/*******************************************************************************
 * Copyright (c) 2004, 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.internal.intro.impl.model;

import java.util.List;
import java.util.Vector;

import org.eclipse.ui.internal.intro.impl.model.url.IntroURLParser;

/*
 * Intro History Model.
 */
public class History {
    // History of Intro Pages and real URL visited by Intro Browser. All
    // elements are all of type HistoryObject.
    private Vector history = new Vector();
    private int navigationLocation = 0;


    // Model class for history objects. A history object may be a url or an
    // Intro page. A url is a regular URL navigated to from a fully qualified
    // link. An intro page may be an IFrame page. IFrame pages are not created
    // for every Help topic navigated in an embedded IFrame. Instead the same
    // IFrame is stored in history as a different object with the IFrameURL set.
    // This way the model actually creates one page for every embedded Help
    // Topic target but the navigation history updates the IFrame accordingly.
    class HistoryObject {
        AbstractIntroPage page;
        String iframeUrl;
        String url;

        HistoryObject(Object location) {
            if (location instanceof String)
                this.url = (String) location;

            if (location instanceof AbstractIntroPage) {
                this.page = (AbstractIntroPage) location;
                // will be set to null if the page is not an IFrame page.
                this.iframeUrl = this.page.getIFrameURL();
            }
        }

        /**
         * returns the history page. If iframe page, updated to correct url.
         * 
         * @return
         */
        AbstractIntroPage getPage() {
            if (page.isIFramePage())
                // when page was stored, the IFrame url was also stored. Make
                // sure to return the same state. The page is the same, only the
                // IFrame url changes.
                page.setIFrameURL(getIFrameUrl());
            return page;
        }

        String getPageId() {
            return page.getId();
        }

        String getIFrameUrl() {
            return iframeUrl;
        }

        String getUrl() {
            return url;
        }

        boolean isURL() {
            return (url != null) ? true : false;
        }

        boolean isIntroPage() {
            return (page != null) ? true : false;
        }

        boolean isIFramePage() {
            return (iframeUrl != null) ? true : false;
        }

    }


    /**
     * Updates the UI navigation history with either a real URL, or a page ID.
     * 
     * @param pageId
     */
    public void updateHistory(String location) {
        // quick exit.
        if (!history.isEmpty() && isSameLocation(location))
            // resetting the same location is useless.
            return;
        doUpdateHistory(location);
    }

    /**
     * Updates the UI navigation history with either a real URL, or a page ID.
     * 
     * @param page
     */
    public void updateHistory(AbstractIntroPage page) {
        // quick exit.
        if (!history.isEmpty() && isSameLocation(page))
            // resetting the same location is useless.
            return;
        doUpdateHistory(page);
    }

    private void doUpdateHistory(Object location) {
        // we got here due to an intro URL listener or an SWT Form hyperlink
        // listener. location may be a url or an IntroPage.
        if (navigationLocation == getHistoryEndPosition())
            // we are at the end of the vector, just push.
            pushToHistory(location);
        else
            // we already navigated. add item at current location, and clear
            // rest of history. (Same as browser behavior.)
            trimHistory(location);
    }


    private boolean isSameLocation(Object location) {
        HistoryObject currentLocation = getCurrentLocation();
        if (location instanceof String && currentLocation.isURL())
            return currentLocation.getUrl().equals(location);

        if (location instanceof AbstractIntroPage
                && currentLocation.isIntroPage()) {

            AbstractIntroPage locationPage = (AbstractIntroPage) location;
            // be carefull here with calling getPage on historyOvject.
            if (!currentLocation.getPageId().equals(locationPage.getId()))
                return false;

            // both pages have same ids, they are either both regular pages or
            // both are Iframe pages. check if they have the same IFrame urls
            if (currentLocation.isIFramePage() && locationPage.isIFramePage())
                return currentLocation.getIFrameUrl().equals(
                    locationPage.getIFrameURL());

            // both pages are not IFrame pages, and they have same id.
            return true;
        }

        return false;
    }


    private void pushToHistory(Object location) {
        history.add(new HistoryObject(location));
        // point the nav location to the end of the vector.
        navigationLocation = getHistoryEndPosition();
    }
    
     public void removeLastHistory() {
        history.remove(getHistoryEndPosition());
        // point the nav location to the end of the vector.
        navigationLocation = getHistoryEndPosition();
    }

    private void trimHistory(Object location) {
        List newHistory = history.subList(0, navigationLocation + 1);
        history = new Vector(newHistory);
        history.add(new HistoryObject(location));
        // point the nav location to the end of the vector.
        navigationLocation = getHistoryEndPosition();
    }

    /**
     * Return the position of the last element in the navigation history. If
     * vector is empty, return 0.
     * 
     * @param vector
     * @return
     */
    private int getHistoryEndPosition() {
        if (history.isEmpty())
            return 0;
        return history.size() - 1;
    }

    public void navigateHistoryBackward() {
        if (badNavigationLocation(navigationLocation - 1))
            // do nothing. We are at the begining.
            return;
        --navigationLocation;
    }

    /**
     * Navigate forward in the history.
     * 
     * @return
     */
    public void navigateHistoryForward() {
        if (badNavigationLocation(navigationLocation + 1))
            // do nothing. We are at the begining.
            return;
        ++navigationLocation;
    }


    private boolean badNavigationLocation(int navigationLocation) {
        if (navigationLocation < 0 || navigationLocation >= history.size())
            // bad nav location.
            return true;
        return false;
    }


    /**
     * Returns true if the current location in the navigation history represents
     * a URL. False if the location is an Intro Page id.
     * 
     * @return Returns the locationIsURL.
     */
    private HistoryObject getCurrentLocation() {
        return (HistoryObject) history.elementAt(navigationLocation);
    }

    public boolean canNavigateForward() {
        return navigationLocation != getHistoryEndPosition() ? true : false;
    }

    public boolean canNavigateBackward() {
        return navigationLocation == 0 ? false : true;
    }

    public boolean currentLocationIsUrl() {
        return getCurrentLocation().isURL();
    }

    public String getCurrentLocationAsUrl() {
        return getCurrentLocation().getUrl();
    }

    public AbstractIntroPage getCurrentLocationAsPage() {
        return getCurrentLocation().getPage();
    }

    public static boolean isURL(String aString) {
        IntroURLParser parser = new IntroURLParser(aString);
        if (parser.hasProtocol())
            return true;
        return false;
    }


    public void clear() {
        history.clear();
        navigationLocation = 0;
    }


}