using Evergreen.Health.Application.Health.Entities;
using Evergreen.Health.Application.Health.Models;
using System.Text.Json;

namespace Evergreen.Health.Application.Health.Services;

// 重庆演示场景：BMI 只给出可手动修改的软硬起点，不是医学或人体工学诊断。
public sealed class MattressComfortService : ITransient
{
    // 演示使用 Open-Meteo 接口；正式商用前应确认许可或替换为有授权的天气源。
    private const string WeatherUrl =
        "https://api.open-meteo.com/v1/forecast?latitude=29.56&longitude=106.55&current=temperature_2m%2Capparent_temperature&timezone=Asia%2FShanghai";
    private static readonly HttpClient WeatherClient = new() { Timeout = TimeSpan.FromSeconds(6) };
    private static readonly SemaphoreSlim WeatherLock = new(1, 1);
    private static WeatherSample? CachedWeather;

    public async Task<MattressComfortOutput> GetAsync(HealthProfile? profile, CancellationToken cancellationToken = default)
    {
        decimal? bmi = null;
        if (profile?.HeightCm > 0 && profile.WeightKg > 0)
        {
            var height = profile.HeightCm.Value / 100m;
            bmi = Math.Round(profile.WeightKg.Value / (height * height), 1);
        }

        var firmness = bmi switch
        {
            < 18.5m => "很软",
            < 24m => "稍软",
            < 28m => "稍硬",
            < 32m => "很硬",
            >= 32m => "最硬",
            _ => null
        };
        var chinaNow = DateTimeOffset.UtcNow.ToOffset(TimeSpan.FromHours(8));
        var winter = chinaNow.Month is 12 or 1 or 2;
        var weather = await ReadWeatherAsync(cancellationToken);
        var heating = 0;
        if (winter && weather?.FeelsLikeCelsius is double feelsLike)
            heating = feelsLike < 8 ? 2 : feelsLike < 16 ? 1 : 0;

        var weatherReason = !winter
            ? "重庆非冬季，床垫加热关闭"
            : weather == null
                ? "重庆天气暂不可用，为安全起见不自动加热"
                : heating == 0
                    ? "重庆处于冬季，但当前体感温度较高，不自动加热"
                    : $"重庆冬季体感 {weather.FeelsLikeCelsius:0.#}℃，建议加热 {heating} 档";

        return new MattressComfortOutput
        {
            Bmi = bmi,
            Firmness = firmness,
            HeatingLevel = heating,
            IsWinter = winter,
            OutdoorTemperatureCelsius = weather?.TemperatureCelsius,
            FeelsLikeCelsius = weather?.FeelsLikeCelsius,
            WeatherAvailable = weather != null,
            WeatherObservedAt = weather?.ObservedAt,
            WeatherReason = weatherReason,
            FirmnessReason = firmness == null
                ? "健康档案尚无身高和体重，暂不自动调节软硬度"
                : $"按 BMI {bmi:0.0} 给出“{firmness}”演示起点，可在设备详情手动调整"
        };
    }

    public static void ApplyTo(PersonalizedSceneConfig config, MattressComfortOutput recommendation)
    {
        config.MattressHeatingLevel = recommendation.HeatingLevel;
        config.MattressLeftFirmness = recommendation.Firmness == null ? 0 : FirmnessLevel(recommendation.Firmness);
        config.MattressRightFirmness = config.MattressLeftFirmness;
    }

    public static int FirmnessLevel(string firmness) => firmness switch
    {
        "最软" => 1, "很软" => 2, "稍软" => 3,
        "稍硬" => 4, "很硬" => 5, "最硬" => 6,
        _ => 0
    };

    public static string? FirmnessName(int level) => level switch
    {
        1 => "最软", 2 => "很软", 3 => "稍软",
        4 => "稍硬", 5 => "很硬", 6 => "最硬",
        _ => null
    };

    private static async Task<WeatherSample?> ReadWeatherAsync(CancellationToken cancellationToken)
    {
        if (CachedWeather is { } cached && DateTimeOffset.UtcNow - cached.FetchedAt < TimeSpan.FromMinutes(30))
            return cached;

        await WeatherLock.WaitAsync(cancellationToken);
        try
        {
            if (CachedWeather is { } fresh && DateTimeOffset.UtcNow - fresh.FetchedAt < TimeSpan.FromMinutes(30))
                return fresh;

            using var response = await WeatherClient.GetAsync(WeatherUrl, cancellationToken);
            response.EnsureSuccessStatusCode();
            await using var stream = await response.Content.ReadAsStreamAsync(cancellationToken);
            using var json = await JsonDocument.ParseAsync(stream, cancellationToken: cancellationToken);
            var current = json.RootElement.GetProperty("current");
            var temperature = current.GetProperty("temperature_2m").GetDouble();
            var feelsLike = current.GetProperty("apparent_temperature").GetDouble();
            var observedAt = current.GetProperty("time").GetString();
            CachedWeather = new WeatherSample(temperature, feelsLike, observedAt, DateTimeOffset.UtcNow);
            return CachedWeather;
        }
        catch (OperationCanceledException) when (cancellationToken.IsCancellationRequested)
        {
            throw;
        }
        catch
        {
            // 天气失败时不使用过期值自动开启加热，冬季也安全关闭。
            return null;
        }
        finally
        {
            WeatherLock.Release();
        }
    }

    private sealed record WeatherSample(
        double TemperatureCelsius, double FeelsLikeCelsius, string? ObservedAt, DateTimeOffset FetchedAt);
}