Merge pull request #8992 from vespa-engine/hakonhall/minimal-template-class

Minimal template class

2 files changed, 96 insertions, 0 deletions

diff --git a/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/file/Templar.java b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/file/Templar.java
new file mode 100644
index 00000000000..113af76972b
--- /dev/null
+++ b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/file/Templar.java
@@ -0,0 +1,75 @@
+// Copyright 2019 Oath Inc. 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;
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * A very simple template engine when there's little complexity and lots of Velocity special characters $ and #,
+ * i.e. typically shell script.
+ *
+ * @author hakonhall
+ */
+public class Templar {
+    private final String template;
+
+    private String prefix = "<%=";
+    private String suffix = "%>";
+
+    private final Map<String, String> settings = new HashMap<>();
+
+    public static Templar fromUtf8File(Path path) {
+        return new Templar(new UnixPath(path).readUtf8File());
+    }
+
+    public Templar(String template) {
+        this.template = template;
+    }
+
+    public Templar set(String name, String value) {
+        settings.put(name, value);
+        return this;
+    }
+
+    public String resolve() {
+        StringBuilder text = new StringBuilder(template.length() * 2);
+
+        int start= 0;
+        int end;
+
+        for (; start < template.length(); start = end) {
+            int prefixStart = template.indexOf(prefix, start);
+
+
+            if (prefixStart == -1) {
+                text.append(template, start, template.length());
+                break;
+            } else {
+                text.append(template, start, prefixStart);
+            }
+
+            int suffixStart = template.indexOf(suffix, prefixStart + prefix.length());
+            if (suffixStart == -1) {
+                throw new IllegalArgumentException("Prefix at offset " + prefixStart + " is not terminated");
+            }
+
+            int prefixEnd = prefixStart + prefix.length();
+            String name = template.substring(prefixEnd, suffixStart).trim();
+            String value = settings.get(name);
+            if (value == null) {
+                throw new IllegalArgumentException("No value is set for name '" + name + "' at offset " + prefixEnd);
+            }
+
+            text.append(value);
+
+            end = suffixStart + suffix.length();
+        }
+
+        return text.toString();
+    }
+
+    public FileWriter getFileWriterTo(Path path) {
+        return new FileWriter(path, this::resolve);
+    }
+}
diff --git a/node-admin/src/test/java/com/yahoo/vespa/hosted/node/admin/task/util/file/TemplarTest.java b/node-admin/src/test/java/com/yahoo/vespa/hosted/node/admin/task/util/file/TemplarTest.java
new file mode 100644
index 00000000000..34b8312d426
--- /dev/null
+++ b/node-admin/src/test/java/com/yahoo/vespa/hosted/node/admin/task/util/file/TemplarTest.java
@@ -0,0 +1,21 @@
+// Copyright 2019 Oath Inc. 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 org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+/**
+ * @author hakonhall
+ */
+public class TemplarTest {
+    @Test
+    public void test() {
+        Templar templar = new Templar("x y <%= foo %>, some other <%=bar%> text");
+        templar.set("foo", "fidelity")
+                .set("bar", "halimov")
+                .set("not", "used");
+
+        assertEquals("x y fidelity, some other halimov text", templar.resolve());
+    }
+}
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