from os import path

import cv2


def file_info(data_folder: str, file_name: str, file_ext: str):
    """
    Receive file type, frame count and frames per second.
    The last two are always None for images.

    :param data_folder: path to data folder
    :param file_name: file name
    :param file_ext: file extension
    :return: file type, frame count, frames per second
    """
    # determine file type
    if file_ext in ['.jpg', '.png']:
        ftype = 'image'
    elif file_ext in ['.mp4']:
        ftype = 'video'
    else:
        raise ValueError

    # determine frames and fps for video files
    if ftype == 'image':
        frames = None
        fps = None
    else:
        file_path = path.join(data_folder, file_name + file_ext)
        video = cv2.VideoCapture(file_path)

        frames = int(video.get(cv2.CAP_PROP_FRAME_COUNT))
        fps = video.get(cv2.CAP_PROP_FPS)

        video.release()

    # return values
    return ftype, frames, fps