Fix native map services and add provider selection

Services/LocationSearchService.cs

@@ -0,0 +1,185 @@
+using System.Globalization;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+using Microsoft.Maui.Devices.Sensors;
+
+namespace LMEMappeCatastaliApp.Services;
+
+public sealed class LocationSearchService
+{
+    private const string NominatimEndpoint = "https://nominatim.openstreetmap.org/search";
+    private const string ArcGisEndpoint = "https://geocode.arcgis.com/arcgis/rest/services/World/GeocodeServer/findAddressCandidates";
+    private readonly HttpClient _httpClient = new()
+    {
+        Timeout = TimeSpan.FromSeconds(20)
+    };
+    private readonly SemaphoreSlim _requestLock = new(1, 1);
+    private readonly Dictionary<string, LocationSearchResult?> _cache = new(StringComparer.OrdinalIgnoreCase);
+    private DateTimeOffset _lastRemoteRequest = DateTimeOffset.MinValue;
+
+    public LocationSearchService()
+    {
+        _httpClient.DefaultRequestHeaders.UserAgent.ParseAdd("LMEMappeCatastali/0.2.2");
+        _httpClient.DefaultRequestHeaders.Accept.ParseAdd("application/json");
+        _httpClient.DefaultRequestHeaders.AcceptLanguage.ParseAdd("it-IT");
+    }
+
+    public async Task<LocationSearchResult?> SearchAsync(string text, CancellationToken cancellationToken = default)
+    {
+        var query = text.Trim();
+        if (string.IsNullOrWhiteSpace(query))
+        {
+            return null;
+        }
+
+        if (TryParseCoordinates(query, out var coordinates))
+        {
+            return coordinates;
+        }
+
+        if (_cache.TryGetValue(query, out var cached))
+        {
+            return cached;
+        }
+
+        var nativeResult = await TryNativeGeocodingAsync(query);
+        if (nativeResult is not null)
+        {
+            _cache[query] = nativeResult;
+            return nativeResult;
+        }
+
+        var arcGisResult = await SearchArcGisAsync(query, cancellationToken);
+        if (arcGisResult is not null)
+        {
+            return arcGisResult;
+        }
+
+        var remoteResult = await SearchNominatimAsync(query, cancellationToken);
+        _cache[query] = remoteResult;
+        return remoteResult;
+    }
+
+    private async Task<LocationSearchResult?> SearchArcGisAsync(string query, CancellationToken cancellationToken)
+    {
+        try
+        {
+            var url = $"{ArcGisEndpoint}?f=json&forStorage=false&sourceCountry=ITA&maxLocations=1&outFields=Match_addr,Addr_type,Score&SingleLine={Uri.EscapeDataString(query)}";
+            using var response = await _httpClient.GetAsync(url, cancellationToken);
+            if (!response.IsSuccessStatusCode)
+            {
+                return null;
+            }
+
+            await using var content = await response.Content.ReadAsStreamAsync(cancellationToken);
+            var payload = await JsonSerializer.DeserializeAsync<ArcGisResponse>(content, cancellationToken: cancellationToken);
+            var candidate = payload?.Candidates?.FirstOrDefault();
+            if (candidate?.Location is null || candidate.Score < 60)
+            {
+                return null;
+            }
+
+            return new LocationSearchResult(candidate.Location.Y, candidate.Location.X, candidate.Address ?? query);
+        }
+        catch (OperationCanceledException)
+        {
+            throw;
+        }
+        catch (Exception)
+        {
+            return null;
+        }
+    }
+
+    private static async Task<LocationSearchResult?> TryNativeGeocodingAsync(string query)
+    {
+        try
+        {
+            var locations = await Geocoding.Default.GetLocationsAsync(query);
+            var location = locations?.FirstOrDefault();
+            return location is null
+                ? null
+                : new LocationSearchResult(location.Latitude, location.Longitude, query);
+        }
+        catch (Exception)
+        {
+            return null;
+        }
+    }
+
+    private async Task<LocationSearchResult?> SearchNominatimAsync(string query, CancellationToken cancellationToken)
+    {
+        await _requestLock.WaitAsync(cancellationToken);
+        try
+        {
+            var wait = TimeSpan.FromSeconds(1) - (DateTimeOffset.UtcNow - _lastRemoteRequest);
+            if (wait > TimeSpan.Zero)
+            {
+                await Task.Delay(wait, cancellationToken);
+            }
+
+            var url = $"{NominatimEndpoint}?format=jsonv2&limit=1&accept-language=it&q={Uri.EscapeDataString(query)}";
+            _lastRemoteRequest = DateTimeOffset.UtcNow;
+            using var response = await _httpClient.GetAsync(url, cancellationToken);
+            if (!response.IsSuccessStatusCode)
+            {
+                throw new HttpRequestException($"Il servizio di ricerca ha risposto {((int)response.StatusCode)}.");
+            }
+
+            await using var content = await response.Content.ReadAsStreamAsync(cancellationToken);
+            var results = await JsonSerializer.DeserializeAsync<List<NominatimResult>>(content, cancellationToken: cancellationToken);
+            var result = results?.FirstOrDefault();
+            if (result is null
+                || !double.TryParse(result.Latitude, NumberStyles.Float, CultureInfo.InvariantCulture, out var latitude)
+                || !double.TryParse(result.Longitude, NumberStyles.Float, CultureInfo.InvariantCulture, out var longitude))
+            {
+                return null;
+            }
+
+            return new LocationSearchResult(latitude, longitude, result.DisplayName ?? query);
+        }
+        finally
+        {
+            _requestLock.Release();
+        }
+    }
+
+    private static bool TryParseCoordinates(string query, out LocationSearchResult? result)
+    {
+        result = null;
+        var parts = query.Split([' ', ',', ';'], StringSplitOptions.TrimEntries | StringSplitOptions.RemoveEmptyEntries);
+        if (parts.Length != 2
+            || !double.TryParse(parts[0], NumberStyles.Float, CultureInfo.InvariantCulture, out var latitude)
+            || !double.TryParse(parts[1], NumberStyles.Float, CultureInfo.InvariantCulture, out var longitude)
+            || Math.Abs(latitude) > 90
+            || Math.Abs(longitude) > 180)
+        {
+            return false;
+        }
+
+        result = new LocationSearchResult(
+            latitude,
+            longitude,
+            $"Coordinate: {latitude:F6}, {longitude:F6}");
+        return true;
+    }
+
+    private sealed record NominatimResult(
+        [property: JsonPropertyName("lat")] string? Latitude,
+        [property: JsonPropertyName("lon")] string? Longitude,
+        [property: JsonPropertyName("display_name")] string? DisplayName);
+
+    private sealed record ArcGisResponse(
+        [property: JsonPropertyName("candidates")] List<ArcGisCandidate>? Candidates);
+
+    private sealed record ArcGisCandidate(
+        [property: JsonPropertyName("address")] string? Address,
+        [property: JsonPropertyName("score")] double Score,
+        [property: JsonPropertyName("location")] ArcGisLocation? Location);
+
+    private sealed record ArcGisLocation(
+        [property: JsonPropertyName("x")] double X,
+        [property: JsonPropertyName("y")] double Y);
+}
+
+public sealed record LocationSearchResult(double Latitude, double Longitude, string Label);