#939 AppendTo for appending content to files

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

@@ -0,0 +1,79 @@
+/*
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2017-2018 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 java.io.IOException;
+import java.io.OutputStream;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.StandardOpenOption;
+import org.cactoos.Output;
+import org.cactoos.text.FormattedText;
+
+/**
+ * Output that appends content to a given file.
+ *
+ * <p>There is no thread-safety guarantee.
+ *
+ * @since 1.0
+ */
+public final class AppendTo implements Output {
+
+    /**
+     * Source of the output.
+     */
+    private final File source;
+
+    /**
+     * Ctor.
+     * @param path Path as a source of a File.
+     */
+    public AppendTo(final Path path) {
+        this(path.toFile());
+    }
+
+    /**
+     * Ctor.
+     * @param source File to which content will be appended.
+     */
+    public AppendTo(final File source) {
+        this.source = source;
+    }
+
+    @Override
+    public OutputStream stream() throws Exception {
+        if (!this.source.exists()) {
+            throw new IOException(
+                new FormattedText(
+                    "Can not append to %s file. It does not exist",
+                    this.source.getAbsolutePath()
+                ).asString()
+            );
+        }
+        return Files.newOutputStream(
+            this.source.toPath(), StandardOpenOption.APPEND
+        );
+    }
+}

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

@@ -0,0 +1,94 @@
+/*
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2017-2018 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 java.io.IOException;
+import org.cactoos.text.FormattedText;
+import org.cactoos.text.JoinedText;
+import org.cactoos.text.RandomText;
+import org.cactoos.text.TextOf;
+import org.hamcrest.MatcherAssert;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.ExpectedException;
+import org.junit.rules.TemporaryFolder;
+import org.llorllale.cactoos.matchers.TextIs;
+
+/**
+ * Test case for {@link AppendTo}.
+ *
+ * @since 1.0
+ * @checkstyle MagicNumber (500 line)
+ * @checkstyle ClassDataAbstractionCouplingCheck (100 lines)
+ */
+public final class AppendToTest {
+
+    /**
+     * Temporary files and folders generator.
+     */
+    @Rule
+    public final TemporaryFolder folder = new TemporaryFolder();
+
+    /**
+     * A rule for handling an exception.
+     */
+    @Rule
+    public final ExpectedException exception = ExpectedException.none();
+
+    /**
+     * Ensures that AppendTo is failing on a negative predicate result.
+     * @throws Exception if fails
+     */
+    @Test
+    public void failsIfFileDoesNotExist() throws Exception {
+        final File source = new File(new RandomText(5).asString());
+        this.exception.expect(IOException.class);
+        this.exception.expectMessage(
+            new FormattedText(
+                "Can not append to %s file. It does not exist",
+                source.getAbsolutePath()
+            ).asString()
+        );
+        new AppendTo(source).stream();
+    }
+
+    /**
+     * Ensures that AppendTo is appending to a given file.
+     * @throws Exception if fails
+     */
+    @Test
+    public void appendsToFile() throws Exception {
+        final File source = this.folder.newFile();
+        final String first = "abdcd";
+        new OutputTo(source).stream().write(first.getBytes());
+        final String second = "efgh";
+        new AppendTo(source).stream().write(second.getBytes());
+        MatcherAssert.assertThat(
+            "Does not contain expected text",
+            new TextOf(source),
+            new TextIs(new JoinedText("", first, second))
+        );
+    }
+}