#!/bin/sh

readonly CONF_LIST="$1"
readonly SERVER_LIST="$2"

help() {
    printf "Usage: $(basename $0) cmd_list server_list\n" >&2
    printf "    cmd_list: A text file containing a list of commands to run.\n" >&2
    printf "    server_list: A text file containing a list of servers to\n" >&2
    printf "    connect to and run commands on.\n\n" >&2
    printf "All commands will be allocated to the first available server.\n" >&2
    printf "Each command must be valid on every server.\n" >&2
    printf "The output will be saved to a text file on the remote systems.\n" >&2
    exit 1
}

run_server() {
    server="$1"
    loop="/tmp/$(basename $PIPE_NAME .fifo)-$server.fifo"
    mkfifo "$loop"
    while read cmd; do
        out_file="$(echo "$cmd" | sed 's/[[:space:].\/]/_/g;s/-//g').out"
        printf "$cmd > $out_file\necho\n"
        printf "$server: $cmd\n" >&2
        read line < "$loop" > /dev/null # Block until command completes
    done | ssh -oBatchMode=yes -oStrictHostKeyChecking=no "$server" "sh" > "$loop"
    rm "$loop"
    echo "Server '$server' finished!" >&2
}

main() {
    PIPE_NAME="$(mktemp /tmp/distributer-XXX.fifo)"
    rm "$PIPE_NAME"
    mkfifo "$PIPE_NAME"
    sed '/^[[:space:]]*$/d' "$CONF_LIST" > "$PIPE_NAME" &
    cat "$SERVER_LIST" | while read server; do
        run_server "$server" < "$PIPE_NAME" > /dev/null &
        echo $!
    done | while read pid; do
        wait $pid
    done
    rm "$PIPE_NAME"
    echo "All jobs finished!"
}

if [ "$#" -eq 2 ]; then
    main
else
    help
fi