"""
Visualization utilities for compression results.
"""

import numpy as np
import cv2
from PIL import Image
from typing import Tuple
import matplotlib.pyplot as plt


def highlight_roi(
    image: Image.Image,
    mask: np.ndarray,
    alpha: float = 0.3,
    color: Tuple[int, int, int] = (0, 255, 0)
) -> Image.Image:
    """
    Highlight ROI regions in image with colored overlay.
    
    Args:
        image: PIL Image
        mask: Binary mask (H, W)
        alpha: Overlay transparency (0-1)
        color: RGB color tuple for ROI highlight
    
    Returns:
        Image with ROI highlighted
    """
    img_array = np.array(image)
    
    # Create colored overlay
    overlay = img_array.copy()
    overlay[mask > 0.5] = color
    
    # Blend
    result = cv2.addWeighted(img_array, 1 - alpha, overlay, alpha, 0)
    
    return Image.fromarray(result)


def create_comparison_grid(
    original: Image.Image,
    compressed: Image.Image,
    mask: np.ndarray,
    bpp: float,
    sigma: float,
    lambda_val: float,
    highlight: bool = True
) -> Image.Image:
    """
    Create side-by-side comparison of original and compressed images.
    
    Args:
        original: Original PIL Image
        compressed: Compressed PIL Image
        mask: Binary mask used
        bpp: Bits per pixel
        sigma: Sigma value used
        lambda_val: Lambda value used
        highlight: Whether to show ROI overlay
    
    Returns:
        Combined comparison image
    """
    fig, axes = plt.subplots(1, 3 if highlight else 2, figsize=(15 if highlight else 10, 5))
    
    # Original
    axes[0].imshow(original)
    axes[0].set_title('Original', fontsize=14)
    axes[0].axis('off')
    
    # Compressed
    axes[1].imshow(compressed)
    axes[1].set_title(f'Compressed (σ={sigma:.2f}, λ={lambda_val}, BPP={bpp:.3f})', fontsize=14)
    axes[1].axis('off')
    
    # ROI overlay
    if highlight:
        highlighted = highlight_roi(original, mask, alpha=0.4, color=(0, 255, 0))
        axes[2].imshow(highlighted)
        axes[2].set_title('ROI Mask (green)', fontsize=14)
        axes[2].axis('off')
    
    plt.tight_layout()
    
    # Convert to PIL Image
    fig.canvas.draw()
    img_array = np.frombuffer(fig.canvas.buffer_rgba(), dtype=np.uint8)
    img_array = img_array.reshape(fig.canvas.get_width_height()[::-1] + (4,))
    img_array = img_array[:, :, :3]  # Remove alpha channel
    plt.close(fig)
    
    return Image.fromarray(img_array)