#!/bin/sh

set -e

if [ -z "$TOR_HOST" ]; then
    echo 'missing $TOR_HOST'
    exit 1
elif [ -z "$ONION_SERVICE_HOST" ]; then
    echo 'missing $ONION_SERVICE_HOST'
    exit 1
elif [ -z "$ONION_SERVICE_PORT" ]; then
    echo 'missing $ONION_SERVICE_PORT'
    exit 1
elif [ -z "$RECIPIENT_ADDRESS" ]; then
    echo 'missing $RECIPIENT_ADDRESS'
    exit 1
fi

sender_address="onion-service-status@$(hostname).local"

ping_onion_service() {(
    if [ ! -z "$VERBOSE" ]; then
        set -x
    fi
    nc -z -w "$TIMEOUT_SECONDS" -x "$TOR_HOST:$TOR_PORT" "$ONION_SERVICE_HOST" "$ONION_SERVICE_PORT"
)}

send_report() {(
    if [ ! -z "$VERBOSE" ]; then
        set -x
    fi
    echo -e "From: ${sender_address}\nSubject: $ONION_SERVICE_HOST:$ONION_SERVICE_PORT $1\n" \
        | sendmail "$RECIPIENT_ADDRESS"
)}

last_state=""
while : ; do
    if ! nc -z -w "$TIMEOUT_SECONDS" "$TOR_HOST" "$TOR_PORT"; then
        echo "failed to connect to tor proxy at $TOR_HOST:$TOR_PORT"
    else
        if ping_onion_service; then
            if [ "$last_state" == "offline" ]; then
                echo went online
                send_report online
            fi
            last_state="online"
        else
            if [ "$last_state" == "online" ]; then
                echo went offline
                send_report offline
            fi
            last_state="offline"
        fi
    fi
    # flush queue
    dma -q1
    sleep "$SLEEP_DURATION"
done