Simplify download file properties (#7519)

* Simplify DownloadFileProperties

1. Fix up/simplify optional API usage around getVersion,
   can return an optional directly from DownloadFileProperties
   to simplify client code

2. Convert saveForZip to be stateful rather than static.

* Remove unused properties in map '*.properties' files, we only use the map version

The map url, time of download, engine version are unused, we only
need the map version in a '.properties' map suffix file.

* Simplify DownloadFileProperties construction

Rather than construct via no-arg and then inject
a version value, we can accept the version value
as a constructor argument.

game-core/src/main/java/games/strategy/engine/framework/map/download/DownloadFile.java

@@ -87,9 +87,10 @@ private Thread newDownloadThread() {
             return;
           }
 
-          final DownloadFileProperties props = new DownloadFileProperties();
-          props.setFrom(download);
-          DownloadFileProperties.saveForZip(download.getInstallLocation(), props);
+          if (download.getVersion() != null) {
+            new DownloadFileProperties(download.getVersion())
+                .saveForZip(download.getInstallLocation());
+          }
 
           downloadListener.downloadStopped(download);
         });

game-core/src/main/java/games/strategy/engine/framework/map/download/DownloadFileProperties.java

@@ -1,26 +1,29 @@
 package games.strategy.engine.framework.map.download;
 
-import games.strategy.engine.ClientContext;
 import java.io.File;
 import java.io.FileInputStream;
 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
-import java.time.LocalDateTime;
-import java.time.ZoneId;
+import java.util.Optional;
 import java.util.Properties;
 import java.util.logging.Level;
+import lombok.NoArgsConstructor;
 import lombok.extern.java.Log;
-import org.triplea.java.DateTimeFormatterUtil;
 import org.triplea.util.Version;
 
 /** Properties file used to know which map versions have been installed. */
 @Log
+@NoArgsConstructor
 class DownloadFileProperties {
   static final String VERSION_PROPERTY = "map.version";
   private final Properties props = new Properties();
 
+  DownloadFileProperties(final Version mapVersion) {
+    props.put(VERSION_PROPERTY, mapVersion.toString());
+  }
+
   static DownloadFileProperties loadForZip(final File zipFile) {
     if (!fromZip(zipFile).exists()) {
       return new DownloadFileProperties();
@@ -35,9 +38,9 @@ static DownloadFileProperties loadForZip(final File zipFile) {
     return downloadFileProperties;
   }
 
-  static void saveForZip(final File zipFile, final DownloadFileProperties props) {
+  void saveForZip(final File zipFile) {
     try (OutputStream fos = new FileOutputStream(fromZip(zipFile))) {
-      props.props.store(fos, null);
+      props.store(fos, null);
     } catch (final IOException e) {
       log.log(
           Level.SEVERE,
@@ -50,25 +53,7 @@ private static File fromZip(final File zipFile) {
     return new File(zipFile.getAbsolutePath() + ".properties");
   }
 
-  Version getVersion() {
-    if (!props.containsKey(VERSION_PROPERTY)) {
-      return null;
-    }
-    return new Version(props.getProperty(VERSION_PROPERTY));
-  }
-
-  private void setVersion(final Version v) {
-    if (v != null) {
-      props.put(VERSION_PROPERTY, v.toString());
-    }
-  }
-
-  void setFrom(final DownloadFileDescription selected) {
-    setVersion(selected.getVersion());
-    props.setProperty("map.url", selected.getUrl());
-    props.setProperty(
-        "download.time",
-        DateTimeFormatterUtil.toDateString(LocalDateTime.now(ZoneId.systemDefault())));
-    props.setProperty("engine.version", ClientContext.engineVersion().toString());
+  Optional<Version> getVersion() {
+    return Optional.ofNullable(props.getProperty(VERSION_PROPERTY)).map(Version::new);
   }
 }

game-core/src/main/java/games/strategy/engine/framework/map/download/FileSystemAccessStrategy.java

@@ -24,8 +24,7 @@ Optional<Version> getMapVersion(final String mapName) {
       return Optional.empty();
     }
 
-    final DownloadFileProperties props = DownloadFileProperties.loadForZip(potentialFile);
-    return (props.getVersion() == null) ? Optional.empty() : Optional.of(props.getVersion());
+    return DownloadFileProperties.loadForZip(potentialFile).getVersion();
   }
 
   static void remove(

game-core/src/main/java/games/strategy/engine/framework/map/download/MapDownloadController.java

@@ -96,7 +96,7 @@ private static DownloadedMaps getDownloadedMaps() {
     return new DownloadedMaps() {
       @Override
       public Optional<Version> getVersionForZipFile(final File mapZipFile) {
-        return Optional.ofNullable(DownloadFileProperties.loadForZip(mapZipFile).getVersion());
+        return DownloadFileProperties.loadForZip(mapZipFile).getVersion();
       }
 
       @Override