import streamlit as st
import cv2
import numpy as np
import tempfile
import os

# Function to reverse the frames of a video and save as a new file
def reverse_video(input_path, output_path):
    """
    Reverse the frames of a video.

    Args:
        input_path (str): Path to the input video file.
        output_path (str): Path to save the reversed video.
    """
    # Open the video file
    cap = cv2.VideoCapture(input_path)
    
    # Check if the video file is successfully opened
    if not cap.isOpened():
        raise ValueError("Error opening video file.")
    
    # Get video properties
    frame_count = int(cap.get(cv2.CAP_PROP_FRAME_COUNT))
    frame_width = int(cap.get(cv2.CAP_PROP_FRAME_WIDTH))
    frame_height = int(cap.get(cv2.CAP_PROP_FRAME_HEIGHT))
    fps = cap.get(cv2.CAP_PROP_FPS)

    # Define the codec and create VideoWriter object
    fourcc = cv2.VideoWriter_fourcc(*'mp4v')
    out = cv2.VideoWriter(output_path, fourcc, fps, (frame_width, frame_height))

    # Read frames in reverse order
    frames = []
    for i in range(frame_count):
        ret, frame = cap.read()
        if not ret:
            break
        frames.append(frame)

    # Ensure frames were read correctly
    if not frames:
        raise ValueError("No frames read from the video file.")

    # Write frames in reverse order to the output video
    for frame in reversed(frames):
        out.write(frame)

    # Release resources
    cap.release()
    out.release()

    # Verify the output file is created
    if not os.path.exists(output_path):
        raise ValueError("Output video file was not created.")

# Streamlit app
st.set_page_config(page_title="Video Reverser App")
st.title("Video Reverser App")

# File uploader for video
uploaded_file = st.file_uploader("Upload a video file", type=["mp4", "avi", "mov", "mkv"])

if uploaded_file is not None:
    # Save the uploaded file to a temporary location
    with tempfile.NamedTemporaryFile(delete=False, suffix=".mp4") as temp_file:
        temp_file.write(uploaded_file.read())
        input_video_path = temp_file.name

    # Reverse the video
    try:
        output_video_path = tempfile.NamedTemporaryFile(delete=False, suffix=".mp4").name
        reverse_video(input_video_path, output_video_path)

        # Display the reversed video
        st.success("Video reversed successfully!")
        st.video(output_video_path)

        # Provide a download button for the reversed video
        with open(output_video_path, "rb") as file:
            st.download_button(
                label="Download Reversed Video",
                data=file,
                file_name="reversed_video.mp4",
                mime="video/mp4"
            )
    except Exception as e:
        st.error(f"An error occurred: {e}")