Fix sort parameters to use field aliases, validate in query object

Overall good, here's one small point:

- function get_solrsort();
+ function get_solrsort($as_array = FALSE);

Generally speaking, a function should have only one return type. I suggest doing something like:

function get_sort_column()

function get_sort_direction()

or always return a structure.

if (!empty($fv['apachesolr_search']['retain-filters']) && $fv['apachesolr_search']['querystring']) {
- $querystring = $fv['apachesolr_search']['querystring'] . '&retain-filters';
+ $querystring = $fv['apachesolr_search']['querystring'] . '&retain-filters=1';
}

This isn't really related, but whatever.

ummm.....

'type' => 'bigass'

?!?

+ $this->parse_sortstring($sortstring);

Too bad we don't have overloading in PHP. Really would be nicer as an overloaded set_solrsort.

public function set_available_sort($field, $sort) {
- $this->available_sorts[$field] = $sort;
+ public function set_available_sort($name, $sort) {
+ // We expect non-aliased sorts to be added.
+ $this->available_sorts[$name] = $sort;
+ }
+

A little unclear about this...

+ protected function parse_sortstring($sortstring) {
+ // Validate and set sort parameter
+ $fields = implode('|', array_keys($this->available_sorts));

Where is the | being used here? The function to set available sorts doesn't look like it would be expecting a pipe in the array key.

Looks good to me.