<?php

function readSensor() {
    $res;
    $output;
    exec("./mkr680-reader", $output, $res);
    $arr = array(
        "temperature" => NULL, 
        "pressure" => NULL,
        "humidity" => NULL,
        "gas resistance" => NULL,
        "iaq (accuracy)" => NULL
    );
    // do a quick sanity check on data usually 224 bytes, 200 is probably good enough
    if(200 > strlen(implode("\n", $output))) { return false; }
    // prepare the output by converting to lowercase and splitting
    foreach($output as $k=>$v) {
        $t = strtok(strtolower($v), ':');
        $output[$k] = array($t, strtok(''));
    }
    // perform the search
    foreach($arr as $k=>$v) {
        foreach($output as $j=>$w) {
            if(0 === strpos($w[0], $k)) {
                $arr[$k] = $w[1];
	        unset($output[$j]);
            }
        }
    }
    // cleanup by removing excess information
    $iaq = trim($arr["iaq (accuracy)"]);
    foreach($arr as $k=>$v) {
        // get first "word", and split on every character
        $v = str_split(strtok(trim($v), ' '), 1);
        $s = "";
        foreach($v as $t) {
            if('.' === $t) { $s .= '.'; continue; }
	    //var_dump($t, 0x32, ord($t), chr($t));
	    if((0x29 < ord($t)) && (0x40 > ord($t))) $s .= $t;
	    else break;
        }
        $arr[$k] = $s;
    }
    // final formatting, unit conversions, precision, etc
    $arr["temperature"]    = $arr["temperature"] . " C";
    $arr["pressure"]       = $arr["pressure"] . " Pa";
    $arr["humidity"]       = $arr["humidity"] . " %";
    $arr["gas resistance"] = $arr["gas resistance"] . " Ohm";
    $arr["iaq (accuracy)"] = $iaq;
    // one last sanity check, everything should be set
    foreach($arr as $v) if(NULL === $v) return false;
    return $arr;
}

$last="";
// monitor the sensor, running mkr680-reader takes about a quarter second, 
while(true) {
    // read data, retry in ten seconds on failure
    if(false === ($now = readSensor())) { sleep(10 /*seconds*/); continue; }
    // only send data if there is a change
    if($last === $now) continue;
    $last = $now;

    // send data to mmcgo
    $now["sensor"] = 'H';
    file_get_contents("http://mmcgo.com/radon/environmental.php", false, stream_context_create(array("http"=>array(
        "method"  => "POST",
        "header"  => "Content-Type: application/x-www-form-urlencoded",
        "content" => http_build_query($now)
    ))));

    //var_dump($last);

    // the sensor takes at least a second before new samples are available
    //usleep(1000 /*uS*/ * 1750 /* and ~250ms for mkr680-reader gives 2 seconds */);
    // thinking about it differently, reading every 15 minutes gives about 100 readings per day
    sleep(15 /*minutes*/ * 60 /*seconds*/);
}