import io
import base64
import numpy as np
import cv2
from PIL import Image


def postprocess_mask(mask):
    kernel = cv2.getStructuringElement(cv2.MORPH_ELLIPSE, (5, 5))
    cleaned = cv2.morphologyEx(mask, cv2.MORPH_OPEN, kernel)
    cleaned = cv2.morphologyEx(cleaned, cv2.MORPH_CLOSE, kernel)
    num_labels, labels, stats, _ = cv2.connectedComponentsWithStats(cleaned, connectivity=8)
    if num_labels <= 1:
        return cleaned
    largest_label = 1 + np.argmax(stats[1:, cv2.CC_STAT_AREA])
    result = np.zeros_like(cleaned)
    result[labels == largest_label] = 255
    return result


def parse_mask_data(mask_data, h, w):
    if isinstance(mask_data, str):
        mask_bytes = base64.b64decode(mask_data)
        mask_img = Image.open(io.BytesIO(mask_bytes))
        mask_np = np.array(mask_img.convert('L'))
    elif isinstance(mask_data, dict) and 'data' in mask_data:
        mask_bytes = base64.b64decode(mask_data['data'])
        mask_img = Image.open(io.BytesIO(mask_bytes))
        mask_np = np.array(mask_img.convert('L'))
    else:
        mask_np = np.array(mask_data, dtype=np.uint8)
    if mask_np.shape != (h, w):
        resample = getattr(Image, 'LANCZOS', getattr(Image, 'NEAREST', None))
        mask_pil = Image.fromarray(mask_np)
        mask_pil = mask_pil.resize((w, h), resample)
        mask_np = np.array(mask_pil)
    binary_mask = np.zeros_like(mask_np, dtype=np.uint8)
    binary_mask[mask_np > 127] = 255
    return postprocess_mask(binary_mask)


def render_overlay(image, mask):
    overlay = image.copy()
    mask_bool = mask == 255
    cyan_tint = np.zeros_like(image)
    cyan_tint[:, :] = (255, 255, 0)
    overlay[mask_bool] = cv2.addWeighted(image, 0.75, cyan_tint, 0.25, 0)[mask_bool]
    contours, _ = cv2.findContours(mask, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)
    cv2.drawContours(overlay, contours, -1, (0, 255, 255), 3)
    _, buffer = cv2.imencode('.png', overlay)
    return base64.b64encode(buffer).decode('utf-8')