// Copyright 2016 The Bazel Authors. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//    http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package com.google.devtools.bazel.e4b.wizard;

import java.io.File;

import org.eclipse.jface.viewers.CheckboxTreeViewer;
import org.eclipse.jface.viewers.ILabelProvider;
import org.eclipse.jface.viewers.ILabelProviderListener;
import org.eclipse.jface.viewers.ITreeContentProvider;
import org.eclipse.jface.viewers.Viewer;
import org.eclipse.swt.SWT;
import org.eclipse.swt.graphics.Image;
import org.eclipse.swt.widgets.Composite;

import com.google.common.collect.ImmutableList;

/**
 * A tree content provider that enable selecting a list of sub-directories of a directory root (the
 * Bazel workspace root).
 */
public class DirectoryTreeContentProvider implements ITreeContentProvider {

  private File root;

  public DirectoryTreeContentProvider(File root) {
    this.root = root;
  }

  @Override
  public void dispose() {}

  @Override
  public void inputChanged(Viewer viewer, Object oldInput, Object newInput) {}

  @Override
  public Object[] getElements(Object inputElement) {
    if (root == null) {
      return new Object[] {};
    }
    // We only have one root
    return new Object[] {root};
  }

  @Override
  public Object[] getChildren(Object parentElement) {
    return ((File) parentElement).listFiles((f) -> (f.isDirectory() && !f.getName().startsWith(".")
        && !f.getName().startsWith("bazel-")));
  }

  @Override
  public Object getParent(Object element) {
    File file = (File) element;
    if (file.equals(root)) {
      return null;
    }
    return file.getParentFile();
  }

  @Override
  public boolean hasChildren(Object element) {
    Object[] childrens = getChildren(element);
    return (childrens != null) && (childrens.length > 0);
  }

  public File getRoot() {
    return root;
  }

  public void setRoot(File root) {
    this.root = root;
  }


  /**
   * Create a tree view that use a FileTreeContentProvider for its content. The created tree view
   * can be used to select branches of a directory tree.
   * 
   * @param container The parent composite for the created tree view.
   * @return A checkbox tree view
   */
  static CheckboxTreeViewer createTreeView(Composite container) {
    final CheckboxTreeViewer tv = new CheckboxTreeViewer(container, SWT.BORDER);
    tv.setContentProvider(new DirectoryTreeContentProvider(null));
    tv.setLabelProvider(new ILabelProvider() {

      @Override
      public void removeListener(ILabelProviderListener listener) {
        // we do not have event notifying listeners, ignore.
      }

      @Override
      public boolean isLabelProperty(Object element, String property) {
        return false;
      }


      @Override
      public void dispose() {}

      @Override
      public void addListener(ILabelProviderListener listener) {
        // we do not have event notifying listeners, ignore.
      }

      @Override
      public Image getImage(Object element) {
        return null;
      }

      @Override
      public String getText(Object element) {
        return ((File) element).getName();
      }
    });
    tv.setInput("root"); // pass a non-null that will be ignored

    tv.addCheckStateListener(event -> setChecked(tv, event.getElement()));

    return tv;
  }

  private static void setChecked(final CheckboxTreeViewer tv, Object element) {
    // When user checks a checkbox in the tree, check all its children and mark parent as greyed
    // When a user uncheck a checkbox, mark the subtree as unchecked and ungrayed and if unique
    // sibling parent as grayed.
    DirectoryTreeContentProvider provider = (DirectoryTreeContentProvider) tv.getContentProvider();

    boolean isChecked = tv.getChecked(element);
    if (tv.getGrayed(element)) {
      isChecked = !isChecked;
    }
    tv.setChecked(element, isChecked);
    tv.setGrayed(element, false);
    if (isChecked) {
      tv.setSubtreeChecked(element, true);
    } else {
      tv.setSubtreeChecked(element, false);
    }
    setGrayed(tv, provider.getParent(element));
  }

  private static void setGrayed(CheckboxTreeViewer tv, Object element) {
    if (element == null) {
      return;
    }
    DirectoryTreeContentProvider provider = (DirectoryTreeContentProvider) tv.getContentProvider();
    boolean checked = tv.getChecked(element);
    boolean grayed = false;
    for (Object object : provider.getChildren(element)) {
      grayed = grayed || tv.getGrayed(object) || tv.getChecked(object);
      checked = checked && tv.getChecked(object) && !tv.getGrayed(element);
    }
    if (checked) {
      tv.setChecked(element, true);
      tv.setGrayed(element, false);
    } else if (grayed) {
      tv.setGrayChecked(element, true);
    } else {
      tv.setChecked(element, false);
      tv.setGrayed(element, false);
    }
    setGrayed(tv, provider.getParent(element));
  }

  /**
   * Set the root of the directory tree view and refresh the view if appropriate
   */
  static void setFileTreeRoot(CheckboxTreeViewer tv, File root) {
    DirectoryTreeContentProvider provider = (DirectoryTreeContentProvider) tv.getContentProvider();
    if ((root == null && provider.getRoot() != null) || !root.equals(provider.getRoot())) {
      provider.setRoot(root);
      tv.refresh();
    }
  }

  /**
   * Returns the list of path selected in <code>tv</code>. It returns the list of checked path
   * without the children of the checked path. Each path is returned as a string giving the relative
   * path from the root of the tree.
   */
  static ImmutableList<String> getSelectPathsRelativeToRoot(CheckboxTreeViewer tv) {
    DirectoryTreeContentProvider provider = (DirectoryTreeContentProvider) tv.getContentProvider();
    String root = provider.root.getAbsolutePath();
    ImmutableList.Builder<String> builder = ImmutableList.builder();
    for (Object element : tv.getCheckedElements()) {
      if (!tv.getGrayed(element)) {
        Object parent = provider.getParent(element);
        if (parent == null || tv.getGrayed(parent)) {
          // Only add this element if its parent is not selected (so it's the root).
          String path = ((File) element).getAbsolutePath();
          // Strip root from path
          if (path.startsWith(root)) {
            path = path.substring(root.length());
            if (path.startsWith("/")) {
              path = path.substring(1);
            }
            builder.add(path);
          }
        }
      }
    }
    return builder.build();
  }
}