#213: RetryScalar

src/main/java/org/cactoos/func/RetryScalar.java

@@ -0,0 +1,86 @@
+/**
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2017 Yegor Bugayenko
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package org.cactoos.func;
+
+import org.cactoos.Func;
+import org.cactoos.Scalar;
+
+/**
+ * Func that will try a few times before throwing an exception.
+ *
+ * <p>There is no thread-safety guarantee.
+ *
+ * @author Yegor Bugayenko ([email protected])
+ * @version $Id$
+ * @param <T> Type of output
+ * @since 0.9
+ */
+public final class RetryScalar<T> implements Scalar<T> {
+
+    /**
+     * Original scalar.
+     */
+    private final Scalar<T> scalar;
+
+    /**
+     * Exit condition.
+     */
+    private final Func<Integer, Boolean> exit;
+
+    /**
+     * Ctor.
+     * @param slr Scalar original
+     */
+    public RetryScalar(final Scalar<T> slr) {
+        // @checkstyle MagicNumberCheck (1 line)
+        this(slr, 3);
+    }
+
+    /**
+     * Ctor.
+     * @param slr Scalar original
+     * @param attempts Maximum number of attempts
+     */
+    public RetryScalar(final Scalar<T> slr, final int attempts) {
+        this(slr, attempt -> attempt >= attempts);
+    }
+
+    /**
+     * Ctor.
+     * @param slr Func original
+     * @param ext Exit condition, returns TRUE if there is no more reason to try
+     */
+    public RetryScalar(final Scalar<T> slr, final Func<Integer, Boolean> ext) {
+        this.scalar = slr;
+        this.exit = ext;
+    }
+
+    @Override
+    public T asValue() throws Exception {
+        return new RetryFunc<>(
+            (Func<Boolean, T>) input -> this.scalar.asValue(),
+            this.exit
+        ).apply(true);
+    }
+}