Merge pull request #20720 from vespa-engine/hakonhall/file-templates

File templates

28 files changed, 1265 insertions, 0 deletions

diff --git a/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/BadTemplateException.java b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/BadTemplateException.java
new file mode 100644
index 00000000000..65d7ebaa02d
--- /dev/null
+++ b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/BadTemplateException.java
@@ -0,0 +1,13 @@
+// Copyright Yahoo. 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.template;
+
+import com.yahoo.vespa.hosted.node.admin.task.util.text.Cursor;
+
+/**
+ * @author hakonhall
+ */
+public class BadTemplateException extends TemplateException {
+    public BadTemplateException(Cursor location, String message) {
+        super(message + " at " + location.calculateLocation().lineAndColumnText());
+    }
+}
diff --git a/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/Form.java b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/Form.java
new file mode 100644
index 00000000000..6b38835e24f
--- /dev/null
+++ b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/Form.java
@@ -0,0 +1,86 @@
+// Copyright Yahoo. 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.template;
+
+import com.yahoo.vespa.hosted.node.admin.task.util.text.CursorRange;
+
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+
+/**
+ * A form is an instance of a template to be filled, e.g. values set for variable sections, etc.
+ *
+ * @see Template
+ * @author hakonhall
+ */
+public class Form {
+    private Form parent = null;
+    private final CursorRange range;
+    private final List<Section> sections;
+
+    private final Map<String, String> values = new HashMap<>();
+    private final Map<String, ListSection> lists;
+
+    Form(CursorRange range, List<Section> sections, Map<String, ListSection> lists) {
+        this.range = new CursorRange(range);
+        this.sections = List.copyOf(sections);
+        this.lists = Map.copyOf(lists);
+    }
+
+    void setParent(Form parent) { this.parent = parent; }
+
+    /** Set the value of a variable, e.g. %{=color}. */
+    public Form set(String name, String value) {
+        values.put(name, value);
+        return this;
+    }
+
+    /** Set the value of a variable and/or if-condition. */
+    public Form set(String name, boolean value) { return set(name, Boolean.toString(value)); }
+
+    public Form set(String name, int value) { return set(name, Integer.toString(value)); }
+    public Form set(String name, long value) { return set(name, Long.toString(value)); }
+
+    public Form set(String name, String format, String first, String... rest) {
+        var args = new Object[1 + rest.length];
+        args[0] = first;
+        System.arraycopy(rest, 0, args, 1, rest.length);
+        var value = String.format(format, args);
+
+        return set(name, value);
+    }
+
+    /** Add an instance of a list section after any previously added (for the given name)  */
+    public Form add(String name) {
+        var section = lists.get(name);
+        if (section == null) {
+            throw new NoSuchNameTemplateException(range, name);
+        }
+        return section.add();
+    }
+
+    public String render() {
+        var buffer = new StringBuilder((int) (range.length() * 1.2 + 128));
+        appendTo(buffer);
+        return buffer.toString();
+    }
+
+    public void appendTo(StringBuilder buffer) {
+        sections.forEach(section -> section.appendTo(buffer));
+    }
+
+    /** Returns a deep copy of this. No changes to this affects the returned form, and vice versa. */
+    Form copy() {
+        var builder = new FormBuilder(range.start());
+        sections.forEach(section -> section.appendCopyTo(builder.topLevelSectionList()));
+        return builder.build();
+    }
+
+    Optional<String> getVariableValue(String name) {
+        String value = values.get(name);
+        if (value != null) return Optional.of(value);
+        if (parent != null) return parent.getVariableValue(name);
+        return Optional.empty();
+    }
+}
diff --git a/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/FormBuilder.java b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/FormBuilder.java
new file mode 100644
index 00000000000..cae5279f68a
--- /dev/null
+++ b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/FormBuilder.java
@@ -0,0 +1,81 @@
+// Copyright Yahoo. 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.template;
+
+import com.yahoo.vespa.hosted.node.admin.task.util.text.Cursor;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * @author hakonhall
+ */
+class FormBuilder {
+    /** The top-level section list in this form. */
+    private final SectionList sectionList;
+    private final List<Section> allSections = new ArrayList<>();
+    private final Map<String, VariableSection> sampleVariables = new HashMap<>();
+    private final Map<String, IfSection> sampleIfSections = new HashMap<>();
+    private final Map<String, ListSection> lists = new HashMap<>();
+
+    FormBuilder(Cursor start) {
+        this.sectionList = new SectionList(start, this);
+    }
+
+    SectionList topLevelSectionList() { return sectionList; }
+
+    void addLiteralSection(LiteralSection section) {
+        allSections.add(section);
+    }
+
+    void addVariableSection(VariableSection section) {
+        // It's OK if the same name is used in an if-directive (as long as the value is boolean,
+        // determined when set on a form).
+
+        ListSection existing = lists.get(section.name());
+        if (existing != null)
+            throw new NameAlreadyExistsTemplateException(section.name(), existing.nameOffset(),
+                                                         section.nameOffset());
+
+        sampleVariables.put(section.name(), section);
+        allSections.add(section);
+    }
+
+    void addIfSection(IfSection section) {
+        // It's OK if the same name is used in a variable section (as long as the value is boolean,
+        // determined when set on a form).
