#!/bin/sh

usage() {
  echo "Combine multiple video files that share the same pattern and extension"
  echo "into a single video file."
  echo ""
  echo "Usage: ${0##*/} <base filename>"
  echo ""
  echo "Arguments:"
  echo "  <base filename>: The name of one of the video files to use as a pattern."
  echo "                   For example, if your files are named video_cut1.mp4,"
  echo "                   video_cut2.mp4, you can provide video_cut1.mp4."
  echo ""
  echo "Example:"
  echo "  ${0##*/} video_cut.mp4"
  echo "  This will combine all files matching video_cut*.mp4 into a single file."
  exit 1
}

# Check if the correct number of arguments are provided
if [ $# -ne 1 ]; then
  usage
fi

# Extract the pattern and extension from the input filename
input_file="$1"
pattern="${input_file%.*}"    # This removes the extension
extension="${input_file##*.}" # This extracts the extension

# Find all video files matching the generated pattern and extension
video_files=$(ls "${pattern}"*."${extension}" 2>/dev/null)

# Check if any files are found
if [ -z "$video_files" ]; then
  echo "No video files found with the pattern '${pattern}*.${extension}'."
  exit 1
fi

# Create a temporary file list for ffmpeg
file_list=$(mktemp)

# Populate the file list with the found video files, properly quoting each full path
for video in "${pattern}"*."${extension}"; do
  full_path=$(realpath "$video")
  echo "file '$full_path'" >>"$file_list"
done

# Combine the videos into a single file using ffmpeg
output_file="${pattern}_combine.${extension}"
ffmpeg -f concat -safe 0 -i "$file_list" -c copy "$output_file" 2>/dev/null

# Clean up the temporary file
cat "$file_list"
rm -f "$file_list"

echo "All videos combined into '$output_file'."