Add fluent builder

2 files changed, 90 insertions, 0 deletions

diff --git a/container-core/src/main/java/com/yahoo/restapi/Json.java b/container-core/src/main/java/com/yahoo/restapi/Json.java
index f6800c05668..94c931e8ad4 100644
--- a/container-core/src/main/java/com/yahoo/restapi/Json.java
+++ b/container-core/src/main/java/com/yahoo/restapi/Json.java
@@ -1,5 +1,6 @@
 package com.yahoo.restapi;
 
+import com.yahoo.slime.Cursor;
 import com.yahoo.slime.Inspector;
 import com.yahoo.slime.ObjectTraverser;
 import com.yahoo.slime.Slime;
@@ -171,4 +172,62 @@ public class Json implements Iterable<Json> {
                 ", path='" + path + '\'' +
                 '}';
     }
+
+    /** Provides a fluent API for building a {@link Slime} instance. */
+    public static class Builder {
+        protected final Cursor cursor;
+
+        public static Builder.Array newArray() { return new Builder.Array(new Slime().setArray()); }
+        public static Builder.Object newObject() { return new Builder.Object(new Slime().setObject()); }
+
+        private Builder(Cursor cursor) { this.cursor = cursor; }
+
+        public static class Array extends Builder {
+            private Array(Cursor cursor) { super(cursor); }
+
+            public Builder.Array add(Builder.Array array) {
+                SlimeUtils.copyArray(array.cursor, cursor.addArray()); return this;
+            }
+            public Builder.Array add(Builder.Object object) {
+                SlimeUtils.copyObject(object.cursor, cursor.addObject()); return this;
+            }
+            public Builder.Array add(Json json) {
+                SlimeUtils.addValue(json.inspector, cursor.addObject()); return this;
+            }
+            /** Note: does not return {@code this}! */
+            public Builder.Array addArray() { return new Array(cursor.addArray()); }
+            /** Note: does not return {@code this}! */
+            public Builder.Object addObject() { return new Object(cursor.addObject()); }
+
+            public Builder.Array add(String value) { cursor.addString(value); return this; }
+            public Builder.Array add(long value) { cursor.addLong(value); return this; }
+            public Builder.Array add(double value) { cursor.addDouble(value); return this; }
+            public Builder.Array add(boolean value) { cursor.addBool(value); return this; }
+        }
+
+        public static class Object extends Builder {
+            private Object(Cursor cursor) { super(cursor); }
+
+            public Builder.Object set(String field, Builder.Array array) {
+                SlimeUtils.copyArray(array.cursor, cursor.setArray(field)); return this;
+            }
+            public Builder.Object set(String field, Builder.Object object) {
+                SlimeUtils.copyObject(object.cursor, cursor.setObject(field)); return this;
+            }
+            public Builder.Object set(String field, Json json) {
+                SlimeUtils.setObjectEntry(json.inspector, field, cursor); return this;
+            }
+            /** Note: does not return {@code this}! */
+            public Builder.Array setArray(String field) { return new Array(cursor.setArray(field)); }
+            /** Note: does not return {@code this}! */
+            public Builder.Object setObject(String field) { return new Object(cursor.setObject(field)); }
+
+            public Builder.Object set(String field, String value) { cursor.setString(field, value); return this; }
+            public Builder.Object set(String field, long value) { cursor.setLong(field, value); return this; }
+            public Builder.Object set(String field, double value) { cursor.setDouble(field, value); return this; }
+            public Builder.Object set(String field, boolean value) { cursor.setBool(field, value); return this; }
+        }
+
+        public Json build() { return Json.of(cursor); }
+    }
 }
diff --git a/container-core/src/test/java/com/yahoo/restapi/JsonTest.java b/container-core/src/test/java/com/yahoo/restapi/JsonTest.java
index 276c9b55ea4..0ef4872c908 100644
--- a/container-core/src/test/java/com/yahoo/restapi/JsonTest.java
+++ b/container-core/src/test/java/com/yahoo/restapi/JsonTest.java
@@ -92,4 +92,35 @@ class JsonTest {
         assertEquals("bar", json.f("string").asString("foo"));
         assertEquals("bar", json.f("string").asOptionalString().orElse("foo"));
     }
+
+    @Test
+    void builds_expected_json() {
+        var expected =
+                """
+                {
+                  "string": "bar",
+                  "integer": 42,
+                  "floaty": 8.25,
+                  "bool": true,
+                  "array": [
+                    1,
+                    2,
+                    3
+                  ],
+                  "quux": {
+                    "corge": "grault"
+                  }
+                }
+                """;
+        var json = Json.Builder.newObject()
+                .set("string", "bar")
+                .set("integer", 42)
+                .set("floaty", 8.25)
+                .set("bool", true)
+                .set("array", Json.Builder.newArray().add(1).add(2).add(3))
+                .set("quux", Json.Builder.newObject().set("corge", "grault"))
+                .build()
+                .toJson(true);
+        assertEquals(expected, json);
+    }
 }