YwxApp.AiChat/Services/OpenAIService.cs

using System.Net.Http;
using System.Net.Http.Headers;
using System.Net.Http.Json;

namespace YwxApp.AiChat.Services
{
    public class OpenAIService : IChatService
    {
        private readonly HttpClient _httpClient;
        private string _modelName = "gpt-3.5-turbo";

        public OpenAIService()
        {
            _httpClient = new HttpClient();
            _httpClient.BaseAddress = new Uri("https://api.openai.com/v1/");
        }

        public void Configure(string apiKey, string modelName = "gpt-3.5-turbo")
        {
            _httpClient.DefaultRequestHeaders.Authorization =
                new AuthenticationHeaderValue("Bearer", apiKey);
            _modelName = modelName;
        }

        public async Task<string> GetResponseAsync(string prompt)
        {
            var requestBody = new
            {
                model = _modelName,
                messages = new[] { new { role = "user", content = prompt } }
            };

            var response = await _httpClient.PostAsJsonAsync("chat/completions", requestBody);
            var responseContent = await response.Content.ReadFromJsonAsync<OpenAIResponse>();

            return responseContent?.Choices[0].Message.Content ?? "No response";
        }

        public class Message
        {
            public string Content { get; set; }
        }
        public class Choice
        {
              public Message Message { get; set; }

        }
        private class OpenAIResponse
        {
            public Choice[] Choices { get; set; }
            
        }
    }
}