+
+        ListSection list = lists.get(section.name());
+        if (list != null)
+            throw new NameAlreadyExistsTemplateException(section.name(), list.nameOffset(),
+                                                         section.nameOffset());
+
+        sampleIfSections.put(section.name(), section);
+        allSections.add(section);
+    }
+
+    void addListSection(ListSection section) {
+        VariableSection variableSection = sampleVariables.get(section.name());
+        if (variableSection != null)
+            throw new NameAlreadyExistsTemplateException(section.name(), variableSection.nameOffset(),
+                                                         section.nameOffset());
+
+        IfSection ifSection = sampleIfSections.get(section.name());
+        if (ifSection != null)
+            throw new NameAlreadyExistsTemplateException(section.name(), ifSection.nameOffset(),
+                                                         section.nameOffset());
+
+        ListSection previous = lists.put(section.name(), section);
+        if (previous != null)
+            throw new NameAlreadyExistsTemplateException(section.name(), previous.nameOffset(),
+                                                         section.nameOffset());
+        allSections.add(section);
+    }
+
+    Form build() {
+        var form = new Form(sectionList.range(), sectionList.sections(), lists);
+        allSections.forEach(section -> section.setForm(form));
+        return form;
+    }
+}
diff --git a/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/IfSection.java b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/IfSection.java
new file mode 100644
index 00000000000..8775e764b4f
--- /dev/null
+++ b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/IfSection.java
@@ -0,0 +1,68 @@
+// Copyright Yahoo. 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.template;
+
+import com.yahoo.vespa.hosted.node.admin.task.util.text.Cursor;
+import com.yahoo.vespa.hosted.node.admin.task.util.text.CursorRange;
+
+import java.util.Optional;
+
+/**
+ * @author hakonhall
+ */
+class IfSection extends Section {
+    private final boolean negated;
+    private final String name;
+    private final Cursor nameOffset;
+    private final SectionList ifSections;
+    private final Optional<SectionList> elseSections;
+
+    IfSection(CursorRange range, boolean negated, String name, Cursor nameOffset,
+              SectionList ifSections, Optional<SectionList> elseSections) {
+        super(range);
+        this.negated = negated;
+        this.name = name;
+        this.nameOffset = nameOffset;
+        this.ifSections = ifSections;
+        this.elseSections = elseSections;
+    }
+
+    String name() { return name; }
+    Cursor nameOffset() { return nameOffset; }
+
+    @Override
+    void appendTo(StringBuilder buffer) {
+        Optional<String> stringValue = form().getVariableValue(name);
+        if (stringValue.isEmpty())
+            throw new TemplateNameNotSetException(name, nameOffset);
+
+        final boolean value;
+        if (stringValue.get().equals("true")) {
+            value = true;
+        } else if (stringValue.get().equals("false")) {
+            value = false;
+        } else {
+            throw new NotBooleanValueTemplateException(name);
+        }
+
+        boolean condition = negated ? !value : value;
+        if (condition) {
+            ifSections.sections().forEach(section -> section.appendTo(buffer));
+        } else if (elseSections.isPresent()) {
+            elseSections.get().sections().forEach(section -> section.appendTo(buffer));
+        }
+    }
+
+    @Override
+    void appendCopyTo(SectionList sectionList) {
+        SectionList ifSectionCopy = new SectionList(ifSections.range().start(), sectionList.formBuilder());
+        ifSections.sections().forEach(section -> section.appendCopyTo(ifSectionCopy));
+
+        Optional<SectionList> elseSectionCopy = elseSections.map(elseSections2 -> {
+            SectionList elseSectionCopy2 = new SectionList(elseSections2.range().start(), sectionList.formBuilder());
+            elseSections2.sections().forEach(section -> section.appendCopyTo(elseSectionCopy2));
+            return elseSectionCopy2;
+        });
+
+        sectionList.appendIfSection(negated, name, nameOffset, range().end(), ifSectionCopy, elseSectionCopy);
+    }
+}
diff --git a/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/ListSection.java b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/ListSection.java
new file mode 100644
index 00000000000..bc68cf96153
--- /dev/null
+++ b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/ListSection.java
@@ -0,0 +1,54 @@
+// Copyright Yahoo. 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.template;
+
+import com.yahoo.vespa.hosted.node.admin.task.util.text.Cursor;
+import com.yahoo.vespa.hosted.node.admin.task.util.text.CursorRange;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * @author hakonhall
+ */
+class ListSection extends Section {
+    private final String name;
+    private final Cursor nameOffset;
+    private final Form body;
+    private final List<Form> elements = new ArrayList<>();
+
+    ListSection(CursorRange range, String name, Cursor nameOffset, Form body) {
+        super(range);
+        this.name = name;
+        this.nameOffset = new Cursor(nameOffset);
+        this.body = body;
+    }
+
+    String name() { return name; }
+    Cursor nameOffset() { return new Cursor(nameOffset); }
+
+    @Override
+    void setForm(Form form) {
+        super.setForm(form);
+        body.setParent(form);
+    }
+
+    Form add() {
+        Form element = body.copy();
+        element.setParent(form());
+        elements.add(element);
+        return element;
+    }
+
+    @Override
+    void appendTo(StringBuilder buffer) {
+        elements.forEach(form -> form.appendTo(buffer));
+    }
+
+    @Override
+    void appendCopyTo(SectionList sectionList) {
+        // avoid copying elements for now
+        // Optimization: Reuse body in copy, since it is only used for copying.
