Fix IO closing & add new useful extensions

dataframe-geo/src/main/kotlin/org/jetbrains/kotlinx/dataframe/geo/GeoDataFrame.kt

@@ -34,12 +34,9 @@ class GeoDataFrame<T : WithGeometry>(val df: DataFrame<T>, val crs: CoordinateRe
      * @return A new `GeoDataFrame` with reprojected geometries and the specified CRS.
      */
     fun applyCrs(targetCrs: CoordinateReferenceSystem): GeoDataFrame<T> {
-        if (crs == null) {
-            return GeoDataFrame(df, targetCrs)
-        }
         if (targetCrs == this.crs) return this
         // Use WGS 84 by default TODO
-        val sourceCRS: CoordinateReferenceSystem = this.crs
+        val sourceCRS: CoordinateReferenceSystem = this.crs ?: DEFAULT_CRS
         val transform = CRS.findMathTransform(sourceCRS, targetCrs, true)
         return GeoDataFrame(
             df.update { geometry }.with { JTS.transform(it, transform) },

dataframe-geo/src/main/kotlin/org/jetbrains/kotlinx/dataframe/geo/io/read.kt

@@ -12,16 +12,25 @@ import java.net.URL
 fun GeoDataFrame.Companion.readGeoJson(path: String): GeoDataFrame<*> = readGeoJson(asURL(path))
 
 fun GeoDataFrame.Companion.readGeoJson(url: URL): GeoDataFrame<*> =
-    (FeatureJSON().readFeatureCollection(url.openStream()) as SimpleFeatureCollection).toGeoDataFrame()
+    url.openStream().use { inputStream ->
+        val featureCollection = FeatureJSON().readFeatureCollection(inputStream) as SimpleFeatureCollection
+        featureCollection.toGeoDataFrame()
+    }
 
 fun DataFrame.Companion.readGeoJson(path: String): GeoDataFrame<*> = GeoDataFrame.readGeoJson(path)
 
 fun DataFrame.Companion.readGeoJson(url: URL): GeoDataFrame<*> = GeoDataFrame.readGeoJson(url)
 
 fun GeoDataFrame.Companion.readShapefile(path: String): GeoDataFrame<*> = readShapefile(asURL(path))
 
-fun GeoDataFrame.Companion.readShapefile(url: URL): GeoDataFrame<*> =
-    ShapefileDataStoreFactory().createDataStore(url).featureSource.features.toGeoDataFrame()
+fun GeoDataFrame.Companion.readShapefile(url: URL): GeoDataFrame<*> {
+    val dataStore = ShapefileDataStoreFactory().createDataStore(url)
+    try {
+        return dataStore.featureSource.features.toGeoDataFrame()
+    } finally {
+        dataStore.dispose()
+    }
+}
 
 fun DataFrame.Companion.readShapefile(path: String): GeoDataFrame<*> = GeoDataFrame.readShapefile(path)
 

dataframe-geo/src/main/kotlin/org/jetbrains/kotlinx/dataframe/geo/io/write.kt

@@ -52,6 +52,7 @@ fun GeoDataFrame<*>.writeShapefile(directory: File) {
         e.printStackTrace()
         transaction.rollback()
     } finally {
+        dataStore.dispose()
         transaction.close()
     }
 }

dataframe-geo/src/main/kotlin/org/jetbrains/kotlinx/dataframe/geo/jts/toMulti.kt

@@ -0,0 +1,41 @@
+package org.jetbrains.kotlinx.dataframe.geo.jts
+
+import org.locationtech.jts.geom.LineString
+import org.locationtech.jts.geom.MultiLineString
+import org.locationtech.jts.geom.MultiPoint
+import org.locationtech.jts.geom.MultiPolygon
+import org.locationtech.jts.geom.Point
+import org.locationtech.jts.geom.Polygon
+
+/**
+ * Converts a [Polygon] to a [MultiPolygon] by wrapping it in a MultiPolygon.
+ *
+ * @receiver Polygon to be converted.
+ * @return A MultiPolygon containing the original Polygon.
+ */
+fun Polygon.toMultiPolygon(): MultiPolygon {
+    val geometryFactory = this.factory
+    return geometryFactory.createMultiPolygon(arrayOf(this))
+}
+
+/**
+ * Converts a [Point] to a [MultiPoint] by wrapping it in a MultiPoint.
+ *
+ * @receiver Point to be converted.
+ * @return A MultiPoint containing the original Point.
+ */
+fun Point.toMultiPoint(): MultiPoint {
+    val geometryFactory = this.factory
+    return geometryFactory.createMultiPoint(arrayOf(this))
+}
+
+/**
+ * Converts a [LineString] to a [MultiLineString] by wrapping it in a MultiLineString.
+ *
+ * @receiver LineString to be converted.
+ * @return A MultiLineString containing the original LineString.
+ */
+fun LineString.toMultiLineString(): MultiLineString {
+    val geometryFactory = this.factory
+    return geometryFactory.createMultiLineString(arrayOf(this))
+}