text/util/Linkify.java

/*
 * 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.text.util;

import android.text.method.LinkMovementMethod;
import android.text.method.MovementMethod;
import android.text.style.URLSpan;
import android.text.Spannable;
import android.text.SpannableString;
import android.text.Spanned;
import android.webkit.WebView;
import android.widget.TextView;

import java.io.UnsupportedEncodingException;
import java.net.URLEncoder;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 *  Linkify take a piece of text and a regular expression and turns all of the
 *  regex matches in the text into clickable links.  This is particularly
 *  useful for matching things like email addresses, web urls, etc. and making
 *  them actionable.
 *
 *  Alone with the pattern that is to be matched, a url scheme prefix is also
 *  required.  Any pattern match that does not begin with the supplied scheme
 *  will have the scheme prepended to the matched text when the clickable url
 *  is created.  For instance, if you are matching web urls you would supply
 *  the scheme <code>http://</code>.  If the pattern matches example.com, which
 *  does not have a url scheme prefix, the supplied scheme will be prepended to
 *  create <code>http://example.com</code> when the clickable url link is
 *  created.
 */

public class Linkify {
    /**
     *  Bit field indicating that web URLs should be matched in methods that
     *  take an options mask
     */
    public static final int WEB_URLS = 0x01;

    /**
     *  Bit field indicating that email addresses should be matched in methods
     *  that take an options mask
     */
    public static final int EMAIL_ADDRESSES = 0x02;

    /**
     *  Bit field indicating that phone numbers should be matched in methods that
     *  take an options mask
     */
    public static final int PHONE_NUMBERS = 0x04;

    /**
     *  Bit field indicating that street addresses should be matched in methods that
     *  take an options mask
     */
    public static final int MAP_ADDRESSES = 0x08;

    /**
     *  Bit mask indicating that all available patterns should be matched in
     *  methods that take an options mask
     */
    public static final int ALL = WEB_URLS | EMAIL_ADDRESSES | PHONE_NUMBERS | MAP_ADDRESSES;

    /**
     * Don't treat anything with fewer than this many digits as a
     * phone number.
     */
    private static final int PHONE_NUMBER_MINIMUM_DIGITS = 5;

    /**
     *  Filters out web URL matches that occur after an at-sign (@).  This is
     *  to prevent turning the domain name in an email address into a web link.
     */
    public static final MatchFilter sUrlMatchFilter = new MatchFilter() {
        public final boolean acceptMatch(CharSequence s, int start, int end) {
            if (start == 0) {
                return true;
            }

            if (s.charAt(start - 1) == '@') {
                return false;
            }

            return true;
        }
    };

    /**
     *  Filters out URL matches that don't have enough digits to be a
     *  phone number.
     */
    public static final MatchFilter sPhoneNumberMatchFilter = new MatchFilter() {
        public final boolean acceptMatch(CharSequence s, int start, int end) {
            int digitCount = 0;

            for (int i = start; i < end; i++) {
                if (Character.isDigit(s.charAt(i))) {
                    digitCount++;
                    if (digitCount >= PHONE_NUMBER_MINIMUM_DIGITS) {
                        return true;
                    }
                }
            }
            return false;
        }
    };

    /**
     *  Transforms matched phone number text into something suitable
     *  to be used in a tel: URL.  It does this by removing everything
     *  but the digits and plus signs.  For instance:
     *  &apos;+1 (919) 555-1212&apos;
     *  becomes &apos;+19195551212&apos;
     */
    public static final TransformFilter sPhoneNumberTransformFilter = new TransformFilter() {
        public final String transformUrl(final Matcher match, String url) {
            return Regex.digitsAndPlusOnly(match);
        }
    };

    /**
     *  MatchFilter enables client code to have more control over
     *  what is allowed to match and become a link, and what is not.
     *
     *  For example:  when matching web urls you would like things like
     *  http://www.example.com to match, as well as just example.com itelf.
     *  However, you would not want to match against the domain in
     *  support@example.com.  So, when matching against a web url pattern you
     *  might also include a MatchFilter that disallows the match if it is
     *  immediately preceded by an at-sign (@).
     */
    public interface MatchFilter {
        /**
         *  Examines the character span matched by the pattern and determines
         *  if the match should be turned into an actionable link.
         *
         *  @param s        The body of text against which the pattern
         *                  was matched
         *  @param start    The index of the first character in s that was
         *                  matched by the pattern - inclusive
         *  @param end      The index of the last character in s that was
         *                  matched - exclusive
         *
         *  @return         Whether this match should be turned into a link
         */
        boolean acceptMatch(CharSequence s, int start, int end);
    }

    /**
     *  TransformFilter enables client code to have more control over
     *  how matched patterns are represented as URLs.
     *
     *  For example:  when converting a phone number such as (919)  555-1212
     *  into a tel: URL the parentheses, white space, and hyphen need to be
     *  removed to produce tel:9195551212.
     */
    public interface TransformFilter {
        /**
         *  Examines the matched text and either passes it through or uses the
         *  data in the Matcher state to produce a replacement.
         *
         *  @param match    The regex matcher state that found this URL text
         *  @param url      The text that was matched
         *
         *  @return         The transformed form of the URL
         */
        String transformUrl(final Matcher match, String url);
    }

