//...
Console.Write("Enter chat message: ");
var prompt = Console.ReadLine();

// Anonymous type for the request body which feels bit "hinky" but, it works and is concise. Alternatively, could define a class for request body for better type safety and maintainability.
var requestObject = new
{
   model = settings.ModelName,
   messages = new[]
   {
      new { role = "user", content = prompt }
   }
};

// Alternatively, a JsonObject and JsonArray for more control over the JSON structure
var requestJson = new JsonObject()
{
   ["model"] = settings.ModelName,
   ["messages"] = new JsonArray
   {
      new JsonObject
      {
         ["role"] = "user",
         ["content"] = prompt
      }
   }
};

// Create HttpClient with required headers. Note that HttpClient should ideally be reused, but for simplicity we're creating a new instance here.
HttpClient httpClient = new()
{
   DefaultRequestHeaders =
   {
      Accept = { new MediaTypeWithQualityHeaderValue("application/json") },
      Authorization = new AuthenticationHeaderValue("Bearer", settings.ApiKey)
   },
   BaseAddress = new Uri(settings.BaseUrl)
};

using var httpResponse = await httpClient.PostAsync("chat/completions", new StringContent(JsonSerializer.Serialize(requestObject), Encoding.UTF8, "application/json"));

httpResponse.EnsureSuccessStatusCode();

using var stream = await httpResponse.Content.ReadAsStreamAsync();
using var responseDocument = await JsonDocument.ParseAsync(stream);

var content = responseDocument.RootElement.GetProperty("choices")[0].GetProperty("message").GetProperty("content").GetString();

Console.WriteLine(content);
Console.WriteLine();

var usage = responseDocument.RootElement.GetProperty("usage");
Console.WriteLine($"Prompt tokens: {usage.GetProperty("prompt_tokens").GetInt32()}");
Console.WriteLine($"Completion tokens: {usage.GetProperty("completion_tokens").GetInt32()}");
Console.WriteLine($"Total tokens: {usage.GetProperty("total_tokens").GetInt32()}");
Console.WriteLine();

Console.WriteLine("Press <Enter> to exit...");
Console.ReadLine();

// Create HttpClient with required headers. Note that HttpClient should ideally be reused, but for simplicity we're creating a new instance here..
using HttpClient httpClient = new()
{
   DefaultRequestHeaders =
   {
      Accept = { new MediaTypeWithQualityHeaderValue("application/json") },
      Authorization = new AuthenticationHeaderValue("Bearer", settings.ApiKey)
   },
   BaseAddress = new Uri(settings.BaseUrl)
};

var jsonSerializerOptions = new JsonSerializerOptions()
{
   // PropertyNamingPolicy removed - [JsonPropertyName] attributes on model handle wire names
   WriteIndented           = false,
   DefaultIgnoreCondition  = JsonIgnoreCondition.WhenWritingNull,
   AllowTrailingCommas     = false,
   ReadCommentHandling     = JsonCommentHandling.Disallow,
   UnmappedMemberHandling  = JsonUnmappedMemberHandling.Skip,
};

Console.Write("Enter chat message: ");
var content = Console.ReadLine();

while (!string.IsNullOrWhiteSpace(content))
{
   var request = new ChatCompletionRequest
   {
      Model = settings.ModelName,
      Messages =
      [
         new ChatMessage { Role = "user", Content = content }
      ],
   };

   try
   {
      using var httpResponse = await httpClient.PostAsJsonAsync("chat/completions", request, jsonSerializerOptions);
      httpResponse.EnsureSuccessStatusCode();

      ChatCompletionResponse? chatCompletionResponse = await httpResponse.Content.ReadFromJsonAsync<ChatCompletionResponse>(jsonSerializerOptions);

      if (chatCompletionResponse != null)
      {
         foreach (var choice in chatCompletionResponse.Choices)
         {
            Console.WriteLine(choice.Message.Content);
         }

         Console.WriteLine();
         if (chatCompletionResponse.Usage != null)
         {
            Console.WriteLine($"Prompt tokens: {chatCompletionResponse.Usage.PromptTokens}");
            Console.WriteLine($"Completion tokens: {chatCompletionResponse.Usage.CompletionTokens}");
            Console.WriteLine($"Total tokens: {chatCompletionResponse.Usage.TotalTokens}");
         }
         Console.WriteLine();
      }
   }
   catch (HttpRequestException ex)
   {
      Console.WriteLine($"Request failed: {(int?)ex.StatusCode} {ex.Message}");
   }
   catch (TaskCanceledException)
   {
      Console.WriteLine("Request timed out.");
   }
   catch (JsonException ex)
   {
      Console.WriteLine($"Failed to parse response: {ex.Message}");
   }

   Console.Write("Enter chat message: ");
   content = Console.ReadLine();
}

public sealed class ChatCompletionRequest
{
   [JsonPropertyName("model")] public required string Model { get; init; }
   [JsonPropertyName("messages")] public required List<ChatMessage> Messages { get; init; }
   [JsonPropertyName("temperature")] public double? Temperature { get; init; }
   [JsonPropertyName("max_tokens")] public int? MaxTokens { get; init; }
   [JsonPropertyName("stream")] public bool? Stream { get; init; }
   [JsonPropertyName("response_format")] public ResponseFormat? ResponseFormat { get; init; }
}

public sealed class ChatMessage
{
   [JsonPropertyName("role")] public required string Role { get; init; }
   [JsonPropertyName("content")] public required string Content { get; init; }
}

public sealed class ResponseFormat
{
   [JsonPropertyName("type")] public required string Type { get; init; }
}

public sealed class ChatCompletionResponse
{
   [JsonPropertyName("id")] public required string Id { get; init; }
   [JsonPropertyName("choices")] public required List<ChatCompletionChoice> Choices { get; init; }
   [JsonPropertyName("usage")] public TokenUsage? Usage { get; init; }
}

public sealed class TokenUsage
{
   [JsonPropertyName("prompt_tokens")] public int? PromptTokens { get; init; }
   [JsonPropertyName("completion_tokens")] public int? CompletionTokens { get; init; }
   [JsonPropertyName("total_tokens")] public int? TotalTokens { get; init; }
}

public sealed class ChatCompletionChoice
{
   [JsonPropertyName("index")] public int Index { get; init; }
   [JsonPropertyName("message")] public required ChatMessage Message { get; init; }
   [JsonPropertyName("finish_reason")] public string? FinishReason { get; init; }
}