using System;
using System.IO;
using System.Net;
using System.Net.Http;
using System.Net.Http.Json;
using System.Security.Cryptography;
using System.Text;
using System.Text.Json;
using System.Threading.Tasks;
using Microsoft.AspNetCore.WebUtilities;
using Paca.Core.Security;
using Paca.Server;
using Xunit;

namespace Paca.Tests.Server;

public class ServerPasskeyAuthTests : IDisposable
{
    private readonly string _libDir = Path.Combine(Path.GetTempPath(), $"vd_passkey_{Guid.NewGuid():N}");

    public ServerPasskeyAuthTests() => Directory.CreateDirectory(_libDir);

    private sealed class EmptyQueue : IQueueAdapter
    {
        public Task<IReadOnlyList<QueueItemDto>> GetItemsAsync() => Task.FromResult<IReadOnlyList<QueueItemDto>>(Array.Empty<QueueItemDto>());
        public Task<string> AddAsync(string url, string? title) => Task.FromResult(Guid.NewGuid().ToString("N"));
        public Task PauseAsync(string id) => Task.CompletedTask;
        public Task ResumeAsync(string id) => Task.CompletedTask;
        public Task CancelAsync(string id) => Task.CompletedTask;
        public event Action? Changed { add { } remove { } }
    }

    [Fact]
    public async Task GetChallenge_ReturnsNewValidChallenge()
    {
        await using var server = await ServerHost.StartAsync(new ServerOptions
        {
            Port = 0,
            Token = "secret-passkey-token",
            LibraryFolder = _libDir,
            Queue = new EmptyQueue()
        });

        using var client = new HttpClient();
        var resp = await client.GetAsync($"http://127.0.0.1:{server.Port}/api/auth/passkey/challenge");
        Assert.Equal(HttpStatusCode.OK, resp.StatusCode);

        var doc = await resp.Content.ReadFromJsonAsync<JsonElement>();
        Assert.True(doc.GetProperty("ok").GetBoolean());
        var challenge = doc.GetProperty("challenge").GetString();
        Assert.False(string.IsNullOrEmpty(challenge));
        Assert.True(doc.TryGetProperty("rpId", out var rpId));
        Assert.Equal("paca.local", rpId.GetString());
    }

    [Fact]
    public async Task Verify_WithValidFido2Assertion_ReturnsSessionToken()
    {
        await using var server = await ServerHost.StartAsync(new ServerOptions
        {
            Port = 0,
            Token = "secret-passkey-token-2",
            DeviceName = "MyTestPc",
            LibraryFolder = _libDir,
            Queue = new EmptyQueue()
        });

        using var client = new HttpClient();

        // 1. 챌린지 요청
        var chalResp = await client.GetAsync($"http://127.0.0.1:{server.Port}/api/auth/passkey/challenge");
        var chalDoc = await chalResp.Content.ReadFromJsonAsync<JsonElement>();
        var challenge = chalDoc.GetProperty("challenge").GetString()!;

        // 2. 가상 FIDO2 자격증명 생성 및 어설션 서명
        var authenticator = VirtualFido2Authenticator.Default;
        var cred = authenticator.CreateCredential("paca.local", "user-1", "test-user");
        var clientDataHash = SHA256.HashData(Encoding.UTF8.GetBytes(challenge));
        var assertion = authenticator.SignChallenge(cred.CredentialId, clientDataHash);

        // 3. Verify 요청
        var verifyReq = new
        {
            challenge = challenge,
            credentialId = cred.CredentialId,
            clientDataHash = WebEncoders.Base64UrlEncode(clientDataHash),
            authenticatorData = WebEncoders.Base64UrlEncode(assertion.AuthenticatorData),
            signature = WebEncoders.Base64UrlEncode(assertion.Signature)
        };

        var verifyResp = await client.PostAsJsonAsync($"http://127.0.0.1:{server.Port}/api/auth/passkey/verify", verifyReq);
        Assert.Equal(HttpStatusCode.OK, verifyResp.StatusCode);

        var verifyDoc = await verifyResp.Content.ReadFromJsonAsync<JsonElement>();
        Assert.True(verifyDoc.GetProperty("ok").GetBoolean());
        Assert.Equal("secret-passkey-token-2", verifyDoc.GetProperty("token").GetString());
        Assert.Equal("MyTestPc", verifyDoc.GetProperty("device").GetString());
    }