    /**
     *  Scans the text of the provided Spannable and turns all occurrences
     *  of the link types indicated in the mask into clickable links.
     *  If the mask is nonzero, it also removes any existing URLSpans
     *  attached to the Spannable, to avoid problems if you call it
     *  repeatedly on the same text.
     */
    public static final boolean addLinks(Spannable text, int mask) {
        if (mask == 0) {
            return false;
        }

        URLSpan[] old = text.getSpans(0, text.length(), URLSpan.class);

        for (int i = old.length - 1; i >= 0; i--) {
            text.removeSpan(old[i]);
        }

        ArrayList<LinkSpec> links = new ArrayList<LinkSpec>();

        if ((mask & WEB_URLS) != 0) {
            gatherLinks(links, text, Regex.WEB_URL_PATTERN,
                new String[] { "http://", "https://" },
                sUrlMatchFilter, null);
        }

        if ((mask & EMAIL_ADDRESSES) != 0) {
            gatherLinks(links, text, Regex.EMAIL_ADDRESS_PATTERN,
                new String[] { "mailto:" },
                null, null);
        }

        if ((mask & PHONE_NUMBERS) != 0) {
            gatherLinks(links, text, Regex.PHONE_PATTERN,
                new String[] { "tel:" },
                sPhoneNumberMatchFilter, sPhoneNumberTransformFilter);
        }

        if ((mask & MAP_ADDRESSES) != 0) {
            gatherMapLinks(links, text);
        }

        pruneOverlaps(links);

        if (links.size() == 0) {
            return false;
        }

        for (LinkSpec link: links) {
            applyLink(link.url, link.start, link.end, text);
        }

        return true;
    }

    /**
     *  Scans the text of the provided TextView and turns all occurrences of
     *  the link types indicated in the mask into clickable links.  If matches
     *  are found the movement method for the TextView is set to
     *  LinkMovementMethod.
     */
    public static final boolean addLinks(TextView text, int mask) {
        if (mask == 0) {
            return false;
        }

        CharSequence t = text.getText();

        if (t instanceof Spannable) {
            if (addLinks((Spannable) t, mask)) {
                addLinkMovementMethod(text);
                return true;
            }

            return false;
        } else {
            SpannableString s = SpannableString.valueOf(t);

            if (addLinks(s, mask)) {
                addLinkMovementMethod(text);
                text.setText(s);

                return true;
            }

            return false;
        }
    }

    private static final void addLinkMovementMethod(TextView t) {
        MovementMethod m = t.getMovementMethod();

        if ((m == null) || !(m instanceof LinkMovementMethod)) {
            if (t.getLinksClickable()) {
                t.setMovementMethod(LinkMovementMethod.getInstance());
            }
        }
    }

    /**
     *  Applies a regex to the text of a TextView turning the matches into
     *  links.  If links are found then UrlSpans are applied to the link
     *  text match areas, and the movement method for the text is changed
     *  to LinkMovementMethod.
     *
     *  @param text         TextView whose text is to be marked-up with links
     *  @param pattern      Regex pattern to be used for finding links
     *  @param scheme       Url scheme string (eg <code>http://</code> to be
     *                      prepended to the url of links that do not have
     *                      a scheme specified in the link text
     */
    public static final void addLinks(TextView text, Pattern pattern, String scheme) {
        addLinks(text, pattern, scheme, null, null);
    }

    /**
     *  Applies a regex to the text of a TextView turning the matches into
     *  links.  If links are found then UrlSpans are applied to the link
     *  text match areas, and the movement method for the text is changed
     *  to LinkMovementMethod.
     *
     *  @param text         TextView whose text is to be marked-up with links
     *  @param p            Regex pattern to be used for finding links
     *  @param scheme       Url scheme string (eg <code>http://</code> to be
     *                      prepended to the url of links that do not have
     *                      a scheme specified in the link text
     *  @param matchFilter  The filter that is used to allow the client code
     *                      additional control over which pattern matches are
     *                      to be converted into links.
     */
    public static final void addLinks(TextView text, Pattern p, String scheme,
            MatchFilter matchFilter, TransformFilter transformFilter) {
        SpannableString s = SpannableString.valueOf(text.getText());

        if (addLinks(s, p, scheme, matchFilter, transformFilter)) {
            text.setText(s);
            addLinkMovementMethod(text);
        }
    }

    /**
     *  Applies a regex to a Spannable turning the matches into
     *  links.
     *
     *  @param text         Spannable whose text is to be marked-up with
     *                      links
     *  @param pattern      Regex pattern to be used for finding links
     *  @param scheme       Url scheme string (eg <code>http://</code> to be
     *                      prepended to the url of links that do not have
     *                      a scheme specified in the link text
     */
    public static final boolean addLinks(Spannable text, Pattern pattern, String scheme) {
        return addLinks(text, pattern, scheme, null, null);
    }

