using Microsoft.Extensions.Options;
using System.Net.Http.Headers;
using System.Net.Http.Json;
using System.Text.Json;

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

public sealed class HomeAssistantClient : IHomeAssistantGateway
{
    private readonly HttpClient _httpClient;
    private readonly HomeAssistantOptions _options;

    public HomeAssistantClient(HttpClient httpClient, IOptions<HomeAssistantOptions> options)
    {
        _httpClient = httpClient;
        _options = options.Value;
        _httpClient.Timeout = TimeSpan.FromSeconds(Math.Clamp(_options.TimeoutSeconds, 3, 60));
    }

    public async Task<IReadOnlyList<HomeAssistantState>> GetStatesAsync(CancellationToken cancellationToken = default)
    {
        using var request = CreateRequest(HttpMethod.Get, "api/states");
        using var response = await SendAsync(request, cancellationToken);
        await EnsureSuccessAsync(response, cancellationToken);
        var states = await response.Content.ReadFromJsonAsync<List<HomeAssistantState>>(cancellationToken: cancellationToken) ?? [];
        await EnrichTemperatureUnitAsync(states, cancellationToken);
        return states;
    }

    // 原生 climate 状态通常省略温度单位，它使用 HA 全局单位系统；不能把缺失直接当作摄氏。
    private async Task EnrichTemperatureUnitAsync(List<HomeAssistantState> states, CancellationToken cancellationToken)
    {
        var targets = states.Where(state => state.EntityId.StartsWith("climate.", StringComparison.OrdinalIgnoreCase) &&
            state.Attributes.ValueKind == JsonValueKind.Object &&
            !state.Attributes.TryGetProperty("temperature_unit", out _)).ToArray();
        if (targets.Length == 0) return;
        using var bounded = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken);
        bounded.CancelAfter(TimeSpan.FromSeconds(2));
        try
        {
            using var request = CreateRequest(HttpMethod.Get, "api/config");
            using var response = await SendAsync(request, bounded.Token);
            await EnsureSuccessAsync(response, bounded.Token);
            using var config = await JsonDocument.ParseAsync(await response.Content.ReadAsStreamAsync(bounded.Token),
                cancellationToken: bounded.Token);
            if (!config.RootElement.TryGetProperty("unit_system", out var units) ||
                units.ValueKind != JsonValueKind.Object || !units.TryGetProperty("temperature", out var temperature) ||
                temperature.ValueKind != JsonValueKind.String) return;
            var unit = temperature.GetString();
            if (unit is not ("°C" or "°F")) return;
            foreach (var state in targets)
            {
                var attributes = state.Attributes.EnumerateObject().ToDictionary(property => property.Name,
                    property => property.Value.Clone(), StringComparer.Ordinal);
                attributes["temperature_unit"] = JsonSerializer.SerializeToElement(unit);
                state.Attributes = JsonSerializer.SerializeToElement(attributes);
            }
        }
        catch (Exception) when (!cancellationToken.IsCancellationRequested)
        {
            // 单位接口不可读时仍保留其他真实状态；空调温度功能按单位未知禁用，不猜测。
        }
        cancellationToken.ThrowIfCancellationRequested();
    }

    public async Task CallServiceAsync(
        string domain,
        string service,
        IReadOnlyDictionary<string, object?> data,
        CancellationToken cancellationToken = default)
    {
        using var request = CreateRequest(HttpMethod.Post, $"api/services/{domain}/{service}");
        request.Content = JsonContent.Create(data);
        using var response = await SendAsync(request, cancellationToken);
        await EnsureSuccessAsync(response, cancellationToken);
    }

    private async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
    {
        try { return await _httpClient.SendAsync(request, cancellationToken); }
        catch (OperationCanceledException exception) when (!cancellationToken.IsCancellationRequested)
        {
            throw new TimeoutException("Home Assistant 请求超时，未确认操作完成", exception);
        }
    }

    private HttpRequestMessage CreateRequest(HttpMethod method, string path)
    {
        if (!_options.Enabled)
            throw new InvalidOperationException("Home Assistant 接入未启用");
        if (string.IsNullOrWhiteSpace(_options.BaseUrl))
            throw new InvalidOperationException("Home Assistant 地址未配置");
        if (string.IsNullOrWhiteSpace(_options.AccessToken))
            throw new InvalidOperationException("Home Assistant 访问令牌未配置");

        var baseUrl = _options.BaseUrl.TrimEnd('/') + "/";
        var request = new HttpRequestMessage(method, new Uri(new Uri(baseUrl), path));
        request.Headers.Authorization = new AuthenticationHeaderValue("Bearer", _options.AccessToken);
        request.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
        return request;
    }

    private static async Task EnsureSuccessAsync(HttpResponseMessage response, CancellationToken cancellationToken)
    {
        if (response.IsSuccessStatusCode) return;
        var body = await response.Content.ReadAsStringAsync(cancellationToken);
        var message = body.Length > 300 ? body[..300] : body;
        throw new HttpRequestException($"Home Assistant 返回 {(int)response.StatusCode}: {message}");
    }
}