Serving Your Personal Tutor with a RESTful API

Serving Your Personal Tutor with a RESTful API Using ASP.NET Core Web API

Welcome to the next step in our journey of building a personal tutor service with ASP.NET Core Web API . In the previous lesson, we focused on the TutorController, which manages tutoring sessions and handles student queries by interacting with both the model and service layers. Now, we will take a significant step forward by creating a RESTful API for our personal tutor service using ASP.NET Core . We'll start by setting up the main ASP.NET Core Web API application, then adapt the TutorController to integrate with ASP.NET Core's session management. Note, that session-based state is used instead of stateless authentication like JWTs because it allows the server to easily manage user-specific data (such as tutoring sessions and conversation history) without requiring the client to handle or resend this information with every request. This simplifies state management for applications that need to track ongoing user interactions.

Understanding RESTful APIs and ASP.NET Core Web API

RESTful APIs are a way for different software systems to communicate over the internet using standard HTTP methods such as GET, POST, PUT, and DELETE . They provide a set of rules that allow programs to exchange data in a structured and predictable way, typically using JSON as the data format. ASP.NET Core Web API is a modern, high-performance framework for building RESTful APIs with C# . It provides a robust set of tools for routing, model binding, validation, dependency injection, and more. With ASP.NET Core, you can easily expose your application's functionality as a web API that can be consumed by web clients, mobile apps, or other services.

Initializing the ASP.NET Core Web API Project

Join the 1M+ learners on CodeSignal

Be a part of our community of 1M+ users who develop and demonstrate their skills on CodeSignal

Shell

dotnet new webapi -n PersonalTutor

using Microsoft.AspNetCore.Builder;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.DependencyInjection;
using PersonalTutor.Controllers;
using PersonalTutor.Services;

var builder = WebApplication.CreateBuilder(args);

// Configure services
builder.Services.AddEndpointsApiExplorer();

// Add session services
builder.Services.AddDistributedMemoryCache();
builder.Services.AddSession(options =>
{
    options.IdleTimeout = TimeSpan.FromMinutes(30);
    options.Cookie.HttpOnly = true;
    options.Cookie.IsEssential = true;
});

// Register TutorService and TutorController as scoped
builder.Services.AddScoped<TutorService>();
builder.Services.AddScoped<TutorController>();

// Register SessionManager as scoped
builder.Services.AddScoped<SessionManager>();

// Configure host and port
builder.WebHost.ConfigureKestrel(serverOptions =>
{
    serverOptions.ListenAnyIP(3000);
});

using System.Text.Json;

var app = builder.Build();

// Use session middleware
app.UseSession();

using System.Text.Json;

var app = builder.Build();

// Use session middleware
app.UseSession();

app.MapGet("/", (HttpContext context) => 
{
    var sessionManager = context.RequestServices.GetRequiredService<SessionManager>();
    sessionManager.EnsureUserSession(context.Session);
    return "Welcome to the Personal Tutor Service!";
});

app.MapGet("/", (HttpContext context) => 
{
    var sessionManager = context.RequestServices.GetRequiredService<SessionManager>();
    sessionManager.EnsureUserSession(context.Session);
    return "Welcome to the Personal Tutor Service!";
});

app.MapPost("/api/create_session", (HttpContext context) =>
{
    var sessionManager = context.RequestServices.GetRequiredService<SessionManager>();
    var tutorController = context.RequestServices.GetRequiredService<TutorController>();
    var userId = sessionManager.GetUserId(context.Session);
    if (string.IsNullOrEmpty(userId))
    {
        return new { data = (object)null, error = "Session expired", status = 401 };
    }
    return tutorController.CreateSession(userId);
});

app.MapPost("/api/create_session", (HttpContext context) =>
{
    var sessionManager = context.RequestServices.GetRequiredService<SessionManager>();
    var tutorController = context.RequestServices.GetRequiredService<TutorController>();
    var userId = sessionManager.GetUserId(context.Session);
    if (string.IsNullOrEmpty(userId))
    {
        return new { data = (object)null, error = "Session expired", status = 401 };
    }
    return tutorController.CreateSession(userId);
});