+
+        sectionList.appendListSection(name, nameOffset, range().end(), body);
+    }
+}
diff --git a/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/LiteralSection.java b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/LiteralSection.java
new file mode 100644
index 00000000000..c03653253af
--- /dev/null
+++ b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/LiteralSection.java
@@ -0,0 +1,26 @@
+// Copyright Yahoo. 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.template;
+
+import com.yahoo.vespa.hosted.node.admin.task.util.text.CursorRange;
+
+/**
+ * Represents a template literal section
+ *
+ * @see Template
+ * @author hakonhall
+ */
+class LiteralSection extends Section {
+    LiteralSection(CursorRange range) {
+        super(range);
+    }
+
+    @Override
+    void appendTo(StringBuilder buffer) {
+        range().appendTo(buffer);
+    }
+
+    @Override
+    void appendCopyTo(SectionList sectionList) {
+        sectionList.appendLiteralSection(range().end());
+    }
+}
diff --git a/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/NameAlreadyExistsTemplateException.java b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/NameAlreadyExistsTemplateException.java
new file mode 100644
index 00000000000..dd92af14609
--- /dev/null
+++ b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/NameAlreadyExistsTemplateException.java
@@ -0,0 +1,22 @@
+// Copyright Yahoo. 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.template;
+
+import com.yahoo.vespa.hosted.node.admin.task.util.text.Cursor;
+import com.yahoo.vespa.hosted.node.admin.task.util.text.CursorRange;
+
+/**
+ * @author hakonhall
+ */
+public class NameAlreadyExistsTemplateException extends TemplateException {
+    public NameAlreadyExistsTemplateException(String name, CursorRange range) {
+        super("Name '" + name + "' already exists in the " + describeSection(range));
+    }
+
+    public NameAlreadyExistsTemplateException(String name, Cursor firstNameLocation,
+                                              Cursor secondNameLocation) {
+        super("Section named '" + name + "' at " +
+              firstNameLocation.calculateLocation().lineAndColumnText() +
+              " conflicts with earlier section with the same name at " +
+              secondNameLocation.calculateLocation().lineAndColumnText());
+    }
+}
diff --git a/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/NoSuchNameTemplateException.java b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/NoSuchNameTemplateException.java
new file mode 100644
index 00000000000..706d347d39d
--- /dev/null
+++ b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/NoSuchNameTemplateException.java
@@ -0,0 +1,13 @@
+// Copyright Yahoo. 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.template;
+
+import com.yahoo.vespa.hosted.node.admin.task.util.text.CursorRange;
+
+/**
+ * @author hakonhall
+ */
+public class NoSuchNameTemplateException extends TemplateException {
+    public NoSuchNameTemplateException(CursorRange range, String name) {
+        super("No such element '" + name + "' in the " + describeSection(range));
+    }
+}
diff --git a/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/NotBooleanValueTemplateException.java b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/NotBooleanValueTemplateException.java
new file mode 100644
index 00000000000..6c6d157bb47
--- /dev/null
+++ b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/NotBooleanValueTemplateException.java
@@ -0,0 +1,11 @@
+// Copyright Yahoo. 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.template;
+
+/**
+ * @author hakonhall
+ */
+public class NotBooleanValueTemplateException extends TemplateException {
+    public NotBooleanValueTemplateException(String name) {
+        super(name + " was set to a non-boolean value: must be true or false");
+    }
+}
diff --git a/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/Section.java b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/Section.java
new file mode 100644
index 00000000000..234915770f8
--- /dev/null
+++ b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/Section.java
@@ -0,0 +1,30 @@
+// Copyright Yahoo. 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.template;
+
+import com.yahoo.vespa.hosted.node.admin.task.util.text.CursorRange;
+
+/**
+ * A section of a template text.
+ *
+ * @see Template
+ * @author hakonhall
+ */
+abstract class Section {
+    private final CursorRange range;
+    private Form form;
+
+    protected Section(CursorRange range) {
+        this.range = range;
+    }
+
+    void setForm(Form form) { this.form = form; }
+
+    /** Guaranteed to return non-null after FormBuilder::build() returns. */
+    protected Form form() { return form; }
+
+    protected CursorRange range() { return range; }
+
+    abstract void appendTo(StringBuilder buffer);
+
+    abstract void appendCopyTo(SectionList sectionList);
+}
diff --git a/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/SectionList.java b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/SectionList.java
new file mode 100644
index 00000000000..b9a8c4e8c41
--- /dev/null
+++ b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/SectionList.java
@@ -0,0 +1,68 @@
+// Copyright Yahoo. 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.template;
+
+import com.yahoo.vespa.hosted.node.admin.task.util.text.Cursor;
+import com.yahoo.vespa.hosted.node.admin.task.util.text.CursorRange;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Optional;
+
+/**
+ * A mutable list of sections at the same level that can be used to build a form, e.g. the if-body.
+ *
+ * @author hakonhall
+ */
+class SectionList {
+    private final Cursor start;
+    private final Cursor end;
+    private final FormBuilder formBuilder;
+
+    private final List<Section> sections = new ArrayList<>();
+
+    SectionList(Cursor start, FormBuilder formBuilder) {
+        this.start = new Cursor(start);
+        this.end = new Cursor(start);
+        this.formBuilder = formBuilder;
+    }
+
+    CursorRange range() { return new CursorRange(start, end); }
+    FormBuilder formBuilder() { return formBuilder; }
+    List<Section> sections() { return List.copyOf(sections); }
+
+    void appendLiteralSection(Cursor end) {
+        CursorRange range = verifyAndUpdateEnd(end);
+        var section = new LiteralSection(range);
+        formBuilder.addLiteralSection(section);
+        sections.add(section);
+    }
+
+    VariableSection appendVariableSection(String name, Cursor nameOffset, Cursor end) {
+        CursorRange range = verifyAndUpdateEnd(end);
+        var section = new VariableSection(range, name, nameOffset);
+        formBuilder.addVariableSection(section);
+        sections.add(section);
+        return section;
+    }
+
+    void appendIfSection(boolean negated, String name, Cursor nameOffset, Cursor end,
+                         SectionList ifSections, Optional<SectionList> elseSections) {
+        CursorRange range = verifyAndUpdateEnd(end);
+        var section = new IfSection(range, negated, name, nameOffset, ifSections, elseSections);
+        formBuilder.addIfSection(section);
+        sections.add(section);
+    }
+
+    void appendListSection(String name, Cursor nameOffset, Cursor end, Form body) {
+        CursorRange range = verifyAndUpdateEnd(end);
+        var section = new ListSection(range, name, nameOffset, body);
+        formBuilder.addListSection(section);
+        sections.add(section);
+    }
+
+    private CursorRange verifyAndUpdateEnd(Cursor newEnd) {
+        var range = new CursorRange(this.end, newEnd);
+        this.end.set(newEnd);
+        return range;
+    }
+}
diff --git a/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/Template.java b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/Template.java
new file mode 100644
index 00000000000..344424c7946
--- /dev/null
+++ b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/Template.java
@@ -0,0 +1,44 @@
+// Copyright Yahoo. 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.template;
+
+/**
+ * The Java representation of a template text.
