing import Union

from config.settings import settings

logger = logging.getLogger(__name__)

# Type alias for model stack
ModelStack = Union["MockModelStack", "RealModelStack"]  # noqa: F821

# Lazy singleton
_model_stack: ModelStack | None = None


def get_model_stack() -> ModelStack:
    """Get model stack based on environment configuration.

    For mock models: Loads mock models immediately (fast, for local dev).
    For real models: Loads all 3 models at startup (~38-43GB total).
    """
    start_time = time.time()

    if settings.mock_models:
        logger.info("Loading MOCK model stack (development mode)")
        from models.mock import MockModelStack

        stack = MockModelStack().load_all()
        elapsed = time.time() - start_time
        logger.info(f"Mock model stack loaded in {elapsed:.2f}s")
        return stack
    else:
        logger.info("Loading REAL model stack (production mode)")
        logger.info(f"Vision model: {settings.vision_model} (FP8 via vLLM)")
        logger.info(f"Embedding model: {settings.embedding_model}")
        logger.info(f"Reranker model: {settings.reranker_model}")
        from models.real import RealModelStack

        # Load all models at startup (simultaneous loading)
        stack = RealModelStack().load_all()
        elapsed = time.time() - start_time
        logger.info(f"Real model stack loaded in {elapsed:.2f}s")
        return stack


def get_models() -> ModelStack:
    """Get or create the singleton model stack.

    Returns fully loaded model stack (all models ready for inference).
    """
    global _model_stack
    if _model_stack is None:
        logger.debug("Model stack not initialized, creating new stack")
        _model_stack = get_model_stack()
    else:
        logger.debug("Returning cached model stack")
    return _model_stack


def reset_models() -> None:
    """Reset the model stack (useful for testing)."""
    global _model_stack
    _model_stack = None