{ cron_task -- minimal example: schedule a daily 3 AM cron task
  and verify the cron expression matches the expected times.

  Build:
    bash build.sh
    /opt/fpcup/fpc/bin/x86_64-linux/fpc -O2 -Sh \
        -Fusrc -Fu../fpc-db/src -Fu../fpc-events/src \
        -FUbuild -FEbuild -obuild/cron_task examples/cron_task.pas

  Run:
    ./build/cron_task }

program cron_task;

{$mode objfpc}{$H+}

uses
  {$IFDEF UNIX}cthreads,{$ENDIF}
  Classes, SysUtils, DateUtils,
  database.types, database.pool,
  log.types, cron.types, cron.runner;

type
  THost = class
  public
    procedure RunTask(const APluginName, ATaskName: string);
    procedure Log(Level: TLogLevel; const Category, Msg: string);
  end;

procedure THost.RunTask(const APluginName, ATaskName: string);
begin
  Writeln('--> ', APluginName, '/', ATaskName);
end;

procedure THost.Log(Level: TLogLevel; const Category, Msg: string);
begin
  Writeln('[', LogLevelChar(Level), '] ', Category, ': ', Msg);
end;

var
  Pool:  TDBPool;
  Sched: TCron;
  Host:  THost;
  T1, T2: TDateTime;
  DBFile: string;
begin
  Writeln('cron expression sanity check (no DB, no thread):');
  T1 := EncodeDate(2026, 5, 5) + EncodeTime(3, 0, 0, 0);
  T2 := EncodeDate(2026, 5, 5) + EncodeTime(3, 1, 0, 0);
  Writeln('  "0 3 * * *" matches 03:00 = ',
          TCron.MatchesCron('0 3 * * *', T1));
  Writeln('  "0 3 * * *" matches 03:01 = ',
          TCron.MatchesCron('0 3 * * *', T2));

  Writeln;
  Writeln('persisting a cron task in system_scheduler:');
  DBFile := '/tmp/fpcsched_cron_' + IntToStr(GetProcessID) + '.sqlite3';
  if FileExists(DBFile) then DeleteFile(DBFile);

  Pool := TDBPool.Create;
  Pool.Init(dbSQLite, DBFile);
  Host := THost.Create;
  try
    Sched := TCron.Create(Pool, @Host.RunTask, nil, @Host.Log);
    try
      Pool.ExecSQL(
        'INSERT INTO system_scheduler ' +
        '(task_name, plugin_name, schedule_type, cron_expr, enabled, ' +
        ' description) VALUES ' +
        '(''nightly'', ''demo'', ''cron'', ''0 3 * * *'', 1, ''nightly run'')');
      Sched.RefreshTasks;
      Writeln('  scheduled -- next_run computed and stored in DB');
    finally
      Sched.Free;
    end;
  finally
    Host.Free;
    Pool.Free;
    DeleteFile(DBFile);
  end;
end.