"""Image processing operations"""
import io
import hashlib
from datetime import datetime
from PIL import Image

from config import (
    ALLOWED_FORMATS, MAX_DIMENSION, MAX_FILE_SIZE,
    RESIZE_TARGET, THUMBNAIL_TARGET
)


def validate_image(img_data: bytes) -> tuple[Image.Image, str]:
    """Validate and open image data"""
    if len(img_data) > MAX_FILE_SIZE:
        raise ValueError(f'File too large: {len(img_data)} bytes')
    
    img_hash = hashlib.sha256(img_data).hexdigest()
    img = Image.open(io.BytesIO(img_data))
    
    if img.format not in ALLOWED_FORMATS:
        raise ValueError(f'Invalid format: {img.format}')
    
    if img.width * img.height > MAX_DIMENSION ** 2:
        raise ValueError(f'Image too large: {img.width}x{img.height}')
    
    return img, img_hash


def determine_processing(filename: str) -> tuple[tuple[int, int], str]:
    """Determine processing type based on filename"""
    fn = filename.lower()
    if '_thumb' in fn:
        return THUMBNAIL_TARGET, 'resize_200x200'
    elif '_grayscale' in fn:
        return None, 'grayscale'
    else:
        return RESIZE_TARGET, 'resize_1024x1024'


def process_image(img: Image.Image, target: tuple[int, int], ptype: str) -> Image.Image:
    """Apply image processing transformations"""
    if ptype == 'grayscale':
        return img.convert('L')
    elif target:
        img.thumbnail(target, Image.Resampling.LANCZOS)
    return img


def save_image(img: Image.Image, original_format: str) -> tuple[bytes, str]:
    """Save processed image to bytes"""
    output = io.BytesIO()
    fmt = original_format or 'JPEG'
    img.save(output, format=fmt, quality=85)
    return output.getvalue(), f'image/{fmt.lower()}'


def get_processed_key(original_key: str) -> str:
    """Generate processed object key"""
    return original_key.replace('uploads/', 'processed/')


def build_result(original_key: str, processed_key: str, orig_size: tuple,
                 img: Image.Image, ptype: str, img_hash: str) -> dict:
    """Build processing result dictionary"""
    return {
        'status': 'success',
        'original_size': orig_size,
        'processed_size': img.size,
        'processing_type': ptype,
        'processed_key': processed_key,
        'timestamp': datetime.utcnow().isoformat(),
        'hash': img_hash
    }