/*******************************************************************************
 * Copyright (c) 2000, 2006 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.ide;

import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.util.zip.CRC32;
import java.util.zip.CheckedInputStream;

import org.eclipse.core.runtime.Assert;
import org.eclipse.core.runtime.IBundleGroup;
import org.eclipse.core.runtime.IBundleGroupProvider;
import org.eclipse.core.runtime.IProduct;
import org.eclipse.core.runtime.Path;
import org.eclipse.core.runtime.Platform;
import org.eclipse.jface.resource.ImageDescriptor;
import org.eclipse.ui.internal.BundleGroupProperties;
import org.eclipse.ui.internal.ProductProperties;

/**
 * The information within this object is obtained from the about INI file.
 * This file resides within an install configurations directory and must be a 
 * standard java property file.  
 * <p>
 * This class is not intended to be instantiated or subclassed by clients.
 * </p>
 */
public final class AboutInfo {
    private ProductProperties productProperties;

    private BundleGroupProperties bundleGroupProperties;

    private Long featureImageCRC;

    private boolean calculatedImageCRC = false;

    /**
     * The information contained in this info will apply to only the argument product.
     */
    public AboutInfo(IProduct product) {
        this.productProperties = new ProductProperties(product);
    }

    /**
     * This info object will apply to the argument bundle group.
     */
    public AboutInfo(IBundleGroup bundleGroup) {
        this.bundleGroupProperties = new BundleGroupProperties(bundleGroup);
    }

    /**
     * Returns the configuration information for the feature with the given id.
     * 
     * @param featureId
     *            the feature id
     * @param versionId
     *            the version id (of the feature)
     * @return the configuration information for the feature
     */
    public static AboutInfo readFeatureInfo(String featureId, String versionId) {
        Assert.isNotNull(featureId);
        Assert.isNotNull(versionId);

        // first see if the id matches the product
        IProduct product = Platform.getProduct();
        if (product != null
                && featureId.equals(ProductProperties.getProductId(product))) {
			return new AboutInfo(product);
		}

        // then check the bundle groups
        IBundleGroup bundleGroup = getBundleGroup(featureId, versionId);
        if (bundleGroup != null) {
			return new AboutInfo(bundleGroup);
		}

        return null;
    }

    private static IBundleGroup getBundleGroup(String id, String versionId) {
        if (id == null || versionId == null) {
			return null;
		}

        IBundleGroupProvider[] providers = Platform.getBundleGroupProviders();
        for (int p = 0; p < providers.length; ++p) {
            IBundleGroup[] groups = providers[p].getBundleGroups();
            for (int g = 0; g < groups.length; ++g) {
				if (id.equals(groups[g].getIdentifier())
                        && versionId.equals(groups[g].getVersion())) {
					return groups[g];
				}
			}
        }

        return null;
    }

    /**
     * Returns the descriptor for an image which can be shown in an "about" dialog 
     * for this product. Products designed to run "headless" typically would not 
     * have such an image.
     * 
     * @return the descriptor for an about image, or <code>null</code> if none
     */
    public ImageDescriptor getAboutImage() {
        return productProperties == null ? null : productProperties
                .getAboutImage();
    }

    /**
     * Returns the descriptor for an image which can be shown in an "about features" 
     * dialog. Products designed to run "headless" typically would not have such an image.
     * 
     * @return the descriptor for a feature image, or <code>null</code> if none
     */
    public ImageDescriptor getFeatureImage() {
        return bundleGroupProperties == null ? null : bundleGroupProperties
                .getFeatureImage();
    }

    /**
     * Returns the simple name of the feature image file.
     * 
     * @return the simple name of the feature image file,
     * or <code>null</code> if none
     */
    public String getFeatureImageName() {
        if (bundleGroupProperties == null) {
			return null;
		}

        URL url = bundleGroupProperties.getFeatureImageUrl();
        return url == null ? null : new Path(url.getPath()).lastSegment();
    }

    /**
     * Returns the CRC of the feature image as supplied in the properties file.
     * 
     * @return the CRC of the feature image, or <code>null</code> if none
     */
    public Long getFeatureImageCRC() {
        if (bundleGroupProperties == null) {
			return null;
		}

        if (!calculatedImageCRC) {
            featureImageCRC = calculateImageCRC(bundleGroupProperties
                    .getFeatureImageUrl());
            calculatedImageCRC = featureImageCRC != null;
        }

        return featureImageCRC;
    }

    /**
     * Calculate a CRC for the feature image
     */
    private static Long calculateImageCRC(URL url) {
        if (url == null) {
			return null;
		}

