Add file editor

4 files changed, 163 insertions, 0 deletions

diff --git a/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/file/Editor.java b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/file/Editor.java
new file mode 100644
index 00000000000..cfd7756ad0e
--- /dev/null
+++ b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/file/Editor.java
@@ -0,0 +1,98 @@
+// Copyright 2018 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+package com.yahoo.vespa.hosted.node.admin.task.util.file;
+
+import com.yahoo.vespa.hosted.node.admin.component.TaskContext;
+
+import java.nio.charset.Charset;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.logging.Logger;
+
+import static com.yahoo.vespa.hosted.node.admin.task.util.file.IOExceptionUtil.uncheck;
+
+/**
+ * An editor meant to edit small line-based files like /etc/fstab.
+ *
+ * @author hakonhall
+ */
+public class Editor {
+    private static final Logger logger = Logger.getLogger(Editor.class.getName());
+    private static final Charset ENCODING = StandardCharsets.UTF_8;
+
+    private static int maxLength = 300;
+
+    private final Path path;
+    private final LineEditor editor;
+
+    public Editor(Path path, LineEditor editor) {
+        this.path = path;
+        this.editor = editor;
+    }
+
+    /**
+     * Read the file which must be encoded in UTF-8, use the LineEditor to edit it,
+     * and any modifications were done write it back and return true.
+     */
+    public boolean converge(TaskContext context) {
+        List<String> lines = uncheck(() -> Files.readAllLines(path, ENCODING));
+        List<String> newLines = new ArrayList<>();
+        StringBuilder diff = new StringBuilder();
+        boolean modified = false;
+
+        for (String line : lines) {
+            LineEdit edit = editor.edit(line);
+            switch (edit.getType()) {
+                case REMOVE:
+                    modified = true;
+                    maybeRemove(diff, line);
+                    break;
+                case REPLACE:
+                    modified = true;
+                    String replacementLine = edit.replacementLine();
+                    newLines.add(replacementLine);
+                    maybeRemove(diff, line);
+                    maybeAdd(diff, replacementLine);
+                    break;
+                case NONE:
+                    newLines.add(line);
+                    break;
+                default: throw new IllegalArgumentException("Unknown EditType " + edit.getType());
+            }
+        }
+
+        List<String> linesToAppend = editor.onComplete();
+        if (!linesToAppend.isEmpty()) {
+            modified = true;
+            newLines.addAll(linesToAppend);
+            linesToAppend.forEach(line -> maybeAdd(diff, line));
+        }
+
+        if (!modified) {
+            return false;
+        }
+
+        String diffDescription = diffTooLarge(diff) ? "" : ":\n" + diff.toString();
+        context.recordSystemModification(logger, "Patching file " + path + diffDescription);
+        uncheck(() -> Files.write(path, newLines, ENCODING));
+        return true;
+    }
+
+    private static void maybeAdd(StringBuilder diff, String line) {
+        if (!diffTooLarge(diff)) {
+            diff.append('+').append(line).append('\n');
+        }
+    }
+
+    private static void maybeRemove(StringBuilder diff, String line) {
+        if (!diffTooLarge(diff)) {
+            diff.append('-').append(line).append('\n');
+        }
+    }
+
+    private static boolean diffTooLarge(StringBuilder diff) {
+        return diff.length() > maxLength;
+    }
+}
diff --git a/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/file/EditorFactory.java b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/file/EditorFactory.java
new file mode 100644
index 00000000000..a167840a8a6
--- /dev/null
+++ b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/file/EditorFactory.java
@@ -0,0 +1,13 @@
+// Copyright 2018 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+package com.yahoo.vespa.hosted.node.admin.task.util.file;
+
+import java.nio.file.Path;
+
+/**
+ * @author hakonhall
+ */
+public class EditorFactory {
+    public Editor create(Path path, LineEditor editor) {
+        return new Editor(path, editor);
+    }
+}
diff --git a/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/file/LineEdit.java b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/file/LineEdit.java
new file mode 100644
index 00000000000..d822b6fae80
--- /dev/null
+++ b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/file/LineEdit.java
@@ -0,0 +1,31 @@
+// Copyright 2018 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+package com.yahoo.vespa.hosted.node.admin.task.util.file;
+
+import javax.annotation.concurrent.Immutable;
+import java.util.Optional;
+
+import static com.yahoo.vespa.hosted.node.admin.task.util.file.LineEdit.Type.REMOVE;
+import static com.yahoo.vespa.hosted.node.admin.task.util.file.LineEdit.Type.REPLACE;
+import static com.yahoo.vespa.hosted.node.admin.task.util.file.LineEdit.Type.NONE;
+
+/**
+ * @author hakonhall
+ */
+@Immutable
+public class LineEdit {
+    enum Type { NONE, REPLACE, REMOVE}
+    private final Type type;
+    private final Optional<String> line;
+
+    public static LineEdit none() { return new LineEdit(NONE, Optional.empty()); }
+    public static LineEdit remove() { return new LineEdit(REMOVE, Optional.empty()); }
+    public static LineEdit replaceWith(String line) { return new LineEdit(REPLACE, Optional.of(line)); }
+
+    private LineEdit(Type type, Optional<String> newLine) {
+        this.type = type;
+        this.line = newLine;
+    }
+
+    public Type getType() { return type; }
+    public String replacementLine() { return line.get(); }
+}
diff --git a/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/file/LineEditor.java b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/file/LineEditor.java
new file mode 100644
index 00000000000..de43eb57074
--- /dev/null
+++ b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/file/LineEditor.java
@@ -0,0 +1,21 @@
+// Copyright 2018 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+package com.yahoo.vespa.hosted.node.admin.task.util.file;
+
+import java.util.List;
+
+/**
+ * @author hakonhall
+ */
+public interface LineEditor {
+    /**
+     * @param line The line of a file.
+     * @return The edited line, or empty if the line should be removed.
+     */
+    LineEdit edit(String line);
+
+    /**
+     * Called after edit() has been called on all lines in the file.
+     * @return Lines to append to the file.
+     */
+    List<String> onComplete();
+}