Squashed commit of the following:

commit af19d2aa593a4b4b068a5bc3707d74378625d774
Author: Christian Klinger <spam@klinch.de>
Date:   Wed Jul 13 12:32:17 2016 +0200

    added sorting functionality.

commit 0030ebebb49bad18fba8e74184d331be5485ed4e
Author: Christian Klinger <spam@klinch.de>
Date:   Fri Jul 8 16:09:16 2016 +0200

    small improvements.

commit 8dc5ee1173ffbc6e689f3197ad4d1ecf700a9374
Author: Christian Klinger <spam@klinch.de>
Date:   Fri Jul 8 12:49:29 2016 +0200

    added location fiter.

commit 63a2da244a6def5cdd76c654bd5a6a0c108cc47b
Author: Christian Klinger <spam@klinch.de>
Date:   Fri Jul 8 12:25:15 2016 +0200

    most filters should work.

commit 847536b34cec0194c58cb41a17006a8bd88f748d
Author: Christian Klinger <spam@klinch.de>
Date:   Tue Jul 5 15:57:38 2016 +0200

    rudimentary filter options.

1 files changed, 205 insertions, 0 deletions

diff --git a/modules-available/statistics/inc/filter.inc.php b/modules-available/statistics/inc/filter.inc.php
new file mode 100644
index 00000000..0f1a0d20
--- /dev/null
+++ b/modules-available/statistics/inc/filter.inc.php
@@ -0,0 +1,205 @@
+<?php
+
+/* base class with rudimentary SQL generation abilities.
+ * WARNING: argument is escaped, but $column and $operator are passed unfiltered into SQL */
+class Filter
+{
+    public $column;
+    public $operator;
+    public $argument;
+    public function __construct($column, $operator, $argument = null)
+    {
+        $this->column = trim($column);
+        $this->operator = trim($operator);
+        $this->argument = trim($argument);
+    }
+    /* returns a where clause and adds needed operators to the passed array */
+    public function whereClause(&$args, &$joins)
+    {
+        global $unique_key;
+        $key = $this->column.'_arg' . ($unique_key++);
+
+        /* check if we have to do some parsing*/
+        if (Page_Statistics::$columns[$this->column]['type'] == 'date') {
+                $args[$key] = strtotime($this->argument);
+        } else {
+                $args[$key] = $this->argument;
+        }
+
+        $op = $this->operator;
+        if ($this->operator == '~') {
+            $op = 'LIKE';
+        } elseif ($this->operator == '!~') {
+            $op = 'NOT LIKE';
+        }
+
+        return $this->column.' '.$op.' :'.$key;
+    }
+    /* parse a query into an array of filters */
+    public static function parseQuery($query)
+    {
+        $operators = ['<=', '>=', '!=', '!~', '=', '~', '<', '>'];
+        $filters = [];
+        foreach (explode(',', $query) as $q) {
+            $q = trim($q);
+                    /* find position of first operator */
+                    $pos = 10000;
+            $operator;
+            foreach ($operators as $op) {
+                $newpos = strpos($q, $op);
+                if ($newpos > -1 && ($newpos < $pos)) {
+                    $pos = $newpos;
+                    $operator = $op;
+                }
+            }
+            if ($pos == 10000) {
+                error_log("couldn't find operator in segment ".$q);
+                            /* TODO */
+                            continue;
+            }
+            $lhs = trim(substr($q, 0, $pos));
+            $rhs = trim(substr($q, $pos + strlen($operator)));
+
+            if ($lhs == 'gbram') {
+                $filters[] = new RamGbFilter($operator, $rhs);
+            } elseif ($lhs == 'state') {
+                    error_log('new state filter with ' . $rhs);
+                $filters[] = new StateFilter($operator, $rhs);
+            } elseif ($lhs == 'hddgb') {
+                $filters[] = new Id44Filter($operator, $rhs);
+            } elseif ($lhs == 'location') {
+                $filters[] = new LocationFilter($operator, $rhs);
+            } elseif ($lhs == 'subnet') {
+                    $filters[] = new SubnetFilter($operator, $rhs);
+            } else {
+                if (array_key_exists($lhs, Page_Statistics::$columns) && Page_Statistics::$columns[$lhs]['column']) {
+                    $filters[] = new Filter($lhs, $operator, $rhs);
+                } else {
+                    Message::addError('invalid-filter');
+                }
+            }
+        }
+
+        return $filters;
+    }
+}
+
+class RamGbFilter extends Filter
+{
+    public function __construct($operator, $argument)
+    {