    /**
     *  Applies a regex to a Spannable turning the matches into
     *  links.
     *
     *  @param s            Spannable whose text is to be marked-up with
     *                      links
     *  @param p            Regex pattern to be used for finding links
     *  @param scheme       Url scheme string (eg <code>http://</code> to be
     *                      prepended to the url of links that do not have
     *                      a scheme specified in the link text
     *  @param matchFilter  The filter that is used to allow the client code
     *                      additional control over which pattern matches are
     *                      to be converted into links.
     */
    public static final boolean addLinks(Spannable s, Pattern p,
            String scheme, MatchFilter matchFilter,
            TransformFilter transformFilter) {
        boolean hasMatches = false;
        String prefix = (scheme == null) ? "" : scheme.toLowerCase();
        Matcher m = p.matcher(s);

        while (m.find()) {
            int start = m.start();
            int end = m.end();
            boolean allowed = true;

            if (matchFilter != null) {
                allowed = matchFilter.acceptMatch(s, start, end);
            }

            if (allowed) {
                String url = makeUrl(m.group(0), new String[] { prefix },
                                     m, transformFilter);

                applyLink(url, start, end, s);
                hasMatches = true;
            }
        }

        return hasMatches;
    }

    private static final void applyLink(String url, int start, int end, Spannable text) {
        URLSpan span = new URLSpan(url);

        text.setSpan(span, start, end, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
    }

    private static final String makeUrl(String url, String[] prefixes,
            Matcher m, TransformFilter filter) {
        if (filter != null) {
            url = filter.transformUrl(m, url);
        }

        boolean hasPrefix = false;

        for (int i = 0; i < prefixes.length; i++) {
            if (url.regionMatches(true, 0, prefixes[i], 0,
                                  prefixes[i].length())) {
                hasPrefix = true;

                // Fix capitalization if necessary
                if (!url.regionMatches(false, 0, prefixes[i], 0,
                                       prefixes[i].length())) {
                    url = prefixes[i] + url.substring(prefixes[i].length());
                }

                break;
            }
        }

        if (!hasPrefix) {
            url = prefixes[0] + url;
        }

        return url;
    }

    private static final void gatherLinks(ArrayList<LinkSpec> links,
            Spannable s, Pattern pattern, String[] schemes,
            MatchFilter matchFilter, TransformFilter transformFilter) {
        Matcher m = pattern.matcher(s);

        while (m.find()) {
            int start = m.start();
            int end = m.end();

            if (matchFilter == null || matchFilter.acceptMatch(s, start, end)) {
                LinkSpec spec = new LinkSpec();
                String url = makeUrl(m.group(0), schemes, m, transformFilter);

                spec.url = url;
                spec.start = start;
                spec.end = end;

                links.add(spec);
            }
        }
    }

    private static final void gatherMapLinks(ArrayList<LinkSpec> links, Spannable s) {
        String string = s.toString();
        String address;
        int base = 0;

        while ((address = WebView.findAddress(string)) != null) {
            int start = string.indexOf(address);

            if (start < 0) {
                break;
            }

            LinkSpec spec = new LinkSpec();
            int length = address.length();
            int end = start + length;

            spec.start = base + start;
            spec.end = base + end;
            string = string.substring(end);
            base += end;

            String encodedAddress = null;

            try {
                encodedAddress = URLEncoder.encode(address,"UTF-8");
            } catch (UnsupportedEncodingException e) {
                continue;
            }

            spec.url = "geo:0,0?q=" + encodedAddress;
            links.add(spec);
        }
    }

    private static final void pruneOverlaps(ArrayList<LinkSpec> links) {
        Comparator<LinkSpec>  c = new Comparator<LinkSpec>() {
            public final int compare(LinkSpec a, LinkSpec b) {
                if (a.start < b.start) {
                    return -1;
                }

                if (a.start > b.start) {
                    return 1;
                }

                if (a.end < b.end) {
                    return 1;
                }

                if (a.end > b.end) {
                    return -1;
                }

                return 0;
            }

            public final boolean equals(Object o) {
                return false;
            }
        };

        Collections.sort(links, c);

        int len = links.size();
        int i = 0;

        while (i < len - 1) {
            LinkSpec a = links.get(i);
            LinkSpec b = links.get(i + 1);
            int remove = -1;

            if ((a.start <= b.start) && (a.end > b.start)) {
                if (b.end <= a.end) {
                    remove = i + 1;
                } else if ((a.end - a.start) > (b.end - b.start)) {
                    remove = i + 1;
                } else if ((a.end - a.start) < (b.end - b.start)) {
                    remove = i;
                }

                if (remove != -1) {
                    links.remove(remove);
                    len--;
                    continue;
                }

            }

            i++;
        }
    }
}

class LinkSpec {
    String url;
    int start;
    int end;
}