<?php
// stuff relating to HighCharts

function hcSeriesOpts($opts) {
    $arr = /* yes, include junk? */ true ?$opts :array();
    // defaults...
    $type = "line";
    $lineWidth = "1";
    $color =  ""; // empty allows highchats to pick defaults
    $yAxis = "1";
    $zIndex = "0";
    $showInLegend = "true";
    $enableMouseTracking = "false";
    $dashStyle = ""; /* longdash dot ... */
    // list of relevant highchart::series properties
    $hcp = "type lineWidth color yAxis zIndex showInLegend enableMouseTracking";
    // either use default values or make use of user provided options
    foreach(explode(' ', $hcp) as $v) {
        $arr[$v] = isset($opts[$v]) ?$opts[$v] :$$v;
    }
    return $arr;
}

/*  converts PHP native array into HighCharts compatible series, by default
 *  returns as the printed Series subset or property of the HighCharts Series
 *  Option Structure.  It looks like a plain text, JavaScript Language syntax
 *  formatted string that is used when creating the `option` variable that is
 *  passed to the `HighCharts.chart('container', options);` in
 *  `/var/www/radon/graph.php`.
 *
 *  This matches the original `graph.php` code, but the number of lines of code
 *  that separate the `id` of each created `HighCharts::Series` is more than ten
 *  and sometimes spans abstractions.  Normally one would use 
 *  `HighCharts::Chart::get(id)` to manipulate the Series at runtime.
 *
 *  An alternative approach would be to store `HighCharts::Series` objects and
 *  manipulate them directly, this might allow for less mistakes.  To test this
 *  set `HcOptsStruct` to `false` and make use of some inline JavaScript
 *
 */
function makeSeries($name, $dataset, $opts = array(), $HcOptsStruct = true) {
    $tstart = microtime(true);
    // fill in any missing highcharts series options
    $opts = hcSeriesOpts($opts);
$t1 = microtime(true);
$temp = "";
    // convert [[time=>{..}, reading=>{..}], ...] to JavaScript compatible string
    foreach($dataset as $koi=>$vul) {
        $temp .= "[{$vul['time']}000,".($vul['reading'])."],";
    }
$t2 = microtime(true);
    // process highcharts series options
    $available = explode(' ', "type color yAxis zIndex");
    $seriesOpts = implode("\n", array(
        "{type:'{$opts["type"]}',",
        "lineWidth:{$opts["lineWidth"]},",
        "color:'{$opts["color"]}',",
        "id:'{$name}',",
        "name:'{$name}',",
        "data: [{$temp}],",
        "enableMouseTracking: {$opts["enableMouseTracking"]},",
        "showInLegend: {$opts["showInLegend"]},",
        "yAxis:{$opts["yAxis"]},",
        "zIndex:{$opts["zIndex"]},",
        "},"
    ));

    // print the HighChart compatible series dataset
    if(true === $HcOptsStruct) { echo $seriesOpts; }
$tend = microtime(true);
$i1 = round(1000*($t1-$tstart));
$i2 = round(1000*($t2-$t1));
$i3 = round(1000*($tend-$t2));
$tot = round(1000*($tend-$tstart));
error_log("makeseries - i1:".$i1.", i2:".$i2.", i3:".$i3." (t:".$tot."ms)");
    // allow usage for inline JavaScript
    return $seriesOpts;
}

require_once("environmental.php");
require_once("rdp.php");

class Sensor {
    /*  should be A,B,C,D, ..., Z
     *  there is some code, that caches readings for the web front-end and uses
     *  a SQLite3 database, `radonCache.db` where a column puts some restrictions
     *  on what the sensor name should be.  Initially the sensor names were just
     *  single characters, but this class allowed more than that.  But now, with
     *  `radonCache.db` name should be able to be converted into an id with a
     *  value of [0..16777215].  Using [A..Z] is fine, it kind of limits us to
     *  24 different sensor clusters, but should be easy enough to add more with
     *  a look-up-table or something
     */
    public $name;
    /*  this is a serial number that identifies the device, some devices have
     *  an electronically identifiable serial, eg: Bluetooth media access control
     */
    public $serial;
    public $sensors;
    public $options;
    public function __construct($name = '', $serial = '', $sensors = 0, $options = NULL) {
        $this->name = $name;
        $this->serial = $serial;
        $this->sensors = $sensors;

        // sensor option, `squishFactor`, is most commonly used option
        if(is_numeric($options)) $this->options = new SensorOptions((float) $options);
        else if("SensorOptions" === get_class($options)) $this->options = clone $options;
        else $this->options = NULL === $options ?new SensorOptions() :$options;
    }
    public function getRadon($qo) {
        if(NULL !== /* query options */ $qo) {
            $rows = CACHE_DB::getCachedData($this->name, "radon", 
                $qo->zoom, $qo->fir, $qo->start, $qo->end
            );
            //return $rows;
            /*  add the most recent non-cached radon reading [mySQL]
             *
             *  [!] getting this reading is unbelievably slow, retrieving
             *      ten thousand rows from the cache database takes the same
             *      time to retrieve a single row from the mySQL radonLog, but
             *      we pay the price since the cache database is infrequently
             *      updated, it is a pity, and a bit disappointing
             */
            $lastReading = $this->radonLogQuery(/* get last reading */ true);
            if($lastReading) {
                if(defined("ARRAY_OF_TIME_READING_PAIRS")) {
                    $rows[] = array_pop($lastReading);
                } else {
                    $rows[0][] = $lastReading[0]["time"];
                    $rows[1][] = $lastReading[0]["reading"];
                }
            }
            return $rows;
        } // else
        return $this->radonLogQuery();
    }
    private function radonLogQuery($lastReading = false) {
		// connect to mysql database radondb
		$db = mysql_connect("localhost", "root", "secom8703");
		mysql_select_db("radondb", $db);
		$sql = "SELECT time, reading FROM radonLog WHERE id='{$this->name}' ORDER BY time ASC";
        if($lastReading) {
            $sql = "SELECT time, reading FROM radonLog WHERE id='{$this->name}' ORDER BY time DESC LIMIT 1";
        }
		if(false === ($result = mysql_query($sql, $db))) { return false; }
		$rows = array();
		while($row = mysql_fetch_array($result, MYSQL_ASSOC)) { $rows[] = $row; }
		mysql_free_result($result);
		// mysql needs clean-up
		mysql_close($db);
		return $rows;
    }
    public function getHumidity($qo){return get_BME860_humidityData($this->name,$qo);}
    public function getFahrenheit($qo){return get_BME860_fahrenheitData($this->name,$qo);}
    public function getIaq($qo){return get_BME860_iaqData($this->name,$qo);}
    public function getUkrumayl($qo){return get_BME860_ukrumaylData($this->name,$qo);}
    public function getWesDust($qo){return get_BME860_wesDust($this->name,$qo);}
    /*  requests for the monkey data, that is when a monkey records the temperature
     *
     *  these sensors are all manually recorded, I do not see a reason at this
     *  point to add query option related features to these datasets
     *      - the data for these sensors are not stored in the cache database
     *      - we are not reliable enough to input data at regular intervals
     *      - because we record because we are reacting to weather, trend lines
     *        will be extraordinarily misleading
     *      - start end ranges are pointless because, again manual saves means
     *        insignificant amount of recordings
     */
    public function getAuxiliary($qo, $kind) {
        switch($kind) {
            case "snow": return getSnowData();
            case "rain": return getRainData();
            case "temperature": return getTemperatureData();
            case "humidity": return getHumidityData();
            default: return array();
        }
    }
}

