using System;
using System.Text.Json;

namespace perubahan;

public static class Auth
{
    internal static bool TryGetUser(HttpContext context, out SafeUser user)
    {
        if (context.Items.TryGetValue("AuthorizedUser", out object? userObj) && userObj is SafeUser safeUser)
        {
            user = safeUser;
            return true;
        }
        
        user = null!;
        return false;
    }

    internal static bool IsAuthorized(HttpContext context, int requiredLevel)
    {
        return TryGetUser(context, out SafeUser user) && user.Level <= requiredLevel;
    }

    internal static Task RejectUnauthorized(HttpContext context)
    {
        context.Response.StatusCode = StatusCodes.Status401Unauthorized;
        return context.Response.WriteAsJsonAsync(new SimpleApiResponse(401, "Unauthorized."), SGContext.Default.SimpleApiResponse);
    }
    internal static void Handle(IApplicationBuilder App)
    {
        App
        .Map("/logout", logout =>
        {
            logout.Run(async runner =>
            {
                if (!HttpMethods.IsGet(runner.Request.Method) || runner.Request.HasJsonContentType() || runner.Request.HasFormContentType)
                {
                    await runner.WriteJsonResponse(StatusCodes.Status400BadRequest, "Improper request to log out.");
                    return;
                }
                runner.Response.Cookies.Append("session", "", Delete);
                if (runner.Items.ContainsKey("AuthorizedUser"))
                {
                    await runner.WriteJsonResponse(StatusCodes.Status200OK, "Log out successful. Authorisation token deleted.");
                }
                else
                {
                    await runner.WriteJsonResponse(StatusCodes.Status200OK, "No user to log out. Authorisation token does not exists.");
                }
            });
        })
        .Map("/login", login =>
        {
            login.Run(async runner =>
            {
                if (runner.Items.ContainsKey("AuthorizedUser"))
                {
                    await runner.WriteJsonResponse(StatusCodes.Status409Conflict, "Log in not allowed when an authorized user is already logged in.");
                }
                else if (runner.Request.ContentType != "application/json")
                {
                    await runner.WriteJsonResponse(StatusCodes.Status400BadRequest, "Request Content-Type mismatch.");
                }
                else
                {
                    LoginUser LoginInfo = (await runner.Request.ReadFromJsonAsync(SGContext.Default.LoginUser))!;
                    if (LoginInfo.Username is null || LoginInfo.Password is null)
                    {
                        await runner.WriteJsonResponse(StatusCodes.Status401Unauthorized, "No valid user information provided.");
                        return;
                    }
                    string SHA256Pass = Convert.ToHexString(SHA256.HashData(Encoding.UTF8.GetBytes(LoginInfo.Password)));
                    if (UserAccounts.TryGetValue(LoginInfo.Username, out User? FoundUser) && FoundUser.Password.Equals(SHA256Pass, StringComparison.InvariantCultureIgnoreCase) && FoundUser.Active)
                    {
                        SafeUser LoggedIn = SafeUser.FromUser(FoundUser);
                        string LoggedInBase64 = Convert.ToBase64String(Encoding.UTF8.GetBytes(JsonSerializer.Serialize(LoggedIn, SGContext.Default.SafeUser)));
                        string Signature = Convert.ToBase64String(SHA256.HashData(Encoding.UTF8.GetBytes(LoggedInBase64 + SecretKey)));
                        runner.Response.Cookies.Append("session", $"{LoggedInBase64}.{Signature}", HttpOnly);
                        await runner.WriteJsonResponse(StatusCodes.Status200OK, "User authorised. Authorisation token created.", LoggedIn);
                    }
                    else
                    {
                        await runner.WriteJsonResponse(StatusCodes.Status401Unauthorized, "Provided user information cannot be authorized");
                    }
                }
            });
        })
        .Map("/gate", auth =>
        {
            auth.Run(async runner =>
            {
                if (runner.Request.ContentType != "application/json")
                {
                    await runner.WriteJsonResponse(StatusCodes.Status400BadRequest, "Request Content-Type mismatch.");
                }
                else
                {
                    LoginUser LoginInfo = (await runner.Request.ReadFromJsonAsync(SGContext.Default.LoginUser))!;
                    if (LoginInfo.Username is null || LoginInfo.Password is null)
                    {
                        await runner.WriteJsonResponse(StatusCodes.Status401Unauthorized, "No valid user information provided.");
                        return;
                    }
                    string SHA256Pass = Convert.ToHexString(SHA256.HashData(Encoding.UTF8.GetBytes(LoginInfo.Password)));
                    if (UserAccounts.TryGetValue(LoginInfo.Username, out User? FoundUser) && FoundUser.Password.Equals(SHA256Pass, StringComparison.InvariantCultureIgnoreCase) && FoundUser.Active)
                    {
                        await runner.WriteJsonResponse(StatusCodes.Status200OK, "User authorised. Operation may continue.", SafeUser.FromUser(FoundUser));
                    }
                    else
                    {
                        await runner.WriteJsonResponse(StatusCodes.Status401Unauthorized, "Provided user information cannot be authorized");
                    }
                }
            });
        })
        .Map("/me", me =>
        {
            me.Run(async runner =>
            {
                if (TryGetUser(runner, out SafeUser user))
                {
                    await runner.WriteJsonResponse(StatusCodes.Status200OK, "Success.", user);
                }
                else
                {
                    await runner.WriteJsonResponse(StatusCodes.Status401Unauthorized, "No user session token is included with the request.");
                }
            });
        })
        .Run(async runner=>
        {
            await runner.WriteJsonResponse(StatusCodes.Status404NotFound);
        })
        ;
    }
}