Create evaluation engine outcome

Encapsulate the result from the evaluation engine, after evaluating rules
against app install metadata, in a class holding the outcome effect and
the rule causing that effect.

Bug: 141971373
Test: N/A
Change-Id: Ib311ab5bd4cdfd233008e7a7684cc99afabd337e

services/core/java/com/android/server/integrity/model/EvaluationOutcome.java

@@ -0,0 +1,67 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.server.integrity.model;
+
+/**
+ * A class encapsulating the result from the evaluation engine after evaluating rules against app
+ * install metadata.
+ *
+ * <p>It contains the outcome effect (whether to allow or block the install), and the rule causing
+ * that effect.
+ */
+public final class EvaluationOutcome {
+
+    public enum Effect {
+        ALLOW,
+        DENY
+    }
+
+    private final Effect mEffect;
+    private final Rule mRule;
+
+    private EvaluationOutcome(Effect effect, Rule rule) {
+        this.mEffect = effect;
+        this.mRule = rule;
+    }
+
+    public Effect getEffect() {
+        return mEffect;
+    }
+
+    public Rule getRule() {
+        return mRule;
+    }
+
+    /**
+     * Create an ALLOW evaluation outcome.
+     *
+     * @return An evaluation outcome with ALLOW effect and empty rule.
+     */
+    public static EvaluationOutcome allow() {
+        return new EvaluationOutcome(Effect.ALLOW, Rule.EMPTY);
+    }
+
+    /**
+     * Create a DENY evaluation outcome.
+     *
+     * @param rule Rule causing the DENY effect.
+     * @return An evaluation outcome with DENY effect and rule causing that effect.
+     */
+    public static EvaluationOutcome deny(Rule rule) {
+        return new EvaluationOutcome(Effect.DENY, rule);
+    }
+}

services/core/java/com/android/server/integrity/model/Rule.java

@@ -25,7 +25,7 @@ import static com.android.internal.util.Preconditions.checkNotNull;
  */
 public final class Rule {
 
-    enum Effect {
+    public enum Effect {
         DENY
     }