using System.Buffers.Binary;
using System.Net.Http.Headers;
using System.Security.Cryptography;
using System.Text.Json;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting.Server;
using Microsoft.AspNetCore.Hosting.Server.Features;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using WebDrop.Api;
using WebDrop.Core;

namespace WebDrop.Api.Tests;

/// <summary>在真实 Kestrel 上启动服务(随机端口、临时数据目录),测试走真实的 HTTP / WebSocket / SSE。</summary>
public sealed class ServerFixture : IAsyncLifetime, IAsyncDisposable
{
    private readonly string _dir = Path.Combine(Path.GetTempPath(), "webdrop-api-" + Guid.NewGuid().ToString("N"));
    private readonly Dictionary<string, string> _overrides;

    public WebApplication App { get; private set; } = null!;
    public HttpClient Http { get; private set; } = null!;
    public Uri BaseUri { get; private set; } = null!;

    public ServerFixture() : this([]) { }

    private ServerFixture(Dictionary<string, string> overrides) => _overrides = overrides;

    /// <summary>xunit 要求 class fixture 只有一个公开构造函数,带配置覆盖的版本走工厂方法。</summary>
    public static ServerFixture WithSettings(Dictionary<string, string> overrides) => new(overrides);

    public async Task InitializeAsync()
    {
        App = WebDropApp.Build([], b =>
        {
            b.Configuration["WebDrop:DataDir"] = _dir;
            b.Configuration["WebDrop:RequestsPerMinute"] = "1000000";
            b.Configuration["WebDrop:ChannelCreatesPerMinute"] = "1000000";
            foreach (var (key, value) in _overrides) b.Configuration[key] = value;
            b.Configuration["urls"] = "http://127.0.0.1:0";
            b.Logging.ClearProviders();
        });
        await App.StartAsync();

        string address = App.Services.GetRequiredService<IServer>().Features.Get<IServerAddressesFeature>()!.Addresses.First();
        BaseUri = new Uri(address);
        Http = new HttpClient { BaseAddress = BaseUri, Timeout = TimeSpan.FromSeconds(30) };
    }

    public async Task DisposeAsync()
    {
        Http.Dispose();
        await App.StopAsync();
        await App.DisposeAsync();
        Microsoft.Data.Sqlite.SqliteConnection.ClearAllPools();
        try { Directory.Delete(_dir, recursive: true); } catch (IOException) { }
    }

    ValueTask IAsyncDisposable.DisposeAsync() => new(DisposeAsync());

    // ───── 客户端侧的凭据与请求构造(模拟浏览器从 K / A 派生出的令牌) ─────

    public sealed class Chan(string id, ChannelMode mode)
    {
        public string Id { get; } = id;
        public ChannelMode Mode { get; } = mode;
        public byte[] ReadToken { get; } = RandomNumberGenerator.GetBytes(32);
        public byte[] WriteToken { get; } = RandomNumberGenerator.GetBytes(32);
        public byte[] OwnerToken { get; } = RandomNumberGenerator.GetBytes(32);
        public byte[] OwnerSecret { get; } = RandomNumberGenerator.GetBytes(32);
        public byte[] MemberSecret { get; } = RandomNumberGenerator.GetBytes(32);

        public Who Owner => new("owner", OwnerToken, OwnerSecret);
        public Who Member => new("write", WriteToken, MemberSecret);
        public Who Reader => new("read", ReadToken, MemberSecret);
    }

    public sealed record Who(string Role, byte[]? Token, byte[] EndpointSecret);

    public static string B64(byte[] bytes) => Codec.Encode(bytes);
    public static string NewId() => B64(RandomNumberGenerator.GetBytes(16));

    public HttpRequestMessage Req(HttpMethod method, string path, Who who, HttpContent? content = null)
    {
        var req = new HttpRequestMessage(method, path) { Content = content };
        req.Headers.Add("X-WD-Role", who.Role);
        if (who.Token is not null) req.Headers.Authorization = new AuthenticationHeaderValue("Bearer", B64(who.Token));
        req.Headers.Add("X-WD-Endpoint", B64(who.EndpointSecret));
        return req;
    }

    public async Task<Chan> CreateAsync(ChannelMode mode = ChannelMode.Enc, object? settings = null)
    {
        var (ch, resp) = await TryCreateAsync(mode, settings);
        using (resp) Assert.Equal(System.Net.HttpStatusCode.Created, resp.StatusCode);
        return ch;
    }

