[+] check cron syntax and next runs asynchronously with 1s delay

Author: pashagolub

forms/framecroneditor.lfm

@@ -1,7 +1,15 @@
 inherited frmCronEditor: TfrmCronEditor
   Width = 472
   ClientWidth = 472
-  object pnlEditor: TPanel[0]
+  inherited pnlButtons: TPanel
+    Width = 472
+    ClientWidth = 472
+    inherited btnCancel: TButton
+      OnClick = FrameExit
+      OnExit = nil
+    end
+  end
+  object pnlEditor: TPanel[1]
     Left = 0
     Height = 304
     Top = 0
@@ -94,12 +102,10 @@ inherited frmCronEditor: TfrmCronEditor
       ParentColor = False
     end
   end
-  inherited pnlButtons: TPanel[1]
-    Width = 472
-    ClientWidth = 472
-    inherited btnCancel: TButton
-      OnClick = FrameExit
-      OnExit = nil
-    end
+  object timerChange: TTimer[2]
+    Enabled = False
+    OnTimer = timerChangeTimer
+    Left = 416
+    Top = 88
   end
 end

forms/framecroneditor.pas

@@ -22,7 +22,9 @@   TfrmCronEditor = class(TBaseFrame)
     lblMonth: TLabel;
     mmRuns: TMemo;
     pnlEditor: TPanel;
+    timerChange: TTimer;
     procedure edCronChange(Sender: TObject);
+    procedure timerChangeTimer(Sender: TObject);
   private
 
   public
@@ -40,39 +42,44 @@ implementation
 { TfrmCronEditor }
 
 procedure TfrmCronEditor.edCronChange(Sender: TObject);
+begin
+  timerChange.Enabled := True; //start timer to update next runs
+end;
+
+procedure TfrmCronEditor.timerChangeTimer(Sender: TObject);
 var
   ValidCron: boolean;
   S: string;
+  Output: string;
 const
   cronRE          = '^(((\d+,)+\d+|(\d+(\/|-)\d+)|(\*(\/|-)\d+)|\d+|\*) +){4}'+
                     '(((\d+,)+\d+|(\d+(\/|-)\d+)|(\*(\/|-)\d+)|\d+|\*) ?)$';
   sqlCronRuns     = 'SELECT to_char(r.r, ''FMDay, FMDD FMMon YYYY at HH24:MI:SS'') FROM '+
                     'generate_series(now(), now() + 10 * :cron :: interval, :cron :: interval) AS r(r) LIMIT 10';
   sqlIntervalRuns = 'SELECT to_char(r.r, ''FMDay, FMDD FMMon YYYY at HH24:MI:SS'') FROM '+
-                    'timetable.cron_runs(now(), $1) AS r(r) LIMIT 10';
+                    'timetable.cron_runs(now(), :cron) AS r(r) LIMIT 10';
   minIntervalLen  = length('@every '); // @ modifier and at least one space char
 begin
+  timerChange.Enabled := False;
   S := edCron.Text;
   ValidCron := S.Trim() = '@reboot';
   if not ValidCron then
     if S.StartsWith('@every ') or S.StartsWith('@after ') then //special values
-    begin
-      ValidCron := (S.Length > minIntervalLen) and dmPgEngine.IsCronValueValid(S);
-      if ValidCron then
-        mmRuns.Text := dmPgEngine.SelectSQL(sqlCronRuns, [S.Substring(minIntervalLen)]);
-    end
+      ValidCron := (S.Length > minIntervalLen)
+                   and dmPgEngine.IsCronValueValid(S)
+                   and dmPgEngine.SelectSQL(sqlCronRuns, [S.Substring(minIntervalLen)], Output)
   else
     with TRegExpr.Create(cronRE) do
     try
-      ValidCron := Exec(S);
-      if ValidCron then
-        mmRuns.Text := dmPgEngine.SelectSQL(sqlIntervalRuns, [S]);
+      ValidCron := Exec(S) and dmPgEngine.SelectSQL(sqlIntervalRuns, [S], Output);
     finally
       Free();
     end;
+  mmRuns.Text := Output;
   if ValidCron then edCron.Color := clDefault else edCron.Color := clRed;
 end;
 
+
 function TfrmCronEditor.GetEditorValue: string;
 begin
   Exit(edCron.Text);

udatamodule.pas

@@ -39,7 +39,7 @@   TdmPgEngine = class(TDataModule)
     procedure Disconnect;
     function IsCronValueValid(const S: string): boolean;
     function IsConnected: boolean;
-    function SelectSQL(const sql: string; params: array of string): string;
+    function SelectSQL(const sql: string; params: array of string; out Output: string): boolean;
     procedure MoveTaskUp(const ATaskID: integer);
     procedure MoveTaskDown(const ATaskID: integer);
     function IsTaskDeleteAllowed: boolean;
@@ -187,13 +187,13 @@ function TdmPgEngine.IsConnected: boolean;
   Result := qryChains.Active and qryTasks.Active;
 end;
 
-function TdmPgEngine.SelectSQL(const sql: string; params: array of string): string;
+function TdmPgEngine.SelectSQL(const sql: string; params: array of string; out Output: string): boolean;
 var
   Q: TSQLQuery;
   i: Integer;
-  NewParams: TSQLDBParams;
 begin
-  Result := '';
+  Result := True;
+  Output := '';
   Q := TSQLQuery.Create(nil);
   try
     Q.DataBase := connMain;
@@ -205,11 +205,18 @@ function TdmPgEngine.SelectSQL(const sql: string; params: array of string): stri
       Q.Open;
       while not Q.EOF do
       begin
-        Result := Result + Q.Fields[0].AsString + LineEnding;
+        Output := Output + Q.Fields[0].AsString + LineEnding;
         Q.Next;
       end;
-    except on E: exception do
-      connMainLog(connMain, detCustom, E.Message);
+    except
+      on E: Exception do
+      begin
+        Result := False;
+        if E is EPQDatabaseError then
+          Output := EPQDatabaseError(E).MESSAGE_PRIMARY
+        else
+          Output := E.Message;
+      end;
     end;
     Q.Close;
   finally