using System.Security.Claims;
using System.Text.Json;
using Microsoft.AspNetCore.Components.Authorization;
using NexusReader.Application.Abstractions.Services;

namespace NexusReader.UI.Shared.Services;

public class NexusAuthenticationStateProvider : AuthenticationStateProvider
{
    private readonly INativeStorageService _storageService;
    private const string TokenKey = "nexus_auth_token";

    public NexusAuthenticationStateProvider(INativeStorageService storageService)
    {
        _storageService = storageService;
    }

    public override async Task<AuthenticationState> GetAuthenticationStateAsync()
    {
        try
        {
            var result = await _storageService.GetSecureString(TokenKey);
            var token = result.IsSuccess ? result.Value : null;

            if (string.IsNullOrWhiteSpace(token))
            {
                return new AuthenticationState(new ClaimsPrincipal(new ClaimsIdentity()));
            }

            var identity = new ClaimsIdentity(ParseClaimsFromJwt(token), "jwt");
            var user = new ClaimsPrincipal(identity);

            return new AuthenticationState(user);
        }
        catch (Exception)
        {
            return new AuthenticationState(new ClaimsPrincipal(new ClaimsIdentity()));
        }
    }

    public void NotifyUserAuthentication(string token)
    {
        var identity = new ClaimsIdentity(ParseClaimsFromJwt(token), "jwt");
        var user = new ClaimsPrincipal(identity);
        var authState = Task.FromResult(new AuthenticationState(user));
        NotifyAuthenticationStateChanged(authState);
    }

    public void NotifyUserLogout()
    {
        var guest = new ClaimsPrincipal(new ClaimsIdentity());
        var authState = Task.FromResult(new AuthenticationState(guest));
        NotifyAuthenticationStateChanged(authState);
    }

    private IEnumerable<Claim> ParseClaimsFromJwt(string jwt)
    {
        var claims = new List<Claim>();
        var payload = jwt.Split('.')[1];

        var jsonBytes = ParseBase64WithoutPadding(payload);
        var keyValuePairs = JsonSerializer.Deserialize<Dictionary<string, object>>(jsonBytes);

        if (keyValuePairs != null)
        {
            claims.AddRange(keyValuePairs.Select(kvp => new Claim(kvp.Key, kvp.Value.ToString() ?? string.Empty)));
        }

        return claims;
    }

    private byte[] ParseBase64WithoutPadding(string base64)
    {
        switch (base64.Length % 4)
        {
            case 2: base64 += "=="; break;
            case 3: base64 += "="; break;
        }
        return Convert.FromBase64String(base64);
    }
}