#!/bin/sh
# mp3me
# author: voidraven
# https://sr.ht/~voidraven/mp3me/
# license: BSD 3-clause
#
# A portable shell script for converting audio files to mp3.
# It works on directories of music in parallel.
#
# Dependencies: ffmpeg, gnu parallel
#
VERSION="0.3.1"

# default bitrate and jobs
BITRATE=320000
# Portable way to get the number of cores available to the system (Linux, BSD, and MacOS)
CORES_AVAIL=$(getconf _NPROCESSORS_ONLN 2>/dev/null || sysctl -n hw.ncpu || echo 2)
# Default number of threads to use (half available cores)
JOBS=$(( CORES_AVAIL / 2 ))

SHIFT=0


# check if the file provided is a has a valid music extension
# cuts off extension and compares it
fun_is_music () {
    L_FILE="$1"
    # ignore directories
    if [ -f "$L_FILE" ] ; then
	# get extension
	L_FILE_EXT="${L_FILE##*.}"
	# get lowercase version
	L_FILE_EXT=$(echo "$L_FILE_EXT" | tr '[:upper:]' '[:lower:]')
	if [ "$L_FILE_EXT" = "flac" ] || [ "$L_FILE_EXT" = "aac" ] || [ "$L_FILE_EXT" = "ogg" ] || [ "$L_FILE_EXT" = "wav" ] || [ "$L_FILE_EXT" = "m4a" ] ; then
	    unset L_FILE L_FILE_EXT
	    return 0    
	fi
	unset L_FILE_EXT
    fi
    unset L_FILE 
    return 1
}


# echoes out all the valid music files in a directory
fun_echo_files () {
    L_LWD=$(pwd)
    cd "$1" || fun_error "failed to enter directory: $1"
    for FILE in * ; do
	if fun_is_music "$FILE" ; then
	    echo "$FILE"
	fi
    done
    cd "$L_LWD" || fun_error "failed to enter directory: $1"
    unset L_LWD
}


# take user input as kbps and return bps
fun_get_bitrate () {
    L_BR="$1"
    if [ "$L_BR" -gt 0 ] && [ "$L_BR" -lt 321 ] ; then
	BITRATE=$((L_BR*1000))
	SHIFT=$((SHIFT+2))
    else
	unset L_BR
	fun_error "bad bitrate value passed in"
    fi
    unset L_BR
}


fun_check_jobs () {
    if [ "$1" -gt 0 ] && [ "$1" -lt 256 ] ; then
	JOBS="$1"
	SHIFT=$((SHIFT+2))
    else
	fun_error "bad number of jobs passed in (0 < j < 256)"
    fi
}


# call this function to start the script
fun_run () {
    echo "mp3me - beginning conversion $1 with $JOBS jobs."
    # SC2086 - yes, we want to split on spaces since we are building a command line
    # SC1083 - yes, the '{}' char are literal parallel uses them
    # shellcheck disable=SC2086,SC1083
    fun_echo_files "$1" | parallel -j $JOBS ffmpeg -hide_banner -nostats -loglevel fatal -i "'$1'"/{} -b:a $BITRATE "'$1'"/{.}.mp3
}


# run when ctrl-c is pressed
fun_cleanup () {
    echo "caught sigint, exiting.."
    exit 0
}


# print help/version info
fun_print_info () {
    echo "mp3me - parallel mp3 converter script"
    fun_print_ver
    echo "license: bsd 3-clause"
    echo "author: voidraven"
    fun_print_usage
    exit 0
}


# print usage info
fun_print_usage () {
    echo "-- usage: --------------------"
    echo "       mp3me ./musicdir          # just use defaults"
    echo "       mp3me -j 8 ./musicdir     # jobs (i.e. threads to start)"
    echo "       mp3me -b 192 ./musicdir   # bitrate - default is 320"
    echo "       mp3me -h                  # shows this help message"
    echo "       mp3me -v                  # show the version info"
}


# print version info
fun_print_ver () {
    echo "mp3me version: $VERSION"
}


# print error message
fun_error () {
    echo "mp3me - error detected"
    echo "$1"
    fun_print_usage
    exit 1
}


while getopts 'b:j:hvi:' OPT ; do
	case "$OPT" in
	b)	fun_get_bitrate "$OPTARG";;
	j)	fun_check_jobs "$OPTARG";;
	h)      fun_print_info;;
	v)      fun_print_ver && exit 0;;
	[?])	fun_error "invalid argument passed in by user";;
	esac
done

shift $SHIFT

DIR=$*
if [ -d "$DIR" ] ; then
    fun_run "$DIR"
else
   fun_error "directory not found: $DIR"
fi

exit 0