Use ChatGPT from Delphi

DelphiChatGPT.pas

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-----------------------------------------------------------------------------

Update #5: add support to select GPT model 3 or 4
Update #4: renamed to AskChatGTPv30 (text-davinci-003),
           AskChatGTPv35 (gpt-3.5-turbo)
Update #3: Added support for gpt-3.5-turbo modal (most up todate, 1/10 cost)
Update #2: Support for non-English languages (thanks Bear Xu)
Update #1: Fixed Json memory leak

-----------------------------------------------------------------------------
How to use:

Get your API Key:
  https://platform.openai.com/account/api-keys

...

uses
  DelphiChatGPT;

var
  LResponse: string;
begin
  LResponse := AskChatGTP(GPT4, YOU_API_KEY, 'What is Embarcadero Delphi');
  WriteLn(LResponse);
end;

Response:

 "Embarcadero Delphi is a rapid application development (RAD) tool for
  Windows, macOS, iOS, and Android. It is a programming language and software
  development kit (SDK) for creating applications for several platforms.
  Delphi is based on Object Pascal and is one of the oldest programming
  languages still in active use. It is used to create applications for
  desktop, mobile, web, and console."

*****************************************************************************)

unit DelphiChatGPT;

interface

type
  TChatGPTModel = (GPT3, GPT4);

function AskChatGPT(const aModel: TChatGPTModel; const aApiKey, aQuestion: string): string;

implementation

uses
  System.Generics.Collections,
  System.SysUtils,
  System.Classes,
  System.Net.HttpClient,
  System.Net.Mime,
  System.JSON;

function AskChatGPT(const aModel: TChatGPTModel; const aApiKey, aQuestion: string): string;
const
  cModel: array[GPT3 .. GPT4] of string = ('gpt-3.5-turbo', 'gpt-4');
var
  LHttpClient: THTTPClient;
  LString: string;
  LJson: TJsonObject;
  LMessages: TJsonArray;
  LMessage: TJsonObject;
  LChoices: TJsonArray;
  LChoice: TJsonObject;
  LText: TJsonObject;
  LPostDataStream: TStringStream;
  LResponse: IHTTPResponse;
begin
  LHttpClient := THTTPClient.Create;
  try
    LHttpClient.CustomHeaders['Authorization'] := 'Bearer ' + aApiKey;
    LHttpClient.CustomHeaders['Content-Type'] := 'application/json';
    LJson := TJsonObject.Create;
    try
      LMessages := TJsonArray.Create;
      try
        LMessage := TJsonObject.Create;
        try
          LMessage.AddPair('role', 'user');
          LMessage.AddPair('content', aQuestion);
          LMessages.Add(LMessage.Clone as TJsonObject);
        finally
          LMessage.Free;
        end;
        LJson.AddPair('model', cModel[aModel]);
        LJson.AddPair('messages', LMessages.Clone as TJsonArray);
        LString := LJson.ToString;
      finally
        LMessages.Free;
      end;
    finally
      LJson.Free;
    end;

    LPostDataStream := TStringStream.Create(LString, TEncoding.UTF8);
    try
      LPostDataStream.Position := 0;
      LResponse := LHttpClient.Post('https://api.openai.com/v1/chat/completions', LPostDataStream);
      LString := LResponse.ContentAsString;
    finally
      LPostDataStream.Free;
    end;
    LJson := TJsonObject.ParseJSONValue(LString) as TJsonObject;
    try
      if LResponse.StatusCode = 200 then
        begin
          LChoices := LJson.GetValue('choices') as TJsonArray;
          LChoice := LChoices.Items[0] as TJsonObject;
          LText := LChoice.GetValue('message') as TJsonObject;
          Result := LText.GetValue('content').Value;
        end
      else
        begin
          LChoice := LJson.GetValue('error') as TJsonObject;
          Result := 'Error: ' + LChoice.GetValue('message').Value;
        end;
    finally
      LJson.Free;
    end;
  finally
    LHttpClient.Free;
  end;
end;

end.