Add offline toggle to prevent downloads

Author: Jonathing

src/main/java/net/minecraftforge/java_version/Disco.java

@@ -63,14 +63,24 @@ public class Disco {
 
     private final File cache;
     private final String provider;
+    private final boolean offline;
 
     public Disco(File cache) {
         this(cache, "https://api.foojay.io/disco/v3.0");
     }
 
+    public Disco(File cache, boolean offline) {
+        this(cache, "https://api.foojay.io/disco/v3.0", offline);
+    }
+
     public Disco(File cache, String provider) {
+        this(cache, provider, false);
+    }
+
+    public Disco(File cache, String provider, boolean offline) {
         this.cache = cache;
         this.provider = provider;
+        this.offline = offline;
     }
 
     protected void debug(String message) {
@@ -87,6 +97,9 @@ public List<Package> getPackages() {
         if (ret != null)
             return ret;
 
+        if (offline)
+            return null;
+
         String url = provider + "/packages/?"
             + "&package_type=jdk" // JDK has everything, could pull just the JRE but who cares.
             + "&directly_downloadable=true" // This doesn't actually seem to do anything but it's in the spec...
@@ -162,6 +175,9 @@ public PackageInfo getInfo(Package pkg) {
         if (ret != null && ret.info != null)
             return ret.info;
 
+        if (offline)
+            return null;
+
         //debug("Downloading package info " + pkg.id);
         String url = provider + "/ids/" + pkg.id;
         String data = DownloadUtils.downloadString(url);
@@ -198,7 +214,7 @@ public File download(Package pkg) {
                     checksums.put(func, info.checksum);
                 else
                     debug("Unknown Checksum " + info.checksum_type + ": " + info.checksum);
-            } else if (info.checksum_uri != null) {
+            } else if (info.checksum_uri != null && !offline) {
                 String raw = DownloadUtils.downloadString(info.checksum_uri);
                 if (raw != null) {
                     String checksum = raw.split(" ")[0];
@@ -217,7 +233,10 @@ public File download(Package pkg) {
         File archive = new File(cache, pkg.filename);
         if (!archive.exists()) {
             if (download == null) {
-                error("Failed to find download link for " + pkg.filename + " (" + pkg.id + ")");
+                if (offline)
+                    error("Offline mode, can't download " + pkg.filename + " (" + pkg.id + ")");
+                else
+                    error("Failed to find download link for " + pkg.filename + " (" + pkg.id + ")");
                 return null;
             }
             debug("Downloading " + download);

src/main/java/net/minecraftforge/java_version/DiscoLocator.java

@@ -31,9 +31,15 @@
  */
 public class DiscoLocator extends JavaHomeLocator {
     private final File cache;
+    private final boolean offline;
 
     public DiscoLocator(File cache) {
+        this(cache, false);
+    }
+
+    public DiscoLocator(File cache, boolean offline) {
         this.cache = cache;
+        this.offline = offline;
     }
 
     @Override
@@ -77,7 +83,7 @@ private List<IJavaInstall> findInternal(int version) {
     @Override
     public IJavaInstall provision(int version) {
         log("Locators failed to find any suitable installs, attempting Disco download");
-        Disco disco = new Disco(cache) { // TODO: [DISCO][Logging] Add a proper logging handler sometime
+        Disco disco = new Disco(cache, offline) { // TODO: [DISCO][Logging] Add a proper logging handler sometime
             @Override
             protected void debug(String message) {
                 DiscoLocator.this.log(message);

src/main/java/net/minecraftforge/java_version/Main.java

@@ -11,6 +11,8 @@
 import java.util.Iterator;
 import java.util.List;
 import java.util.Set;
+
+import joptsimple.AbstractOptionSpec;
 import joptsimple.OptionParser;
 import joptsimple.OptionSet;
 import joptsimple.OptionSpec;
@@ -30,6 +32,9 @@ public static void main(String[] args) throws Exception {
                 "Directory to store data needed for this program")
                 .withRequiredArg().ofType(File.class).defaultsTo(new File("cache"));
 
+        AbstractOptionSpec<Void> offlineO = parser.accepts("offline",
+                "Do not attempt to download any JDKs, only use the cache");
+
         OptionSpec<Integer> versionO = parser.accepts("version",
                 "Major version of java to try and locate")
                 .withOptionalArg().ofType(Integer.class);
@@ -43,7 +48,7 @@ public static void main(String[] args) throws Exception {
             return;
         }
         File cache = options.valueOf(cacheO);
-        DiscoLocator disco = new DiscoLocator(cache);
+        DiscoLocator disco = new DiscoLocator(cache, options.has(offlineO));
 
         List<IJavaLocator> locators = new ArrayList<>();
         locators.add(new JavaHomeLocator());

src/main/java/net/minecraftforge/java_version/api/IJavaLocator.java

@@ -64,4 +64,8 @@ static IJavaLocator home() {
     static IJavaLocator disco(File cache) {
         return new DiscoLocator(cache);
     }
+
+    static IJavaLocator disco(File cache, boolean offline) {
+        return new DiscoLocator(cache, offline);
+    }
 }