/*  all queries should use query options
 *
 *  - what date range are you looking for?
 *      I want every single temperature sample from millions of recorded samples
 *      starting from the beginning of time so that I can look at the last one
 *      to see what the temperature is right now - probably a bad idea?
 *  - how zoomed in is the user? 
 *      Is anyone interested in counting ant antenna viewing a wall sized image
 *      of the entire earth?  Most users ask for this, but we know that it
 *      would be ridiculous to service this request; for viewing small details
 *      you also want a proportionally small viewing window
 *  - what is the interest of the user?
 *      Maybe they want general trend lines
 *      Maybe they just need to know the exact temperature an hour ago
 *      Maybe they want atmospheric noise / currents for random number generation
 *
 *  This is just here to standardize requests, we can add validation, and
 *  whatever later
 */
class QueryOptions {
    public $start;
    public $end;
    public $zoom;
    public $fir;
    // [!] defaults means that we do not want to use the cache
    public function __construct($start=false, $end=false, $zoom=NO_USE_RADON_CACHE, $fir=false) {
        $this->start = $start;
        $this->end = $end;
        $this->zoom = $zoom;
        $this->fir = $fir;
    }
    /*  [?] setting zoom to false will cause `environmental.php`
     *      `getColumnHelper` to retrieve data from the MySQL database.
     *
     *  okay? okay.
     */
    public function useCache() { return NO_USE_RADON_CACHE !== $this->zoom; }
}

/*  sensor type masks (_FANTASTIC_SENSOR_TYPE)
 *  when adding a sensor type:
 *  add a mask here
 *  the interface to store and access the data is probably done in
 *  `environmental.php`
 *  look at the Dataset::typeIdLUT because you'll probably want to add something
 *  there for improving performance of looking at samples.
 *  SensorOptions::squishFactor should probably be extended to add a default
 *  value for how much samples deviate from each other (sample noise).
 */
define("RADON",         1);
define("CELSIUS",       2);
define("FAHRENHEIT",    4);
define("UKRUMAYL",      8);
define("IAQ",           16);
define("WESDUST",       32);
define("HUMIDITY",      64);

/*  see sensor type masks (_FANTASTIC_SENSOR_TYPE)
 *  the interface in `db-frontend.php` does not understand sensor type
 *  masks and this Class compresses them anyways (Dataset::getBit), so
 *  we are just going to map the two things together here.
 *
 *  when I was researching I found `environmental.php` that uses these
 *  constants but the interface is pretty thin (just a set of identical
 *  routines)
 *
 *  the key is the bit mask offset, the value is the `radonLog` MYSQL
 *  database column header
 *
 *  [!] in PHP 5 define only allows scalar (int, float, string, bool, or null)
 *      had to make a class just to do the same thing...
 *      //define("TYPE_ID_TO_COL_HEADER_LUT", array(
 */
Class TYPE_ID_TO_COL_HEADER {
    static public function LUT($type) { 
        $lookUpTable = array(
            Dataset::getBit(RADON) => "radon",
            Dataset::getBit(CELSIUS) => "celsius",
            //Dataset::getBit(FAHRENHEIT) => "does not exist in database, see Celsius",
            Dataset::getBit(UKRUMAYL) => "pascal",
            Dataset::getBit(IAQ) => "indoor_air_quality",
            Dataset::getBit(WESDUST) => "gas_resistance",
            Dataset::getBit(HUMIDITY) => "humidity"
        );
        return $lookUpTable[$type];
    }
}
/*  [!] not id 
 *
 *  external users do not use the id, they use masks, id is what is used by
 *  Dataset internally and in the cached database
 *
 */
Class COL_HEADER_TO_TYPE_MASK {
    static public function LUT($col) { 
        $lookUpTable = array(
            "radon" => RADON,
            "celsius" => CELSIUS,
            "pascal" => UKRUMAYL,
            "indoor_air_quality" => IAQ,
            "gas_resistance" => WESDUST,
            "humidity" => HUMIDITY,
        );
        return $lookUpTable[$col];
    }
}

// sensor clusters
define("BOSCH_BME680",  CELSIUS | UKRUMAYL | IAQ | WESDUST | HUMIDITY);
define("RADON_EYE",     RADON);
define("AIR_THINGS",    RADON);

// BME680 sensors H, I, J
Class DEFAULT_BOSCH_BME680 {
    static public function SQUISH_FACTOR() { 
        /*  2022 October - these initial values are a good starting place
         *  and were calculated after a year of recording, getting the standard
         *  deviation, and finally dividing by 100
         *
         *  while these values probably offer very little in terms of reducing
         *  the number of points needed represent a line, they are going to be
         *  close, in a logarithmic sense, to where change occurs more frequently
         */
        return array(
            "celsius"               => 6.0 / 100,
            "humidity"              => 5.9 / 100,
            "pascal"                => 745.0 / 100,
            "gas_resistance"        => 250000.0 / 100,
            "indoor_air_quality"    => 63.0 / 100,
            "iaq_accuracy"          => 0.92 / 100
        );
    }
}

Class Dataset {
    public $parentSensorCluster;
    private $sensorId;
    public $mask;
    private $typeId;
    public $datasetId;
    private $zoom;
    private $fir;
    public $stats;

    public function __construct($sensor) {
        $this->parentSensorCluster = $sensor;
        // make sure name is converted to an integer number if it is a letter
        $this->sensorId = Dataset::toSensorId($sensor->name);
        $this->stats = new DatasetStatistics();
    }
    /*  because our parent is a cluster of sensors, we use late binding to
     *  split the cluster into individual sensors.  This is somewhat
     *  obscure so users might accidentally create a Dataset without proper
     *  initialization (for each sensor in the sensor mask bit field, each
     *  zoom, and each fir, create a Dataset, see:
     *      Dataset::makeAllDatasetsFromInternet(...) for an example
     *
     *  applies to:
     *      Dataset::getTypeName()
     *      Dataset::getZoom()
     *      Dataset::getFIR()
     */
    private function errNotReady($property) {
        throw new Exception(
            "Dataset {$property} is not known until after " . 
            __CLASS__ . 
            "->setDatasetId is called."
        );
    }
    // returns sensor id
    public function getInternalSensorId() { return $this->sensorId; }
    // returns database header type as text, (Celsius, radon, etc)
    public function getTypeName() {
        if(!isset($this->typeId)) $this->errNotReady("type");
        return TYPE_ID_TO_COL_HEADER::LUT($this->typeId);
    }
    public function getZoom() {
        if(!isset($this->zoom)) $this->errNotReady("zoom");
        return $this->zoom;
    }
    public function getFIR() {
        if(!isset($this->fir)) $this->errNotReady("fir");
        return $this->fir;
    }
    static public function toSensorId($name) {
        if(is_int($name)) return $name;
        if(ctype_alpha($name)) return ord($name);
        throw new Exception(
            "radonCache.db wants sensor names to be convertible into integer type"
        );
    }
    public function setDatasetId($sensorMask, $zoom, $fir) {
        $this->zoom = $zoom;
        $this->fir = $fir;
        $this->mask = $sensorMask;
        $this->typeId = Dataset::getBit($sensorMask);
        $this->datasetId = Dataset::generateDatasetId(
            $this->sensorId,
            $this->typeId,
            $zoom,
            $fir
        );
        return $this->datasetId;
    }
    /*  converts sensor type (masks) to a more compressed format, eg: `HUMIDITY` is
     *  6.  Sensor type masks are kinda clunky but make it easy to specify a sensor
     *  type as well as a cluster of sensors as a single named thing, like
     *  `BOSCH_BME680`.  The only problem is that we may want to add more sensor
     *  types later and the `sensorLog` in `radonCache.db` has limited space to
     *  store unique sensor identifying information.  There are 8 bits to store 255
     *  unique sensor types and 24 bits to store 16,777,215 unique sensor clusters
     *
     *  using sensor type masks directly would only allow 8 unique sensor types
     *
     *  see: _FANTASTIC_SENSOR_TYPE
     */
    static public function getBit($sensorTypeMask, $o = 0) {
        while(++$o) if(!intval($sensorTypeMask /= 2)) return $o - 1;
    }
    /*  each cluster may have multiple sensors, but are stored in a bit-field
     *  we need a way to split the bit field into separate sensors without knowing
     *  what the sensors are, this is fine, we do not care if it is a RADON or
     *  HUMIDITY sensor, each have their own bit indice, we just need to know if
     *  one or both, or some other sensor
     */
    static public function getSensorMasks($sensorBitField) {
        $arr = array();
        $idx = /* sensor type masks start at one */ 1;
        while(true) {
            if(1 /* bit-wise AND */ & $sensorBitField) $arr[] = $idx;
            // shift bits to the right
            $sensorBitField >>= 1;
            // shift indice bit to the left
            $idx <<= 1;
            if(0 === $sensorBitField) break;
        }
        return $arr;
    }
    /*   just in case SQLITE3 INTEGERS or whatever language we are using is
     *   signed, we can only use 31 of 32 bits, here is one possibility:
     *
     *      14 bits = 16,384    sensors
     *       7 bits = 128       types of sensors
     *       5 bits = 32        different zooms
     *       5 bits = 32        different FIR
     */
    static public function generateDatasetId($sensorName, $sensorType, $zoom, $fir) {
        // restrict variables to prevent overlap in bitfield
        if((0 > $sensorName)        || (16383 < $sensorName))
            throw new Exception("sensor name must be less than 16384");
        if((0 > $sensorType)        || (127 < $sensorType))
            throw new Exception("sensor type mask must be less than 128");
        if((0 > $zoom)              || (31 < $zoom))
            throw new Exception("zoom must be less than 32");
        if((0 > $fir)               || (31 < $fir))
            throw new Exception("fir must be less than 32, was [{$fir}]");
        return
            (131072 * $sensorName) |
            (1024   * $sensorType) |
            (32     * $zoom) |
            (1      * $fir);
    }

