#!/bin/env bash
# Craig Jennings <c@cjennings.net>
# convenience utility to convert all media files not in opus format in current directory to opus.
# flags for recursive or specific filename supported.

# Default values of arguments
delete_after_conversion=false
filename=""
recursive=false

# Usage info
show_help() {
    cat << EOF
Usage: ${0##*/} [-h] [-d] [-r] [-f FILE]
Convert audio/video files to the Opus format.

    -h          display this help and exit
    -d          delete source files after conversion
    -r          convert files recursively in current and subdirectories
    -f FILE     convert a specific file.

Note: The '-f' and '-r' options are mutually exclusive.
      If no file is given, works on all non-opus media files in the current directory.
      Requires the ffmpeg installation.
EOF
}

# Check for the existence of ffmpeg
if ! command -v ffmpeg &> /dev/null; then
    echo "Cannot proceed: ffmpeg not found on path."
    exit 1
fi

# Identify arguments; quit if invalid argument
while getopts ":df:rh" opt; do
    case ${opt} in
        d)
            delete_after_conversion=true
            ;;
        f)
            filename=$OPTARG
            ;;
        r)
            recursive=true
            ;;
        h)
            show_help
            exit 0
            ;;
        \?)
            echo "Invalid option: -$OPTARG" >&2
            show_help
            exit 1
            ;;
    esac
done

# Display error and quit if incompatible arguments
if [ "$recursive" = true ] && [ -n "$filename" ]
then
    echo "The -f and -r options cannot be used together."
    show_help
    exit 1
fi

# Convert function checks mime-type and converts/deletes a single file
convert() {
    f=$1
    # Check the mime-type of the file
    mime_type=$(file -b --mime-type "$f")
    # If the file is an audio or video file and not already in opus format then convert it to opus
    if [[ $mime_type == video/* || $mime_type == audio/* ]] && [[ $f != *.opus ]]; then
        ffmpeg -i "$f" "${f%.*}.opus"
        # If the '-d' option was specified, delete the original file after conversion
        if $delete_after_conversion; then
            rm "$f"
        fi
    fi
}

# Use above convert function based on user's intended set of files
if [ "$recursive" = true ]
then
    # convert all media files in current and child directories
    find . -type f -exec bash -c 'convert "$0"' {} \;
elif [[ -n $filename ]]
then
    # if filename is not empty, convert only this file
    convert $filename
else
    # Convert all
    echo "All non-opus media files in the current directory will be converted. Originals are kept."
    read -p "Proceed? (Y/n) " -n 1 -r
    echo
    if [[ $REPLY =~ ^[Yy]$ ]]
    then
        # Iterate over each file in the directory and convert
        for f in *; do
            convert $f
        done
    fi
fi