+ *
+ * <p>A template is a sequence of literal text and dynamic sections defined by %{...} directives:</p>
+ *
+ * <pre>
+ *     template: section*
+ *     section: literal | variable | list
+ *     literal: plain text not containing %{
+ *     variable: %{=id}
+ *     if: %{if [!]id}template[%{else}template]%{end}
+ *     list: %{list id}template%{end}
+ *     id: a valid Java identifier
+ * </pre>
+ *
+ * <p>If the directive's end delimiter (}) is preceded by a "-" char, then any newline (\n)
+ * immediately following the end delimiter is removed.</p>
+ *
+ * <p>To use the template create a form ({@link #newForm()}), fill the form (e.g.
+ * {@link Form#set(String, String) Form.set()}), and render the String ({@link Form#render()}).</p>
+ *
+ * @see Form
+ * @see TemplateFile
+ * @author hakonhall
+ */
+public class Template {
+    private final Form form;
+
+    public static Template from(String text) { return from(text, new TemplateDescriptor()); }
+
+    public static Template from(String text, TemplateDescriptor descriptor) {
+        return TemplateParser.parse(text, descriptor).template();
+    }
+
+    Template(Form form) {
+        this.form = form;
+    }
+
+    public Form newForm() { return form.copy(); }
+
+}
diff --git a/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/TemplateDescriptor.java b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/TemplateDescriptor.java
new file mode 100644
index 00000000000..05d4f82d8d3
--- /dev/null
+++ b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/TemplateDescriptor.java
@@ -0,0 +1,30 @@
+// Copyright Yahoo. 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.template;
+
+/**
+ * Specifies the how to interpret a template text.
+ *
+ * @author hakonhall
+ */
+public class TemplateDescriptor {
+
+    private String startDelimiter = "%{";
+    private String endDelimiter = "}";
+
+    public TemplateDescriptor() {}
+
+    public TemplateDescriptor(TemplateDescriptor that) {
+        this.startDelimiter = that.startDelimiter;
+        this.endDelimiter = that.endDelimiter;
+    }
+
+    /** Use these delimiters instead of the standard "%{" and "}" to start and end a template directive. */
+    public TemplateDescriptor setDelimiters(String startDelimiter, String endDelimiter) {
+        this.startDelimiter = Token.verifyDelimiter(startDelimiter);
+        this.endDelimiter = Token.verifyDelimiter(endDelimiter);
+        return this;
+    }
+
+    public String startDelimiter() { return startDelimiter; }
+    public String endDelimiter() { return endDelimiter; }
+}
diff --git a/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/TemplateException.java b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/TemplateException.java
new file mode 100644
index 00000000000..f231583de52
--- /dev/null
+++ b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/TemplateException.java
@@ -0,0 +1,18 @@
+// Copyright Yahoo. 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.template;
+
+import com.yahoo.vespa.hosted.node.admin.task.util.text.CursorRange;
+
+/**
+ * @author hakonhall
+ */
+public class TemplateException extends RuntimeException {
+    public TemplateException(String message) { super(message); }
+
+    protected static String describeSection(CursorRange range) {
+        var startLocation = range.start().calculateLocation();
+        var endLocation = range.end().calculateLocation();
+        return "template section starting at line " + startLocation.line() + " and column " + startLocation.column() +
+               ", and ending at line " + endLocation.line() + " and column " + endLocation.column();
+    }
+}
diff --git a/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/TemplateFile.java b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/TemplateFile.java
new file mode 100644
index 00000000000..0c1a26f4f65
--- /dev/null
+++ b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/TemplateFile.java
@@ -0,0 +1,20 @@
+// Copyright Yahoo. 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.template;
+
+import com.yahoo.vespa.hosted.node.admin.task.util.file.UnixPath;
+
+import java.nio.file.Path;
+
+/**
+ * Parses a template file, see {@link Template} for details.
+ *
+ * @author hakonhall
+ */
+public class TemplateFile {
+    public static Template read(Path path) { return read(path, new TemplateDescriptor()); }
+
+    public static Template read(Path path, TemplateDescriptor descriptor) {
+        String content = new UnixPath(path).readUtf8File();
+        return Template.from(content, descriptor);
+    }
+}
diff --git a/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/TemplateNameNotSetException.java b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/TemplateNameNotSetException.java
new file mode 100644
index 00000000000..d65c2a7c4d6
--- /dev/null
+++ b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/TemplateNameNotSetException.java
@@ -0,0 +1,13 @@
+// Copyright Yahoo. 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.template;
+
+import com.yahoo.vespa.hosted.node.admin.task.util.text.Cursor;
+
+/**
+ * @author hakonhall
+ */
+public class TemplateNameNotSetException extends TemplateException {
+    public TemplateNameNotSetException(String name, Cursor nameOffset) {
+        super("Variable at " + nameOffset.calculateLocation().lineAndColumnText() + " has not been set: " + name);
+    }
+}
diff --git a/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/TemplateParser.java b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/TemplateParser.java
new file mode 100644
index 00000000000..93a83a3d29f
--- /dev/null
+++ b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/TemplateParser.java
@@ -0,0 +1,161 @@
+// Copyright Yahoo. 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.template;
+
+import com.yahoo.vespa.hosted.node.admin.task.util.text.Cursor;
+
+import java.util.EnumSet;
+import java.util.Optional;
+
+/**
+ * Parses a template String, see {@link Template} for details.
