import os
import cv2
from tqdm import tqdm

# ================= User Configuration =================
INPUT_FOLDER = "bus"          # Name of the input video folder
PREFIX = "08"                 # Output prefix (must match category index)

# Category index reference:
# 01  street_ca
# 02  street_au
# 03  street_cn
# 04  street_eu
# 05  street_kr
# 06  street_us
# 07  highway
# 08  bus

ROOT_DIR = r"your_root_path"        # Root directory of raw videos
CLIPS_DIR = r"your_clips_path" # Output directory for extracted frames

SAMPLING_FPS = 2        # Frames sampled per second
TRIM_HEAD_SEC = 180     # Trim first N seconds
TRIM_TAIL_SEC = 180     # Trim last N seconds
# ======================================================


def sanitize_filename(name: str) -> str:
    """Remove illegal characters from file names."""
    return "".join(c for c in name if c.isalnum() or c in (" ", "-", "_")).strip()


def process_videos(input_dir, clips_dir, prefix, folder_name):
    output_main_dir = os.path.join(clips_dir, f"{prefix}_{folder_name}")
    os.makedirs(output_main_dir, exist_ok=True)

    video_files = sorted([
        f for f in os.listdir(input_dir)
        if f.lower().endswith(('.mp4', '.mkv', '.avi', '.mov'))
    ])

    print(f"\nFound {len(video_files)} video files")

    video_index = 0

    # Optional: specify a video file name to start processing from
    start_from = None  

    for filename in video_files:
        if start_from is not None:
            if filename != start_from:
                print(f"Skip: {filename}")
                video_index += 1
                continue
            else:
                print(f"Start from specified video: {filename}")
                start_from = None

        file_path = os.path.join(input_dir, filename)
        print(f"\nProcessing video: {file_path}")

        cap = cv2.VideoCapture(file_path)
        if not cap.isOpened():
            print("Failed to open video file")
            continue

        fps = cap.get(cv2.CAP_PROP_FPS)
        total_frames = int(cap.get(cv2.CAP_PROP_FRAME_COUNT))
        duration = total_frames / fps

        print(f"Duration: {duration:.2f} seconds")

        if duration < TRIM_HEAD_SEC + TRIM_TAIL_SEC:
            print("Skip: video too short after trimming")
            cap.release()
            continue

        start_frame = int(TRIM_HEAD_SEC * fps)
        end_frame = int(total_frames - TRIM_TAIL_SEC * fps)
        extract_interval = max(1, int(fps / SAMPLING_FPS))

        video_name = os.path.splitext(filename)[0]
        safe_video_name = sanitize_filename(video_name)
        output_subdir = os.path.join(output_main_dir, f"{prefix}_{video_index:05d}")
        os.makedirs(output_subdir, exist_ok=True)

        cap.set(cv2.CAP_PROP_POS_FRAMES, start_frame)
        frame_count = 0
        saved_count = 0

        for _ in tqdm(
            range(end_frame - start_frame),
            desc=f"Extracting {safe_video_name}",
            ncols=100
        ):
            ret, frame = cap.read()
            if not ret:
                break

            if frame_count % extract_interval == 0:
                output_file = os.path.join(
                    output_subdir,
                    f"{prefix}_{video_index:05d}_{saved_count:06d}.jpg"
                )
                cv2.imwrite(
                    output_file,
                    frame,
                    [int(cv2.IMWRITE_JPEG_QUALITY), 90]
                )
                saved_count += 1

            frame_count += 1

        cap.release()
        print(f"Saved {saved_count} frames to {output_subdir}")
        video_index += 1


def main():
    input_dir = os.path.join(ROOT_DIR, INPUT_FOLDER)

    if not os.path.isdir(input_dir):
        print(f"Invalid input directory: {input_dir}")
        return

    print(f"Start processing folder: {input_dir}")
    process_videos(input_dir, CLIPS_DIR, PREFIX, INPUT_FOLDER)
    print("\nAll videos processed.")


if __name__ == "__main__":
    main()