Building the Tutor Service Layer in C#

using System;
using System.IO;
using System.Net.Http;
using PersonalTutor.Models;

namespace PersonalTutor.Services
{
    public class TutorService
    {
        private SessionManager sessionManager;
        private HttpClient httpClient;
        private string systemPrompt;

        public TutorService()
        {
            sessionManager = new SessionManager();
            httpClient = new HttpClient();
            systemPrompt = LoadSystemPrompt("data/system_prompt.txt");
        }

        // ... other methods will be added here
    }
}

public async Task<string> ProcessQuery(string studentId, string sessionId, string query)
{
    var session = sessionManager.GetSession(studentId, sessionId);
    if (session == null)
    {
        throw new ArgumentException("Session not found");
    }

    // Add student query
    sessionManager.AddMessage(studentId, sessionId, "user", query);

    try
    {
        // Retrieve the conversation using the SessionManager
        var conversation = sessionManager.GetConversation(studentId, sessionId)
            .Select(msg => new { role = msg.Role, content = msg.Content })
            .ToArray();

        // Prepare API key and endpoint
        var apiKey = Environment.GetEnvironmentVariable("OPENAI_API_KEY");
        var baseUri = Environment.GetEnvironmentVariable("OPENAI_BASE_URL");
        if (string.IsNullOrEmpty(apiKey))
        {
            throw new InvalidOperationException("OPENAI_API_KEY environment variable is not set.");
        }
        if (string.IsNullOrEmpty(baseUri))
        {
            throw new InvalidOperationException("OPENAI_BASE_URL environment variable is not set.");
        }
        var endpoint = baseUri.TrimEnd('/') + "/v1/chat/completions";

        // Prepare payload
        var payload = new
        {
            model = "deepseek-ai/DeepSeek-V3",
            messages = conversation,
            temperature = 0.7,
            max_tokens = 500
        };
        var jsonPayload = JsonSerializer.Serialize(payload);

        // Prepare HTTP request
        using var request = new HttpRequestMessage(HttpMethod.Post, endpoint);
        request.Headers.Authorization = new AuthenticationHeaderValue("Bearer", apiKey);
        request.Content = new StringContent(jsonPayload, Encoding.UTF8, "application/json");

        // Send request
        var response = await httpClient.SendAsync(request);
        var body = await response.Content.ReadAsStringAsync();

        if (!response.IsSuccessStatusCode)
        {
            throw new InvalidOperationException($"Error from DeepSeek API ({response.StatusCode}): {body}");
        }

        using var doc = JsonDocument.Parse(body);
        var aiMessage = doc.RootElement
                           .GetProperty("choices")[0]
                           .GetProperty("message")
                           .GetProperty("content")
                           .GetString()
                           ?.Trim() ?? "";

        // Add AI response to session history
        sessionManager.AddMessage(studentId, sessionId, "assistant", aiMessage);

        return aiMessage;
    }
    catch (Exception e)
    {
        throw new InvalidOperationException($"Error getting AI response: {e.Message}");
    }
}