from PIL import Image
import numpy as np
import imageio.v3 as iio
from typing import List

def frames_to_video(frames: List[Image.Image], fps: int, file_path: str) -> str:
    """Converts a list of PIL images to a video file (MP4)."""
    
    # Convert PIL images to numpy arrays (RGB)
    video_data = [np.array(frame.convert("RGB")) for frame in frames]
    
    # Save video using imageio
    # We rely on the external imageio-ffmpeg dependency for libx264 encoding
    iio.imwrite(
        file_path, 
        video_data, 
        fps=fps, 
        codec='libx264', 
        quality=8, # High quality setting (range 0-10, default 5)
        pixelformat='yuv420p' # Ensures compatibility with most players/browsers
    )
    return file_path