Add support for server-side feature flags

service/src/main/java/org/whispersystems/textsecuregcm/controllers/FeatureFlagsController.java

@@ -0,0 +1,72 @@
+package org.whispersystems.textsecuregcm.controllers;
+
+import com.codahale.metrics.annotation.Timed;
+import com.google.common.annotations.VisibleForTesting;
+import org.whispersystems.textsecuregcm.storage.FeatureFlagsManager;
+
+import javax.ws.rs.DELETE;
+import javax.ws.rs.FormParam;
+import javax.ws.rs.HeaderParam;
+import javax.ws.rs.PUT;
+import javax.ws.rs.Path;
+import javax.ws.rs.PathParam;
+import javax.ws.rs.WebApplicationException;
+import javax.ws.rs.core.Response;
+import java.nio.charset.StandardCharsets;
+import java.security.MessageDigest;
+import java.util.List;
+import java.util.stream.Collectors;
+
+@Path("/v1/featureflag")
+public class FeatureFlagsController {
+
+    private final FeatureFlagsManager featureFlagsManager;
+    private final List<byte[]>        authorizedTokens;
+
+    public FeatureFlagsController(final FeatureFlagsManager featureFlagsManager, final List<String> authorizedTokens) {
+        this.featureFlagsManager = featureFlagsManager;
+        this.authorizedTokens    = authorizedTokens.stream().map(token -> token.getBytes(StandardCharsets.UTF_8)).collect(Collectors.toList());
+    }
+
+    @Timed
+    @PUT
+    @Path("/{featureFlag}")
+    public void set(@HeaderParam("Token") final String token, @PathParam("featureFlag") final String featureFlag, @FormParam("active") final boolean active) {
+        if (!isAuthorized(token)) {
+            throw new WebApplicationException(Response.Status.UNAUTHORIZED);
+        }
+
+        featureFlagsManager.setFeatureFlag(featureFlag, active);
+    }
+
+    @Timed
+    @DELETE
+    @Path("/{featureFlag}")
+    public void delete(@HeaderParam("Token") final String token, @PathParam("featureFlag") final String featureFlag) {
+        if (!isAuthorized(token)) {
+            throw new WebApplicationException(Response.Status.UNAUTHORIZED);
+        }
+
+        featureFlagsManager.deleteFeatureFlag(featureFlag);
+    }
+
+    @VisibleForTesting
+    boolean isAuthorized(final String token) {
+        if (token == null) {
+            return false;
+        }
+
+        final byte[] tokenBytes = token.getBytes(StandardCharsets.UTF_8);
+
+        boolean authorized = false;
+
+        for (final byte[] authorizedToken : authorizedTokens) {
+            //noinspection IfStatementMissingBreakInLoop
+            if (MessageDigest.isEqual(authorizedToken, tokenBytes)) {
+                authorized = true;
+            }
+        }
+        
+        return authorized;
+    }
+}