MethodReferenceReplacementVisitor.java

package xapi.dev.components;

import com.github.javaparser.ast.expr.*;
import com.github.javaparser.ast.visitor.VoidVisitorAdapter;
import xapi.dev.ui.ContainerMetadata;

import java.util.Optional;
import java.util.concurrent.atomic.AtomicInteger;

import static com.github.javaparser.ASTHelper.extractAttrValue;
import static com.github.javaparser.ASTHelper.extractStringValue;

/**
 * @author James X. Nelson (james@wetheinter.net)
 *         Created on 5/29/16.
 */
public class MethodReferenceReplacementVisitor extends VoidVisitorAdapter<ContainerMetadata> {

  protected static final AtomicInteger random = new AtomicInteger();

  public static MethodReferenceReplacementVisitor mutateExpression(UiContainerExpr container, ContainerMetadata metadata) {
    MethodReferenceReplacementVisitor visitor = new MethodReferenceReplacementVisitor();
    container.accept(visitor, metadata);
    return visitor;
  }

  private UiContainerExpr container;
  private UiAttrExpr attr;

  @Override
  public void visit(
      UiContainerExpr n, ContainerMetadata arg
  ) {
    final UiContainerExpr oldContainer = container;
    container = n;
    super.visit(n, arg);
    container = oldContainer;
  }

  @Override
  public void visit(
      UiAttrExpr n, ContainerMetadata arg
  ) {
    final UiAttrExpr oldAttr = attr;
    attr = n;
    super.visit(n, arg);
    attr = oldAttr;
  }

  @Override
  public void visit(
      MethodReferenceExpr n, ContainerMetadata arg
  ) {
    container.removeAttribute(attr);
    final Optional<UiAttrExpr> idAttr = container.getAttribute("id");
    String ident;
    if (idAttr.isPresent()) {
      ident = extractAttrValue(idAttr.get());
    } else {
      ident = "gen"+Integer.toString(random.incrementAndGet(), 32);
      container.addAttribute(true, new UiAttrExpr(
          new NameExpr("id"), false, new StringLiteralExpr(ident)
      ));
    }
    // Now, knowing the ident, we can add a modifier to find and wire up our reference at runtime.
    // for now, we're going to hack in only event handlers...
    String attrName = attr.getNameString();
    if (attrName.startsWith("on")) {
      attrName = attrName.substring(2);
    }

    String elementType = arg.getElementTypeImported();
    String name = attrName.toLowerCase();
    String scopedName = extractStringValue(n.getScope());
    boolean isThis = scopedName.equals("this");
    boolean is$This = scopedName.equals("$this");
    if (is$This) {
      arg.ensure$this();
    }
    arg.addModifier(ele ->
      elementType + " " + ident + " = " +
          ele + ".querySelector(\"#" + ident + "\");"
    );
    arg.addModifier(ele ->
      ident + ".addEventListener(\"" + name + "\","
    );
    if (is$This) {
      arg.addModifier(ele -> n.toSource());
    } else {
      arg.addModifier(ele ->
        "todo->{}"
      );
    }
    arg.addModifier(ele ->
      ");"
    );
    super.visit(n, arg);
  }

}