app.MapPost("/api/send_query", async (HttpContext context) =>
{
    var sessionManager = context.RequestServices.GetRequiredService<SessionManager>();
    var tutorController = context.RequestServices.GetRequiredService<TutorController>();
    using var reader = new StreamReader(context.Request.Body);
    var body = await reader.ReadToEndAsync();

    if (string.IsNullOrWhiteSpace(body))
    {
        context.Response.StatusCode = 400;
        await context.Response.WriteAsJsonAsync(new { data = (object)null, error = "Empty request body", status = 400 });
        return;
    }

    JsonElement data;
    try
    {
        data = JsonSerializer.Deserialize<JsonElement>(body);
    }
    catch (JsonException)
    {
        context.Response.StatusCode = 400;
        await context.Response.WriteAsJsonAsync(new { data = (object)null, error = "Invalid JSON", status = 400 });
        return;
    }

    var userId = sessionManager.GetUserId(context.Session);
    if (string.IsNullOrEmpty(userId))
    {
        context.Response.StatusCode = 401;
        await context.Response.WriteAsJsonAsync(new { data = (object)null, error = "Session expired", status = 401 });
        return;
    }

    var result = await tutorController.SendQuery(userId, data);
    if (result is { status: int statusCode })
    {
        context.Response.StatusCode = statusCode;
    }
    await context.Response.WriteAsJsonAsync(result);
});

// Run the application
app.Run();

app.MapPost("/api/send_query", async (HttpContext context) =>
{
    var sessionManager = context.RequestServices.GetRequiredService<SessionManager>();
    var tutorController = context.RequestServices.GetRequiredService<TutorController>();
    using var reader = new StreamReader(context.Request.Body);
    var body = await reader.ReadToEndAsync();

    if (string.IsNullOrWhiteSpace(body))
    {
        context.Response.StatusCode = 400;
        await context.Response.WriteAsJsonAsync(new { data = (object)null, error = "Empty request body", status = 400 });
        return;
    }

    JsonElement data;
    try
    {
        data = JsonSerializer.Deserialize<JsonElement>(body);
    }
    catch (JsonException)
    {
        context.Response.StatusCode = 400;
        await context.Response.WriteAsJsonAsync(new { data = (object)null, error = "Invalid JSON", status = 400 });
        return;
    }

    var userId = sessionManager.GetUserId(context.Session);
    if (string.IsNullOrEmpty(userId))
    {
        context.Response.StatusCode = 401;
        await context.Response.WriteAsJsonAsync(new { data = (object)null, error = "Session expired", status = 401 });
        return;
    }

    var result = await tutorController.SendQuery(userId, data);
    if (result is { status: int statusCode })
    {
        context.Response.StatusCode = statusCode;
    }
    await context.Response.WriteAsJsonAsync(result);
});

// Run the application
app.Run();

builder.Services.AddDistributedMemoryCache();
builder.Services.AddSession(options =>
{
    options.IdleTimeout = TimeSpan.FromMinutes(30);
    options.Cookie.HttpOnly = true;
    options.Cookie.IsEssential = true;
});

builder.Services.AddDistributedMemoryCache();
builder.Services.AddSession(options =>
{
    options.IdleTimeout = TimeSpan.FromMinutes(30);
    options.Cookie.HttpOnly = true;
    options.Cookie.IsEssential = true;
});

app.UseSession();

using System;
using System.Text.Json;
using System.Threading.Tasks;
using PersonalTutor.Services;

namespace PersonalTutor.Controllers
{
    public class TutorController
    {
        private readonly TutorService _tutorService;

        public TutorController(TutorService tutorService)
        {
            _tutorService = tutorService;
        }
        
