FairEmail/app/src/main/java/eu/faircode/email/HtmlHelper.java

package eu.faircode.email;

/*
    This file is part of FairEmail.

    FairEmail is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    FairEmail is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with FairEmail.  If not, see <http://www.gnu.org/licenses/>.

    Copyright 2018-2019 by Marcel Bokhorst (M66B)
*/

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.text.TextUtils;
import android.util.Base64;

import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;
import org.jsoup.nodes.Element;
import org.jsoup.nodes.Node;
import org.jsoup.nodes.TextNode;
import org.jsoup.safety.Whitelist;
import org.jsoup.select.NodeTraversor;
import org.jsoup.select.NodeVisitor;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URL;
import java.util.Arrays;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class HtmlHelper {
    private static final int PREVIEW_SIZE = 250;
    private static Pattern pattern = Pattern.compile("([http|https]+://[\\w\\S(\\.|:|/)]+)");
    private static final List<String> heads = Arrays.asList("p", "h1", "h2", "h3", "h4", "h5", "tr");
    private static final List<String> tails = Arrays.asList("br", "dd", "dt", "p", "h1", "h2", "h3", "h4", "h5");

    static String getBody(String html) {
        return Jsoup.parse(html).body().html();
    }

    static String sanitize(String html, boolean quotes) {
        Document document = Jsoup.parse(Jsoup.clean(html, Whitelist
                .relaxed()
                .addProtocols("img", "src", "cid")
                .addProtocols("img", "src", "data")));

        for (Element tr : document.select("tr"))
            tr.after("<br>");

        for (Element img : document.select("img")) {
            boolean linked = false;
            for (Element parent : img.parents())
                if ("a".equals(parent.tagName())) {
                    linked = true;
                    break;
                }
            if (!linked) {
                String src = img.attr("src");
                if (src.startsWith("http://") || src.startsWith("https://")) {
                    Element a = document.createElement("a");
                    a.attr("href", src);
                    img.replaceWith(a);
                    a.appendChild(img);
                }
            }
        }

        if (!quotes)
            for (Element quote : document.select("blockquote"))
                quote.text("&#8230;");

        NodeTraversor.traverse(new NodeVisitor() {
            @Override
            public void head(Node node, int depth) {
                if (node instanceof TextNode) {
                    String text = ((TextNode) node).text();
                    Matcher matcher = pattern.matcher(text);
                    while (matcher.find()) {
                        String ref = matcher.group();
                        text = text.replace(ref, String.format("<a href=\"%s\">%s</a>", ref, ref));
                    }
                    node.before(text);
                    ((TextNode) node).text("");
                }
            }

            @Override
            public void tail(Node node, int depth) {
            }
        }, document.body());

        return document.body().html();
    }

    static Drawable decodeImage(String source, Context context, long id, boolean show) {
        int px = Helper.dp2pixels(context, 48);

        if (TextUtils.isEmpty(source)) {
            Drawable d = context.getResources().getDrawable(R.drawable.baseline_broken_image_24, context.getTheme());
            d.setBounds(0, 0, px, px);
            return d;
        }

        boolean embedded = source.startsWith("cid:");
        boolean data = source.startsWith("data:");
        Log.i("Image embedded=" + embedded + " data=" + data + " source=" + source);

        if (show) {
            // Embedded images
            if (embedded) {
                String cid = "<" + source.substring(4) + ">";
                EntityAttachment attachment = DB.getInstance(context).attachment().getAttachment(id, cid);
                if (attachment == null) {
                    Drawable d = context.getResources().getDrawable(R.drawable.baseline_broken_image_24, context.getTheme());
                    d.setBounds(0, 0, px, px);
                    return d;
                } else if (!attachment.available) {
                    Drawable d = context.getResources().getDrawable(R.drawable.baseline_photo_library_24, context.getTheme());
                    d.setBounds(0, 0, px, px);
                    return d;
                } else {
                    File file = EntityAttachment.getFile(context, attachment.id);
                    Drawable d = Drawable.createFromPath(file.getAbsolutePath());
                    if (d == null) {
                        d = context.getResources().getDrawable(R.drawable.baseline_broken_image_24, context.getTheme());
                        d.setBounds(0, 0, px, px);
                    } else
                        d.setBounds(0, 0, d.getIntrinsicWidth(), d.getIntrinsicHeight());
                    return d;
                }
            }

