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YongeStreet/Services/DataService.cs

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+using DuckDB.NET.Data;
+
+namespace YongeStreet.Services;
+
+public record Road(int RelationId, List<List<double>> Points);
+
+public record CityOverview(string Name, double TotalStreetSize, IList<int> AvailableYears);
+
+public record CityRoadLengthStats(string Name, double MunicipalRoadLength, int Year);
+
+public class DataService
+{
+    private static readonly List<string> CITY_STREET_HIGHWAY = ["primary", 
+        "primary_link",
+        "secondary", 
+        "secondary_link",
+        "tertiary",
+        "tertiary_link",
+        "residential",
+    "unclassified"];
+    private readonly string path = "/home/didier/dev/YongeStreet/real.duckdb";
+
+    public IList<Road> GetRoads(string city, int year)
+    {
+        using var duckDBConnection = new DuckDBConnection($"Data Source={path};ACCESS_MODE=READ_ONLY");
+        duckDBConnection.Open();
+
+        using var command = duckDBConnection.CreateCommand();
+        command.CommandText = """
+                                  SELECT relation_id, points 
+                                  FROM city_road 
+                                  WHERE city_name = $city_name 
+                                        AND extract_date = $extract_date
+                                        AND list_contains($allowed_highway, highway)
+                              """;
+        command.Parameters.Add(new DuckDBParameter("city_name", city));
+        command.Parameters.Add(new DuckDBParameter("extract_date", new DateOnly(year, 1, 1)));
+        command.Parameters.Add(new DuckDBParameter("allowed_highway", CITY_STREET_HIGHWAY));
+        using var reader = command.ExecuteReader();
+
+        var ret = new List<Road>();
+        while (reader.Read())
+        {
+            var points = reader.GetFieldValue<List<List<double>>>(1);
+            ret.Add(new Road(reader.GetInt32(0), points));
+        }
+
+        return ret;
+    }
+
+    public IList<CityOverview> GetCityOverview()
+    {
+        using var duckDBConnection = new DuckDBConnection($"Data Source={path};ACCESS_MODE=READ_ONLY");
+        duckDBConnection.Open();
+
+        using var command = duckDBConnection.CreateCommand();
+        command.CommandText = """
+                                  SELECT city_name, 
+                                         SUM(length) FILTER (list_contains($allowed_highway, highway) AND extract_date = (Date '2025-01-01')) AS length,
+                                         LIST(DISTINCT extract('year' FROM extract_date)) AS available_years
+                                  FROM city_road 
+                                  GROUP BY city_name
+                                  ORDER BY length desc
+                                  LIMIT 100
+                              """;
+        command.Parameters.Add(new DuckDBParameter("allowed_highway", CITY_STREET_HIGHWAY));
+        using var reader = command.ExecuteReader();
+
+        var ret = new List<CityOverview>();
+        while (reader.Read())
+            ret.Add(new CityOverview(reader.GetString(0),
+                reader.GetDouble(1),
+                reader.GetFieldValue<List<int>>(2)));
+
+        return ret;
+    }
+    
+    public IList<CityRoadLengthStats> GetCityRoadLengthStats(string city)
+    {
+        using var duckDBConnection = new DuckDBConnection($"Data Source={path};ACCESS_MODE=READ_ONLY");
+        duckDBConnection.Open();
+
+        using var command = duckDBConnection.CreateCommand();
+        command.CommandText = """
+                                  SELECT SUM(length) FILTER (list_contains($allowed_highway, highway)) AS length,
+                                         extract('year' FROM extract_date) AS year
+                                  FROM city_road 
+                                  WHERE city_name = $city_name 
+                                  GROUP BY extract_date
+                                  ORDER BY year DESC
+                              """;
+        command.Parameters.Add(new DuckDBParameter("city_name", city));
+        command.Parameters.Add(new DuckDBParameter("allowed_highway", CITY_STREET_HIGHWAY));
+        using var reader = command.ExecuteReader();
+
+        var ret = new List<CityRoadLengthStats>();
+        while (reader.Read())
+        {
+            ret.Add(new CityRoadLengthStats(city, 
+                reader.GetInt32(0), 
+                reader.GetInt32(1)));
+        }
+
+        return ret;
+    }
+    
+    
+    
+}