/*******************************************************************************
 * Copyright (c) 2000, 2005 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.ui.wizards.datatransfer;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import org.eclipse.core.runtime.IProgressMonitor;
import org.eclipse.jface.operation.IRunnableWithProgress;
import org.eclipse.jface.operation.ModalContext;
import org.eclipse.ui.dialogs.FileSystemElement;

import org.eclipse.ui.internal.wizards.datatransfer.DataTransferMessages;

/**
 *	Operation responsible for traversing a specified file system position
 *	recursively and building
 *	-	a tree that represents the container structure
 *	-	a collection containing all files meeting a specified extension criteria
 *
 *	This is implemented as an Operation in order to provide an escape to the user
 *	(the Cancel button) if the operation drags on for too long
 */
public class SelectFilesOperation implements IRunnableWithProgress {
    IProgressMonitor monitor;

    Object root;

    IImportStructureProvider provider;

    String desiredExtensions[];

    FileSystemElement result;

    /**
     * Creates a new <code>SelectFilesOperation</code>.
     */
    public SelectFilesOperation(Object rootObject,
            IImportStructureProvider structureProvider) {
        super();
        root = rootObject;
        provider = structureProvider;
    }

    /**
     * Creates and returns a <code>FileSystemElement</code> if the specified
     * file system object merits one.  The criteria for this are:
     * - if the file system object is a container then it must have either a
     *   child container or an associated file
     * - if the file system object is a file then it must have an extension
     *   suitable for selection
     */
    protected FileSystemElement createElement(FileSystemElement parent,
            Object fileSystemObject) throws InterruptedException {
        ModalContext.checkCanceled(monitor);
        boolean isContainer = provider.isFolder(fileSystemObject);
        String elementLabel = parent == null ? provider
                .getFullPath(fileSystemObject) : provider
                .getLabel(fileSystemObject);

        if (!isContainer && !hasDesiredExtension(elementLabel))
            return null;

        FileSystemElement result = new FileSystemElement(elementLabel, parent,
                isContainer);
        result.setFileSystemObject(fileSystemObject);

        if (isContainer) {
            boolean haveChildOrFile = false;
            List children = provider.getChildren(fileSystemObject);
            if (children == null)
                children = new ArrayList(1);
            Iterator childrenEnum = children.iterator();
            while (childrenEnum.hasNext()) {
                if (createElement(result, childrenEnum.next()) != null)
                    haveChildOrFile = true;
            }

            if (!haveChildOrFile && parent != null) {
                parent.removeFolder(result);
                result = null;
            }
        }

        return result;
    }

    /**
     * Returns the extension portion of the passed filename string.
     */
    protected String getExtensionFor(String filename) {
        int nIndex = filename.lastIndexOf('.');

        if (nIndex >= 0)
            return filename.substring(nIndex + 1);

        return "";//$NON-NLS-1$

    }

    /**
     * Returns the resulting root file system element.
     */
    public FileSystemElement getResult() {
        return result;
    }

    /**
     * Returns a boolean indicating whether the extension of the passed filename
     * is one of the extensions specified as desired by the filter.
     */
    protected boolean hasDesiredExtension(String filename) {
        if (desiredExtensions == null) // ie.- all extensions are fine
            return true;

        int extensionsSize = desiredExtensions.length;
        for (int i = 0; i < extensionsSize; i++) {
            if (getExtensionFor(filename)
                    .equalsIgnoreCase(desiredExtensions[i]))
                return true;
        }

        return false;
    }

    /**
     * Runs the operation.
     */
    public void run(IProgressMonitor monitor) throws InterruptedException {
        try {
            this.monitor = monitor;
            monitor.beginTask(DataTransferMessages.DataTransfer_scanningMatching, IProgressMonitor.UNKNOWN);
            result = createElement(null, root);
            if (result == null) {
                result = new FileSystemElement(provider.getLabel(root), null,
                        provider.isFolder(root));
                result.setFileSystemObject(root);
            }
        } finally {
            monitor.done();
        }
    }

    /**
     * Sets the file extensions which are desired.  A value of <code>null</code>
     * indicates that all files should be kept regardless of extension.
     */
    public void setDesiredExtensions(String[] extensions) {
        desiredExtensions = extensions;
    }
}