    /*  flatten out all combinations of sensors, zoom, and fir
     *  also break individual sensors out of their clusters
     *
     *  [?] with three BOSCH_BME680, three AIR_THINGS, and two RADON_EYE
     *      sensors, three zoom and five fir we should have 300 combinations
     *      of different data sets
     *
     *  [?] this is just a helper function to abstract the messy stuff regarding
     *      making all the different datasets for each sensor, uses TheInternet
     *      to initialize all the different identifying properties for each sensor
     *      we get an array of all the different properties of each dataset
     */
    static public function makeAllDatasetsFromInternet($internet) {
        $sensors = $internet->cloneAllSensors();
        $datasets = array();
        foreach($sensors as $cluster) {
            $nameRule = false || is_int($cluster->name) || 
                (ctype_alpha($cluster->name) && 1 === strlen($cluster->name));
            // ignore names that we cannot handle
            if(false === $nameRule) continue;
            /*  separate clusters of sensors, a cluster contains a bit-field that
             *  marks which sensors are onboard, for example a BOSCH_BME860 has
             *  air quality sensor, temperature sensor, etc
             */
            foreach(Dataset::getSensorMasks($cluster->sensors) as $sensorMask) {
                if(false) var_dump(
                    "sensor: {$cluster->name}",
                    Dataset::toSensorId($cluster->name),
                    "mask: {$sensorMask}"
                );
                // and another for each fir
                foreach($internet->availableFIR as $fir) {
                    // a dataset is created for each zoom
                    foreach($internet->availableZoom as $zoom) {
                        $dataset = new Dataset($cluster);
                        $dataset->setDatasetId($sensorMask, $zoom, $fir);
                        if(false) var_dump(
                            "dataset zoom[{$zoom}] fir[{$fir}]: ",
                            $dataset->setDatasetId($zoom, $fir)
                        );
                        // store each dataset in a flattened array
                        $datasets[] = $dataset;
                    }
                }
            }
        }
        /*  with the messy stuff handled, we can work on all datasets without worrying
         *  about the specifics of each one
         */
        if(false) var_dump(count($datasets));
        return $datasets;
    }
    // helper routine to get filtered and simplified data for a given dataset
    static public function retrieveReducedData($dataset, $start = false, $end = false, &$cache = NULL) {
        // get all input data (or partial if a start and end range are given)
        if((NULL === $cache) or (NULL === $cache->rows)) {
            // we need an interface to get data from the database
            $data = new DataSqueeze();
            $cache = new CachedDatasetData($data->getRows(
                $dataset->parentSensorCluster,
                $dataset->getTypeName(),
                $start,
                $end
            ));
            $cache->sql = $data->sql;
        } // otherwise use cached rows
        if(defined("PRINT_DATA_SOURCE_SQL")) var_dump("sql: {$cache->sql}");
        // run the FIR filter on our data, try to use cached work
        if(NULL === $cache->filtered) {
            // figure out the default FIR delay
            $delay = $dataset->parentSensorCluster->options->getSampleDepth();
            // update the default FIR with this dataset's multiplier
            $delay *= FIR_DELAY_MULTIPLIER::LUT($dataset->fir);
            // get the sample period for this sensor (to regenerate data)
            $period = $dataset->parentSensorCluster->options->getSamplePeriod();
            $cache->filtered = DataSqueeze::simpleFIR($cache->rows, $delay, $period);
            /*  this is not really needed, but probably will not trigger under normal
             *
             *  if it does, might be helpful to a debugger
             */
            if(0 === count($cache->filtered[0])) {
                var_dump("[!] there were {$cache->rowCount} but no rows after filtering");
                for($i = count($cache->someRows); $i--;) {
                    if(!isset($cache->someRows[0][$i])) break;
                    echo(
                        "time {$cache->someRows[0][$i]} " . 
                        "reading {$cache->someRows[1][$i]}" . PHP_EOL
                    );
                }
                var_dump("[!] there is a problem, probably simple FIR to blame");
                var_dump("delay was [{$delay}] period was [{$period}]");
                return array();
            }
        }
        // initialize algorithm to reduce number of points needed to represent dataset
        $rdp = new RamerDouglasPeucker($cache->filtered);
        // get predefined epsilon for this type of sensor
        $epsilon = $dataset->parentSensorCluster->options->getSquishFactor(
            $dataset->getTypeName()
        );
        if(defined("USE_SMALLER_FLOATS")) {
            $epsilon /= 100.0;
        }
        if(defined("USE_INTEGER_MATHS")) {
            $epsilon = intval($epsilon * 100);
        }
        // recompute epsilon baseline using FIR to bias adjustment
        $epsilon *= FIR_DELAY_MULTIPLIER::SQUISH_FACTOR_ADJUSTMENT($dataset->fir);
        $res = $rdp->getRDP($epsilon);
        // update statistics
        $dataset->stats->epsilon = $epsilon;
        $dataset->stats->rowCount = $cache->rowCount;
        $dataset->stats->filteredCount = count($cache->filtered[0]);
        $dataset->stats->rdpCount = count($res);
        $dataset->stats->rdpPerpendicular = $rdp->called;
        return $res;
    }
}

/*  minimal structure that can be saved between calls to Dataset::retrieveReducedData
 *  in order to save CPU time
 */
class CachedDatasetData {
    public $filtered = NULL;
    public $rows = NULL;
    public $sql;
    // since rows are cleared, this must be saved so it can later be reported on
    public $rowCount;
    // some of the rows are saved, to help facilitate debugging
    public $someRows;
    public function __construct($rows = NULL) {
        if(NULL !== $rows) {
            $this->someRows = array(array(), array());
            // copy 10 rows
            for($i = 10; $i--;) {
                if(!isset($rows[0][$i])) break;
                $this->someRows[0][$i] = $rows[0][$i];
                $this->someRows[1][$i] = $rows[1][$i];
            }
            $this->rows = $rows;
            $this->rowCount = count($rows[0]);
        }
    }
}

class DatasetStatistics {
    public $rowCount;
    public $filteredCount;
    public $rdpCount;
    public $epsilon;
    public $rdpPerpendicular;
}


/*  sensor options
 *
 *  we started running into issues with the sensors collecting too much data,
 *  or at least too much for our hardware's bandwidth
 *
 *  each sensor needs to be looked at more carefully, and the data that it
 *  produces needs to be interpreted by a computer before a person looks at it
 *
 *  to keep the sensors together in the same place (this document), the list
 *  of sensors needs to accommodate additional properties being added to sensors
 */
class SensorOptions {
    /*  the epsilon that will be used for this sensor when data is processed
     *  by the Ramer-Douglas-Peucker algorithm
     *  each sensor will have it's own epsilon depending on it's minimum,
     *  maximum, and overall signal noise
     */
    private $squishFactor;

