Added "storagePolicy" setting, including startup validation.

Possible values are:

FOLLOWED_AND_VIEWED (default)
FOLLOWED
VIEWED
ALL
NONE

Nothing is affected by this setting yet, but this will be added shortly.

src/main/java/org/qortal/controller/arbitrary/ArbitraryDataManager.java

@@ -42,6 +42,13 @@ public class ArbitraryDataManager extends Thread {
 
 	private volatile boolean isStopping = false;
 
+	public enum StoragePolicy {
+		FOLLOWED_AND_VIEWED,
+		FOLLOWED,
+		VIEWED,
+		ALL,
+		NONE
+	}
 
 	/**
 	 * Map of recent requests for ARBITRARY transaction data file lists.

src/main/java/org/qortal/settings/Settings.java

@@ -5,10 +5,7 @@ import java.io.FileNotFoundException;
 import java.io.FileReader;
 import java.io.IOException;
 import java.io.Reader;
-import java.util.HashMap;
+import java.util.*;
-import java.util.List;
-import java.util.Locale;
-import java.util.Map;
 
 import javax.xml.bind.JAXBContext;
 import javax.xml.bind.JAXBException;
@@ -24,9 +21,11 @@ import org.eclipse.persistence.exceptions.XMLMarshalException;
 import org.eclipse.persistence.jaxb.JAXBContextFactory;
 import org.eclipse.persistence.jaxb.UnmarshallerProperties;
 import org.qortal.block.BlockChain;
+import org.qortal.controller.arbitrary.ArbitraryDataManager.*;
 import org.qortal.crosschain.Bitcoin.BitcoinNet;
 import org.qortal.crosschain.Litecoin.LitecoinNet;
 import org.qortal.crosschain.Dogecoin.DogecoinNet;
+import org.qortal.utils.EnumUtils;
 
 // All properties to be converted to JSON via JAXB
 @XmlAccessorType(XmlAccessType.FIELD)
@@ -263,6 +262,9 @@ public class Settings {
 	/** Data storage path (for temporary data). */
 	private String tempDataPath = "data/_temp";
 
+	/** Storage policy to indicate which data should be hosted */
+	private String storagePolicy = "FOLLOWED_AND_VIEWED";
+
 	/** Whether to validate every layer when building arbitrary data, or just the final layer */
 	private boolean validateAllDataLayers = false;
 
@@ -417,6 +419,13 @@ public class Settings {
 
 		if (this.apiKey != null && this.apiKey.trim().length() < 8)
 			throwValidationError("apiKey must be at least 8 characters");
+
+		try {
+			StoragePolicy.valueOf(this.storagePolicy);
+		} catch (IllegalArgumentException ex) {
+			String possibleValues = EnumUtils.getNames(StoragePolicy.class, ", ");
+			throwValidationError(String.format("storagePolicy must be one of: %s", possibleValues));
+		}
 	}
 
 	// Getters / setters
@@ -766,6 +775,10 @@ public class Settings {
 		return this.tempDataPath;
 	}
 
+	public StoragePolicy getStoragePolicy() {
+		return StoragePolicy.valueOf(this.storagePolicy);
+	}
+
 	public boolean shouldValidateAllDataLayers() {
 		return this.validateAllDataLayers;
 	}

src/main/java/org/qortal/utils/EnumUtils.java

@@ -0,0 +1,15 @@
+package org.qortal.utils;
+
+import java.util.Arrays;
+
+public class EnumUtils {
+
+    public static String[] getNames(Class<? extends Enum<?>> e) {
+        return Arrays.stream(e.getEnumConstants()).map(Enum::name).toArray(String[]::new);
+    }
+
+    public static String getNames(Class<? extends Enum<?>> e, String delimiter) {
+        return String.join(delimiter, EnumUtils.getNames(e));
+    }
+
+}