feat: Support KML BalloonStyle template (#606)

Author: jeffdgr8

library/src/main/java/com/google/maps/android/data/Renderer.java

@@ -50,6 +50,7 @@
 import com.google.maps.android.data.kml.KmlPlacemark;
 import com.google.maps.android.data.kml.KmlPoint;
 import com.google.maps.android.data.kml.KmlStyle;
+import com.google.maps.android.data.kml.KmlUtil;
 
 import android.graphics.Bitmap;
 import android.os.Bundle;
@@ -1010,7 +1011,7 @@ private void setMarkerInfoWindow(KmlStyle style, Marker marker,
         boolean hasBalloonOptions = style.hasBalloonStyle();
         boolean hasBalloonText = style.getBalloonOptions().containsKey("text");
         if (hasBalloonOptions && hasBalloonText) {
-            marker.setTitle(style.getBalloonOptions().get("text"));
+            marker.setTitle(KmlUtil.substituteProperties(style.getBalloonOptions().get("text"), placemark));
             createInfoWindow();
         } else if (hasBalloonOptions && hasName) {
             marker.setTitle(placemark.getProperty("name"));

library/src/main/java/com/google/maps/android/data/kml/KmlPlacemark.java

@@ -6,7 +6,7 @@
 import com.google.maps.android.data.Feature;
 import com.google.maps.android.data.Geometry;
 
-import java.util.HashMap;
+import java.util.Map;
 
 /**
  * Represents a placemark which is either a {@link com.google.maps.android.data.kml.KmlPoint},
@@ -29,7 +29,7 @@ public class KmlPlacemark extends Feature {
      * @param properties properties hashmap to store
      */
     public KmlPlacemark(Geometry geometry, String style, KmlStyle inlineStyle,
-                        HashMap<String, String> properties) {
+                        Map<String, String> properties) {
         super(geometry, style, properties);
         mStyle = style;
         mInlineStyle = inlineStyle;

library/src/main/java/com/google/maps/android/data/kml/KmlUtil.java

@@ -0,0 +1,32 @@
+package com.google.maps.android.data.kml;
+
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+/**
+ * Utility methods for KML
+ */
+public class KmlUtil {
+
+    /**
+     * Substitute property values in BalloonStyle text template
+     *
+     * @param template text template
+     * @param placemark placemark to get property values from
+     * @return string with property values substituted
+     */
+    public static String substituteProperties(String template, KmlPlacemark placemark) {
+        StringBuffer sb = new StringBuffer();
+        Pattern pattern = Pattern.compile("\\$\\[(.+?)]");
+        Matcher matcher = pattern.matcher(template);
+        while (matcher.find()) {
+            String property = matcher.group(1);
+            String value = placemark.getProperty(property);
+            if (value != null) {
+                matcher.appendReplacement(sb, value);
+            }
+        }
+        matcher.appendTail(sb);
+        return sb.toString();
+    }
+}

library/src/test/java/com/google/maps/android/data/kml/KmlUtilTest.java

@@ -0,0 +1,32 @@
+package com.google.maps.android.data.kml;
+
+import org.junit.Test;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import static org.junit.Assert.assertEquals;
+
+public class KmlUtilTest {
+
+    @Test
+    public void testSubstituteProperties() {
+        Map<String, String> properties = new HashMap<>();
+        properties.put("name", "Bruce Wayne");
+        properties.put("description", "Batman");
+        properties.put("Snippet", "I am the night");
+        KmlPlacemark placemark = new KmlPlacemark(null, null, null, properties);
+
+        String result1 = KmlUtil.substituteProperties("$[name] is my name", placemark);
+        assertEquals("Bruce Wayne is my name", result1);
+
+        String result2 = KmlUtil.substituteProperties("Also known as $[description]", placemark);
+        assertEquals("Also known as Batman", result2);
+
+        String result3 = KmlUtil.substituteProperties("I say \"$[Snippet]\" often", placemark);
+        assertEquals("I say \"I am the night\" often", result3);
+
+        String result4 = KmlUtil.substituteProperties("My address is $[address]", placemark);
+        assertEquals("When property doesn't exist, placeholder is left in place", "My address is $[address]", result4);
+    }
+}