    /*  read the documentation for your sensor carefully, or maybe even contact
     *  the manufacturer of the sensor to find out how many samples need to be
     *  collected before one can get the advertised precision
     */
    private $sampleDepth;

    /*  used to regenerate or decompress data stored on disk, the sample period
     *  is the time in between samples, this is generally set by the individual
     *  sensors, a scheme was created to save disk space by only saving samples
     *  when a value changes from the previous value.  This value can be determined
     *  by finding the smallest period between any two samples, but explicitly
     *  setting it saves us the work.
     */
    private $samplePeriod;

    public function __construct($squishFactor = NULL, $sampleDepth = 0, $samplePeriod = 1) {
        /*  some standard deviations for sensors after running for several
         *  months (the /10 is not part of the standard deviation, it is
         *  used to give a "wide birth", we are giving ten times the estimated
         *  needed detail when drawing simplified lines)
         *
         *  these are used to help draw simplified lines or graphs of sensor
         *  data.  the value represents the distance a simplified line can be
         *  from a reading before it needs to be redrawn.
         *
         *  each sensor captures reading using different units, for example the
         *  radon sensor might capture picocurries per liter and store values
         *  as an integer resulting in values covering two or three magnitudes,
         *  where an air quality sensor might capture parts per million with
         *  values spanning more than six magnitudes.
         *
         *  for complex sensors like the BME680 where each sensor is made of
         *  multiple sensors, we use an array to represent each squish factor
         *  per individual type of sensor, for the radon only sensors, initialize
         *  squish factor as a (double) or (float), we will take care of the rest
         *
         *  also for by default just use these pre-recorded epsilon values for
         *  all BME680 sensors
         */
        $this->squishFactor = NULL === $squishFactor
            ? DEFAULT_BOSCH_BME680::SQUISH_FACTOR()
            : array("radon" => $squishFactor)
        ;
        $this->sampleDepth = intval($sampleDepth);
        $this->samplePeriod = intval($samplePeriod /* seconds */);
    }
    public function setSamplePeriod($period = 1) {
        $this->samplePeriod = intval($period /* in seconds */);
    }
    // gets the number of seconds between samples
    public function getSamplePeriod() {
        return $this->samplePeriod;
    }
    public function setSampleDepth($samples = 0) {
        $this->sampleDepth = intval($samples);
    }
    // gets the amount of delay that should be used for a simple FIR filter
    public function getSampleDepth() {
        return $this->sampleDepth;
    }
    // gets appropriate epsilon for sensor reading Ramer-Douglas-Peucker simplification
    public function getSquishFactor($type = "radon") {
        /*  radon type sensors each have their own epsilon, they are placed in
         *  areas where radon fluctuates at different rates, using the same
         *  epsilon might lead to missing small changes or getting too many
         *  data-points
         */
        return !isset($this->squishFactor[$type])
            ? 0.001 
            : $this->squishFactor[$type];
    }

}

/*  zooms are cached, these names identify three views of the same data
 *  that represent different data-sets that appear similar to each other
 */
define("ZOOM_96_HOURS",     1);
define("ZOOM_MONTH",        2);
define("ZOOM_YEAR",         3);
define("ZOOM_DEFAULT",      ZOOM_96_HOURS);

/*  [!] not a valid "zoom", but is the default query option that disables
 *      the use of the cache and all features that come with it
 */
define("NO_USE_RADON_CACHE", false);

/*  finite impulse responses are cached, these names identify views of the same
 *  data that represent data-sets that are distinct from each other but share
 *  similar trends
 */
define("FIR_OFF",           0);
define("FIR_1_HOUR",        1);
define("FIR_96_HOURS",      2);
define("FIR_MONTH",         3);
define("FIR_YEAR",          4);
define("FIR_DEFAULT",       FIR_1_HOUR);

/*  used to increase the delay by some multiple in order to increase visibility
 *  of trend lines in noisy signals
 */
class FIR_DELAY_MULTIPLIER {
    static public function LUT($fir) {
        $arr = array(      /*  these are unit-less, but we 
                               assume other operand is an hour  */
            FIR_OFF         => /*    0 */ 0,
            FIR_1_HOUR      => /*    1 */ 1,
            FIR_96_HOURS    => /*   96 */ 8,
            FIR_MONTH       => /*  744 */ 62,
            FIR_YEAR        => /* 8760 */ 730,
            // see above: copy the FIR_1_HOUR value
            FIR_DEFAULT     => /*      */ 1
        );
        return isset($arr[$fir]) ? $arr[$fir] : $arr[FIR_DEFAULT];
    }
    static public function SQUISH_FACTOR_ADJUSTMENT($fir) {
        $arr = array(
            FIR_1_HOUR      => 1.0,
            FIR_96_HOURS    => 10.0,
            FIR_MONTH       => 100.0,
            FIR_YEAR        => 1000.0,
            /*  [!] squish factor is only used for RDP, all values in cache are
             *  subject to the RDP algorithm, we do not have enough space
             *  to store all decompress corrected readings from sensors
             */
            FIR_OFF         => 1.0,
            FIR_DEFAULT     => 1.0
        );
        return isset($arr[$fir]) ? $arr[$fir] : $arr[FIR_DEFAULT];
    }
}

