KLib.Windows.EventLog.pas

{
  KLib Version = 3.0
  The Clear BSD License

  Copyright (c) 2020 by Karol De Nery Ortiz LLave. All rights reserved.
  zitrokarol@gmail.com

  Redistribution and use in source and binary forms, with or without
  modification, are permitted (subject to the limitations in the disclaimer
  below) provided that the following conditions are met:

  * Redistributions of source code must retain the above copyright notice,
  this list of conditions and the following disclaimer.

  * Redistributions in binary form must reproduce the above copyright
  notice, this list of conditions and the following disclaimer in the
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  software without specific prior written permission.

  NO EXPRESS OR IMPLIED LICENSES TO ANY PARTY'S PATENT RIGHTS ARE GRANTED BY
  THIS LICENSE. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
  CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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  PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
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}

unit KLib.Windows.EventLog;

interface

type
  TEventLog = class
  private
    handle: THandle;
    procedure checkEventLogHandle;
    procedure Write(entryType: Word; eventId: Cardinal; value: string);
  public
    applicationName: string;

    constructor Create(applicationName: string);
    procedure writeInfo(value: string);
    procedure writeWarning(value: string);
    procedure writeError(value: string);
    class procedure addEventApplicationToRegistry(applicationName: string; fileName: string); // Requires admin rights. Typically called once-off during the application's installation
    class procedure deleteEventApplicationFromRegistry(applicationName: string); // Requires admin rights.
    class function getRegistryKey(applicationName: string): string;
    destructor Destroy; overload; override;
  end;

implementation

uses
  KLib.Windows, KLib.Constants,
  Winapi.Windows,
  System.Win.Registry,
  System.SysUtils;

constructor TEventLog.Create(applicationName: string);
begin
  Self.applicationName := applicationName;
end;

procedure TEventLog.writeInfo(value: string);
begin
  Write(EVENTLOG_INFORMATION_TYPE, 1, value);
end;

procedure TEventLog.writeWarning(value: string);
begin
  Write(EVENTLOG_WARNING_TYPE, 2, value);
end;

procedure TEventLog.writeError(value: string);
begin
  Write(EVENTLOG_ERROR_TYPE, 3, value);
end;

procedure TEventLog.checkEventLogHandle;
begin
  if handle = 0 then
  begin
    handle := RegisterEventSource(nil, PChar(applicationName));
  end;
  if handle <= 0 then
  begin
    raise Exception.Create('Could not obtain Event Log handle.');
  end;
end;

procedure TEventLog.Write(entryType: Word; eventId: Cardinal; value: string);
begin
  checkEventLogHandle;
  ReportEvent(handle, entryType, 0, eventId, nil, 1, 0, @value, nil);
end;

class procedure TEventLog.addEventApplicationToRegistry(applicationName: string; fileName: string);
const
  ERR_MSG = 'Error updating the registry. This action requires administrative rights: ';
var
  _regKey: string;
begin
  _regKey := getRegistryKey(applicationName);
  try
    writeIn_HKEY_LOCAL_MACHINE(_regKey, 'EventMessageFile', fileName, FORCE);
    writeIn_HKEY_LOCAL_MACHINE(_regKey, 'TypesSupported', 7, FORCE);
  except
    on E: Exception do
    begin
      raise Exception.Create(ERR_MSG + e.Message);
    end;
  end;
end;

class procedure TEventLog.deleteEventApplicationFromRegistry(applicationName: string);
var
  _regKey: string;
begin
  _regKey := getRegistryKey(applicationName);
  deleteKeyInHKEY_LOCAL_MACHINE(_regKey);
end;

class function TEventLog.getRegistryKey(applicationName: string): string;
var
  regKey: string;
begin
  regKey := EVENTLOG_APPLICATION_REGKEY + '\' + applicationName;

  Result := regKey;
end;

destructor TEventLog.Destroy;
begin
  if handle > 0 then
  begin
    DeregisterEventSource(handle);
  end;
end;

end.