#255: InputWithFallback

src/main/java/org/cactoos/io/InputWithFallback.java

@@ -0,0 +1,95 @@
+/**
+ * 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.io;
+
+import java.io.IOException;
+import java.io.InputStream;
+import org.cactoos.Func;
+import org.cactoos.Input;
+import org.cactoos.func.IoCheckedFunc;
+
+/**
+ * Input that returns an alternative input if the main one throws
+ * {@link IOException}.
+ *
+ * <p>There is no thread-safety guarantee.
+ *
+ * @author Yegor Bugayenko (yegor256@gmail.com)
+ * @version $Id$
+ * @since 0.9
+ */
+public final class InputWithFallback implements Input {
+
+    /**
+     * The main one.
+     */
+    private final Input main;
+
+    /**
+     * The alternative one.
+     */
+    private final IoCheckedFunc<IOException, Input> alternative;
+
+    /**
+     * Ctor.
+     * @param input Main input
+     * @param alt Alternative
+     */
+    public InputWithFallback(final Input input, final Input alt) {
+        this(input, error -> alt);
+    }
+
+    /**
+     * Ctor.
+     * @param input Main input
+     * @param alt Alternative
+     */
+    public InputWithFallback(final Input input,
+        final Func<IOException, Input> alt) {
+        this(input, new IoCheckedFunc<>(alt));
+    }
+
+    /**
+     * Ctor.
+     * @param input Main input
+     * @param alt Alternative
+     */
+    public InputWithFallback(final Input input,
+        final IoCheckedFunc<IOException, Input> alt) {
+        this.main = input;
+        this.alternative = alt;
+    }
+
+    @Override
+    public InputStream stream() throws IOException {
+        InputStream stream;
+        try {
+            stream = this.main.stream();
+        } catch (final IOException ex) {
+            stream = this.alternative.apply(ex).stream();
+        }
+        return stream;
+    }
+
+}

src/test/java/org/cactoos/io/InputWithFallbackTest.java

@@ -0,0 +1,61 @@
+/**
+ * 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.io;
+
+import java.io.File;
+import org.cactoos.TextHasString;
+import org.cactoos.text.BytesAsText;
+import org.hamcrest.MatcherAssert;
+import org.hamcrest.Matchers;
+import org.junit.Test;
+
+/**
+ * Test case for {@link InputWithFallback}.
+ *
+ * @author Yegor Bugayenko (yegor256@gmail.com)
+ * @version $Id$
+ * @since 0.9
+ * @checkstyle JavadocMethodCheck (500 lines)
+ */
+public final class InputWithFallbackTest {
+
+    @Test
+    public void readsAlternativeInput() {
+        MatcherAssert.assertThat(
+            "Can't read alternative source",
+            new BytesAsText(
+                new InputAsBytes(
+                    new InputWithFallback(
+                        new FileAsInput(
+                            new File("/this-file-is-absent-for-sure.txt")
+                        ),
+                        new BytesAsInput("hello, world!")
+                    )
+                )
+            ),
+            new TextHasString(Matchers.endsWith("world!"))
+        );
+    }
+
+}