+ *
+ * @author hakonhall
+ */
+class TemplateParser {
+    private final TemplateDescriptor descriptor;
+    private final Cursor start;
+    private final Cursor current;
+    private final FormBuilder formBuilder;
+
+    static TemplateParser parse(String text, TemplateDescriptor descriptor) {
+        return parse(new TemplateDescriptor(descriptor), new Cursor(text), EnumSet.of(Sentinel.EOT));
+    }
+
+    private static TemplateParser parse(TemplateDescriptor descriptor, Cursor start, EnumSet<Sentinel> sentinel) {
+        var parser = new TemplateParser(descriptor, start);
+        parser.parse(parser.formBuilder.topLevelSectionList(), sentinel);
+        return parser;
+    }
+
+    private enum Sentinel { ELSE, END, EOT }
+
+    private TemplateParser(TemplateDescriptor descriptor, Cursor start) {
+        this.descriptor = descriptor;
+        this.start = new Cursor(start);
+        this.current = new Cursor(start);
+        this.formBuilder = new FormBuilder(start);
+    }
+
+    Template template() { return new Template(formBuilder.build()); }
+
+    private Sentinel parse(SectionList sectionList, EnumSet<Sentinel> sentinels) {
+        do {
+            current.advanceTo(descriptor.startDelimiter());
+            if (!current.equals(start)) {
+                sectionList.appendLiteralSection(current);
+            }
+
+            if (current.eot()) {
+                if (!sentinels.contains(Sentinel.EOT)) {
+                    throw new BadTemplateException(current,
+                                                   "Missing end directive for section started at " +
+                                                   start.calculateLocation().lineAndColumnText());
+                }
+                return Sentinel.EOT;
+            }
+
+            Optional<Sentinel> sentinel = parseSection(sectionList, sentinels);
+            if (sentinel.isPresent()) return sentinel.get();
+        } while (true);
+    }
+
+    private Optional<Sentinel> parseSection(SectionList sectionList, EnumSet<Sentinel> sentinels) {
+        current.skip(descriptor.startDelimiter());
+
+        if (current.skip(Token.VARIABLE_DIRECTIVE_CHAR)) {
+            parseVariableSection(sectionList);
+        } else {
+            var startOfType = new Cursor(current);
+            String type = skipId().orElseThrow(() -> new BadTemplateException(current, "Missing section name"));
+
+            switch (type) {
+                case "else":
+                    if (!sentinels.contains(Sentinel.ELSE))
+                        throw new BadTemplateException(startOfType, "Extraneous 'else'");
+                    parseEndDirective();
+                    return Optional.of(Sentinel.ELSE);
+                case "end":
+                    if (!sentinels.contains(Sentinel.END))
+                        throw new BadTemplateException(startOfType, "Extraneous 'end'");
+                    parseEndDirective();
+                    return Optional.of(Sentinel.END);
+                case "if":
+                    parseIfSection(sectionList);
+                    break;
+                case "list":
+                    parseListSection(sectionList);
+                    break;
+                default:
+                    throw new BadTemplateException(startOfType, "Unknown section '" + type + "'");
+            }
+        }
+
+        return Optional.empty();
+    }
+
+    private void parseVariableSection(SectionList sectionList) {
+        var nameStart = new Cursor(current);
+        String name = parseId();
+        parseEndDelimiter(true);
+        sectionList.appendVariableSection(name, nameStart, current);
+    }
+
+    private void parseEndDirective() {
+        parseEndDelimiter(true);
+    }
+
+    private void parseListSection(SectionList sectionList) {
+        skipRequiredWhitespaces();
+        var startOfName = new Cursor(current);
+        String name = parseId();
+        parseEndDelimiter(true);
+
+        TemplateParser bodyParser = parse(descriptor, current, EnumSet.of(Sentinel.END));
+        current.set(bodyParser.current);
+
+        sectionList.appendListSection(name, startOfName, current, bodyParser.formBuilder.build());
+    }
+
+    private void parseIfSection(SectionList sectionList) {
+        skipRequiredWhitespaces();
+        boolean negated = current.skip(Token.NEGATE_CHAR);
+        current.skipWhitespaces();
+        var startOfName = new Cursor(current);
+        String name = parseId();
+        parseEndDelimiter(true);
+
+        SectionList ifSectionList = new SectionList(current, formBuilder);
+        Sentinel ifSentinel = parse(ifSectionList, EnumSet.of(Sentinel.ELSE, Sentinel.END));
+
+        Optional<SectionList> elseSectionList = Optional.empty();
+        if (ifSentinel == Sentinel.ELSE) {
+            elseSectionList = Optional.of(new SectionList(current, formBuilder));
+            parse(elseSectionList.get(), EnumSet.of(Sentinel.END));
+        }
+
+        sectionList.appendIfSection(negated, name, startOfName, current, ifSectionList, elseSectionList);
+    }
+
+    private void skipRequiredWhitespaces() {
+        if (!current.skipWhitespaces()) {
+            throw new BadTemplateException(current, "Expected whitespace");
+        }
+    }
+
+    private String parseId() {
+        return skipId().orElseThrow(() -> new BadTemplateException(current, "Expected identifier"));
+    }
+
+    private Optional<String> skipId() { return Token.skipId(current); }
+
+    private boolean parseEndDelimiter(boolean skipNewline) {
+        boolean removeNewline = current.skip(Token.REMOVE_NEWLINE_CHAR);
+        if (!current.skip(descriptor.endDelimiter()))
+            throw new BadTemplateException(current, "Expected section end (" + descriptor.endDelimiter() + ")");
+
+        if (skipNewline && removeNewline)
+            current.skip('\n');
+
+        return removeNewline;
+    }
+}
diff --git a/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/Token.java b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/Token.java
new file mode 100644
index 00000000000..a83dab72025
--- /dev/null
+++ b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/Token.java
@@ -0,0 +1,60 @@
+// Copyright Yahoo. 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.template;
+
+import com.yahoo.vespa.hosted.node.admin.task.util.text.Cursor;
+import com.yahoo.vespa.hosted.node.admin.task.util.text.CursorRange;
+
+import java.util.Optional;
+
+/**
+ * @author hakonhall
+ */
+class Token {
+    static final char NEGATE_CHAR = '!';
+    static final char REMOVE_NEWLINE_CHAR = '-';
+    static final char VARIABLE_DIRECTIVE_CHAR = '=';
+
+    static Optional<String> skipId(Cursor cursor) {
+        if (cursor.eot() || !isIdStart(cursor.getChar())) return Optional.empty();
+
+        Cursor start = new Cursor(cursor);
+        cursor.increment();
+
+        while (!cursor.eot() && isIdPart(cursor.getChar()))
+            cursor.increment();
+
+        return Optional.of(new CursorRange(start, cursor).string());
+    }
+
+    /** A delimiter either starts a directive (e.g. %{) or ends it (e.g. }). */
+    static String verifyDelimiter(String delimiter) {
+        if (!isAsciiToken(delimiter)) {
+            throw new IllegalArgumentException("Invalid delimiter: '" + delimiter + "'");
+        }
+        return delimiter;
+    }
+
+    /** Returns true for a non-empty string with only ASCII token characters. */
+    private static boolean isAsciiToken(String string) {
+        if (string.isEmpty()) return false;
+        for (char c : string.toCharArray()) {
+            if (!isAsciiTokenChar(c)) return false;
+        }
+        return true;
+    }
+
+    /** Returns true if char is a printable ASCII character except space (isgraph(3)). */
+    private static boolean isAsciiTokenChar(char c) {
+        // 0x1F unit separator
+        // 0x20 space
+        // 0x21 !
