Wetterdienst

2026-08-23 20:51:19 +02:00
parent cc973418f3
commit 1b32166ce0
21 changed files with 1186 additions and 3 deletions
@@ -0,0 +1,78 @@
+using System.Globalization;
+using System.Net.Http.Json;
+using System.Text.Json.Serialization;
+using LehrerApp.Core.Models;
+
+namespace LehrerApp.Api;
+
+public interface IGeocoder
+{
+    Task<GeocodingResult?> GeocodeAsync(SchoolLocationRequest address, CancellationToken cancellationToken);
+}
+
+public sealed record GeocodingResult(double Latitude, double Longitude, string DisplayName);
+
+/// <summary>Einmalige, explizit ausgelöste Adressauflösung über den öffentlichen OSM-Nominatim-
+/// Dienst. Kein Autocomplete; die dauerhafte Ergebnisspeicherung übernimmt SchoolWeatherStore.</summary>
+public sealed class NominatimGeocoder(HttpClient http) : IGeocoder
+{
+    private static readonly SemaphoreSlim RequestGate = new(1, 1);
+    private static DateTime _lastRequestAt = DateTime.MinValue;
+
+    public async Task<GeocodingResult?> GeocodeAsync(SchoolLocationRequest address,
+        CancellationToken cancellationToken)
+    {
+        var structured = Query(new Dictionary<string, string>
+        {
+            ["street"] = address.Street,
+            ["postalcode"] = address.PostalCode,
+            ["city"] = address.City,
+        });
+        var result = await SearchRespectingRateLimitAsync(structured, cancellationToken);
+        if (result is not null) return result;
+
+        // Manche Schulen/Ortsteile sind bei OSM anders adressiert. Ein kontrollierter zweiter
+        // Versuch mit der gesamten Suchzeile ist robuster, bleibt aber weit weg vom 1-rps-Limit.
+        var freeForm = string.Join(", ", new[]
+        {
+            address.SchoolName, address.Street, $"{address.PostalCode} {address.City}", "Deutschland",
+        }.Where(x => !string.IsNullOrWhiteSpace(x)));
+        return await SearchRespectingRateLimitAsync(
+            Query(new Dictionary<string, string> { ["q"] = freeForm }), cancellationToken);
+    }
+
+    private async Task<GeocodingResult?> SearchRespectingRateLimitAsync(string query,
+        CancellationToken cancellationToken)
+    {
+        await RequestGate.WaitAsync(cancellationToken);
+        try
+        {
+            var wait = TimeSpan.FromSeconds(1) - (DateTime.UtcNow - _lastRequestAt);
+            if (wait > TimeSpan.Zero) await Task.Delay(wait, cancellationToken);
+            _lastRequestAt = DateTime.UtcNow;
+            var candidates = await http.GetFromJsonAsync<List<NominatimCandidate>>(
+                $"search?format=jsonv2&limit=1&countrycodes=de{query}", cancellationToken);
+            var candidate = candidates?.FirstOrDefault();
+            if (candidate is null ||
+                !double.TryParse(candidate.Lat, NumberStyles.Float, CultureInfo.InvariantCulture, out var latitude) ||
+                !double.TryParse(candidate.Lon, NumberStyles.Float, CultureInfo.InvariantCulture, out var longitude))
+                return null;
+            return new(latitude, longitude, candidate.DisplayName ?? "");
+        }
+        finally { RequestGate.Release(); }
+    }
+
+    private static string Query(IReadOnlyDictionary<string, string> values) => string.Concat(
+        values.Where(x => !string.IsNullOrWhiteSpace(x.Value))
+              .Select(x => $"&{Uri.EscapeDataString(x.Key)}={Uri.EscapeDataString(x.Value.Trim())}"));
+
+    private sealed class NominatimCandidate
+    {
+        [JsonPropertyName("lat")]
+        public string? Lat { get; set; }
+        [JsonPropertyName("lon")]
+        public string? Lon { get; set; }
+        [JsonPropertyName("display_name")]
+        public string? DisplayName { get; set; }
+    }
+}