app.py

import gradio as gr
import cv2
import numpy as np
import os
import io
import base64
import tempfile # Make sure tempfile is imported
import math   # Import math for ceiling function

# --- Helper Function ---
# (Keep the get_frame_from_video function exactly as it was)
def get_frame_from_video(video_path, frame_number):
    """Reads a specific frame from a video file."""
    if not video_path or not os.path.exists(video_path):
        return None, "Error: Video file not found or path is invalid."

    cap = cv2.VideoCapture(video_path)
    if not cap.isOpened():
        try: cap.release()
        except Exception: pass
        return None, f"Error: Could not open video file: {video_path}"

    total_frames = int(cap.get(cv2.CAP_PROP_FRAME_COUNT))
    frame_number = int(frame_number)

    if total_frames <= 0:
        cap.release()
        return None, f"Error: Video file seems to have no frames or is corrupted: {os.path.basename(video_path)}"

    max_frame = total_frames - 1
    if frame_number < 0 or frame_number > max_frame:
        cap.release()
        return None, f"Error: Frame number {frame_number} is out of bounds (0-{max_frame})."

    # Ensure frame number doesn't exceed max_frame even after calculation
    frame_number = min(frame_number, max_frame)

    cap.set(cv2.CAP_PROP_POS_FRAMES, frame_number)
    ret, frame = cap.read()
    cap.release()

    if not ret:
        # Attempt to read the last valid frame if the target failed (might happen near the end)
        if frame_number > 0:
            cap = cv2.VideoCapture(video_path)
            cap.set(cv2.CAP_PROP_POS_FRAMES, max_frame)
            ret_last, frame_last = cap.read()
            cap.release()
            if ret_last:
                 return cv2.cvtColor(frame_last, cv2.COLOR_BGR2RGB), f"Could not read frame {frame_number}. Showing last valid frame {max_frame}/{max_frame}."
        return None, f"Error: Could not read frame {frame_number}."


    frame_rgb = cv2.cvtColor(frame, cv2.COLOR_BGR2RGB)
    status_message = f"Showing frame {frame_number}/{max_frame}." # Basic status
    return frame_rgb, status_message

# --- Gradio Callback Functions ---

# 1. Function triggered when a video file is uploaded
def load_video(video_path):
    """Loads the video, gets its properties, updates the slider, displays the first frame, and hides download links."""
    if video_path is None:
        # Reset UI elements, including FPS state
        return {
            video_path_state: None,
            fps_state: 0.0, # Reset FPS
            frame_slider: gr.Slider(minimum=0, maximum=0, value=0, step=1, interactive=False),
            frame_display: None,
            info_text: "Please upload a video file (e.g., MP4).",
            jpg_download_output: gr.File(value=None, visible=False),
            png_download_output: gr.File(value=None, visible=False)
        }

    cap = cv2.VideoCapture(video_path)
    fps = 0.0 # Initialize fps
    if not cap.isOpened():
        try: cap.release();
        except: pass
        return {
            video_path_state: None,
            fps_state: 0.0, # Reset FPS
            frame_slider: gr.Slider(minimum=0, maximum=0, value=0, step=1, interactive=False),
            frame_display: None,
            info_text: f"Error: Could not open video file: {os.path.basename(video_path)}",
            jpg_download_output: gr.File(value=None, visible=False),
            png_download_output: gr.File(value=None, visible=False)
        }

    total_frames = int(cap.get(cv2.CAP_PROP_FRAME_COUNT))
    fps = cap.get(cv2.CAP_PROP_FPS) # Get FPS here

    # Validate total_frames and fps
    if total_frames <= 0 or not fps or fps <= 0:
         cap.release()
         error_msg = f"Error: Could not read valid metadata (frames={total_frames}, fps={fps}) from {os.path.basename(video_path)}."
         return {
            video_path_state: None,
            fps_state: 0.0, # Reset FPS
            frame_slider: gr.Slider(minimum=0, maximum=0, value=0, step=1, interactive=False),
            frame_display: None,
            info_text: error_msg,
            jpg_download_output: gr.File(value=None, visible=False),
            png_download_output: gr.File(value=None, visible=False)
        }

    duration = total_frames / fps
    cap.release()

    first_frame, status = get_frame_from_video(video_path, 0)

