"""
MPS optimizations for Vortex model on Apple Silicon.
Uses PyTorch MPS backend with MPS-compatible ops only.
"""

import torch
import torch.nn as nn
from typing import Optional, Dict, Any


def optimize_for_mps(
    model: nn.Module,
    config: Dict,
    use_sdpa: bool = True,
) -> nn.Module:
    """
    Apply MPS optimizations to model.

    Args:
        model: VortexModel
        config: Model config
        use_sdpa: Use PyTorch scaled dot product attention (MPS compatible)

    Returns:
        Optimized model
    """
    device = torch.device("mps")

    # Move to MPS
    model = model.to(device)

    # Set dtype - MPS supports float32 and float16 (bfloat16 limited)
    dtype_str = config.get("dtype", "bfloat16")
    if dtype_str == "bfloat16":
        # MPS has limited bfloat16 support, use float16
        dtype = torch.float16
    else:
        dtype = torch.float32

    model = model.to(dtype)

    # Replace Flash Attention with standard SDPA
    if use_sdpa:
        model = _apply_sdpa(model)
        print("Applied PyTorch SDPA for MPS")

    return model


def _apply_sdpa(model: nn.Module) -> nn.Module:
    """
    Replace custom attention with PyTorch SDPA.
    SDPA is optimized for MPS backend.
    """
    for name, module in model.named_modules():
        if hasattr(module, 'attn') and hasattr(module.attn, 'forward_optimized'):
            # Use the SDPA path
            original_forward = module.attn.forward

            def sdpa_forward(self, x, *args, **kwargs):
                return self._standard_attention(x, kwargs.get('attention_mask'))

            module.attn.forward = sdpa_forward.__get__(module.attn, type(module.attn))

    return model


def get_mps_memory_usage() -> Dict[str, float]:
    """Get current MPS memory usage in GB."""
    if not torch.backends.mps.is_available():
        return {"error": "MPS not available"}

    # MPS doesn't have direct memory query, use unified memory
    import psutil
    process = psutil.Process()
    memory_info = process.memory_info()

    return {
        "rss_gb": memory_info.rss / 1e9,  # Resident set size
        "vms_gb": memory_info.vms / 1e9,  # Virtual memory size
    }


def profile_model_mps(
    model: nn.Module,
    input_ids: torch.Tensor,
    num_warmup: int = 10,
    num_runs: int = 50,
) -> Dict[str, float]:
    """
    Profile model performance on MPS.

    Args:
        model: Model to profile
        input_ids: Example input
        num_warmup: Number of warmup runs
        num_runs: Number of profiling runs

    Returns:
        Dictionary with timing statistics
    """
    model.eval()
    device = next(model.parameters()).device
    input_ids = input_ids.to(device)

    # Warmup
    with torch.no_grad():
        for _ in range(num_warmup):
            _ = model(input_ids)
            # MPS is async, need to wait
            if device.type == "mps":
                torch.mps.synchronize()

    # Profile
    if device.type == "mps":
        torch.mps.synchronize()
    import time
    start = time.time()

    with torch.no_grad():
        for _ in range(num_runs):
            _ = model(input_ids)
            if device.type == "mps":
                torch.mps.synchronize()

    elapsed = time.time() - start

    avg_time = elapsed / num_runs
    tokens_per_sec = input_ids.shape[1] / avg_time

    return {
        "avg_time_sec": avg_time,
        "tokens_per_sec": tokens_per_sec,
    }


def test_mps_optimize():
    """Test MPS optimizations."""
    if not torch.backends.mps.is_available():
        print("MPS not available, skipping test")
        return

    from models.vortex_model import VortexModel
    from configs.vortex_7b_config import VORTEX_7B_CONFIG

    config = VORTEX_7B_CONFIG.copy()
    config["d_model"] = 512
    config["num_layers"] = 2
    config["num_heads"] = 8
    config["vocab_size"] = 1000

    model = VortexModel(config)
    print(f"Model parameters: {model.get_num_params():,}")

    # Optimize for MPS
    model = optimize_for_mps(model, config, use_sdpa=True)

    # Test forward
    batch_size = 2
    seq_len = 128
    input_ids = torch.randint(0, config["vocab_size"], (batch_size, seq_len)).to("mps")

    with torch.no_grad():
        output = model(input_ids)
        logits = output["logits"]

    print(f"Output shape: {logits.shape}")
    print("MPS optimize test passed!")


if __name__ == "__main__":
    test_mps_optimize()