+        // ...
+        // 0x7E ~
+        // 0x7F del
+        return 0x20 < c && c < 0x7F;
+    }
+
+    // Our identifiers are equivalent to a Java identifiers.
+    private static boolean isIdStart(char c) { return Character.isJavaIdentifierStart(c); }
+    private static boolean isIdPart(char c) { return Character.isJavaIdentifierPart(c); }
+}
diff --git a/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/VariableSection.java b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/VariableSection.java
new file mode 100644
index 00000000000..bf211a01190
--- /dev/null
+++ b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/VariableSection.java
@@ -0,0 +1,37 @@
+// Copyright Yahoo. 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.template;
+
+import com.yahoo.vespa.hosted.node.admin.task.util.text.Cursor;
+import com.yahoo.vespa.hosted.node.admin.task.util.text.CursorRange;
+
+/**
+ * Represents a template variable section
+ *
+ * @see Template
+ * @author hakonhall
+ */
+class VariableSection extends Section {
+    private final String name;
+    private final Cursor nameOffset;
+
+    VariableSection(CursorRange range, String name, Cursor nameOffset) {
+        super(range);
+        this.name = name;
+        this.nameOffset = nameOffset;
+    }
+
+    String name() { return name; }
+    Cursor nameOffset() { return new Cursor(nameOffset); }
+
+    @Override
+    void appendTo(StringBuilder buffer) {
+        String value = form().getVariableValue(name)
+                             .orElseThrow(() -> new TemplateNameNotSetException(name, nameOffset));
+        buffer.append(value);
+    }
+
+    @Override
+    void appendCopyTo(SectionList sectionList) {
+        sectionList.appendVariableSection(name, nameOffset, range().end());
+    }
+}
diff --git a/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/package-info.java b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/package-info.java
new file mode 100644
index 00000000000..5bb8f656305
--- /dev/null
+++ b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/template/package-info.java
@@ -0,0 +1,5 @@
+// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+@ExportPackage
+package com.yahoo.vespa.hosted.node.admin.task.util.template;
+
+import com.yahoo.osgi.annotation.ExportPackage;
diff --git a/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/text/Cursor.java b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/text/Cursor.java
new file mode 100644
index 00000000000..2fc3f8bac60
--- /dev/null
+++ b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/text/Cursor.java
@@ -0,0 +1,165 @@
+// Copyright Yahoo. 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.text;
+
+import java.util.Objects;
+
+/**
+ * Cursor is a mutable offset into a fixed String, and useful for String parsing.
+ *
+ * @author hakonhall
+ */
+// @Mutable
+public class Cursor {
+    private final String text;
+    private int offset;
+    private TextLocation locationCache;
+
+    /** Creates a pointer to the first char of {@code text}, which is EOT if {@code text} is empty. */
+    public Cursor(String text) { this(text, 0, new TextLocation()); }
+
+    public Cursor(Cursor that) { this(that.text, that.offset, that.locationCache); }
+
+    private Cursor(String text, int offset, TextLocation location) {
+        this.text = Objects.requireNonNull(text);
+        this.offset = offset;
+        this.locationCache = Objects.requireNonNull(location);
+    }
+
+    /** Returns the substring of {@code text} starting at {@link #offset()} (to EOT). */
+    @Override
+    public String toString() { return text.substring(offset); }
+
+    public String fullText() { return text; }
+    public int offset() { return offset; }
+    public boolean bot() { return offset == 0; }
+    public boolean eot() { return offset == text.length(); }
+    public boolean startsWith(char c) { return offset < text.length() && text.charAt(offset) == c; }
+    public boolean startsWith(String prefix) { return text.startsWith(prefix, offset); }
+
+    /** @throws IndexOutOfBoundsException if {@link #eot()}. */
+    public char getChar() { return text.charAt(offset); }
+
+    /** The number of chars between pointer and EOT. */
+    public int length() { return text.length() - offset; }
+
+    /** Calculate the current text location in O(length(text)). */
+    public TextLocation calculateLocation() {
+        if (offset < locationCache.offset()) {
+            locationCache = new TextLocation();
+        } else if (offset == locationCache.offset()) {
+            return locationCache;
+        }
+
+        int lineIndex = locationCache.lineIndex();
+        int columnIndex = locationCache.columnIndex();
+        for (int i = locationCache.offset(); i < offset; ++i) {
+            if (text.charAt(i) == '\n') {
+                ++lineIndex;
+                columnIndex = 0;
+            } else {
+                ++columnIndex;
+            }
+        }
+
+        locationCache = new TextLocation(offset, lineIndex, columnIndex);
+        return locationCache;
+    }
+
+    public void set(Cursor that) {
+        if (that.text != text) {
+            throw new IllegalArgumentException("'that' doesn't refer to the same text");
+        }
+
+        this.offset = that.offset;
+    }
+
+    /** Advance substring.length() if this startsWith the substring, returning true if so. */
+    public boolean skip(String substring) {
+        if (startsWith(substring)) {
+            offset += substring.length();
+            return true;
+        } else {
+            return false;
+        }
+    }
+
+    public boolean skip(char c) {
+        if (startsWith(c)) {
+            ++offset;
+            return true;
+        } else {
+            return false;
+        }
+    }
+
+    /** If the current char is a whitespace, skip it and return true. */
+    public boolean skipWhitespace() {
+        if (!eot() && Character.isWhitespace(getChar())) {
+            ++offset;
+            return true;
+        } else {
+            return false;
+        }
+    }
+
+    /** Returns true if at least one whitespace was skipped. */
+    public boolean skipWhitespaces() {
+        if (skipWhitespace()) {
+            while (skipWhitespace())
+                ++offset;
+            return true;
+        } else {
+            return false;
+        }
+    }
+
+    /** Return false if eot(), otherwise advance to the next char and return true. */
+    public boolean increment() {
+        if (eot()) return false;
+        ++offset;
+        return true;
+    }
+
+    /**
+     * Advance {@code distance} chars until bot() or eot() is reached (distance may be negative),
+     * and return true if this cursor moved the full distance.
