x2y

#!/usr/bin/env bash

the_name="x2y"

print_usage() {
  echo "Usage: $the_name [(-f | --format) <format>] <file>[:<format>] ..."
  echo
  echo "OPTIONS"
  echo "  -h, --help                        Display this help message"
  echo "  -f <format>, --format <format>    Set default output format"
  echo
  echo "EXAMPLES"
  echo "  $the_name --format mp3 *.opus"
  echo "  $the_name foo:pdf bar:png"
}

convert_with_ffmpeg() {
  ffmpeg -i "$1" "$2"
}

convert_with_imagemagick() {
  convert "$1" "$2"
}

convert_with_pdftoppm() {
  input_file="$1"
  output_file="$2"
  output_format=${output_file##*.}
  output_base="$(basename "$output_file" ."$output_format")"

  case $output_format in
  png)
    command="pdftoppm -png"
    ;;
  jpeg | jpg)
    command="pdftoppm -jpeg"
    ;;
  tiff)
    command="pdftoppm -tiff"
    ;;
  *)
    echo "Error: Output format must be PNG/JPEG/TIFF for PDF conversion"
    exit 1
    ;;
  esac

  "$command" "$input_file" "$output_base"
}

# Transform long options to short ones for `getopts`
for arg in "$@"; do
  shift
  case "$arg" in
  "--help")
    set -- "$@" "-h"
    ;;
  "--format")
    set -- "$@" "-f"
    ;;
  *)
    set -- "$@" "$arg"
    ;;
  esac
done

format=

while getopts ":hf:" opt; do
  case ${opt} in
  h)
    print_usage
    exit 0
    ;;
  f)
    format=$OPTARG
    ;;
  *)
    echo "Invalid option: $opt"
    print_usage
    exit 2
    ;;
  esac
done

# Remove processed options
shift $((OPTIND - 1))

if [ $# -eq 0 ]; then
  print_usage
  exit 1
fi

for arg in "$@"; do
  if [[ -z $format ]]; then
    if [[ $arg == *:* ]]; then
      input_file="${arg%:*}"
      output_format="${arg#*:}"
      output_file="${input_file%.*}.$output_format"
    else
      print_usage
      exit 2
    fi
  else
    input_file="$arg"
    output_file="${input_file%.*}.$format"
  fi

  if [ ! -f "$input_file" ]; then
    echo "Error: Input file '$input_file' does not exist"
    exit 1
  fi

  mime_type="$(file --brief --mime-type "$input_file")"

  case "$mime_type" in
  audio/* | video/*)
    convert_cmd=convert_with_ffmpeg
    ;;
  image/*)
    convert_cmd=convert_with_imagemagick
    ;;
  application/pdf)
    convert_cmd=convert_with_pdftoppm
    ;;
  *)
    echo "Error: Unsupported MIME type '$mime_type'"
    ;;
  esac

  $convert_cmd "$input_file" "$output_file"
done