Issue #128 Add runtime-compiled JsonPath

Co-authored-by: simbo1905 <simbo1905@60hertz.com>

Author: cursoragent

json-java21-jsonpath/src/main/java/json/java21/jsonpath/JsonPath.java

@@ -77,11 +77,13 @@ static List<JsonValue> query(String path, JsonValue json) {
     ///
     /// This method is idempotent: if the receiver is already compiled, it returns itself.
     /// Implementations that do not support runtime compilation may return themselves.
-    JsonPath compile();
+    default JsonPath compile() {
+        return JsonPathCompiler.compile(this);
+    }
 
     /// Returns a (potentially) runtime-compiled version of the provided JsonPath.
     static JsonPath compile(JsonPath path) {
         Objects.requireNonNull(path, "path must not be null");
-        return path.compile();
+        return JsonPathCompiler.compile(path);
     }
 }

json-java21-jsonpath/src/main/java/json/java21/jsonpath/JsonPathAstBacked.java

@@ -0,0 +1,10 @@
+package json.java21.jsonpath;
+
+/// Marker for `JsonPath` implementations backed by a `JsonPathAst.Root`.
+///
+/// This is intentionally package-private so tests in this package can inspect internals,
+/// while keeping the public API surface small.
+interface JsonPathAstBacked {
+    JsonPathAst.Root ast();
+}
+

json-java21-jsonpath/src/main/java/json/java21/jsonpath/JsonPathAstPath.java

@@ -9,7 +9,7 @@
 /// Package-private AST-backed `JsonPath` implementation.
 ///
 /// This is the behavior-preserving interpreter that walks `JsonPathAst` at runtime.
-final class JsonPathAstPath implements JsonPath {
+final class JsonPathAstPath implements JsonPath, JsonPathAstBacked {
 
     private static final Logger LOG = Logger.getLogger(JsonPathAstPath.class.getName());
 
@@ -26,17 +26,12 @@ public List<JsonValue> query(JsonValue json) {
         return JsonPathAstInterpreter.evaluate(ast, json);
     }
 
-    @Override
-    public JsonPath compile() {
-        // Compiler-backed implementation is added later; keep behavior-preserving no-op for now.
-        return this;
-    }
-
     @Override
     public String toString() {
         return JsonPathAstInterpreter.reconstruct(ast);
     }
 
+    @Override
     JsonPathAst.Root ast() {
         return ast;
     }

json-java21-jsonpath/src/main/java/json/java21/jsonpath/JsonPathCompiled.java

@@ -0,0 +1,6 @@
+package json.java21.jsonpath;
+
+/// Marker for `JsonPath` implementations that are already runtime-compiled.
+interface JsonPathCompiled extends JsonPath {
+}
+

json-java21-jsonpath/src/main/java/json/java21/jsonpath/JsonPathCompiledPath.java

@@ -0,0 +1,44 @@
+package json.java21.jsonpath;
+
+import jdk.sandbox.java.util.json.JsonValue;
+
+import java.util.List;
+import java.util.Objects;
+
+/// A `JsonPath` backed by a runtime-compiled generated class.
+///
+/// This wrapper intentionally does not retain the AST; it only retains the generated Java source
+/// (for diagnostics/debugging) and delegates evaluation to the compiled instance.
+final class JsonPathCompiledPath implements JsonPathCompiled {
+
+    private final String expression;
+    private final String generatedClassName;
+    private final String javaSource;
+    private final JsonPath delegate;
+
+    JsonPathCompiledPath(String expression, String generatedClassName, String javaSource, JsonPath delegate) {
+        this.expression = Objects.requireNonNull(expression, "expression must not be null");
+        this.generatedClassName = Objects.requireNonNull(generatedClassName, "generatedClassName must not be null");
+        this.javaSource = Objects.requireNonNull(javaSource, "javaSource must not be null");
+        this.delegate = Objects.requireNonNull(delegate, "delegate must not be null");
+    }
+
+    @Override
+    public List<JsonValue> query(JsonValue json) {
+        return delegate.query(json);
+    }
+
+    @Override
+    public String toString() {
+        return expression;
+    }
+
+    String generatedClassName() {
+        return generatedClassName;
+    }
+
+    String javaSource() {
+        return javaSource;
+    }
+}
+