+     */
+    public boolean advance(int distance) {
+        int newOffset = offset + distance;
+        if (newOffset < 0) {
+            this.offset = 0;
+            return false;
+        } else if (newOffset > text.length()) {
+            this.offset = text.length();
+            return false;
+        } else {
+            this.offset = newOffset;
+            return true;
+        }
+    }
+
+    /** Advance pointer until start of needle is found (and return true), or EOT is reached (and return false). */
+    public boolean advanceTo(String needle) {
+        int index = text.indexOf(needle, offset);
+        if (index == -1) {
+            offset = text.length();
+            return false; // and eot() is true
+        } else {
+            offset = index;
+            return true; // and eot() is false
+        }
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+        Cursor cursor = (Cursor) o;
+        return offset == cursor.offset && text.equals(cursor.text);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(text, offset);
+    }
+}
diff --git a/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/text/CursorRange.java b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/text/CursorRange.java
new file mode 100644
index 00000000000..23ac69ccee2
--- /dev/null
+++ b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/text/CursorRange.java
@@ -0,0 +1,38 @@
+// Copyright Yahoo. 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.text;
+
+/**
+ * A start- and end- offset in an underlying String.
+ *
+ * @author hakonhall
+ */
+public class CursorRange {
+    private final Cursor start;
+    private final Cursor end;
+
+    @SuppressWarnings("StringEquality")
+    public CursorRange(Cursor start, Cursor end) {
+        if (start.fullText() != end.fullText()) {
+            throw new IllegalArgumentException("start and end points to different texts");
+        }
+
+        if (start.offset() > end.offset()) {
+            throw new IllegalArgumentException("start offset " + start.offset() +
+                                               " is beyond end offset " + end.offset());
+        }
+
+        this.start = new Cursor(start);
+        this.end = new Cursor(end);
+    }
+
+    public CursorRange(CursorRange that) {
+        this.start = new Cursor(that.start);
+        this.end = new Cursor(that.end);
+    }
+
+    public Cursor start() { return new Cursor(start); }
+    public Cursor end() { return new Cursor(end); }
+    public int length() { return end.offset() - start.offset(); }
+    public String string() { return start.fullText().substring(start.offset(), end.offset()); }
+    public void appendTo(StringBuilder buffer) { buffer.append(start.fullText(), start.offset(), end.offset()); }
+}
diff --git a/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/text/TextLocation.java b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/text/TextLocation.java
new file mode 100644
index 00000000000..32441c842b0
--- /dev/null
+++ b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/task/util/text/TextLocation.java
@@ -0,0 +1,30 @@
+// Copyright Yahoo. 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.text;
+
+/**
+ * The location within an implied multi-line String.
