namespace Shogi.UI.Identity;

using Microsoft.AspNetCore.Components.Authorization;
using System.Net.Http.Json;
using System.Security.Claims;
using System.Text;
using System.Text.Json;

/// <summary>
/// Handles state for cookie-based auth.
/// </summary>
public class CookieAuthenticationStateProvider : AuthenticationStateProvider, IAccountManagement
{
	/// <summary>
	/// Map the JavaScript-formatted properties to C#-formatted classes.
	/// </summary>
	private readonly JsonSerializerOptions jsonSerializerOptions = new()
	{
		PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
	};

	/// <summary>
	/// Special auth client.
	/// </summary>
	private readonly HttpClient _httpClient;

	/// <summary>
	/// Authentication state.
	/// </summary>
	private bool _authenticated = false;

	/// <summary>
	/// Default principal for anonymous (not authenticated) users.
	/// </summary>
	private readonly ClaimsPrincipal Unauthenticated =
					new(new ClaimsIdentity());

	/// <summary>
	/// Create a new instance of the auth provider.
	/// </summary>
	/// <param name="httpClientFactory">Factory to retrieve auth client.</param>
	public CookieAuthenticationStateProvider(IHttpClientFactory httpClientFactory)
					=> _httpClient = httpClientFactory.CreateClient("Auth");

	/// <summary>
	/// Register a new user.
	/// </summary>
	/// <param name="email">The user's email address.</param>
	/// <param name="password">The user's password.</param>
	/// <returns>The result serialized to a <see cref="FormResult"/>.
	/// </returns>
	public async Task<FormResult> RegisterAsync(string email, string password)
	{
		string[] defaultDetail = ["An unknown error prevented registration from succeeding."];

		try
		{
			// make the request
			var result = await _httpClient.PostAsJsonAsync("register", new
			{
				email,
				password
			});

			// successful?
			if (result.IsSuccessStatusCode)
			{
				return new FormResult { Succeeded = true };
			}

			// body should contain details about why it failed
			var details = await result.Content.ReadAsStringAsync();
			var problemDetails = JsonDocument.Parse(details);
			var errors = new List<string>();
			var errorList = problemDetails.RootElement.GetProperty("errors");

			foreach (var errorEntry in errorList.EnumerateObject())
			{
				if (errorEntry.Value.ValueKind == JsonValueKind.String)
				{
					errors.Add(errorEntry.Value.GetString()!);
				}
				else if (errorEntry.Value.ValueKind == JsonValueKind.Array)
				{
					errors.AddRange(
									errorEntry.Value.EnumerateArray().Select(
													e => e.GetString() ?? string.Empty)
									.Where(e => !string.IsNullOrEmpty(e)));
				}
			}

			// return the error list
			return new FormResult
			{
				Succeeded = false,
				ErrorList = problemDetails == null ? defaultDetail : [.. errors]
			};
		}
		catch { }

		// unknown error
		return new FormResult
		{
			Succeeded = false,
			ErrorList = defaultDetail
		};
	}

	/// <summary>
	/// User login.
	/// </summary>
	/// <param name="email">The user's email address.</param>
	/// <param name="password">The user's password.</param>
	/// <returns>The result of the login request serialized to a <see cref="FormResult"/>.</returns>
	public async Task<FormResult> LoginAsync(string email, string password)
	{
		try
		{
			// login with cookies
			var result = await _httpClient.PostAsJsonAsync("login?useCookies=true", new
			{
				email,
				password
			});

			// success?
			if (result.IsSuccessStatusCode)
			{
				// need to refresh auth state
				NotifyAuthenticationStateChanged(GetAuthenticationStateAsync());

				// success!
				return new FormResult { Succeeded = true };
			}
		}
		catch { }

		// unknown error
		return new FormResult
		{
			Succeeded = false,
			ErrorList = ["Invalid email and/or password."]
		};
	}

	/// <summary>
	/// Get authentication state.
	/// </summary>
	/// <remarks>
	/// Called by Blazor anytime and authentication-based decision needs to be made, then cached
	/// until the changed state notification is raised.
	/// </remarks>
	/// <returns>The authentication state asynchronous request.</returns>
	public override async Task<AuthenticationState> GetAuthenticationStateAsync()
	{
		_authenticated = false;

		// default to not authenticated
		var user = Unauthenticated;

		try
		{
			// the user info endpoint is secured, so if the user isn't logged in this will fail
			var userResponse = await _httpClient.GetAsync("manage/info");

			// throw if user info wasn't retrieved
			userResponse.EnsureSuccessStatusCode();

			// user is authenticated,so let's build their authenticated identity
			var userJson = await userResponse.Content.ReadAsStringAsync();
			var userInfo = JsonSerializer.Deserialize<UserInfo>(userJson, jsonSerializerOptions);

			if (userInfo != null)
			{
				// in our system name and email are the same
				var claims = new List<Claim>
				{
					new(ClaimTypes.Name, userInfo.Email),
					new(ClaimTypes.Email, userInfo.Email)
				};

				// add any additional claims
				claims.AddRange(
								userInfo.Claims
									.Where(c => c.Key != ClaimTypes.Name && c.Key != ClaimTypes.Email)
									.Select(c => new Claim(c.Key, c.Value)));

				// tap the roles endpoint for the user's roles
				var rolesResponse = await _httpClient.GetAsync("roles");

				// throw if request fails
				rolesResponse.EnsureSuccessStatusCode();

				// read the response into a string
				var rolesJson = await rolesResponse.Content.ReadAsStringAsync();

				// deserialize the roles string into an array
				var roles = JsonSerializer.Deserialize<RoleClaim[]>(rolesJson, jsonSerializerOptions);

				// if there are roles, add them to the claims collection
				if (roles?.Length > 0)
				{
					foreach (var role in roles)
					{
						if (!string.IsNullOrEmpty(role.Type) && !string.IsNullOrEmpty(role.Value))
						{
							claims.Add(new Claim(role.Type, role.Value, role.ValueType, role.Issuer, role.OriginalIssuer));
						}
					}
				}

				// set the principal
				var id = new ClaimsIdentity(claims, nameof(CookieAuthenticationStateProvider));
				user = new ClaimsPrincipal(id);
				_authenticated = true;
			}
		}
		catch { }

		// return the state
		return new AuthenticationState(user);
	}

	public async Task LogoutAsync()
	{
		const string Empty = "{}";
		var emptyContent = new StringContent(Empty, Encoding.UTF8, "application/json");
		await _httpClient.PostAsync("logout", emptyContent);
		NotifyAuthenticationStateChanged(GetAuthenticationStateAsync());
	}

	public async Task<bool> CheckAuthenticatedAsync()
	{
		await GetAuthenticationStateAsync();
		return _authenticated;
	}

	public class RoleClaim
	{
		public string? Issuer { get; set; }
		public string? OriginalIssuer { get; set; }
		public string? Type { get; set; }
		public string? Value { get; set; }
		public string? ValueType { get; set; }
	}
}