import base64
from io import BytesIO
from PIL import Image

def pil_to_base64(image: Image.Image) -> str:
    """Converts a PIL Image to a base64 encoded string."""
    buffered = BytesIO()
    image.save(buffered, format="PNG")
    return base64.b64encode(buffered.getvalue()).decode("utf-8")

def images_to_gemini_parts(images: list[Image.Image]) -> list[dict]:
    """
    Converts a list of PIL Images to parts format suitable for Gemini-Pro-Vision API.
    Resizes images if too large to fit within typical API limits.
    """
    parts = []
    for img in images:
        if img:
            # Create a copy to avoid modifying the original PIL image object
            img_copy = img.copy() 
            
            # Resize image to avoid API limits and speed up processing, maintaining aspect ratio.
            # Gemini-Pro-Vision usually supports up to 4k, but a smaller size like 1500px is safer and faster.
            max_dim = 1500 
            if img_copy.width > max_dim or img_copy.height > max_dim:
                img_copy.thumbnail((max_dim, max_dim), Image.Resampling.LANCZOS)

            img_base64 = pil_to_base64(img_copy)
            parts.append({
                "mime_type": "image/png", # PNG is generally safe for base64 encoding
                "data": img_base64
            })
    return parts