(Re)Add tracking of ticket history

Add a %ticket_history table to track ticket states over time, correlated to
the user account changing the ticket. Then, tickets are tracked to the table
when (re)opened, closed, overdue, transferred and assigned.

include/class.ticket.php

@@ -723,6 +723,7 @@ class Ticket{
 
         $sql.=' WHERE ticket_id='.db_input($this->getId());
 
+        $this->track('closed');
         return (db_query($sql) && db_affected_rows());
     }
 
@@ -736,6 +737,7 @@ class Ticket{
 
         //TODO: log reopen event here 
 
+        $this->track('reopened');
         return (db_query($sql) && db_affected_rows());
     }
 
@@ -1044,6 +1046,7 @@ class Ticket{
 
         $this->onOverdue($whine);
 
+        $this->track('overdue');
         return true;
     }
 
@@ -1109,6 +1112,7 @@ class Ticket{
             }
          }
 
+         $this->track('transferred');
          return true;
     }
 
@@ -1122,6 +1126,7 @@ class Ticket{
 
         $this->onAssign($note, $alert);
 
+        $this->track('assigned');
         return true;
     }
 
@@ -1140,6 +1145,7 @@ class Ticket{
 
         $this->onAssign($note, $alert);
 
+        $this->track('assigned');
         return true;
     }
 
@@ -1343,6 +1349,22 @@ class Ticket{
         return $this->postNote($title,$note,false,'system');
     }
 
+    // History log -- used for statistics generation (pretty reports)
+    function track($state, $staff=null) {
+        global $thisstaff;
+
+        if ($staff === null) {
+            if ($thisstaff) $staff=$thisstaff->getUserName();
+            else $staff='SYSTEM';               # XXX: Security Violation ?
+        }
+
+        return db_query('INSERT INTO '.TICKET_HISTORY_TABLE
+            .' SET ticket_id='.db_input($this->getId())
+            .', timestamp=NOW(), state='.db_input($state)
+            .', staff='.db_input($staff))
+            && db_affected_rows() == 1;
+    }
+
     //Insert Internal Notes 
     function postNote($title,$note,$alert=true,$poster='') {        
         global $thisstaff,$cfg;