#!/bin/bash

# Function to print usage instructions
usage() {
  echo "Usage: $0 input_file HH:MM:SS_1 HH:MM:SS_2 ... HH:MM:SS_N"
  exit 1
}

# Check if there are at least two arguments (input file and one time code)
if [ "$#" -lt 2 ]; then
  usage
fi

# Get the input file and validate its existence
input_file="$1"
if [ ! -f "$input_file" ]; then
  echo "Error: File '$input_file' does not exist."
  exit 1
fi

# Extract file extension and base name
extension="${input_file##*.}"
base_name="${input_file%.*}"

# Get the duration of the input file using ffprobe
duration=$(ffprobe -v error -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 "$input_file")
if [ -z "$duration" ]; then
  echo "Error: Unable to determine the duration of the file."
  exit 1
fi
duration=${duration%.*} # Convert to integer seconds

# Get the list of time codes
time_codes=("${@:2}")
# Add the end of the video to the list of time codes
time_codes+=("$(printf '%02d:%02d:%02d\n' $((duration/3600)) $((duration%3600/60)) $((duration%60)))")

# Function to convert HH:MM:SS to seconds
time_to_seconds() {
  local time="$1"
  IFS=: read -r hh mm ss <<< "$time"
  echo $((10#$hh * 3600 + 10#$mm * 60 + 10#$ss))
}

# Validate each time code
for time in "${time_codes[@]}"; do
  total_seconds=$(time_to_seconds "$time")
  if [ "$total_seconds" -gt "$duration" ]; then
    echo "Error: Time code $time exceeds video duration."
    exit 1
  fi
done

# Process each segment
previous_time="00:00:00"
for i in "${!time_codes[@]}"; do
  current_time="${time_codes[i]}"
  if [ "$i" -eq $((${#time_codes[@]} - 1)) ]; then
    # If this is the last time code, process until the end of the video
    current_time=$(printf '%02d:%02d:%02d\n' $((duration/3600)) $((duration%3600/60)) $((duration%60)))
  fi

  current_seconds=$(time_to_seconds "$current_time")
  previous_seconds=$(time_to_seconds "$previous_time")
  segment_duration=$((current_seconds - previous_seconds))

  if [ "$segment_duration" -le 0 ]; then
    echo "Error: Invalid time range $previous_time to $current_time."
    exit 1
  fi

  # Generate output file name
  output_file="${base_name}_${previous_time}-${current_time}.${extension}"

  echo "Creating segment: $output_file"
  
  if [ "$previous_time" == "00:00:00" ]; then
    # For the first segment, ensure that it starts from the very first frame (avoiding keyframe issues)
    ffmpeg -y -i "$input_file" -ss "$previous_time" -to "$current_time" -c:v copy -c:a copy -c:s copy -map 0 -copyts -vsync 1 "$output_file"
  else
    # For subsequent segments, simply seek and copy streams
    ffmpeg -y -i "$input_file" -ss "$previous_time" -to "$current_time" -c:v copy -c:a copy -c:s copy -map 0 -copyts "$output_file"
  fi

  previous_time="$current_time"
done

echo "Splitting completed successfully."