    /// <summary>创建频道并返回原始响应,用于测试验证码等失败路径。</summary>
    public async Task<(Chan Chan, HttpResponseMessage Resp)> TryCreateAsync(
        ChannelMode mode = ChannelMode.Enc, object? settings = null, string? capToken = null)
    {
        var ch = new Chan(NewId(), mode);
        var body = new Dictionary<string, object?>
        {
            ["id"] = ch.Id,
            ["mode"] = mode == ChannelMode.Enc ? "enc" : "raw",
            ["owner_hash"] = B64(TokenHash.Compute(ch.OwnerToken)),
            ["write_hash"] = B64(TokenHash.Compute(ch.WriteToken)),
        };
        if (mode == ChannelMode.Enc) body["read_hash"] = B64(TokenHash.Compute(ch.ReadToken));
        if (settings is not null) body["settings"] = settings;

        using var req = Req(HttpMethod.Post, "/api/v1/channels", ch.Owner, JsonBody(body));
        if (capToken is not null) req.Headers.Add("X-WD-Cap", capToken);
        return (ch, await Http.SendAsync(req));
    }

    public static StringContent JsonBody(object value) =>
        new(JsonSerializer.Serialize(value), System.Text.Encoding.UTF8, "application/json");

    public static ByteArrayContent Bytes(byte[] bytes)
    {
        var c = new ByteArrayContent(bytes);
        c.Headers.ContentType = new MediaTypeHeaderValue("application/octet-stream");
        return c;
    }

    public async Task<HttpResponseMessage> JoinAsync(Chan ch, Who who) =>
        await Http.SendAsync(Req(HttpMethod.Post, $"/api/v1/channels/{ch.Id}/seats", who));

    public async Task<HttpResponseMessage> AppendAsync(Chan ch, Who who, byte[] frame, string? maxDownloads = null)
    {
        var req = Req(HttpMethod.Post, $"/api/v1/channels/{ch.Id}/frames", who, Bytes(frame));
        if (maxDownloads is not null) req.Headers.Add("X-WD-Max-Downloads", maxDownloads);
        return await Http.SendAsync(req);
    }

    public async Task<(HttpResponseMessage Resp, byte[] Body)> GetBytesAsync(string path, Who who)
    {
        var resp = await Http.SendAsync(Req(HttpMethod.Get, path, who));
        return (resp, await resp.Content.ReadAsByteArrayAsync());
    }

    public static async Task<JsonElement> ReadJsonAsync(HttpResponseMessage resp) =>
        JsonDocument.Parse(await resp.Content.ReadAsStringAsync()).RootElement;

    public static async Task AssertErrorAsync(HttpResponseMessage resp, int status, string code)
    {
        Assert.Equal(status, (int)resp.StatusCode);
        Assert.Equal(code, (await ReadJsonAsync(resp)).GetProperty("error").GetString());
    }

    // ───── 帧与日志的线格式 ─────

    public const int EncPayload = 1024 + 16;
    public const byte FinalEnc = 1 | 8;
    public const byte GatedEnc = 4 | 8;
    public const byte GatedFinalEnc = 4 | 8 | 1;

    public static byte[] Frame(string itemId, uint index, byte flags, int payloadLength, byte fill = 0x42)
    {
        Codec.TryDecodeExact(itemId, 16, out var item);
        var bytes = new byte[26 + payloadLength];
        bytes[0] = 1;
        bytes[1] = flags;
        item.CopyTo(bytes, 2);
        BinaryPrimitives.WriteUInt32BigEndian(bytes.AsSpan(18), index);
        BinaryPrimitives.WriteUInt32BigEndian(bytes.AsSpan(22), (uint)payloadLength);
        bytes.AsSpan(26).Fill(fill);
        return bytes;
    }

    public sealed record Rec(long Seq, LogKind Kind, byte[] Body);

    /// <summary>解析 log 接口返回的记录拼接:seq(8) ‖ kind(1) ‖ body。frame 的 body 自带 payload_len,其余定长。</summary>
    public static List<Rec> ParseLog(byte[] data)
    {
        var list = new List<Rec>();
        int p = 0;
        while (p < data.Length)
        {
            long seq = BinaryPrimitives.ReadInt64BigEndian(data.AsSpan(p));
            var kind = (LogKind)data[p + 8];
            int bodyLen = kind switch
            {
                LogKind.Frame => 26 + (int)BinaryPrimitives.ReadUInt32BigEndian(data.AsSpan(p + 9 + 22)),
                LogKind.Tombstone => 17,
                LogKind.Announce => 25,
                _ => throw new InvalidOperationException("未知记录类型"),
            };
            list.Add(new Rec(seq, kind, data[(p + 9)..(p + 9 + bodyLen)]));
            p += 9 + bodyLen;
        }
        return list;
    }

    public static Rec ParseOne(byte[] data) => Assert.Single(ParseLog(data));
}