        public object CreateSession(string userId)
        {
            if (string.IsNullOrEmpty(userId))
            {
                return new { data = (object)null, error = "Session expired", status = 401 };
            }
            var chatId = _tutorService.CreateSession(userId);
            return new
            {
                data = new { session_id = chatId, message = "Tutoring session created successfully" },
                error = (string)null,
                status = 200
            };
        }
        
        public async Task<object> SendQuery(string userId, JsonElement data)
        {
            if (string.IsNullOrEmpty(userId))
            {
                return new { data = (object)null, error = "Session expired", status = 401 };
            }
            
            string sessionId = "";
            string userQuery = "";
            
            if (data.TryGetProperty("session_id", out var sessionIdElement))
            {
                sessionId = sessionIdElement.GetString();
            }
            
            if (data.TryGetProperty("query", out var queryElement))
            {
                userQuery = queryElement.GetString();
            }
            
            if (string.IsNullOrEmpty(sessionId) || string.IsNullOrEmpty(userQuery))
            {
                return new { data = (object)null, error = "Missing session_id or query", status = 400 };
            }
                
            try
            {
                var aiResponse = await _tutorService.ProcessQuery(userId, sessionId, userQuery);
                return new { data = new { response = aiResponse }, error = (string)null, status = 200 };
            }
            catch (ArgumentException e)
            {
                return new { data = (object)null, error = e.Message, status = 404 };
            }
            catch (Exception e)
            {
                return new { data = (object)null, error = e.Message, status = 500 };
            }
        }
    }
}

using System;
using System.Text.Json;
using System.Threading.Tasks;
using PersonalTutor.Services;

namespace PersonalTutor.Controllers
{
    public class TutorController
    {
        private readonly TutorService _tutorService;

        public TutorController(TutorService tutorService)
        {
            _tutorService = tutorService;
        }
        
        public object CreateSession(string userId)
        {
            if (string.IsNullOrEmpty(userId))
            {
                return new { data = (object)null, error = "Session expired", status = 401 };
            }
            var chatId = _tutorService.CreateSession(userId);
            return new
            {
                data = new { session_id = chatId, message = "Tutoring session created successfully" },
                error = (string)null,
                status = 200
            };
        }
        
        public async Task<object> SendQuery(string userId, JsonElement data)
        {
            if (string.IsNullOrEmpty(userId))
            {
                return new { data = (object)null, error = "Session expired", status = 401 };
            }
            
            string sessionId = "";
            string userQuery = "";
            
            if (data.TryGetProperty("session_id", out var sessionIdElement))
            {
                sessionId = sessionIdElement.GetString();
            }
            
            if (data.TryGetProperty("query", out var queryElement))
            {
                userQuery = queryElement.GetString();
            }
            
            if (string.IsNullOrEmpty(sessionId) || string.IsNullOrEmpty(userQuery))
            {
                return new { data = (object)null, error = "Missing session_id or query", status = 400 };
            }
                
            try
            {
                var aiResponse = await _tutorService.ProcessQuery(userId, sessionId, userQuery);
                return new { data = new { response = aiResponse }, error = (string)null, status = 200 };
            }
            catch (ArgumentException e)
            {
                return new { data = (object)null, error = e.Message, status = 404 };
            }
            catch (Exception e)
            {
                return new { data = (object)null, error = e.Message, status = 500 };
            }
        }
    }
}

using System.Text.Json;

var app = builder.Build();

// Use session middleware
app.UseSession();

app.MapGet("/", (HttpContext context) => 
{
    var sessionManager = context.RequestServices.GetRequiredService<SessionManager>();
    sessionManager.EnsureUserSession(context.Session);
    return "Welcome to the Personal Tutor Service!";
});

app.MapPost("/api/create_session", (HttpContext context) =>
{
    var sessionManager = context.RequestServices.GetRequiredService<SessionManager>();
    var tutorController = context.RequestServices.GetRequiredService<TutorController>();
    var userId = sessionManager.GetUserId(context.Session);
    if (string.IsNullOrEmpty(userId))
    {
        return new { data = (object)null, error = "Session expired", status = 401 };
    }
    return tutorController.CreateSession(userId);
});

app.MapPost("/api/send_query", async (HttpContext context) =>
{
    var sessionManager = context.RequestServices.GetRequiredService<SessionManager>();
    var tutorController = context.RequestServices.GetRequiredService<TutorController>();
    using var reader = new StreamReader(context.Request.Body);
    var body = await reader.ReadToEndAsync();

    if (string.IsNullOrWhiteSpace(body))
    {
        context.Response.StatusCode = 400;
        await context.Response.WriteAsJsonAsync(new { data = (object)null, error = "Empty request body", status = 400 });
        return;
    }

