playlist

#!/usr/bin/env bash

err() {
	echo "$(color red)$@$(color off)" >&2
}
warn() {
	echo "$(color blue)$@$(color off)" >&2
}
die() {
	err $@
	exit 1
}

usage="playlist <command> [queued actions] < [queued actions]"

while [ $# -gt 0 ]; do
	case "$1" in
		-q|--quiet)
			warn() {
				return
			}
			shift
			;;
		-n|--name)
			shift
			set -u
			cmd_name="$1"
			set +u
			shift
			;;
		-f|--foreground)
			foreground=true
			logfile="/dev/stdout"
			shift
			;;
		-*)
			die "unknown flag: $1"
			;;
		*)
			break
			;;
	esac
done

test -n "$1" || die "$usage"
cmd="$1"; shift
: ${cmd_name:="$(echo $cmd | cut -d ' ' -f 1)"}
plist="$cmd_name.plist"
: ${logfile:=$cmd_name.log}

if test -e "$plist"; then
	if ! test -f $plist
		then die "$plist exists and is not a regular file"
	fi
	warn "using existing playlist: $plist"
fi

# add args to playlist
while [ $# -gt 0 ]; do
	echo "$1" >> $plist
	shift
done

# add stdin to playlist
if read -t 0
	then cat >> $plist
fi

not_locked() {
	exec 4<>"$1.lock"; flock -n 4
}
plist_runner() {
	if not_locked "$plist"; then
		warn "started runner"
		while [ -s "$plist" ] ; do
			echo "$cmd $(head -1 "$plist")"
			$cmd "$(head -1 "$plist")" || echo $(head -1 "$plist") >> "failed-$plist"
			sed -i 1d "$plist"
		done > "$logfile"
		rm "$plist"
		trash-put "$logfile" 2>/dev/null &&
		warn "Playlist completed. use \`trash-restore\` to retrieve log"
	fi
}

if [ -n "$foreground" ]
then plist_runner
else plist_runner&
fi