+        parent::__construct('mbram', $operator, $argument);
+    }
+    public function whereClause(&$args, &$joins)
+    {
+        global $SIZE_RAM;
+        $lower = floor(Page_Statistics::findBestValue($SIZE_RAM, (int) $this->argument, false) * 1024 - 100);
+        $upper = ceil(Page_Statistics::findBestValue($SIZE_RAM, (int) $this->argument, true) * 1024 + 100);
+        if ($this->operator == '=') {
+            return " mbram BETWEEN $lower AND $upper";
+        } elseif ($this->operator == '<') {
+            return " mbram < $lower";
+        } elseif ($this->operator  == '<=') {
+            return " mbram <= $upper";
+        } elseif ($this->operator == '>') {
+            return " mbram > $upper";
+        } elseif ($this->operator == '>=') {
+            return " mbram >= $lower";
+        } elseif ($this->operator == '!=') {
+            return " (mbram < $lower OR mbram > $upper)";
+        } else {
+            error_log("unimplemented operator in RamGbFilter: $this->operator");
+
+            return ' 1';
+        }
+    }
+}
+class Id44Filter extends Filter
+{
+    public function __construct($operator, $argument)
+    {
+        parent::__construct('id44mb', $operator, $argument);
+    }
+    public function whereClause(&$args, &$joins)
+    {
+        global $SIZE_ID44;
+        $lower = floor(Page_Statistics::findBestValue($SIZE_ID44, $this->argument, false) * 1024 - 100);
+        $upper = ceil(Page_Statistics::findBestValue($SIZE_ID44, $this->argument, true) * 1024 + 100);
+
+        if ($this->operator == '=') {
+            return " id44mb BETWEEN $lower AND $upper";
+        } elseif ($this->operator == '!=') {
+            return " id44mb < $lower OR id44mb > $upper";
+        } elseif ($this->operator == '<=') {
+            return " id44mb < $upper";
+        } elseif ($this->operator == '>=') {
+            return " id44mb > $lower";
+        } elseif ($this->operator == '<') {
+            return " id44mb < $lower";
+        } elseif ($this->operator == '>') {
+            return " id44mb > $upper";
+        } else {
+            error_log("unimplemented operator in Id44Filter: $this->operator");
+
+            return ' 1';
+        }
+    }
+}
+class StateFilter extends Filter
+{
+    public function __construct($operator, $argument)
+    {
+        $this->operator = $operator;
+        $this->argument = $argument;
+    }
+
+    public function whereClause(&$args, &$joins)
+    {
+        $neg = $this->operator == '!=' ? 'NOT ' : '';
+        if ($this->argument === 'on') {
+            return " $neg (lastseen + 600 > UNIX_TIMESTAMP() ) ";
+        } elseif ($this->argument === 'off') {
+            return " $neg (lastseen + 600 < UNIX_TIMESTAMP() ) ";
+        } elseif ($this->argument === 'idle') {
+            return " $neg (lastseen + 600 > UNIX_TIMESTAMP() AND logintime = 0 ) ";
+        } elseif ($this->argument === 'occupied') {
+            return " $neg (lastseen + 600 > UNIX_TIMESTAMP() AND logintime <> 0 ) ";
+        } else {
+            Message::addError('invalid-filter');
+
+            return ' 1';
+        }
+    }
+}
+
+class LocationFilter extends Filter
+{
+        public function __construct($operator, $argument) {
+                parent::__construct('locationid', $operator, $argument);
+        }
+
+        public function whereClause(&$args, &$joins) {
+             settype($this->argument, 'int');
+            if ($this->argument === 0) {
+                 $joins[] = 'LEFT JOIN subnet s ON (INET_ATON(machine.clientip) BETWEEN s.startaddr AND s.endaddr)';
+                 return 'machine.locationid IS NULL AND s.locationid IS NULL';
+             } else {
+                 $joins[] = ' INNER JOIN subnet ON (INET_ATON(clientip) BETWEEN startaddr AND endaddr) ';
+                 $args['lid'] = $this->argument;
+                 $neg = $this->operator == '=' ? '' : 'NOT';
+                 return "$neg (subnet.locationid = :lid OR machine.locationid = :lid)";
+             }
+        }
+}
+
+class SubnetFilter extends Filter
+{
+        public function __construct($operator, $argument) {
+                parent::__construct(null, $operator, $argument);
+        }
+        public function whereClause(&$args, &$joins) {
+                $argument = preg_replace('/[^0-9\.:]/', '', $this->argument);
+                return " clientip LIKE '$argument%'";
+        }
+}
+