#!/bin/bash
# parallel.sh - bash script for filtering/parallelising using sed.
# (C) 2023 Felix Hauri - felix@f-hauri.ch
# Licensed under terms of GPL v3. www.gnu.org

prog=${0##*/}
usage() {
    cat <<-EOUsage
	Usage: $prog -t <tags> [-b <re>] [-a <re>] command args
	  -h   	      show this
	  -t <tags>   coma separated liste of tags to send to separated tasks
	     	      or single tag, '-t' option could be submited multiple times
	  -b <re>     sed regex to match before tags
	  -a <re>     sed regex to match after tags
	  command     Any command to be run once for each tag.
	  	      Special string "<RE>" will be replaced by current tag.
	EOUsage
}
die() {
    echo >&2 "ERROR $prog: $*"
    exit 1
}
while getopts "ht:a:b:" opt; do
    case $opt in
	h ) usage; exit ;;
	t ) IFS=, read -a crttags <<<"$OPTARG"
	    tags+=("$crttags");;
	b ) before=$OPTARG ;;
	a ) after=$OPTARG ;;
	*) die Wrong argument. ;;
    esac
done
shift $((OPTIND-1))

[[ -v tags ]] || die "No tags submited"
(( $# )) || die "No command submited"

sedcmd='' paren=''
declare -i crtFd=4
for re in "${tags[@]}";do
    printf -v crtcmd '%q ' "${@//\<RE\>/$re}"
    printf -v crtcmd ' -e \47%s/%s/{s/%s//;w/dev/fd/%d\47 %d> >(exec %s) ' \
	   "$paren" "$before$re$after"{,} $crtFd $crtFd "$crtcmd"
    paren='};'
    sedcmd+="$crtcmd" crtFd+=1
done
sedcmd+=" -e '$paren'"

eval sed -n "$sedcmd"