    JsonElement data;
    try
    {
        data = JsonSerializer.Deserialize<JsonElement>(body);
    }
    catch (JsonException)
    {
        context.Response.StatusCode = 400;
        await context.Response.WriteAsJsonAsync(new { data = (object)null, error = "Invalid JSON", status = 400 });
        return;
    }

    var userId = sessionManager.GetUserId(context.Session);
    if (string.IsNullOrEmpty(userId))
    {
        context.Response.StatusCode = 401;
        await context.Response.WriteAsJsonAsync(new { data = (object)null, error = "Session expired", status = 401 });
        return;
    }

    var result = await tutorController.SendQuery(userId, data);
    if (result is { status: int statusCode })
    {
        context.Response.StatusCode = statusCode;
    }
    await context.Response.WriteAsJsonAsync(result);
});

// Run the application
app.Run();

builder.Services.AddDistributedMemoryCache();
builder.Services.AddSession(options =>
{
    options.IdleTimeout = TimeSpan.FromMinutes(30);
    options.Cookie.HttpOnly = true;
    options.Cookie.IsEssential = true;
});

app.UseSession();

using System;
using System.Text.Json;
using System.Threading.Tasks;
using PersonalTutor.Services;

namespace PersonalTutor.Controllers
{
    public class TutorController
    {
        private readonly TutorService _tutorService;

        public TutorController(TutorService tutorService)
        {
            _tutorService = tutorService;
        }
        
        public object CreateSession(string userId)
        {
            if (string.IsNullOrEmpty(userId))
            {
                return new { data = (object)null, error = "Session expired", status = 401 };
            }
            var chatId = _tutorService.CreateSession(userId);
            return new
            {
                data = new { session_id = chatId, message = "Tutoring session created successfully" },
                error = (string)null,
                status = 200
            };
        }
        
        public async Task<object> SendQuery(string userId, JsonElement data)
        {
            if (string.IsNullOrEmpty(userId))
            {
                return new { data = (object)null, error = "Session expired", status = 401 };
            }
            
            string sessionId = "";
            string userQuery = "";
            
            if (data.TryGetProperty("session_id", out var sessionIdElement))
            {
                sessionId = sessionIdElement.GetString();
            }
            
            if (data.TryGetProperty("query", out var queryElement))
            {
                userQuery = queryElement.GetString();
            }
            
            if (string.IsNullOrEmpty(sessionId) || string.IsNullOrEmpty(userQuery))
            {
                return new { data = (object)null, error = "Missing session_id or query", status = 400 };
            }
                
            try
            {
                var aiResponse = await _tutorService.ProcessQuery(userId, sessionId, userQuery);
                return new { data = new { response = aiResponse }, error = (string)null, status = 200 };
            }
            catch (ArgumentException e)
            {
                return new { data = (object)null, error = e.Message, status = 404 };
            }
            catch (Exception e)
            {
                return new { data = (object)null, error = e.Message, status = 500 };
            }
        }
    }
}

Serving Your Personal Tutor with a RESTful API Using ASP.NET Core Web API

Understanding RESTful APIs and ASP.NET Core Web API

Initializing the ASP.NET Core Web API Project

Join the 1M+ learners on CodeSignal

Building the App and Defining Routes

Adding Session Management with ASP.NET Core Middleware

Creating the TutorController

Defining Request Models and Handling JSON

Managing Student Sessions

Summary and Next Steps