using Furion.DependencyInjection;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;
using System.Net.WebSockets;
using System.Text;
using System.Text.Json;

namespace Evergreen.Health.Application.Health.Integrations.HomeAssistant;

public sealed class HomeAssistantRegistryService : ISingleton
{
    private readonly HomeAssistantOptions _options;
    private readonly ILogger<HomeAssistantRegistryService> _logger;
    private readonly SemaphoreSlim _lock = new(1, 1);
    private HomeAssistantRegistries? _cachedRegistries;
    private static readonly TimeSpan CacheDuration = TimeSpan.FromMinutes(5);

    public HomeAssistantRegistryService(
        IOptions<HomeAssistantOptions> options,
        ILogger<HomeAssistantRegistryService> logger)
    {
        _options = options.Value;
        _logger = logger;
    }

    public async Task<HomeAssistantRegistries?> GetRegistriesAsync(CancellationToken cancellationToken = default)
    {
        if (_cachedRegistries is not null && DateTimeOffset.UtcNow - _cachedRegistries.CachedAt < CacheDuration)
        {
            return _cachedRegistries;
        }

        await _lock.WaitAsync(cancellationToken);
        try
        {
            if (_cachedRegistries is not null && DateTimeOffset.UtcNow - _cachedRegistries.CachedAt < CacheDuration)
            {
                return _cachedRegistries;
            }

            var registries = await FetchRegistriesFromWebSocketAsync(cancellationToken);
            if (registries is not null)
            {
                _cachedRegistries = registries;
            }
            return _cachedRegistries;
        }
        catch (Exception ex) when (ex is not OperationCanceledException || !cancellationToken.IsCancellationRequested)
        {
            _logger.LogWarning("通过 WebSocket 读取 Home Assistant 注册表失败：{Message}", ex.Message);
            return _cachedRegistries;
        }
        finally
        {
            _lock.Release();
        }
    }

    private async Task<HomeAssistantRegistries?> FetchRegistriesFromWebSocketAsync(CancellationToken cancellationToken)
    {
        if (!_options.Enabled || string.IsNullOrWhiteSpace(_options.BaseUrl) || string.IsNullOrWhiteSpace(_options.AccessToken))
        {
            return null;
        }

        var wsUri = ConvertToWebSocketUri(_options.BaseUrl);
        using var cts = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken);
        cts.CancelAfter(TimeSpan.FromSeconds(Math.Clamp(_options.TimeoutSeconds, 5, 20)));

        using var ws = new ClientWebSocket();
        ws.Options.KeepAliveInterval = TimeSpan.FromSeconds(15);

        try
        {
            await ws.ConnectAsync(wsUri, cts.Token);

            // 1. 等待 auth_required
            var authRequiredJson = await ReceiveTextMessageAsync(ws, cts.Token);
            using (var doc = JsonDocument.Parse(authRequiredJson))
            {
                var type = doc.RootElement.GetProperty("type").GetString();
                if (type != "auth_required")
                {
                    throw new InvalidOperationException($"Home Assistant WebSocket 未按预期发送 auth_required，实际接收：{type}");
                }
            }

            // 2. 发送认证消息
            var authMessage = JsonSerializer.Serialize(new
            {
                type = "auth",
                access_token = _options.AccessToken
            });
            await SendTextMessageAsync(ws, authMessage, cts.Token);

            // 3. 等待 auth_ok
            var authResultJson = await ReceiveTextMessageAsync(ws, cts.Token);
            using (var doc = JsonDocument.Parse(authResultJson))
            {
                var type = doc.RootElement.GetProperty("type").GetString();
                if (type != "auth_ok")
                {
                    var msg = doc.RootElement.TryGetProperty("message", out var m) ? m.GetString() : "认证失败";
                    throw new InvalidOperationException($"Home Assistant WebSocket 认证失败：{msg}");
                }
            }

            // 4. 获取设备注册表 (id: 1)
            var devicesJson = await SendCommandAsync(ws, 1, "config/device_registry/list", cts.Token);
            var devices = ParseRegistryResult<List<HomeAssistantDeviceRegistryItem>>(devicesJson) ?? [];

            // 5. 获取实体注册表 (id: 2)
            var entitiesJson = await SendCommandAsync(ws, 2, "config/entity_registry/list", cts.Token);
            var entities = ParseRegistryResult<List<HomeAssistantEntityRegistryItem>>(entitiesJson) ?? [];

            // 6. 获取区域注册表 (id: 3)
            var areasJson = await SendCommandAsync(ws, 3, "config/area_registry/list", cts.Token);
            var areas = ParseRegistryResult<List<HomeAssistantAreaRegistryItem>>(areasJson) ?? [];

            try
            {
                await ws.CloseAsync(WebSocketCloseStatus.NormalClosure, "Completed", cts.Token);
            }
            catch
            {
                // 忽略正常关闭异常
            }

            return new HomeAssistantRegistries
            {
                Devices = devices,
                Entities = entities,
                Areas = areas,
                CachedAt = DateTimeOffset.UtcNow
            };
        }
        catch (Exception ex) when (ex is not OperationCanceledException || !cancellationToken.IsCancellationRequested)
        {
            _logger.LogWarning("连接 Home Assistant WebSocket 发生异常：{Message}", ex.Message);
            return null;
        }
    }

    private static async Task<string> SendCommandAsync(ClientWebSocket ws, int id, string type, CancellationToken cancellationToken)
    {
        var command = JsonSerializer.Serialize(new { id, type });
        await SendTextMessageAsync(ws, command, cancellationToken);
        return await ReceiveTextMessageAsync(ws, cancellationToken);
    }

    private static T? ParseRegistryResult<T>(string responseJson)
    {
        using var doc = JsonDocument.Parse(responseJson);
        var root = doc.RootElement;
        if (root.TryGetProperty("success", out var success) && success.GetBoolean())
        {
            if (root.TryGetProperty("result", out var result))
            {
                return JsonSerializer.Deserialize<T>(result.GetRawText());
            }
        }
        return default;
    }

    private static async Task SendTextMessageAsync(ClientWebSocket ws, string text, CancellationToken cancellationToken)
    {
        var bytes = Encoding.UTF8.GetBytes(text);
        await ws.SendAsync(new ArraySegment<byte>(bytes), WebSocketMessageType.Text, true, cancellationToken);
    }

    private static async Task<string> ReceiveTextMessageAsync(ClientWebSocket ws, CancellationToken cancellationToken)
    {
        var buffer = new byte[8192];
        using var ms = new MemoryStream();
        while (true)
        {
            var result = await ws.ReceiveAsync(new ArraySegment<byte>(buffer), cancellationToken);
            if (result.MessageType == WebSocketMessageType.Close)
            {
                throw new WebSocketException("WebSocket 服务端已关闭连接");
            }
            ms.Write(buffer, 0, result.Count);
            if (result.EndOfMessage)
            {
                break;
            }
        }
        return Encoding.UTF8.GetString(ms.ToArray());
    }

    private static Uri ConvertToWebSocketUri(string baseUrl)
    {
        var url = baseUrl.TrimEnd('/');
        if (url.StartsWith("https://", StringComparison.OrdinalIgnoreCase))
        {
            url = "wss://" + url[8..] + "/api/websocket";
        }
        else if (url.StartsWith("http://", StringComparison.OrdinalIgnoreCase))
        {
            url = "ws://" + url[7..] + "/api/websocket";
        }
        else
        {
            url = "ws://" + url + "/api/websocket";
        }
        return new Uri(url);
    }
}