+ *
+ * @author hakonhall
+ */
+//@Immutable
+public class TextLocation {
+    private final int offset;
+    private final int lineIndex;
+    private final int columnIndex;
+
+    public TextLocation() { this(0, 0, 0); }
+
+    public TextLocation(int offset, int lineIndex, int columnIndex) {
+        this.offset = offset;
+        this.lineIndex = lineIndex;
+        this.columnIndex = columnIndex;
+    }
+
+    public int offset() { return offset; }
+    public int lineIndex() { return lineIndex; }
+    public int line() { return lineIndex + 1; }
+    public int columnIndex() { return columnIndex; }
+    public int column() { return columnIndex + 1; }
+
+    public String lineAndColumnText() { return "line " + line() + " and column " + column(); }
+}
diff --git a/node-admin/src/test/java/com/yahoo/vespa/hosted/node/admin/task/util/template/TemplateFileTest.java b/node-admin/src/test/java/com/yahoo/vespa/hosted/node/admin/task/util/template/TemplateFileTest.java
new file mode 100644
index 00000000000..40913184a67
--- /dev/null
+++ b/node-admin/src/test/java/com/yahoo/vespa/hosted/node/admin/task/util/template/TemplateFileTest.java
@@ -0,0 +1,73 @@
+// Copyright Yahoo. 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.template;
+
+import org.junit.jupiter.api.Test;
+
+import java.nio.file.Path;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+/**
+ * @author hakonhall
+ */
+class TemplateFileTest {
+    @Test
+    void verifyVariableSection() {
+        Form form = getForm("template1.tmp");
+        form.set("varname", "varvalue");
+        assertEquals("variable section 'varvalue'\n" +
+                     "end of text\n", form.render());
+    }
+
+    @Test
+    void verifySimpleListSection() {
+        Form form = getForm("template1.tmp");
+        form.set("varname", "varvalue")
+            .add("listname")
+            .set("varname", "different varvalue")
+            .set("varname2", "varvalue2");
+        assertEquals("variable section 'varvalue'\n" +
+                     "same variable section 'different varvalue'\n" +
+                     "different variable section 'varvalue2'\n" +
+                     "between ends\n" +
+                     "end of text\n", form.render());
+    }
+
+    @Test
+    void verifyNestedListSection() {
+        Form form = getForm("template2.tmp");
+        Form A0 = form.add("listA");
+        Form A0B0 = A0.add("listB");
+        Form A0B1 = A0.add("listB");
+
+        Form A1 = form.add("listA");
+        Form A1B0 = A1.add("listB");
+        assertEquals("body A\n" +
+                     "body B\n" +
+                     "body B\n" +
+                     "body A\n" +
+                     "body B\n",
+                     form.render());
+    }
+
+    @Test
+    void verifyVariableReferences() {
+        Form form = getForm("template3.tmp");
+        form.set("varname", "varvalue")
+            .set("innerVarSetAtTop", "val2");
+        form.add("l");
+        form.add("l")
+            .set("varname", "varvalue2");
+        assertEquals("varvalue\n" +
+                     "varvalue\n" +
+                     "inner varvalue\n" +
+                     "val2\n" +
+                     "inner varvalue2\n" +
+                     "val2\n",
+                     form.render());
+    }
+
+    private Form getForm(String filename) {
+        return TemplateFile.read(Path.of("src/test/resources/" + filename)).newForm();
+    }
+}
\ No newline at end of file
diff --git a/node-admin/src/test/java/com/yahoo/vespa/hosted/node/admin/task/util/template/TemplateTest.java b/node-admin/src/test/java/com/yahoo/vespa/hosted/node/admin/task/util/template/TemplateTest.java
new file mode 100644
index 00000000000..8d503dd4784
--- /dev/null
+++ b/node-admin/src/test/java/com/yahoo/vespa/hosted/node/admin/task/util/template/TemplateTest.java
@@ -0,0 +1,79 @@
+// Copyright Yahoo. 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.template;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+/**
+ * @author hakonhall
+ */
+public class TemplateTest {
+    @Test
+    void verifyNewlineRemoval() {
+        Form form = makeForm("a%{list a}\n" +
+                             "b%{end}\n" +
+                             "c%{list c-}\n" +
+                             "d%{end-}\n" +
+                             "e\n");
+        form.add("a");
+        form.add("c");
+
+        assertEquals("a\n" +
+                     "b\n" +
+                     "cde\n",
+                     form.render());
+    }
+
+    @Test
+    void verifyIfSection() {
+        Template template = Template.from("Hello%{if cond} world%{end}!");
+        assertEquals("Hello world!", template.newForm().set("cond", true).render());
+        assertEquals("Hello!", template.newForm().set("cond", false).render());
+    }
+
+    @Test
+    void verifyComplexIfSection() {
+        Template template = Template.from("%{if cond-}\n" +
+                                          "var: %{=varname}\n" +
+                                          "if: %{if !inner}inner is false%{end}\n" +
+                                          "list: %{list formname}element%{end}\n" +
+                                          "%{end-}\n");
+
+        assertEquals("", template.newForm().set("cond", false).render());
+
+        assertEquals("var: varvalue\n" +
+                     "if: \n" +
+                     "list: \n",
+                     template.newForm()
+                             .set("cond", true)
+                             .set("varname", "varvalue")
+                             .set("inner", true)
+                             .render());
+
+        Form form = template.newForm()
+                            .set("cond", true)
+                            .set("varname", "varvalue")
+                            .set("inner", false);
+        form.add("formname");
+
+        assertEquals("var: varvalue\n" +
+                     "if: inner is false\n" +
+                     "list: element\n", form.render());
+    }
+
+    @Test
+    void verifyElse() {
+        var template = Template.from("%{if cond-}\n" +
+                                     "if body\n" +
+                                     "%{else-}\n" +
+                                     "else body\n" +
+                                     "%{end-}\n");
+        assertEquals("if body\n", template.newForm().set("cond", true).render());
+        assertEquals("else body\n", template.newForm().set("cond", false).render());
+    }
+
+    private Form makeForm(String templateText) {
+        return Template.from(templateText).newForm();
+    }
+}
diff --git a/node-admin/src/test/resources/template1.tmp b/node-admin/src/test/resources/template1.tmp
new file mode 100644
index 00000000000..3468709cc2e
--- /dev/null
+++ b/node-admin/src/test/resources/template1.tmp
@@ -0,0 +1,10 @@
+variable section '%{=varname}'
+%{list listname-}
+same variable section '%{=varname}'
+different variable section '%{=varname2}'
+%{list innerlistname-}
+inner form text
+%{end-}
+between ends
+%{end-}
+end of text
diff --git a/node-admin/src/test/resources/template2.tmp b/node-admin/src/test/resources/template2.tmp
new file mode 100644
index 00000000000..3bfa30ec7d3
--- /dev/null
+++ b/node-admin/src/test/resources/template2.tmp
@@ -0,0 +1,4 @@
+%{list listA-}body A
+%{list listB-}body B
+%{end-}
+%{end-}
diff --git a/node-admin/src/test/resources/template3.tmp b/node-admin/src/test/resources/template3.tmp
new file mode 100644
index 00000000000..454b01761b5
--- /dev/null
+++ b/node-admin/src/test/resources/template3.tmp
@@ -0,0 +1,6 @@
+%{=varname}
+%{=varname}
+%{list l-}
+inner %{=varname}
+%{=innerVarSetAtTop}
+%{end-}