            // Data URI
            if (data)
                try {
                    // "<img src=\"data:image/png;base64,iVBORw0KGgoAAA" +
                    // "ANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4" +
                    // "//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU" +
                    // "5ErkJggg==\" alt=\"Red dot\" />";

                    String base64 = source.substring(source.indexOf(',') + 1);
                    byte[] bytes = Base64.decode(base64.getBytes(), 0);

                    Bitmap bm = BitmapFactory.decodeByteArray(bytes, 0, bytes.length);
                    if (bm == null)
                        throw new IllegalArgumentException("decode byte array failed");

                    Drawable d = new BitmapDrawable(context.getResources(), bm);
                    d.setBounds(0, 0, bm.getWidth(), bm.getHeight());
                    return d;
                } catch (IllegalArgumentException ex) {
                    Log.w(ex);
                    Drawable d = context.getResources().getDrawable(R.drawable.baseline_broken_image_24, context.getTheme());
                    d.setBounds(0, 0, px, px);
                    return d;
                }

            // Get cache folder
            File dir = new File(context.getCacheDir(), "images");
            if (!dir.exists())
                dir.mkdir();

            InputStream is = null;
            OutputStream os = null;
            try {
                // Create unique file name
                File file = new File(dir, id + "_" + source.hashCode());

                // Get input stream
                if (file.exists()) {
                    Log.i("Using cached " + file);
                    is = new BufferedInputStream(new FileInputStream(file));
                } else {
                    Log.i("Downloading " + source);
                    try {
                        is = new URL(source).openStream();
                    } catch (IOException ex) {
                        Log.w(ex);
                        Drawable d = context.getResources().getDrawable(R.drawable.baseline_cloud_off_24, context.getTheme());
                        d.setBounds(0, 0, px, px);
                        return d;
                    }
                }

                // Decode image from stream
                Bitmap bm = BitmapFactory.decodeStream(is);
                if (bm == null)
                    throw new IllegalArgumentException("decode stream failed");

                // Cache bitmap
                if (!file.exists()) {
                    os = new BufferedOutputStream(new FileOutputStream(file));
                    bm.compress(Bitmap.CompressFormat.PNG, 100, os);
                }

                // Create drawable from bitmap
                Drawable d = new BitmapDrawable(context.getResources(), bm);
                d.setBounds(0, 0, bm.getWidth(), bm.getHeight());
                return d;
            } catch (Throwable ex) {
                // Show warning icon
                Log.e(ex);
                Drawable d = context.getResources().getDrawable(R.drawable.baseline_broken_image_24, context.getTheme());
                d.setBounds(0, 0, px, px);
                return d;
            } finally {
                // Close streams
                if (is != null) {
                    try {
                        is.close();
                    } catch (IOException e) {
                        Log.w(e);
                    }
                }
                if (os != null) {
                    try {
                        os.close();
                    } catch (IOException e) {
                        Log.w(e);
                    }
                }
            }
        } else {
            // Show placeholder icon
            int resid = (embedded || data ? R.drawable.baseline_photo_library_24 : R.drawable.baseline_image_24);
            Drawable d = context.getResources().getDrawable(resid, context.getTheme());
            d.setBounds(0, 0, px, px);
            return d;
        }
    }

    static String getPreview(String body) {
        String text = (body == null ? null : Jsoup.parse(body).text());
        return (text == null ? null : text.substring(0, Math.min(text.length(), PREVIEW_SIZE)));
    }

    static String getText(String html) {
        final StringBuilder sb = new StringBuilder();

        NodeTraversor.traverse(new NodeVisitor() {
            public void head(Node node, int depth) {
                if (node instanceof TextNode)
                    sb.append(((TextNode) node).text());
                else {
                    String name = node.nodeName();
                    if (name.equals("li"))
                        sb.append("\n * ");
                    else if (name.equals("dt"))
                        sb.append("  ");
                    else if (heads.contains(name))
                        sb.append("\n");
                }
            }

            public void tail(Node node, int depth) {
                String name = node.nodeName();
                if (tails.contains(name))
                    sb.append("\n");
                else if (name.equals("a"))
                    sb.append(" <").append(node.absUrl("href")).append(">");
            }
        }, Jsoup.parse(html));

        return sb.toString();
    }
}