Added functions to get information about:

- active time of a member
  - state of a member
  - joining date of a member
... and a method to fetch all active people.

app/Person.php

@@ -3,8 +3,82 @@
 namespace App;
 
 use Illuminate\Database\Eloquent\Model;
+use Carbon\Carbon;
+use App\MemberState;
 
 class Person extends Model
 {
-    //
+    /*
+     * Return true, if the person is active member, return false otherwise.
+     *
+     * @return boolean
+     */
+    public function isActiveMember()
+    {
+        $latest = $this->hasMany('\App\MemberState')
+                       ->orderBy('joining_date', 'desc')
+                       ->first();
+    
+        if (is_null($latest)) {
+            return false;
+        } else {
+            return is_null($latest['leaving_date']);
+        }
+    }
+
+    /*
+     * Return a collection of all persons which are active members.
+     *
+     * @return Illuminate\Database\Eloquent\Collection
+     */
+    public static function active()
+    {
+        return Person::join('member_states', 'people.id', '=', 'member_states.person_id')
+                     ->where('member_states.leaving_date', null)
+                     ->select('person_id as id', 'title', 'name_or_company',
+                              'surname', 'date_of_birth', 'city', 'street',
+                              'postal_code', 'email', 'mobile', 'phone',
+                              'people.created_at', 'people.updated_at')
+                     ->get();
+    }
+
+    /*
+     * Return the last date since when the person is an active member.
+     * 
+     * @return Carbon\Carbon
+     */
+    public function activeSince()
+    {
+        $latest = $this->hasMany('\App\MemberState')
+                       ->orderBy('joining_date', 'desc')
+                       ->first();
+    
+        return Carbon::parse($latest['joining_date']);
+    }
+
+    /*
+     * Returns the active time of the person until now in years.
+     *
+     * @return float
+     */
+    public function activeTime()
+    {
+        $activeTimes = $this->hasMany('\App\MemberState')->get();
+        
+        $diff = 0;
+
+        foreach ($activeTimes as $period) {
+            $start = Carbon::parse($period['joining_date']);
+            $end = is_null($period['leaving_date']) ?
+                   Carbon::now() :
+                   Carbon::parse($period['leaving_date']);
+            
+            $diffYears = Carbon::parse($start)->diffInYears($end);
+            $diffDays = Carbon::parse($start)->diffInDays($end);
+
+            $diff += $diffYears + $diffDays / 365 - $diffYears;
+        }
+
+        return $diff;
+    }
 }