// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
package com.google.dart.compiler;

import com.google.dart.compiler.ast.ASTVisitor;
import com.google.dart.compiler.ast.DartClass;
import com.google.dart.compiler.ast.DartIdentifier;
import com.google.dart.compiler.ast.DartMethodInvocation;
import com.google.dart.compiler.ast.DartParameterizedTypeNode;
import com.google.dart.compiler.ast.DartPropertyAccess;
import com.google.dart.compiler.ast.DartTypeNode;
import com.google.dart.compiler.ast.DartUnit;
import com.google.dart.compiler.resolver.Element;
import com.google.dart.compiler.resolver.ElementKind;
import com.google.dart.compiler.type.InterfaceType;
import com.google.dart.compiler.type.Type;
import com.google.dart.compiler.type.TypeKind;

import java.net.URI;

/**
 * A visitor that fills in {@link LibraryDeps} for a compilation unit.
 */
public class LibraryDepsVisitor extends ASTVisitor<Void> {
  /**
   * Fill in {@link LibraryDeps} from a {@link DartUnit}.
   */
  static void exec(DartUnit unit, LibraryDeps.Source source) {
    LibraryDepsVisitor v = new LibraryDepsVisitor(source);
    unit.accept(v);
  }

  private final LibraryDeps.Source source;
  private Element currentClass;

  private LibraryDepsVisitor(LibraryDeps.Source source) {
    this.source = source;
  }

  @Override
  public Void visitIdentifier(DartIdentifier node) {
    Element target = node.getElement();
    ElementKind kind = ElementKind.of(target);
    // Add dependency on the field or method.
    switch (kind) {
      case FIELD:
      case METHOD: {
        Element enclosing = target.getEnclosingElement();
        addHoleIfUnqualifiedSuper(node, enclosing);
        if (enclosing.getKind().equals(ElementKind.LIBRARY)) {
          addElementDependency(target);
        }
        break;
      }
    }
    // Add dependency on the computed type of identifiers.
    switch (kind) {
      case NONE:
        source.addHole(node.getName());
        break;
      case DYNAMIC:
        break;
      default: {
        Type type = target.getType();
        if (type != null) {
          Element element = type.getElement();
          if (ElementKind.of(element).equals(ElementKind.CLASS)) {
            addElementDependency(element);
          }
        }
        break;
      }
    }
    return null;
  }

  @Override
  public Void visitPropertyAccess(DartPropertyAccess node) {
    if (node.getQualifier() instanceof DartIdentifier) {
      DartIdentifier qualifier = (DartIdentifier) node.getQualifier();
      Element target = qualifier.getElement();
      if (target != null && target.getKind() == ElementKind.LIBRARY) {
        // Handle library prefixes normally.
        // The prefix part of the qualifier doesn't contain any resolvable library source info.
        return super.visitPropertyAccess(node);
      }
    }
    // Skip rhs of property accesses, so that all identifiers we visit will be unqualified.
    if (node.isCascade()) {
      return null;
    }
    return node.getQualifier().accept(this);
  }

  @Override
  public Void visitClass(DartClass node) {
    currentClass = node.getElement();
    node.visitChildren(this);
    currentClass = null;
    return null;
  }

  @Override
  public Void visitParameterizedTypeNode(DartParameterizedTypeNode node) {
    if (TypeKind.of(node.getType()).equals(TypeKind.INTERFACE)) {
      addElementDependency(((InterfaceType) node.getType()).getElement());
    }
    node.visitChildren(this);
    return null;
  }

  @Override
  public Void visitTypeNode(DartTypeNode node) {
    if (TypeKind.of(node.getType()).equals(TypeKind.INTERFACE)) {
      addElementDependency(((InterfaceType) node.getType()).getElement());
    }
    node.visitChildren(this);
    return null;
  }

  /**
   * Add a 'hole' for the given identifier, if its declaring class is a superclass of the current
   * class. A 'hole' dependency specifies a name that, if filled by something in the library scope,
   * would require this unit to be recompiled.
   * 
   * This situation occurs because names in the library scope bind more strongly than unqualified
   * superclass members.
   */
  private void addHoleIfUnqualifiedSuper(DartIdentifier node, Element holder) {
    if (isQualified(node)) {
      return;
    }
    if (ElementKind.of(holder) == ElementKind.CLASS && holder != currentClass) {
      source.addHole(node.getName());
    }
  }

  /**
   * Adds a direct dependency on the unit providing given {@link Element}.
   */
  private void addElementDependency(Element element) {
    DartSource elementSource = (DartSource) element.getSourceInfo().getSource();
    if (elementSource != null) {
      LibrarySource library = elementSource.getLibrary();
      if (library != null) {
        URI libUri = library.getUri();
        LibraryDeps.Dependency dep = new LibraryDeps.Dependency(libUri, elementSource.getName(),
            elementSource.getLastModified());
        source.addDep(dep);
      }
    }
  }

  /**
   * @return <code>true</code> if given {@link DartIdentifier} is "name" part of qualified property
   *         access or method invocation.
   */
  private static boolean isQualified(DartIdentifier node) {
    if (node.getParent() instanceof DartPropertyAccess) {
      return ((DartPropertyAccess) node.getParent()).getName() == node;
    }
    if (node.getParent() instanceof DartMethodInvocation) {
      return ((DartMethodInvocation) node.getParent()).getFunctionName() == node;
    }
    return false;
  }
}