1:  2:  3:  4:  5:  6:  7:  8:  9: 10: 11: 12: 13: 14: 15: 16: 17: 18: 19: 20: 21: 22: 23: 24: 25: 26: 27: 28: 29: 30: 31: 32: 33: 34: 35: 36: 37: 38: 39: 40: 41: 42: 43: 44: 45: 46: 47: 48: 49: 50: 51: 52: 53: 54: 55: 56: 57: 58: 59: 60: 61: 62: 63: 64: 65: 66: 67: 68: 69: 70: 71: 72: 73: 74: 75: 76: 77: 78: 79: 80: 81: 82: 83: 

<?php
class Item_quantity extends CI_Model
{
    public function exists($item_id, $location_id)
    {
        $this->db->from('item_quantities');
        $this->db->where('item_id', $item_id);
        $this->db->where('location_id', $location_id);

        return ($this->db->get()->num_rows() == 1);
    }
    
    public function save($location_detail, $item_id, $location_id)
    {
        if(!$this->exists($item_id, $location_id))
        {
            return $this->db->insert('item_quantities', $location_detail);
        }

        $this->db->where('item_id', $item_id);
        $this->db->where('location_id', $location_id);

        return $this->db->update('item_quantities', $location_detail);
    }
    
    public function get_item_quantity($item_id, $location_id)
    {     
        $this->db->from('item_quantities');
        $this->db->where('item_id', $item_id);
        $this->db->where('location_id', $location_id);
        $result = $this->db->get()->row();
        if(empty($result) == TRUE)
        {
            //Get empty base parent object, as $item_id is NOT an item
            $result = new stdClass();

            //Get all the fields from items table (TODO to be reviewed)
            foreach($this->db->list_fields('item_quantities') as $field)
            {
                $result->$field = '';
            }

            $result->quantity = 0;
        }
        
        return $result;   
    }
    
    /*
     * changes to quantity of an item according to the given amount.
     * if $quantity_change is negative, it will be subtracted,
     * if it is positive, it will be added to the current quantity
     */
    public function change_quantity($item_id, $location_id, $quantity_change)
    {
        $quantity_old = $this->get_item_quantity($item_id, $location_id);
        $quantity_new = $quantity_old->quantity + intval($quantity_change);
        $location_detail = array('item_id' => $item_id, 'location_id' => $location_id, 'quantity' => $quantity_new);

        return $this->save($location_detail, $item_id, $location_id);
    }
    
    /*
    * Set to 0 all quantity in the given item
    */
    public function reset_quantity($item_id)
    {
        $this->db->where('item_id', $item_id);

        return $this->db->update('item_quantities', array('quantity' => 0));
    }
    
    /*
    * Set to 0 all quantity in the given list of items
    */
    public function reset_quantity_list($item_ids)
    {
        $this->db->where_in('item_id', $item_ids);

        return $this->db->update('item_quantities', array('quantity' => 0));
    }
}
?>