/*  necessary data caching
 *
 *  After testing the filter and RDP algorithm I found that the RadonEye and other
 *  devices that save data every five minutes takes too much CPU time.  The original
 *  method for displaying data to the end user had some deficiencies, for example
 *  the data was saved only when a change was discovered, the previous output
 *  would extrapolate a line between the two saved values, but as all sampled data
 *  should have only displayed the captured data points.  To incorporate extrapolated
 *  lines we need to consider all points sampled between changes, then decide a
 *  strategy for extrapolating a line.  For sensor 'R', 95 thousand samples it
 *  takes about 7 seconds to regenerate / decompress missing samples, and run all
 *  samples through RDP, where nearly 2 million square root calcuations are 
 *  performed.  Using more RAM does speed up the process but with the limitation
 *  of 128MB under PHP we'd need around 3 orders of magnitude more RAM.  (128 
 *  Gigabytes would be reasonable)
 *
 *  Even with the increased RAM we'd only improve speed by ten, definitely less
 *  than a hundred giving us unacceptable delay.  For example ten years down the
 *  road means 70 seconds, divide by less than 1 hundred is going to be around
 *  a second for a single sensor.
 *
 *  So we need to cache.
 *
 *  What should be cached:
 *  zoom: 3 days, month, year
 *  levels of FIR: same as above, but additionally default
 *
 *  zoom has to do with how many data points are provided to the end user, affects
 *  should not be noticeable to an end user, but data is heavily modified, this
 *  is a form of down-sampling
 *
 *  FIR levels have to do with overall trends, affects are noticeable to an end
 *  user, this is a form of averaging in the time domain
 *
 *  there will be zoom * levels different data-sets per sensor, so [12] total
 *  per sensor, but, those 12 sets will still be smaller than the original data, 
 *  I hope.
 *
 *  sensorLog table in SQLite3 cached database:
 *  id, time, sensor, dataset, value
 *  dataset is a multiple of 128 and the zoom, then sum with the level of FIR
 *  sensor is a multiple of 128 and the name, then sum with the sensor type
 *
 *  sensorLog combines both the radonLog and the boche_bme680 tables, data
 *  is interpolated and may change from minute to minute.  Because of the
 *  interpolation timestamps for a given event may not match exactly with the
 *  original data, values for a given event may not match exactly values in the
 *  original data, the goal of the downsampling and trend averaging techniques
 *  is to represent the signal in the ways that is most useful to an end user
 *  down sampling has to be cached at multiple sample depths to prevent a user
 *  from noticing the "missing" data, trends have to be cached at different FIR
 *  levels to provide different views of the same data to a user so that they
 *  can see the signal through the noise
 *
 *  create an ephemeral database that has less data, this way the end user can
 *  continue to request `all` of the possible data
 */
class CACHE_DB {
    const DB_FILE = "radonCache.db";
    const DATASET_INDEX =
        "CREATE INDEX IF NOT EXISTS datasetIndex ON sensorLog(dataset);";
    const TIME_INDEX =
        "CREATE INDEX IF NOT EXISTS timeIndex ON sensorLog(time);";
    /*  when querying, always use `time` and `dataset` column to make use of index
     */
    static private function QUERY($query = NULL, $order = "") {
        // setup a default query
        if(NULL === $query) {
            $query = "SELECT time, reading";
            $order = "ORDER BY time ASC";
        }
        return "
            {$query}
            FROM sensorLog 
            WHERE
                dataset = :dataset
                AND time >= :start
                AND time <= :end
            {$order};
        ";
    }
    static private function CREATE($disk = false) {
        return "
            CREATE TABLE IF NOT EXISTS sensorLog(
                time INTEGER NOT NULL, 
                dataset INTEGER NOT NULL,
                reading FLOAT" . ($disk ? ", \nUNIQUE(time, dataset)" : "") ."
            );
        ";
    }
    /*  cluster is what we call the sensor name, naming scheme has been: 'A', 'B', 
     *  'C', etc.  This rule has been solidified as the cached database, `radonCache.db`
     *  uses a scheme to store all sensor readings in a single table with a single
     *  column identifying both which sensor and from what cluster a reading came
     *  from.
     *
     *  cluster is a sensor that is actually multiple sensors, a single device that
     *  because the sensors are soldered to it, that it is impossible to move
     *  individual sensors without moving the other sensors in the cluster
     *
     *  the sensor type identifies which sensor in the sensor cluster that data is
     *  being requested for
     *
     *  zoom is what data the user is looking at
     *      - ZOOM_DEFAULT
     *      - ZOOM_96_HOURS
     *      - ZOOM_MONTH
     *      - ZOOM_YEAR
     *  fir is how much filtering the user wants
     *      - FIR_DEFAULT
     *      - FIR_OFF
     *      - FIR_1_HOURS
     *      - FIR_96_HOURS
     *      - FIR_MONTH
     *      - FIR_YEAR
     */
    static public function getCachedData($clusterName, $sensorType, $zoom = ZOOM_DEFAULT, $fir = FIR_DEFAULT, $start = 0, $end = PHP_INT_MAX) {
        $dbDisk = new SQLite3(CACHE_DB::DB_FILE);
        $diskSelect = $dbDisk->prepare(CACHE_DB::QUERY());
        /*  cluster can either be a letter: 'A', 'B', 'C', etc 
         *  or the integer id of the sensor
         */
        $sensorId = Dataset::toSensorId($clusterName);
        /*  sensor type can either be string: 'radon', 'celsius', etc
         *  or mask:: RADON, CELSIUS, etc
         */
        $mask = is_int($sensorType)
            ? $sensorType
            : COL_HEADER_TO_TYPE_MASK::LUT($sensorType);
        $typeId = Dataset::getBit($mask);
        $datasetId = Dataset::generateDatasetId($sensorId, $typeId, $zoom, $fir);
        // update our SQL statement
        $diskSelect->bindValue("dataset", $datasetId);
        $diskSelect->bindValue("start", $start);
        $diskSelect->bindValue("end", $end);
        // run it
        $results = $diskSelect->execute();
        // PHP does not do so well storing non-scalar values
        $rows = array(array(/* times */), array(/* readings */));
        /*  get results
         *  cached database values are not aware of MySQL integer based storage
         *  scheme, where integers are used in place of floating point values
         *  by multiplying the float by 100 and then removing all decimal points
         *
         *  the cached database stores FIR values of the above MySQL values
         *  which reintroduces unnecessary precision (any precision beyond two
         *  decimal points) and stores those values as float
         *
         *  [!] make sure to get rid of the unnecessary precision, it is
         *      wasteful and misleading - round readings to no decimal points
         *      or maybe just convert to integers
         */
        while($row = $results->fetchArray()) {
            $rows[0][] = $row["time"];
            $rows[1][] = intval($row["reading"],0);
        }
        // done unless we need to support older frontends
        if(false === defined("ARRAY_OF_TIME_READING_PAIRS")) return $rows;
        /*  CACHE_DB uses reduced memory: array([time array], [reading array])
         *  the frontend was written before this optimization was found, so that
         *  nothing needs to be changed in the frontend code we would need to 
         *  put the results back to a format that matches -or- we could optimze
         *  the frontend
         *
         *  I am certainly being lazy, I don't want to look through the frontend
         *  code, the optimizations are probably not even relevant on versions
         *  of PHP older than 5.3, for which the optimizations were written
         *
         *  [?] I think the memory limits have been lifted, so re-inflating the
         *      array without changes to the frontend should be fine, besides
         *      that, less memory is uses retrieving data than processing it
         */
        $arr = array();
        for($i = count($rows[0]); $i--;)
            $arr[] = array(
                "time"=>array_pop($rows[0]),
                "reading"=>array_pop($rows[1])
            );
        return array_reverse($arr);
    }
    /*  [?] 20 sensors, about 10 months of data takes about 25 minutes to process on
     *      an 800MHz CPU and 16 Gigabyte RAM, produces a 17 Megabyte file
     *
     *      After testing to see if one can see the difference between compressed
     *      data and uncompressed data and determining if there was value in
     *      filtering input data we needed a way to validate if it was possible to
     *      bring these features to the frontend.  Here we create all the different
     *      outputs from our input data and store them to disk in a cache.  Various
     *      ways of processing and storing the data are explored.  Currently it takes
     *      a bit too long to generate all the data, with optimizations it went from
     *      25 minutes to 13 minutes.
     *
     *      A feature was added to partially update the cache, this makes it so one
     *      can update a single sensor in less than a second.  Still pretty slow.
     *
     *      The time needed to store data is dominated by the need to update, with
     *      updates, actually the DELETE taking almost all the CPU time.  Processing
     *      data is also slow, with the PHP implementation of the algorithm being
     *      really slow.
     *
     *      some notes about SQLite3 database optimizations - adding indices
     *      increases disk space usage:
     *      36 Megabytes with UNIQUE constraint on dataset and time
     *      48 Megabytes with INDEX on dataset
     *      43 Megabytes with INDEX on time and dataset (no UNIQUE constraint)
     *
     *      the fourth parameter, clusterName was added to allow a single cluster
     *      to do a partial update on just it's sensors.  It is important to set
     *      reasonable start and end times when doing a partial update, this is
     *      somewhat complicated to figure out and currently not implemented well
     *      as one would probably want to vary the start and end times based on
     *      the level of finite impulse response filtering (this is kinda handled
     *      internally, but you still need to provide a good start time)
     *
     *      We added an additional Finite Impulse Response filter, FIR_OFF, this
     *      means there are more datasets, the disk requirements doubled and I
     *      think we are sitting at just under 100 Megabytes for the cache after
     *      one year of recording
     */
    static public function createCacheDb($startTime = 0, $endTime = PHP_INT_MAX, $reset = false, $clusterName = false) {
        //define("PRINT_DATA_SOURCE_SQL", NULL);
        /*  this seems to make things worse, possibly because larger epsilons passed
         *  to RDP algorithm are taking longer to compute
         *
         *  this makes the database bigger (possibly)
         *  and does not improve performance
         */
        //define("USE_SMALLER_FLOATS", NULL);
        /*  this does not seem to help much: 23 minutes
         *  without we get nearly 25 minutes
         */
        //define("USE_INTEGER_MATHS", NULL);
        /*  storing rows in memory between look-ups saves a very small amount of
         *  time when compared to the amount of time doing other work
         *
         *  investigated when storing 12 datasets for each of all sensors was taking
         *  between 25 minutes and 45 minutes to complete
         *
         *  (the time difference seems to be the chosen epsilon and RDP algorithm
         *   where larger epsilons are taking longer to compute)
         *
         *  might save a minute or two
         */
        //define("VERBOSE_DB_INSERT_LOGGING", NULL);
        define("USE_CACHED_ROWS", NULL);
        define("USE_CACHED_FIR", NULL);
        /*  improves DELETE which is used a bit when doing partial updates to 
         *  database.  It does increase disk space used by 30% but gives a big
         *  boost to speed.  I am not sure why the DELETE was not using the UNIQUE
         *  constraint index, but whatever.  Normally DELETE does not use a large
         *  portion of time, but in the case where we are doing a partial update
         *  and deleting two rows and adding a couple the DELETE operation was
         *  consuming 98% of the CPU time.
         */
        define("USE_INDEX_ON_DATASET", NULL);
        /*  the unique constraint gives an SQL index when queries use the `time`
         *  and `dataset` columns.  We pay a price for this when writing new
         *  entries to the database, but gain speed whenever we read
         *
         *  also we never query the :memory: database so creating indices does not
         *  make sense, only do this for the disk backed database
         */
        //define("USE_CONSTRAINT", NULL);
        define("USE_INDEX_ON_TIME", NULL);
        define("FLUSH_DB_AT_ONCE", NULL); // faster, uses more RAM
        $CREATE = function($disk = false) { return "
            CREATE TABLE IF NOT EXISTS sensorLog(
                time INTEGER NOT NULL, 
