/*
 * Copyright (C) 2010 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 com.android.browser;

import android.net.Uri;
import android.util.Patterns;
import android.webkit.URLUtil;

import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * Utility methods for Url manipulation
 */
public class UrlUtils {

    static final Pattern ACCEPTED_URI_SCHEMA = Pattern.compile(
            "(?i)" + // switch on case insensitive matching
            "(" +    // begin group for schema
            "(?:http|https|file):\\/\\/" +
            "|(?:inline|data|about|javascript):" +
            ")" +
            "(.*)" );

    // Google search
    private final static String QUICKSEARCH_G = "http://www.google.com/m?q=%s";
    private final static String QUERY_PLACE_HOLDER = "%s";

    // Regular expression to strip http:// and optionally
    // the trailing slash
    private static final Pattern STRIP_URL_PATTERN =
            Pattern.compile("^http://(.*?)/?$");

    private UrlUtils() { /* cannot be instantiated */ }

    /**
     * Strips the provided url of preceding "http://" and any trailing "/". Does not
     * strip "https://". If the provided string cannot be stripped, the original string
     * is returned.
     *
     * TODO: Put this in TextUtils to be used by other packages doing something similar.
     *
     * @param url a url to strip, like "http://www.google.com/"
     * @return a stripped url like "www.google.com", or the original string if it could
     *         not be stripped
     */
    public static String stripUrl(String url) {
        if (url == null) return null;
        Matcher m = STRIP_URL_PATTERN.matcher(url);
        if (m.matches()) {
            return m.group(1);
        } else {
            return url;
        }
    }

    protected static String smartUrlFilter(Uri inUri) {
        if (inUri != null) {
            return smartUrlFilter(inUri.toString());
        }
        return null;
    }

    /**
     * Attempts to determine whether user input is a URL or search
     * terms.  Anything with a space is passed to search.
     *
     * Converts to lowercase any mistakenly uppercased schema (i.e.,
     * "Http://" converts to "http://"
     *
     * @return Original or modified URL
     *
     */
    public static String smartUrlFilter(String url) {
        return smartUrlFilter(url, true);
    }

    /**
     * Attempts to determine whether user input is a URL or search
     * terms.  Anything with a space is passed to search if canBeSearch is true.
     *
     * Converts to lowercase any mistakenly uppercased schema (i.e.,
     * "Http://" converts to "http://"
     *
     * @param canBeSearch If true, will return a search url if it isn't a valid
     *                    URL. If false, invalid URLs will return null
     * @return Original or modified URL
     *
     */
    public static String smartUrlFilter(String url, boolean canBeSearch) {
        String inUrl = url.trim();
        boolean hasSpace = inUrl.indexOf(' ') != -1;

        Matcher matcher = ACCEPTED_URI_SCHEMA.matcher(inUrl);
        if (matcher.matches()) {
            // force scheme to lowercase
            String scheme = matcher.group(1);
            String lcScheme = scheme.toLowerCase();
            if (!lcScheme.equals(scheme)) {
                inUrl = lcScheme + matcher.group(2);
            }
            if (hasSpace && Patterns.WEB_URL.matcher(inUrl).matches()) {
                inUrl = inUrl.replace(" ", "%20");
            }
            return inUrl;
        }
        if (!hasSpace) {
            if (Patterns.WEB_URL.matcher(inUrl).matches()) {
                return URLUtil.guessUrl(inUrl);
            }
        }
        if (canBeSearch) {
            return URLUtil.composeSearchUrl(inUrl,
                    QUICKSEARCH_G, QUERY_PLACE_HOLDER);
        }
        return null;
    }

    /* package */ static String fixUrl(String inUrl) {
        // FIXME: Converting the url to lower case
        // duplicates functionality in smartUrlFilter().
        // However, changing all current callers of fixUrl to
        // call smartUrlFilter in addition may have unwanted
        // consequences, and is deferred for now.
        int colon = inUrl.indexOf(':');
        boolean allLower = true;
        for (int index = 0; index < colon; index++) {
            char ch = inUrl.charAt(index);
            if (!Character.isLetter(ch)) {
                break;
            }
            allLower &= Character.isLowerCase(ch);
            if (index == colon - 1 && !allLower) {
                inUrl = inUrl.substring(0, colon).toLowerCase()
                        + inUrl.substring(colon);
            }
        }
        if (inUrl.startsWith("http://") || inUrl.startsWith("https://"))
            return inUrl;
        if (inUrl.startsWith("http:") ||
                inUrl.startsWith("https:")) {
            if (inUrl.startsWith("http:/") || inUrl.startsWith("https:/")) {
                inUrl = inUrl.replaceFirst("/", "//");
            } else inUrl = inUrl.replaceFirst(":", "://");
        }
        return inUrl;
    }

    // Returns the filtered URL. Cannot return null, but can return an empty string
    /* package */ static String filteredUrl(String inUrl) {
        if (inUrl == null) {
            return "";
        }
        if (inUrl.startsWith("content:")
                || inUrl.startsWith("browser:")) {
            return "";
        }
        return inUrl;
    }

}