/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * 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 android.webkit;

import android.text.TextUtils;
import java.util.regex.Pattern;
import libcore.net.MimeUtils;

/**
 * Two-way map that maps MIME-types to file extensions and vice versa.
 *
 * <p>See also {@link java.net.URLConnection#guessContentTypeFromName}
 * and {@link java.net.URLConnection#guessContentTypeFromStream}. This
 * class and {@code URLConnection} share the same MIME-type database.
 */
public class MimeTypeMap {
    private static final MimeTypeMap sMimeTypeMap = new MimeTypeMap();

    private MimeTypeMap() {
    }

    /**
     * Returns the file extension or an empty string iff there is no
     * extension. This method is a convenience method for obtaining the
     * extension of a url and has undefined results for other Strings.
     * @param url
     * @return The file extension of the given url.
     */
    public static String getFileExtensionFromUrl(String url) {
        if (!TextUtils.isEmpty(url)) {
            int fragment = url.lastIndexOf('#');
            if (fragment > 0) {
                url = url.substring(0, fragment);
            }

            int query = url.lastIndexOf('?');
            if (query > 0) {
                url = url.substring(0, query);
            }

            int filenamePos = url.lastIndexOf('/');
            String filename =
                0 <= filenamePos ? url.substring(filenamePos + 1) : url;

            // if the filename contains special characters, we don't
            // consider it valid for our matching purposes:
            if (!filename.isEmpty() &&
                Pattern.matches("[a-zA-Z_0-9\\.\\-\\(\\)\\%]+", filename)) {
                int dotPos = filename.lastIndexOf('.');
                if (0 <= dotPos) {
                    return filename.substring(dotPos + 1);
                }
            }
        }

        return "";
    }

    /**
     * Return true if the given MIME type has an entry in the map.
     * @param mimeType A MIME type (i.e. text/plain)
     * @return True iff there is a mimeType entry in the map.
     */
    public boolean hasMimeType(String mimeType) {
        return MimeUtils.hasMimeType(mimeType);
    }

    /**
     * Return the MIME type for the given extension.
     * @param extension A file extension without the leading '.'
     * @return The MIME type for the given extension or null iff there is none.
     */
    public String getMimeTypeFromExtension(String extension) {
        return MimeUtils.guessMimeTypeFromExtension(extension);
    }

    // Static method called by jni.
    private static String mimeTypeFromExtension(String extension) {
        return MimeUtils.guessMimeTypeFromExtension(extension);
    }

    /**
     * Return true if the given extension has a registered MIME type.
     * @param extension A file extension without the leading '.'
     * @return True iff there is an extension entry in the map.
     */
    public boolean hasExtension(String extension) {
        return MimeUtils.hasExtension(extension);
    }

    /**
     * Return the registered extension for the given MIME type. Note that some
     * MIME types map to multiple extensions. This call will return the most
     * common extension for the given MIME type.
     * @param mimeType A MIME type (i.e. text/plain)
     * @return The extension for the given MIME type or null iff there is none.
     */
    public String getExtensionFromMimeType(String mimeType) {
        return MimeUtils.guessExtensionFromMimeType(mimeType);
    }

    /**
     * If the given MIME type is null, or one of the "generic" types (text/plain
     * or application/octet-stream) map it to a type that Android can deal with.
     * If the given type is not generic, return it unchanged.
     *
     * @param mimeType MIME type provided by the server.
     * @param url URL of the data being loaded.
     * @param contentDisposition Content-disposition header given by the server.
     * @return The MIME type that should be used for this data.
     */
    /* package */ String remapGenericMimeType(String mimeType, String url,
            String contentDisposition) {
        // If we have one of "generic" MIME types, try to deduce
        // the right MIME type from the file extension (if any):
        if ("text/plain".equals(mimeType) ||
                "application/octet-stream".equals(mimeType)) {

            // for attachment, use the filename in the Content-Disposition
            // to guess the mimetype
            String filename = null;
            if (contentDisposition != null) {
                filename = URLUtil.parseContentDisposition(contentDisposition);
            }
            if (filename != null) {
                url = filename;
            }
            String extension = getFileExtensionFromUrl(url);
            String newMimeType = getMimeTypeFromExtension(extension);
            if (newMimeType != null) {
                mimeType = newMimeType;
            }
        } else if ("text/vnd.wap.wml".equals(mimeType)) {
            // As we don't support wml, render it as plain text
            mimeType = "text/plain";
        } else {
            // It seems that xhtml+xml and vnd.wap.xhtml+xml mime
            // subtypes are used interchangeably. So treat them the same.
            if ("application/vnd.wap.xhtml+xml".equals(mimeType)) {
                mimeType = "application/xhtml+xml";
            }
        }
        return mimeType;
    }

    /**
     * Get the singleton instance of MimeTypeMap.
     * @return The singleton instance of the MIME-type map.
     */
    public static MimeTypeMap getSingleton() {
        return sMimeTypeMap;
    }
}