                dataset INTEGER NOT NULL,
                reading FLOAT" . ($disk ? ", \nUNIQUE(time, dataset)" : "") ."
            );
        "; };
        /*  [?] maybe print a warning later if database exists and user wants to
         *      perform a full cache refresh (this is the most probable use, but
         *      also the most wasteful)
         *
         *  [??] regarding disk backed using magnetic VS ssd VS ramdisk
         *       `sudo mount -t tmpfs -o rw,size=64M tmpfs tmpfs` did not improve
         *       SQLite3 performance, so we are hitting CPU before disk
         */
        if(true === $reset) unlink(CACHE_DB::DB_FILE);
        $fileExists = file_exists(CACHE_DB::DB_FILE);
        $dbDisk = new SQLite3(CACHE_DB::DB_FILE);
        $db = new SQLite3(":memory:");
        /*  enable the write ahead log for disk backed storage
         *  this does not help the :memory: backed storage as it cannot use `wal`
         *  after testing this it does not seem like these optimizations do not
         *  seem to help me
         */
        //$dbDisk->exec("PRAGMA journal_mode = wal;");
        //$dbDisk->exec("PRAGMA synchronous = NORMAL;");
        // double speed on write, but power failure during write will corrupt db
        $dbDisk->exec("PRAGMA synchronous = OFF;");
        // set 64Mb cache (up from 2Mb default) - this does not seem to help
        //$dbDisk->exec("PRAGMA cache_size = -64000;");
        $db->exec(CACHE_DB::CREATE());
        $dbDisk->exec(CACHE_DB::CREATE(/* unique index */ defined("USE_CONSTRAINT")));
        if(defined("USE_INDEX_ON_DATASET")) $dbDisk->exec(CACHE_DB::DATASET_INDEX);
        if(defined("USE_INDEX_ON_TIME")) $dbDisk->exec(CACHE_DB::TIME_INDEX);
        // temporarily give memory db access to the disk db
        $db->exec("ATTACH DATABASE './" . CACHE_DB::DB_FILE . "' AS disk");
        // prepare all queries, use standard prepared interface
        $diskSelect = $dbDisk->prepare(CACHE_DB::QUERY(/* use defaults */));
        $diskDelete = $dbDisk->prepare(CACHE_DB::QUERY("DELETE"));
        $diskDeleteCheck = $dbDisk->prepare(CACHE_DB::QUERY("SELECT COUNT(*)"));
        // setup the column mapping for inserts
        $arr = array("time", "dataset", "reading");
        $cols = implode(", ", $arr);
        array_walk($arr, function (&$v) { $v = ":{$v}"; });
        $bindings = implode(", ", $arr);
        // [!] careful, importing data uses PHP bound variables
        $boundTime; $boundDataset; $boundReading;
        $stmt = $db->prepare("INSERT INTO sensorLog({$cols}) VALUES({$bindings})");
        $stmt->bindParam(":time",    $boundTime,    SQLITE3_INTEGER);
        $stmt->bindParam(":dataset", $boundDataset, SQLITE3_INTEGER);
        $stmt->bindParam(":reading", $boundReading, SQLITE3_FLOAT);
        // TheInternet has a list of all the sensor clusters
        $internet = new TheInternet();
        // expand the list into all possible views of the data (Datasets)
        $datasets = Dataset::makeAllDatasetsFromInternet($internet);
        // see: USE_CACHED_ROWS
        $cache = new CachedDatasetData(); 
        $previous = array(NULL, NULL, NULL);
        // work on all datasets -- unless profiling for speed optimizations
        //define("PROFILE_S_SLOWEST", NULL);
        // allow partial updates for just a single cluster of sensors
        if(false !== $clusterName) $clusterName = Dataset::toSensorId($clusterName);
        foreach($datasets as $dataset) {
            /*  make sure start and end are integers before we go stuffing those
             *  values into SQL
             *  [?] also since start time is modified, re-initialize it every
             *  iteration
             */
            $start = intval($startTime);
            $end = intval($endTime);
            $lastSameTimestamp = $start;
            if(defined("PROFILE_S_SLOWEST") or (false !== $clusterName)) {
                $skip = false;
                if($clusterName !== $dataset->getInternalSensorId()) $skip = true;
                if('S' !== $dataset->parentSensorCluster->name) $skip = true;
                //if(FIR_DEFAULT !== $dataset->getFIR()) $skip = true;
                //if(FIR_YEAR    !== $dataset->getFIR()) $skip = true;
                if($skip) {
                    //echo "skipping..." . PHP_EOL;
                    continue;
                }
            }
            /*  we should backtrack the time a little bit to try to reduce
             *  discontinuity when doing a partial update to the cache
             *
             *  this is a minimum, it is more than likely that the database will
             *  not have a reading at this timestamp, and there is a somewhat
             *  likely chance that the reading after this timestamp will be so far
             *  away that the amount of data going into the filter would not be
             *  enough to fill it
             *
             *  TODO:
             *  we should make sure the filter knows our start time so it can start
             *  there...
             */
            if(0 !== $start) {
                $seconds = FIR_DELAY_MULTIPLIER::LUT($dataset->getFIR()) *
                    60  /* minutes in an hour */ *
                    60  /* seconds in an hour */
                ;
                //var_dump("need to go back {$seconds} seconds before {$start}");
                if($start >= $seconds) $start -= $seconds;
            }
            $filterDepth = $dataset->parentSensorCluster->options->getSampleDepth();
            $filterDepth *= FIR_DELAY_MULTIPLIER::LUT($dataset->getFIR());
            /*  using a row cache means we can skip SQL reads when a dataset uses
             *  the same rows
             *
             *  [?] if we are careful about how the datasets are organized we can
             *      hit this optimization more often, worse case we might miss this
             *      optimization every time ::frown face::
             *
             *  use some truth tables to determine if we can use cached data
             */
            $previousCluster = $dataset->getInternalSensorId() === $previous[0];
            $previousType    = $dataset->getTypeName() === $previous[1];
            $previousDepth   = $filterDepth === $previous[2];
            if(defined("USE_CACHED_ROWS") and NULL !== $cache->rows) {
                $cache->rows = ($previousCluster and $previousType)
                    ? /* no change needed */ $cache->rows
                    : /* need to read SQL */ NULL;
                if(NULL !== $cache->rows) {
                    if(defined("VERBOSE_DB_INSERT_LOGGING"))
                        echo "[?] using cached rows..." . PHP_EOL;
                }
            } else $cache->rows = NULL;
            if(defined("USE_CACHED_FIR") and NULL !== $cache->filtered) {
                $cache->filtered = ($previousCluster and $previousType and $previousDepth)
                    ? /* no change needed */ $cache->filtered
                    : /* need to read SQL */ NULL;
                if(NULL !== $cache->filtered) {
                    if(defined("VERBOSE_DB_INSERT_LOGGING"))
                        echo "[?] using cached fir data..." . PHP_EOL;
                }
            } else $cache->filtered = NULL;
            // record the previous SQL read markers, in-case we want to use caching
            $previous[0] = $dataset->getInternalSensorId();
            $previous[1] = $dataset->getTypeName();
            $previous[2] = $filterDepth;
            $t0 = microtime(true);
            // store some data to later run a health-check on what we are doing
            $data = Dataset::retrieveReducedData($dataset, $start, $end, $cache);
            //var_dump($dataset->stats);
            $data = array_reverse($data, /* keep keys */ true);
            $t0 = "(cpu time " . number_format(1000 * (microtime(true) - $t0), 2) . "ms)";
            //if(empty($data)) { var_dump("no records found"); }
            if(defined("VERBOSE_DB_INSERT_LOGGING")) var_dump(
                "{$t0} done processing cluster {$dataset->parentSensorCluster->name} " .
                "input " . count($cache->filtered[0]) . " rows " .
                "output " . count($data) . " rows " .
                "sensor: {$dataset->getTypeName()} " .
                "datasetId:{$dataset->datasetId} " .
                "filter depth:{$filterDepth}"
            );
            $t0 = microtime(true);
            $keptRows = 0;
            /*  checking before delete takes some time, but on average ends up
             *  saving a bit of time, go figure
             *
             *  I cannot find out why this is, SQLite3 documentation and internet
             *  people say DELETE is expensive so if we can avoid it we save time
             */
            if(0 !== $start) {
                /*  try to reduce the amount of writing to the database, find the
                 *  timestamp when values start to change and only write those
                 */
                $diskSelect->bindValue("dataset", $dataset->datasetId);
                $diskSelect->bindValue("start", $start);
                $diskSelect->bindValue("end", $end);
                $results = $diskSelect->execute();
                while($row = $results->fetchArray()) {
                    if(isset($data[$row["time"]])) {
                        // compare if float-point values are similar
                        $a = $row["reading"];
                        $b = $data[$row["time"]];
                        //var_dump("compare [{$a}] and [{$b}]");
                        if(abs($a - $b) > .00001) break;
                        $keptRows++;
                        $lastSameTimestamp = $row["time"] + 1;
                        //var_dump("keeping {$lastSameTimestamp}");
                        unset($data[$row["time"]]);
                    }
                }
                //var_dump("keeping [{$keptRows}] rows");
                $diskSelect->reset();
            }
            $t0 = "(select cpu time " . number_format(1000 * (microtime(true) - $t0), 2) . "ms)";
            if(defined("VERBOSE_DB_INSERT_LOGGING")) var_dump(
                "{$t0} done checking for extra writes" .
                " avoided {$keptRows} rows"
            ); 
            $t0 = microtime(true);
            // prepare to remove all entries from the disk
            if(0 === count($data)) {
                //var_dump("skipping DELETE operation, nothing to add");
            } else {
                $diskDeleteCheck->bindValue("dataset", $dataset->datasetId);
                $diskDeleteCheck->bindValue("start", $lastSameTimestamp);
                $diskDeleteCheck->bindValue("end", $end);
                $res = $diskDeleteCheck->execute();
                $res = $res->fetchArray();
                $rowsWouldDelete = $res["COUNT(*)"];
                //var_dump("rows caught by delete: {$rowsWouldDelete}");
                if(0 === $rowsWouldDelete) {
                    //var_dump("skipping DELETE operation, nothing would delete");
                } else {
                    $diskDelete->bindValue("dataset", $dataset->datasetId);
                    $diskDelete->bindValue("start", $lastSameTimestamp);
                    $diskDelete->bindValue("end", $end);
                    $diskDeleteCheck->reset();
                    $diskDelete->execute();
                    $diskDelete->reset();
                }
            }
            $t0 = "(delete cpu time " . 
                number_format(1000 * (microtime(true) - $t0), 2) . "ms)";
            if(defined("VERBOSE_DB_INSERT_LOGGING")) var_dump(
                "{$t0} done clearing old data"
            );
            $t0 = microtime(true);
            $boundDataset = intval($dataset->datasetId);
            //$db->exec("BEGIN TRANSACTION;");
            while($row = array_slice($data, -1, 1, true)) {
                // remove sliced indice
                array_pop($data);
                // load the database
                $boundTime = intval(key($row));
                $boundReading = (float) array_pop($row);
                $stmt->execute();
                $stmt->reset();
            }
            //$db->exec("END TRANSACTION;");
            if(!defined("FLUSH_DB_AT_ONCE")) {
                // flush memory to disk on every dataset to prevent using too much memory
                $db->exec(
                    "INSERT INTO disk.sensorLog ({$cols}) SELECT {$cols} FROM sensorLog;");
                $db->exec("DELETE FROM sensorLog;");
            }
            $t0 = "(cpu time " . number_format(1000 * (microtime(true) - $t0), 2) . "ms)";
            if(defined("VERBOSE_DB_INSERT_LOGGING")) var_dump(
                "{$t0} done saving cluster {$dataset->parentSensorCluster->name} " .
                "rdp: {$dataset->stats->rdpCount} " .
                "sensor: {$dataset->getTypeName()} " .
                "datasetId:{$dataset->datasetId}"
            );
            if(defined("VERBOSE_DB_INSERT_LOGGING")) echo PHP_EOL;
        }
        if(defined("FLUSH_DB_AT_ONCE")) {
            $db->exec("INSERT INTO disk.sensorLog ({$cols}) SELECT {$cols} FROM sensorLog;");
        }
        if((true === $reset) and (true === $fileExists)) {
            trigger_error(
                "[?] removing `" .
                CACHE_DB::DB_FILE .
                "` would be significantly faster " .
                "for full cache refreshing",
                E_USER_WARNING
            );
        }
    }

