# This program depends on the https://chiselapp.com/user/schelte/repository/mqtt/home MQT library being installed at the /home/folk/mqtt directory
Start process mqtt {
    Wish $::thisProcess receives statements like \
        [list /someone/ wishes MQTT publish /...anything/]
    Wish $::thisProcess receives statements like \
        [list $::thisNode has step count /...anything/]
    Wish $::thisProcess shares statements like \
        [list MQTT claims message /message/ topic /topic/ timestamp /timestamp/]

    ::tcl::tm::path add /home/folk/mqtt
    package require mqtt

    set client [mqtt new]
    set ::mqttclient $client

    proc cb {topic content status} {
        set message [encoding convertfrom utf-8 $content]
        puts "MQTT CALLBACK: $topic: $message"
        set now [clock milliseconds]
        Assert MQTT claims message $message topic $topic timestamp $now

        # Retract all events that are more than 5 seconds old.
        set events [Statements::findMatches [list MQTT claims message /message/ topic /topic/ timestamp /timestamp/]]
        foreach event $events {
            dict with event {
                if {$now - $timestamp > 5000} {
                    Retract MQTT claims message $message topic $topic timestamp $timestamp
                }
            }
        }
    }
    $client connect test-client localhost 1883
    $client subscribe "#" cb

    When /someone/ wishes MQTT publish /m/ on topic /t/ at timestamp /ts/ {
        # puts "publishing $m on $t at $ts"
        $::mqttclient publish "$t" "$m"
    }

    while true {
        # Step for folk, update for TCL and MQTT
        Step
        update
    }
}