#! /bin/bash

if [[ -z $1 ]]
then
    echo "Too few arguments. Pass -h or --help to get summary of options."
    exit 1
elif [[ ($1 = "-h" || $1 = "--help") && -n $2 ]]
then
    echo "Invalid usage. Do not specify anything after '-h' or '--help'!"
    exit 1
elif [[ $1 = "-h" || $1 = "--help" ]]
then
    printf "%s" "This script compounds list of audio files in specified directory, "
    printf "%s\n" "and places that list into /tmp/${USER}_mpv/."
    printf "%s" "This is useful, considering limited mpv capabilities to distinguish "
    printf "%s\n" "regular files from audio files."
    printf "%s\n\n" "Available options:"
    printf "%s\n" "-h (--help) — display this help."
    printf "%s\n" "-p (--path) — specify working directory. By default, current one is used."
    printf "%s" "-n (--name) — specify name for list. By default, script will use listN "
    printf "%s" "template. So that if there are no files in /tmp/${USER}_mpv, script will create "
    printf "%s" "list1, then list2 and so on. If you run this script twice witout specifying -n "
    printf "%s" "for the same directory, you will get two same lists with different names. "
    printf "%s" "However, if you run this script twice with the same -n, lists will be "
    printf "%s\n" " concatenated, which may be undesired behaviour. For this you have "
    printf "%s" "-r (--remove) option. It is used with -n and ensures that list is overwrited."
    printf "%s" "-d (--default) use default values. If you don't want to specify anything "
    printf "%s" "then you should specify this option. This is made to prevent you from running "
    printf "%s\n" "a script which purpose is unknown to you. -d overrides other options!"
    printf "%s" "-t (--tempname) exists just in case some wizard occupied ${USER}_mpv directory "
    printf "%s\n" "in /tmp and you cannot write in there. It specifies directory name within /tmp."
    printf "%s" "-b (--basedir). If for some reason you do not want to use /tmp, you can set "
    printf "%s\n" "basedir — value, that will substitute /tmp. Note that basedir must exist."
    printf "%s\n" "There must be no '/' in list- or tempname, otherwise you are on your own."
    exit 0
fi

while (( "$#" ))
do
    case $1 in
        -p|--path)
            WORKDIR="$2"
            shift 2
            ;;
        -n|--name)
            LISTNAME="$2"
            shift 2
            ;;
        -d|--default)
            DEFAULT=1
            break
            ;;
        -t|--tempname)
            TEMPNAME="$2"
            shift 2
            ;;
        -b|--basedir)
            BASEDIR="$2"
            shift 2
            ;;
        -r|--remove)
            REMOVE=1
            shift
            ;;
        *)
            echo "Unrecognized option '$1'. Run '-h' or '--help'"
            exit 1
            ;;
    esac
done

DEFAULT_WORKDIR="$(pwd)"
DEFAULT_TEMPNAME="${USER}_mpv"
DEFAULT_BASEDIR=/tmp

if (( $DEFAULT ))
then
    WORKDIR="$DEFAULT_WORKDIR"
    TEMPNAME="$DEFAULT_TEMPNAME"
    BASEDIR="$DEFAULT_BASEDIR"
else
    WORKDIR="${WORKDIR:-$DEFAULT_WORKDIR}"
    [[ -d $WORKDIR ]] || (
    echo "Working directory you specified is not directory! Run '-h' or '--help'"
    exit 1
    )
    TEMPNAME="${TEMPNAME:-$DEFAULT_TEMPNAME}"
    BASEDIR="${BASEDIR:-$DEFAULT_BASEDIR}"
    [[ -d $BASEDIR ]] || (
    echo "Base directory you specified is not directory! Run '-h' or '--help'"
    exit 1
    )

    # In case BASEDIR or WORKDIR have "/" at the end, we need to remove it
    [[ ${WORKDIR: -1} = "/" ]] && WORKDIR="${WORKDIR:0: -1}"
    [[ ${BASEDIR: -1} = "/" ]] && BASEDIR="${BASEDIR:0: -1}"
fi

# Set list name
mkdir -p "$BASEDIR/$TEMPNAME"
if [[ -z $LISTNAME ]]
then
    LISTLASTNUMBER="$(ls -1 "$BASEDIR/$TEMPNAME" | egrep "^list[0-9]+$" | sort -V | tail -n1 | sed 's/list//')"
    if [[ -z $LISTLASTNUMBER ]]
    then
        LISTNAME="list1"
    else
        LISTNAME="list$(( ++LISTLASTNUMBER ))"
    fi
fi

(( REMOVE )) && {
    [[ $LISTNAME =~ ^list[0-9]+$ ]] && {
        echo "You can use -r only when list name does not match listN pattern! Exiting."
        exit 1
        }
    rm "$BASEDIR/$TEMPNAME/$LISTNAME"
    }
while read FILE
do
    # This dance with readlink is needed because when you specify relative paths with -p
    # everything messes quite a bit.
    FILE="$( readlink -f "$WORKDIR/$FILE" )"
    if [[ $(file --mime-type -b "$FILE" | sed -E 's/^(audio)(\/.+)/\1/') = "audio" ]]
    then
        echo "$FILE" >> "$BASEDIR/$TEMPNAME/$LISTNAME"
    fi
done <<< "$(ls -1 "$WORKDIR")"