}

/*  unnecessary cruft, automatically names stuff, sits in-between the routines
 *  that get the data and the code that draws stuff
 *
 *  the code that was supplying the highcharts wanted data, names, colors and
 *  then on top of that there were a bunch of sensors that have names like
 *  'A', 'B', 'C', and nothing taking responsibility for these things
 *
 *  user wants a highchart series
 *
 *  maybe user wants to specify some stuff, color, time range, etc, try to 
 *  accommodate those things
 *
 *  [?] availableZoom and availableFIR can be combined to represent multiple
 *      views of some data.  A data-set is cached for each combination of zoom
 *      and FIR, when this was written there were 3 available zooms and 4
 *      available FIR meaning there would be 12 data-sets cached per sensor.
 *      a sensor cluster, like the BOSCH_BME680, with it's 5 sensors will have
 *      60 cached data-sets
 */
Class TheInternet {
    public $inline = false;
    private $output = array();
    private $sensors = array();
    private $whatUsersWant;
    public $availableZoom = array(
        ZOOM_DEFAULT,
        ZOOM_96_HOURS,
        ZOOM_MONTH,
        ZOOM_YEAR,
    );
    public $availableFIR = array(
        FIR_OFF,
        FIR_DEFAULT,
        FIR_1_HOUR,
        FIR_96_HOURS,
        FIR_MONTH,
        FIR_YEAR,
    );
    public function __construct() {
        /*  [?] notes about the values saved here
         *
         *  the sensors that we monitor are all different and in general try
         *  their best to report accurate information.  They all have their own
         *  way of maintaining precision, some, I've made some mistakes and
         *  thrown away, for example the temperature sensors, I am pretty
         *  sure I lost resolution trying save space on the server. (I should
         *  have multiplied the values by a few magnitudes and saved integer
         *  values to avoid floating point storage)  Anyways, all the sensors
         *  have very little memory and either make great use of that memory,
         *  or not at all.  Either way, the filters on the sensors are limited.
         *
         *  We can make really big filters, adjust for phase shift, down sample,
         *  all the things - because we have lots of memory and processing power
         *
         *  `TheInternet` abstracts some of the complexities of the sensors
         *  so that users can ask for things without specifying specific details
         *  that are kinda necessary for what they are asking for.  There is no
         *  place for these things in the underlying routines either, so they
         *  end up here, in the middle.  For example, the Ramer-Douglas-Peucker
         *  algorithm that is used for line simplification wants an `epsilon`
         *  value so it knows how tightly to keep it's output to the input it
         *  is given.
         *
         *  notes about specific values:
         *  squish factor: see frontend/tests-and-demos/rdp-algo.php
         *  sample depth: resolution should be 1 hour for most the sensors
         *  sample period: read the datasheets for each sensor
         */