    [Fact]
    public async Task Verify_WithInvalidSignature_Returns401()
    {
        await using var server = await ServerHost.StartAsync(new ServerOptions
        {
            Port = 0,
            Token = "secret-passkey-token-3",
            LibraryFolder = _libDir,
            Queue = new EmptyQueue()
        });

        using var client = new HttpClient();

        var chalResp = await client.GetAsync($"http://127.0.0.1:{server.Port}/api/auth/passkey/challenge");
        var chalDoc = await chalResp.Content.ReadFromJsonAsync<JsonElement>();
        var challenge = chalDoc.GetProperty("challenge").GetString()!;

        var authenticator = VirtualFido2Authenticator.Default;
        var cred = authenticator.CreateCredential("paca.local", "user-2", "test-user-2");
        var clientDataHash = SHA256.HashData(Encoding.UTF8.GetBytes(challenge));
        var assertion = authenticator.SignChallenge(cred.CredentialId, clientDataHash);

        // 위조 서명
        var tamperedSignature = (byte[])assertion.Signature.Clone();
        tamperedSignature[0] ^= 0xFF;

        var verifyReq = new
        {
            challenge = challenge,
            credentialId = cred.CredentialId,
            clientDataHash = WebEncoders.Base64UrlEncode(clientDataHash),
            authenticatorData = WebEncoders.Base64UrlEncode(assertion.AuthenticatorData),
            signature = WebEncoders.Base64UrlEncode(tamperedSignature)
        };

        var verifyResp = await client.PostAsJsonAsync($"http://127.0.0.1:{server.Port}/api/auth/passkey/verify", verifyReq);
        Assert.Equal(HttpStatusCode.Unauthorized, verifyResp.StatusCode);
    }

    [Fact]
    public async Task Verify_ReplayAttack_Returns401()
    {
        await using var server = await ServerHost.StartAsync(new ServerOptions
        {
            Port = 0,
            Token = "secret-passkey-token-4",
            LibraryFolder = _libDir,
            Queue = new EmptyQueue()
        });

        using var client = new HttpClient();

        var chalResp = await client.GetAsync($"http://127.0.0.1:{server.Port}/api/auth/passkey/challenge");
        var chalDoc = await chalResp.Content.ReadFromJsonAsync<JsonElement>();
        var challenge = chalDoc.GetProperty("challenge").GetString()!;

        var authenticator = VirtualFido2Authenticator.Default;
        var cred = authenticator.CreateCredential("paca.local", "user-3", "test-user-3");
        var clientDataHash = SHA256.HashData(Encoding.UTF8.GetBytes(challenge));
        var assertion = authenticator.SignChallenge(cred.CredentialId, clientDataHash);

        var verifyReq = new
        {
            challenge = challenge,
            credentialId = cred.CredentialId,
            clientDataHash = WebEncoders.Base64UrlEncode(clientDataHash),
            authenticatorData = WebEncoders.Base64UrlEncode(assertion.AuthenticatorData),
            signature = WebEncoders.Base64UrlEncode(assertion.Signature)
        };

        // 1차 성공
        var first = await client.PostAsJsonAsync($"http://127.0.0.1:{server.Port}/api/auth/passkey/verify", verifyReq);
        Assert.Equal(HttpStatusCode.OK, first.StatusCode);

        // 동일 챌린지 재사용 (Replay 공격) -> 401 거부
        var second = await client.PostAsJsonAsync($"http://127.0.0.1:{server.Port}/api/auth/passkey/verify", verifyReq);
        Assert.Equal(HttpStatusCode.Unauthorized, second.StatusCode);
    }

    public void Dispose()
    {
        try { Directory.Delete(_libDir, recursive: true); } catch (IOException) { }
    }
}