tablelib: MDL-22011 refactor flexible_table::get_sql_sort into severa…

…l smaller methods.

Also, change assignemnt to use a separate static method, rather than overloading get_sql_sort.

lib/tablelib.php

@@ -530,43 +530,67 @@ function setup() {
         } else if (!in_array('flexible', explode(' ', $this->attributes['class']))) {
             $this->attributes['class'] = trim('flexible ' . $this->attributes['class']);
         }
+    }
 
+    /**
+     * Get the order by clause from the session, for the table with id $uniqueid.
+     * @param string $uniqueid the identifier for a table.
+     * @return SQL fragment that can be used in an ORDER BY clause.
+     */
+    public static function get_sort_for_table($uniqueid) {
+        global $SESSION;
+        if(empty($SESSION->flextable[$uniqueid])) {
+           return '';
+        }
+
+        $sess = &$SESSION->flextable[$uniqueid];
+        if (empty($sess->sortby)) {
+            return '';
+        }
+
+        return self::construct_order_by($sess->sortby);
     }
 
     /**
-     * @param string $uniqueid used to identify the table you want the sql sort
-     * string for when method is called as a static method.
-     * @return string sql to put after ORDER BY or empty string if there is
-     * none.
+     * Prepare an an order by clause from the list of columns to be sorted.
+     * @param array $cols column name => SORT_ASC or SORT_DESC
+     * @return SQL fragment that can be used in an ORDER BY clause.
      */
-    function get_sql_sort($uniqueid = NULL) {
-        if($uniqueid === NULL) {
-            // "Non-static" function call
-            if(!$this->setup) {
-               return false;
+    public static function construct_order_by($cols) {
+        $bits = array();
+
+        foreach($cols as $column => $order) {
+            if ($order == SORT_ASC) {
+                $bits[] = $column . ' ASC';
+            } else {
+                $bits[] = $column . ' DESC';
             }
-            $sess = &$this->sess;
         }
-        else {
-            // "Static" function call
-            global $SESSION;
-            if(empty($SESSION->flextable[$uniqueid])) {
-               return '';
-            }
-            $sess = &$SESSION->flextable[$uniqueid];
+
+        return implode(', ', $bits);
+    }
+
+    /**
+     * @return SQL fragment that can be used in an ORDER BY clause.
+     */
+    public function get_sql_sort() {
+        return self::construct_order_by($this->get_sort_columns());
+    }
+
+    /**
+     * Get the columns to sort by, in the form required by {@link construct_order_by()}.
+     * @return array column name => SORT_... constant.
+     */
+    public function get_sort_columns() {
+        if (!$this->setup) {
+            throw new coding_exception('Cannot call get_sort_columns until you have called setup.');
         }
 
-        if(!empty($sess->sortby)) {
-            $sortstring = '';
-            foreach($sess->sortby as $column => $order) {
-                if(!empty($sortstring)) {
-                    $sortstring .= ', ';
-                }
-                $sortstring .= $column.($order == SORT_ASC ? ' ASC' : ' DESC');
-            }
-            return $sortstring;
+        if (empty($this->sess->sortby)) {
+            return array();
         }
-        return '';
+
+        return $this->sess->sortby;
     }
 
     /**

mod/assignment/lib.php

@@ -909,7 +909,7 @@ function display_submission($extra_javascript = '') {
                                                                       AND s.assignment = '.$this->assignment->id.' '.
                    'WHERE u.id IN ('.implode(',', $users).') ';
 
-            if ($sort = flexible_table::get_sql_sort('mod-assignment-submissions')) {
+            if ($sort = flexible_table::get_sort_for_table('mod-assignment-submissions')) {
                 $sort = 'ORDER BY '.$sort.' ';
             }