#!/usr/bin/env bash
# set -euxo pipefail # uncomment this for debugging

###################################
# INSTRUCTIONS
# 1. Set Artist, Album, Timestamps and Track Names below
# 2. Save split.sh into the folder with file to be split
# 3. ./split.sh <m4a file to be split>
###################################

artist="The Artist"
album="My Album"

# Timestamps are in seconds
# start_time;end_time;song_title
timestamps=$(cat << EOF
    0;300;First Song
    302;600;Second Song
    602;900;Third Song
    902;1200;Fourth Song
EOF
)

###################################
# DO NOT EDIT BELOW HERE
###################################
mkdir -p "${artist}/${album}"
track=1
while read -r name
do
    IFS=";" read -ra fields <<<"${name}"
    startpos=${fields[0]}
    endpos=${fields[1]}
    title=${fields[2]}
    length=$(( endpos-startpos ))
    tr=$(printf "%02d" ${track})
    ffmpeg -nostdin \
        -ss "${startpos}" \
        -i "${1}" -vn -c copy \
        -t "${length}" \
        -metadata title="${title}" \
        -metadata artist="${artist}" \
        -metadata track="${track}" \
        -metadata album="${album}" \
        -metadata album_artist="${artist}" \
        "${artist}/${album}/${tr} ${title}.m4a"
    (( "track++" ))
done <<< "${timestamps}"