    if first_frame is None:
        # FPS is valid here, but first frame failed
        return {
            video_path_state: None,
            fps_state: 0.0, # Reset FPS as we can't proceed
            frame_slider: gr.Slider(minimum=0, maximum=0, value=0, step=1, interactive=False),
            frame_display: None,
            info_text: f"Error reading first frame: {status}",
            jpg_download_output: gr.File(value=None, visible=False),
            png_download_output: gr.File(value=None, visible=False)
        }

    info = (
        f"Video: {os.path.basename(video_path)}\n"
        f"Total Frames: {total_frames}\n"
        f"FPS: {fps:.2f}\n"
        f"Duration: {duration:.2f} seconds\n"
        f"Use slider or video controls." # Updated instruction
    )
    slider_max = max(0, total_frames - 1)

    return {
        video_path_state: video_path,
        fps_state: fps, # Store the valid FPS
        frame_slider: gr.Slider(minimum=0, maximum=slider_max, value=0, step=1, interactive=True),
        frame_display: first_frame,
        info_text: info + "\n" + status,
        jpg_download_output: gr.File(value=None, visible=False),
        png_download_output: gr.File(value=None, visible=False)
    }

# 2. Function triggered when the slider value changes (on release)
def update_frame_on_slider(video_path, frame_number):
    """Gets and displays the frame, updates status, and hides download links."""
    if video_path is None:
        return None, "No video loaded.", gr.File(value=None, visible=False), gr.File(value=None, visible=False)
    frame_number = int(frame_number)
    frame, status = get_frame_from_video(video_path, frame_number)
    return frame, status, gr.File(value=None, visible=False), gr.File(value=None, visible=False)


# 3. Function to prepare and save the frame temporarily
# (Keep the save_frame_temporarily function exactly as it was)
def save_frame_temporarily(video_path, frame_number, image_format):
    """Saves the frame temporarily and returns the file path."""
    if video_path is None:
        return None, "No video loaded to download from."

    frame_number = int(frame_number)
    frame, status = get_frame_from_video(video_path, frame_number)

    if frame is None:
        return None, status # Return error status from get_frame

    # Ensure frame is uint8
    if frame.dtype != np.uint8:
        if frame.max() <= 1.0:
            frame = (frame * 255).astype(np.uint8)
        else:
            frame = frame.astype(np.uint8) # Potential clipping

    # Choose suffix and encode
    suffix = f".{image_format}"
    frame_bgr = cv2.cvtColor(frame, cv2.COLOR_RGB2BGR) # Convert for OpenCV saving

    if image_format == "jpeg":
        ret, buffer = cv2.imencode('.jpg', frame_bgr)
    elif image_format == "png":
        ret, buffer = cv2.imencode('.png', frame_bgr)
    else:
        return None, f"Unsupported format: {image_format}"

    if not ret:
        return None, f"Error encoding frame {frame_number} to {image_format}."

    try:
        temp_file = tempfile.NamedTemporaryFile(suffix=suffix, delete=False)
        temp_file.write(buffer)
        temp_file.close()
        file_path = temp_file.name
        status = f"Frame {frame_number} ready. Click link below to download {image_format.upper()}."
        return file_path, status
    except Exception as e:
        if 'temp_file' in locals() and temp_file:
             try: os.unlink(temp_file.name)
             except OSError: pass
        return None, f"Error creating temporary file: {e}"

# 4. NEW Function: Triggered when video is paused
def sync_slider_on_pause(video_path, fps, pause_time: gr.Number):
    """Updates the slider value based on the video pause time."""
    print(f"Pause event: video_path={video_path}, fps={fps}, pause_time={pause_time}") # Debug print
    if video_path is None or not fps or fps <= 0 or pause_time is None:
        print("Skipping slider sync due to invalid inputs.")
        # Return an update that does nothing if inputs are invalid
        return gr.Slider() # No change update

    # Calculate frame number - use math.ceil to lean towards the frame *after* the pause time
    # Or use int() for the frame *at* or *before* the pause time. Let's use int() for simplicity.
    calculated_frame = int(pause_time * fps)

