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//
// header file ...
//
typedef void __fastcall (__closure *TSearchURLEvent)(TObject *Sender, const String URL);
typedef void __fastcall (__closure *TURLErrorEvent)(TObject *Sender, const String URL, const String Msg);

class TWebRobot : public TThread
{
private:
    TIdHTTP    *        FHTTP;
    TURLErrorEvent    FURLErrorEvent;
    int                FSleepTime;
    TSearchURLEvent    FSearchURLEvent;
   
    void __fastcall UpdateURL(const String URL);
    void __fastcall UpdateError(const String Msg);
   
protected:
    void __fastcall URLCallback();
    void __fastcall ErrorCallback();
   
public:
    __fastcall TWebRobot();
    virtual __fastcall ~TWebRobot();
   
    String __fastcall GetURLText(const String URL);
   
public:
    __property int SleepTime = {read = FSleepTime, write = FSleepTime};
    __property TSearchURLEvent OnSearchURL = {read = FOnSearchURL, write = FOnSearchURL};
    __property TURLErrorEvent OnURLError = {read = FOnURLError, write = FOnURLError};
};

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extern String CurrentURL;
extern String ErrorMsg;
extern RTL_CRITICAL_SECTION    CriticalSection;

//
// cpp file ....
//
String CurrentURL = "";
String ErrorMsg = "";
RTL_CRITICAL_SECTION    CriticalSection = {0, };

//----------------------------------------------------------------------------
__fastcall TWebRobot::TWebRobot() : TThread(true)
{
    FSleepTime = 3000;
    FHTTP = new TIdHTTP(NULL);
    FHTTP->Request->UserAgent = "DevBot";
    FHTTP->ReadTimeout = 10000;
    FreeOnTerminate = true;
    ::InitializeCriticalSection(&CriticalSection);
}
//----------------------------------------------------------------------------
__fastcall TWebRobot::~TWebRobot()
{
    FHTTP->Free();
    ::DeleteCriticalSection(&CriticalSection);
}
//----------------------------------------------------------------------------
void __fastcall TWebRobot::ErrorCallback()
{
    if(FURLErrorEvent)
        FURLErrorEvent(this, CurrentURL, ErrorMsg);
}
//----------------------------------------------------------------------------
String __fastcall TWebRobot::GetURLText(const String URL)
{
    try
    {
        UpdateURL(URL);
        Synchronize(URLCallback);
        return FHTTP->Get(URL);
    }
    catch(Exception &E)
    {
        UpdateError(E.Message);
        Synchronize(ErrorCallback);
        return "";
    }
}
//----------------------------------------------------------------------------
void __fastcall TWebRobot::UpdateError(const String Msg)
{
    ::EnterCriticalSection(&CriticalSection);
    try
    {
        ErrorMsg = Msg;
    }
    __finally
    {
        ::LeaveCriticalSection(&CriticalSection);
    }
}
//----------------------------------------------------------------------------
void __fastcall TWebRobot::UpdateURL(const String URL)
{
    ::EnterCriticalSection(&CriticalSection);
    try
    {
        CurrentURL = URL;
    }
    __finally
    {
        ::LeaveCriticalSection(&CriticalSection);
    }
}
//----------------------------------------------------------------------------
void __fastcall TWebRobot::URLCallback()
{
    if(FSearchURLEvent)
        FSearchURLEvent(this, CurrentURL);
}
//----------------------------------------------------------------------------