"""Utilities for detecting and managing compute devices (CPU/GPU)."""

import torch
from typing import List, Tuple


class DeviceManager:
    """Manages device detection and selection for transcription."""

    def __init__(self):
        """Initialize device manager and detect available devices."""
        self.available_devices = self._detect_devices()
        self.current_device = self.available_devices[0] if self.available_devices else "cpu"

    def _detect_devices(self) -> List[str]:
        """
        Detect available compute devices.

        Returns:
            List of available device names
        """
        devices = ["cpu"]

        # Check for CUDA (NVIDIA GPU)
        if torch.cuda.is_available():
            devices.append("cuda")

        # Check for MPS (Apple Silicon GPU)
        if hasattr(torch.backends, 'mps') and torch.backends.mps.is_available():
            devices.append("mps")

        return devices

    def get_device_info(self) -> List[Tuple[str, str]]:
        """
        Get detailed information about available devices.

        Returns:
            List of (device_name, device_description) tuples
        """
        info = []

        for device in self.available_devices:
            if device == "cpu":
                info.append(("cpu", "CPU"))
            elif device == "cuda":
                try:
                    gpu_name = torch.cuda.get_device_name(0)
                    info.append(("cuda", f"CUDA GPU: {gpu_name}"))
                except:
                    info.append(("cuda", "CUDA GPU"))
            elif device == "mps":
                info.append(("mps", "Apple Silicon GPU (MPS)"))

        return info

    def set_device(self, device: str) -> bool:
        """
        Set the current device for transcription.

        Args:
            device: Device name ('cpu', 'cuda', 'mps', or 'auto')

        Returns:
            True if device was set successfully, False otherwise
        """
        if device == "auto":
            # Auto-select best available device
            if "cuda" in self.available_devices:
                self.current_device = "cuda"
            elif "mps" in self.available_devices:
                self.current_device = "mps"
            else:
                self.current_device = "cpu"
            return True

        if device in self.available_devices:
            self.current_device = device
            return True

        return False

    def get_device(self) -> str:
        """
        Get the currently selected device.

        Returns:
            Current device name
        """
        return self.current_device

    def is_gpu_available(self) -> bool:
        """
        Check if any GPU is available.

        Returns:
            True if CUDA or MPS is available
        """
        return "cuda" in self.available_devices or "mps" in self.available_devices

    def get_device_for_whisper(self) -> str:
        """
        Get device string formatted for faster-whisper.

        Returns:
            Device string for faster-whisper ('cpu', 'cuda', etc.)
        """
        if self.current_device == "mps":
            # faster-whisper doesn't support MPS, fall back to CPU
            return "cpu"
        return self.current_device

    def get_compute_type(self) -> str:
        """
        Get the appropriate compute type for the current device.

        Returns:
            Compute type string for faster-whisper
        """
        if self.current_device == "cuda":
            # Use float16 for GPU for better performance
            return "float16"
        else:
            # Use int8 for CPU for better performance
            return "int8"

    def __repr__(self) -> str:
        return f"DeviceManager(current={self.current_device}, available={self.available_devices})"