        InputStream in = null;
        try {
            CRC32 checksum = new CRC32();
            in = new CheckedInputStream(url.openStream(), checksum);

            // the contents don't matter, the read just needs a place to go
            byte[] sink = new byte[2048];
            while (true) {
				if (in.read(sink) <= 0) {
					break;
				}
			}

            return new Long(checksum.getValue());
        } catch (IOException e) {
            return null;
        } finally {
            if (in != null) {
				try {
                    in.close();
                } catch (IOException e) {
                    // do nothing
                }
			}
        }
    }

    /**
     * Returns a label for the feature plugn, or <code>null</code>.
     */
    public String getFeatureLabel() {
        if (productProperties != null) {
			return productProperties.getProductName();
		}
        if (bundleGroupProperties != null) {
			return bundleGroupProperties.getFeatureLabel();
		}
        return null;
    }

    /**
     * Returns the id for this feature.
     * 
     * @return the feature id
     */
    public String getFeatureId() {
        String id = null;
        if (productProperties != null) {
			id = productProperties.getProductId();
		} else if (bundleGroupProperties != null) {
			id = bundleGroupProperties.getFeatureId();
		}
        return id != null ? id : ""; //$NON-NLS-1$ 
    }

    /**
     * Returns the text to show in an "about" dialog for this product.
     * Products designed to run "headless" typically would not have such text.
     * 
     * @return the about text, or <code>null</code> if none
     */
    public String getAboutText() {
        return productProperties == null ? null : productProperties
                .getAboutText();
    }

    /**
     * Returns the application name or <code>null</code>.
     * Note this is never shown to the user.
     * It is used to initialize the SWT Display.
     * <p>
     * On Motif, for example, this can be used
     * to set the name used for resource lookup.
     * </p>
     *
     * @return the application name, or <code>null</code>
     * 
     * @see org.eclipse.swt.widgets.Display#setAppName
     */
    public String getAppName() {
        return productProperties == null ? null : productProperties
                .getAppName();
    }

    /**
     * Returns the product name or <code>null</code>.
     * This is shown in the window title and the About action.
     *
     * @return the product name, or <code>null</code>
     */
    public String getProductName() {
        return productProperties == null ? null : productProperties
                .getProductName();
    }

    /**
     * Returns the provider name or <code>null</code>.
     *
     * @return the provider name, or <code>null</code>
     */
    public String getProviderName() {
        return bundleGroupProperties == null ? null : bundleGroupProperties
                .getProviderName();
    }

    /**
     * Returns the feature version id.
     *
     * @return the version id of the feature
     */
    public String getVersionId() {
        return bundleGroupProperties == null ? "" : bundleGroupProperties.getFeatureVersion(); //$NON-NLS-1$
    }

    /**
     * Returns a <code>URL</code> for the welcome page.
     * Products designed to run "headless" typically would not have such an page.
     * 
     * @return the welcome page, or <code>null</code> if none
     */
    public URL getWelcomePageURL() {
        if (productProperties != null) {
			return productProperties.getWelcomePageUrl();
		}
        if (bundleGroupProperties != null) {
			return bundleGroupProperties.getWelcomePageUrl();
		}
        return null;
    }

    /**
     * Returns the ID of a perspective in which to show the welcome page.
     * May be <code>null</code>.
     * 
     * @return the welcome page perspective id, or <code>null</code> if none
     */
    public String getWelcomePerspectiveId() {
        return bundleGroupProperties == null ? null : bundleGroupProperties
                .getWelcomePerspective();
    }

    /**
     * Returns a <code>String</code> for the tips and trick href.
     * 
     * @return the tips and tricks href, or <code>null</code> if none
     */
    public String getTipsAndTricksHref() {
        return bundleGroupProperties == null ? null : bundleGroupProperties
                .getTipsAndTricksHref();
    }

    /**
     * Return an array of image descriptors for the window images to use for
     * this product. The expectations is that the elements will be the same
     * image rendered at different sizes. Products designed to run "headless"
     * typically would not have such images.
     * 
     * @return an array of the image descriptors for the window images, or
     *         <code>null</code> if none
     * @since 3.0
     */
    public ImageDescriptor[] getWindowImages() {
        return productProperties == null ? null : productProperties
                .getWindowImages();
    }
}