    # Get the current max of the slider to prevent going out of bounds
    # This requires the slider component itself to be passed, which is complex.
    # Alternative: Re-read total frames here (less efficient but simpler state management)
    cap = cv2.VideoCapture(video_path)
    if cap.isOpened():
        total_frames = int(cap.get(cv2.CAP_PROP_FRAME_COUNT))
        cap.release()
        if total_frames > 0:
            max_frame = total_frames - 1
            # Clamp the calculated frame to the valid range
            target_frame = max(0, min(calculated_frame, max_frame))
            print(f"Calculated frame: {calculated_frame}, Target frame: {target_frame}")
            return gr.Slider(value=target_frame)
        else:
             print("Skipping slider sync because total_frames <= 0.")
             return gr.Slider() # No change
    else:
         print("Skipping slider sync because video couldn't be opened.")
         return gr.Slider() # No change


# --- Gradio Interface ---
with gr.Blocks() as demo:
    gr.Markdown("# Video Frame Explorer and Downloader")
    gr.Markdown("Upload a video file (like MP4), use the slider OR pause the video to select a frame. Click a 'Prepare' button, then click the link that appears to download.")

    video_path_state = gr.State(None)
    fps_state = gr.State(0.0) # NEW state for FPS

    with gr.Row():
        with gr.Column(scale=1):
            # Assign elem_id for potential JS interaction if needed later
            video_input = gr.Video(label="Upload Video", sources=["upload"], format="mp4", elem_id="video_player")
            info_text = gr.Textbox(label="Video Info / Status", interactive=False, lines=5)
            jpg_download_output = gr.File(label="JPG Download Link", visible=False, interactive=False)
            png_download_output = gr.File(label="PNG Download Link", visible=False, interactive=False)

        with gr.Column(scale=2):
            frame_display = gr.Image(label="Selected Frame", type="numpy", interactive=False)
            # Assign elem_id for potential JS interaction
            frame_slider = gr.Slider(
                minimum=0, maximum=0, value=0, step=1,
                label="Frame Number", interactive=False, elem_id="frame_slider"
            )
            with gr.Row():
                prepare_jpg_button = gr.Button("Prepare JPG Download")
                prepare_png_button = gr.Button("Prepare PNG Download")


    # --- Component Interactions ---

    # 1. Video Upload/Clear
    video_input.upload(
        fn=load_video,
        inputs=video_input,
        # Include fps_state in outputs
        outputs=[video_path_state, fps_state, frame_slider, frame_display, info_text, jpg_download_output, png_download_output]
    )
    video_input.clear(
        fn=load_video,
        inputs=video_input,
         # Include fps_state in outputs
        outputs=[video_path_state, fps_state, frame_slider, frame_display, info_text, jpg_download_output, png_download_output]
    )

    # 2. Slider Release (hides download links)
    frame_slider.release(
        fn=update_frame_on_slider,
        inputs=[video_path_state, frame_slider],
        outputs=[frame_display, info_text, jpg_download_output, png_download_output]
    )

    # 3. Prepare JPG Download Button Click
    prepare_jpg_button.click(
        fn=save_frame_temporarily,
        inputs=[video_path_state, frame_slider, gr.Textbox("jpeg", visible=False)],
        outputs=[jpg_download_output, info_text]
    ).then(
       lambda: {jpg_download_output: gr.File(visible=True), png_download_output: gr.File(visible=False)},
       outputs=[jpg_download_output, png_download_output]
    )

    # 4. Prepare PNG Download Button Click
    prepare_png_button.click(
        fn=save_frame_temporarily,
        inputs=[video_path_state, frame_slider, gr.Textbox("png", visible=False)],
        outputs=[png_download_output, info_text]
    ).then(
        lambda: {png_download_output: gr.File(visible=True), jpg_download_output: gr.File(visible=False)},
        outputs=[png_download_output, jpg_download_output]
    )

    # 5. NEW: Video Pause Event
    # The 'pause_time' argument to sync_slider_on_pause comes from the event data
    video_input.pause(
        fn=sync_slider_on_pause,
        inputs=[video_path_state, fps_state], # Pass needed state
        outputs=[frame_slider] # Update the slider value
    )
    # Optional: Trigger frame update immediately after slider syncs from pause
    # video_input.pause(...).then(
    #    fn=update_frame_on_slider,
    #    inputs=[video_path_state, frame_slider], # Use the NEW slider value
    #    outputs=[frame_display, info_text, jpg_download_output, png_download_output]
    # )


# --- Launch the App ---
if __name__ == "__main__":
    demo.launch(debug=True) # Add debug=True for easier troubleshooting