        // this is just a list of the sensors in one place
        $this->sensors['H'] = new Sensor('H', "DEADBEEF", BOSCH_BME680);
        $this->sensors['I'] = new Sensor('I', "DEADPORK", BOSCH_BME680);
        $this->sensors['J'] = new Sensor('J', "HELLOCAT", BOSCH_BME680);

        $this->sensors['A'] = new Sensor('A', "A",        AIR_THINGS,   106.0 / 100);
        $this->sensors['B'] = new Sensor('B', "B",        AIR_THINGS,   58.0  / 100);
        $this->sensors['C'] = new Sensor('C', "C",        AIR_THINGS,   335.0 / 100);
        $this->sensors['R'] = new Sensor('R', "R",        RADON_EYE,    62.0  / 100);
        $this->sensors['S'] = new Sensor('S', "S",        RADON_EYE,    24.0  / 100);
        $this->sensors["monkey"] = new Sensor("Ohhh Ahhhh!");

        // inform sensor API about the sampleDepth for the automated sensors
        $this->sensors['R']->options->setSampleDepth(/*every  5 min is*/ 12 /*per hour*/);
        $this->sensors['S']->options->setSampleDepth(/*every  5 min is*/ 12 /*per hour*/);
        $this->sensors['H']->options->setSampleDepth(/*every 15 min is*/  4 /*per hour*/);
        $this->sensors['I']->options->setSampleDepth(/*every 15 min is*/  4 /*per hour*/);
        $this->sensors['J']->options->setSampleDepth(/*every 15 min is*/  4 /*per hour*/);

        // inform sensor API about the samplePeriod for the automated sensors
        $this->sensors['R']->options->setSamplePeriod( 5 * 60 /* seconds */);
        $this->sensors['S']->options->setSamplePeriod( 5 * 60 /* seconds */);
        $this->sensors['H']->options->setSamplePeriod(15 * 60 /* seconds */);
        $this->sensors['I']->options->setSamplePeriod(15 * 60 /* seconds */);
        $this->sensors['J']->options->setSamplePeriod(15 * 60 /* seconds */);
        
        // user does not want Fahrenheit, they want temperature, translate request
        $this->whatUsersWant = TheCutePaletteAndSomeOtherStuff::wordWords();

        // available zoom and FIR might have unnecessary defaults
        $this->availableZoom = array_unique($this->availableZoom);
        $this->availableFIR = array_unique($this->availableFIR);
    }

    // returns a *copy* of the sensor
    public function cloneAllSensors() {
        $arr = array();
        foreach($this->sensors as $sensor) $arr[] = new Sensor(
            $sensor->name,
            $sensor->serial,
            $sensor->sensors,
            $sensor->options
        );
        return $arr;
    }

    // [!] returns a copy of the sensors
    public function getSensor($letter) {
        /*  clone would only do a shallow copy and we would lose SensorOptions
         *  instead, try to create a new sensor and provide it all the same
         *  parameters as the original
         *
         *  [alternatively we can give the user our sensor, but that might get
         *   a bit out of hand, maybe this does, idontknow]
         */
        return isset($this->sensors[$letter]) 
            ? new Sensor(
                $this->sensors[$letter]->name,
                $this->sensors[$letter]->serial,
                $this->sensors[$letter]->sensors,
                $this->sensors[$letter]->options
            )
            : NULL;
    }

    /*  The front end does not currently know what sensors are available, nor
     *  does it provide an interface to select which sensors are of interest
     *  to the end user.
     *
     *  Names, colors, or general user options are not set, or known, when
     *  requests are made, they tend to ask for things that the backend cannot
     *  provide
     *
     *  This interface protects the backend from these unknowns and tries to pick
     *  things that make sense.  In a way, it is kind of a dumpster fire with
     *  nobody taking responsibility for these kinds of things, but it does serve
     *  a purpose and will exist until it doesn't
     *
     *  other has a bunch of parameters that are jumbled together
     *  some of them are for highcharts, some are for running last minute routines
     *  on the data, some that affect what data is queried...
     */
    public function iotSmartAlexaSiriCloud($em = 'H', $what = "radon", $other = array()) {
        $auxFn = isset($other["auxFn"]) ?$other["auxFn"] :NULL;
        // manual read auxiliary measurements have different titles
        $title = isset($other["auxFn"]) ?ucfirst($other["auxFn"]) :"{$em}_{$what}";
        // check if we were passed query options, otherwise assign none
        $queryOptions = (
            isset($other["queryOptions"]) and
            ("QueryOptions" === get_class($other["queryOptions"]))
        ) ? $other["queryOptions"] : NULL;
        // radon detectors get special id
        $title = "radon" === $what ?"detector{$em}" :$title;
        // switch out implicit "temperature" for explicit "Fahrenheit"
        $get = $this->whatUsersWant[$what];
$td1 = microtime(true);
        // read data from disk or wherever it comes from
        $data = $this->sensors[$em]->$get($queryOptions, $auxFn);
$td2 = microtime(true);
        // run a user supplied function on the data before presentation
        if(isset($other["dataFn"])) { array_walk($data, $other["dataFn"]); }
$td3 = microtime(true);
error_log("data - i1: ".(round(($td2-$td1)*1000))."ms, i2: ".(round(($td3-$td2)*1000))."ms");
        // [!] this prints to STDOUT, do not let the assignment fool you
        // generate the highcharts series
        $this->output[] = new Series(
            $em,
            $get,
            makeSeries($title, $data, $other, false === $this->inline)
        );
    }
    public function getInlineJS_objs($var) {
        $arr = array();
        foreach($this->output as $o) {
            $arr[] = "{$var}.push(new Series('{$o->em}','{$o->type}',{$o->data}));";
        }
        return implode(PHP_EOL, $arr);
    }
}

Class Series {
    public $em;
    public $type;
    public $data;
    public function __construct($em = 'H', $type = 'radon', $data = NULL) {
        // no need to initialize anything when not used
        if(NULL === $data) return;
        $this->em = $em;
        $this->type = $type;
        $this->data = $data;
    }
    static public function asJavaScript() {
        return implode(' ', array_map("trim", explode(PHP_EOL,"class Series {
            constructor(em, type, data) {
                this.em = em;
                this.type=type;
                this.data=data;
            }
        };")));
    }
}

/*  scheme to override the color choices made for highcharts
 *  and provide some optional UI functionality like grouping similar graph
 *  data, like all radon measurements could are of the same class, they could
 *  be averaged, turned off together, whatever
 *
 *  after reading documentation, highcharts says that yes chart can be modified
 *  at runtime using highchart::chart api as well as highchart::series api
 *
 *  charts API for adding series at runtime, do not use at render time
 *  highcharts::addSeries(options, [,redraw] [,animation]) returns highcharts::Series
 *  highcharts::get(id) returns series or whatever by id
 *
 *  also provide a common reference for translating user requested data types
 *  and actual datatypes, for example, mapping temperature to Fahrenheit
 *
 */
require_once("test-pattern.php");
Class TheCutePaletteAndSomeOtherStuff {
    // user does not want Fahrenheit, they want temperature, translate request
    static public function wordWords() {
        // order these in the same order you want to pull from colors
        return array(
            "radon" => "getRadon",
            "humidity" => "getHumidity",
            "temperature" => "getFahrenheit",
            "indoor_air_quality" => "getIaq",
            "pressure" => "getUkrumayl",
            "wesDust" => "getWesDust",
            "aux" => "getAuxiliary"
        );
    }
    public function activateJavaScriptSuperPowers() {
    }
}