Innovenergy_trunk/csharp/App/Backend/Services/WeatherService.cs

using Flurl.Http;
using Newtonsoft.Json;

namespace InnovEnergy.App.Backend.Services;

public static class WeatherService
{
    public record DailyWeather(
        string Date,
        double TempMin,
        double TempMax,
        double SunshineHours,
        double PrecipitationMm,
        string Description
    );

    private static readonly Dictionary<string, (double Lat, double Lon)> GeoCache = new();

    /// <summary>
    /// Returns a 7-day weather forecast for the given city, or null on any failure.
    /// </summary>
    public static async Task<List<DailyWeather>?> GetForecastAsync(string? city, string? country, string? region = null)
    {
        if (string.IsNullOrWhiteSpace(city))
            return null;

        try
        {
            var coords = await GeocodeAsync(city, region);
            if (coords == null)
                return null;

            var (lat, lon) = coords.Value;
            return await FetchForecastAsync(lat, lon);
        }
        catch (Exception ex)
        {
            Console.Error.WriteLine($"[WeatherService] Error fetching forecast for '{city}': {ex.Message}");
            return null;
        }
    }

    /// <summary>
    /// Formats a forecast list into a compact text block for AI prompt injection.
    /// </summary>
    public static string FormatForPrompt(List<DailyWeather> forecast)
    {
        var lines = forecast.Select(d =>
        {
            var date = DateTime.Parse(d.Date);
            var dayName = date.ToString("ddd dd MMM");
            return $"- {dayName}: {d.TempMin:F0}–{d.TempMax:F0}°C, {d.Description}, {d.SunshineHours:F1}h sunshine, {d.PrecipitationMm:F0}mm rain";
        });

        return "WEATHER FORECAST (next 7 days):\n" + string.Join("\n", lines);
    }

    /// <summary>
    /// Extracts a geocodable city name from a Location field that may contain a full address.
    /// Handles Swiss formats like "Street 5, 8604 Volketswil" → "Volketswil"
    /// Also tries the Region field as fallback.
    /// </summary>
    private static IEnumerable<string> ExtractSearchTerms(string city, string? region)
    {
        // If it contains a comma, try the part after the last comma (often "PostalCode City")
        if (city.Contains(','))
        {
            var afterComma = city.Split(',').Last().Trim();
            // Strip leading postal code (digits) → "8604 Volketswil" → "Volketswil"
            var withoutPostal = System.Text.RegularExpressions.Regex.Replace(afterComma, @"^\d+\s*", "").Trim();
            if (!string.IsNullOrEmpty(withoutPostal))
                yield return withoutPostal;
            if (!string.IsNullOrEmpty(afterComma))
                yield return afterComma;
        }

        // Try the raw value as-is
        yield return city;

        // Fallback to Region
        if (!string.IsNullOrWhiteSpace(region))
            yield return region;
    }

    private static async Task<(double Lat, double Lon)?> GeocodeAsync(string city, string? region = null)
    {
        if (GeoCache.TryGetValue(city, out var cached))
            return cached;

        foreach (var term in ExtractSearchTerms(city, region))
        {
            var url = $"https://geocoding-api.open-meteo.com/v1/search?name={Uri.EscapeDataString(term)}&count=1&language=en";
            var json = await url.GetStringAsync();
            var data = JsonConvert.DeserializeObject<dynamic>(json);

            if (data?.results != null && data.results.Count > 0)
            {
                var lat = (double)data.results[0].latitude;
                var lon = (double)data.results[0].longitude;

                GeoCache[city] = (lat, lon);
                Console.WriteLine($"[WeatherService] Geocoded '{city}' (matched on '{term}') → ({lat:F4}, {lon:F4})");
                return (lat, lon);
            }
        }

        Console.WriteLine($"[WeatherService] Could not geocode location: '{city}'");
        return null;
    }

    private static async Task<List<DailyWeather>?> FetchForecastAsync(double lat, double lon)
    {
        var url = $"https://api.open-meteo.com/v1/forecast"
                + $"?latitude={lat}&longitude={lon}"
                + "&daily=temperature_2m_max,temperature_2m_min,sunshine_duration,precipitation_sum,weathercode"
                + "&timezone=Europe/Zurich&forecast_days=7";

        var json = await url.GetStringAsync();
        var data = JsonConvert.DeserializeObject<dynamic>(json);

        if (data?.daily == null)
            return null;

        var dates   = data.daily.time;
        var tempMax = data.daily.temperature_2m_max;
        var tempMin = data.daily.temperature_2m_min;
        var sun     = data.daily.sunshine_duration;
        var precip  = data.daily.precipitation_sum;
        var codes   = data.daily.weathercode;

        var forecast = new List<DailyWeather>();
        for (int i = 0; i < dates.Count; i++)
        {
            forecast.Add(new DailyWeather(
                Date:             (string)dates[i],
                TempMin:          (double)tempMin[i],
                TempMax:          (double)tempMax[i],
                SunshineHours:    Math.Round((double)sun[i] / 3600.0, 1),
                PrecipitationMm:  (double)precip[i],
                Description:      WeatherCodeToDescription((int)codes[i])
            ));
        }

        Console.WriteLine($"[WeatherService] Fetched {forecast.Count}-day forecast.");
        return forecast;
    }

    private static string WeatherCodeToDescription(int code) => code switch
    {
        0      => "Clear sky",
        1      => "Mainly clear",
        2      => "Partly cloudy",
        3      => "Overcast",
        45     => "Fog",
        48     => "Depositing rime fog",
        51     => "Light drizzle",
        53     => "Moderate drizzle",
        55     => "Dense drizzle",
        61     => "Slight rain",
        63     => "Moderate rain",
        65     => "Heavy rain",
        66     => "Light freezing rain",
        67     => "Heavy freezing rain",
        71     => "Slight snow",
        73     => "Moderate snow",
        75     => "Heavy snow",
        77     => "Snow grains",
        80     => "Slight showers",
        81     => "Moderate showers",
        82     => "Violent showers",
        85     => "Slight snow showers",
        86     => "Heavy snow showers",
        95     => "Thunderstorm",
        96     => "Thunderstorm with slight hail",
        99     => "Thunderstorm with heavy hail",
        _      => "Unknown"
    };
}