Experiment: LanguageTool support

PRIVACY.md

@@ -31,7 +31,7 @@ FairEmail **can use** these services if they are explicitly enabled (off by defa
 * [Spamcop](https://www.spamcop.net/) – [Privacy policy](https://www.spamcop.net/fom-serve/cache/168.html)
 * [Barracuda](https://www.barracudacentral.org/rbl/how-to-use) – [Privacy policy](https://www.barracuda.com/company/legal/trust-center/data-privacy/privacy-policy)
 * [Thunderbird autoconfiguration](https://developer.mozilla.org/docs/Mozilla/Thunderbird/Autoconfiguration) – [Privacy policy](https://www.mozilla.org/privacy/)
-
+* [LanguageTool](https://languagetool.org/) – [Privacy policy](https://languagetool.org/legal/privacy)
 
 FairEmail **can access** the websites at the domain names of email addresses
 if [Brand Indicators for Message Identification](https://en.wikipedia.org/wiki/Brand_Indicators_for_Message_Identification) (BIMI)

app/src/main/java/eu/faircode/email/FragmentCompose.java

@@ -81,6 +81,7 @@ import android.text.style.ImageSpan;
 import android.text.style.ParagraphStyle;
 import android.text.style.QuoteSpan;
 import android.text.style.RelativeSizeSpan;
+import android.text.style.SuggestionSpan;
 import android.text.style.URLSpan;
 import android.util.LogPrinter;
 import android.util.Pair;
@@ -1814,6 +1815,15 @@ public class FragmentCompose extends FragmentBase {
         for (int i = 0; i < m.size(); i++)
             bottom_navigation.findViewById(m.getItem(i).getItemId()).setOnLongClickListener(null);
 
+        if (!BuildConfig.PLAY_STORE_RELEASE)
+            bottom_navigation.findViewById(R.id.action_save).setOnLongClickListener(new View.OnLongClickListener() {
+                @Override
+                public boolean onLongClick(View view) {
+                    onLanguageTool();
+                    return true;
+                }
+            });
+
         bottom_navigation.findViewById(R.id.action_send).setOnLongClickListener(new View.OnLongClickListener() {
             @Override
             public boolean onLongClick(View v) {
@@ -2379,6 +2389,53 @@ public class FragmentCompose extends FragmentBase {
         popupMenu.showWithIcons(context, anchor);
     }
 
+    private void onLanguageTool() {
+        etBody.clearComposingText();
+
+        Bundle args = new Bundle();
+        args.putCharSequence("text", etBody.getText());
+
+        new SimpleTask<List<LanguageTool.Suggestion>>() {
+            @Override
+            protected void onPreExecute(Bundle args) {
+                setBusy(true);
+            }
+
+            @Override
+            protected void onPostExecute(Bundle args) {
+                setBusy(false);
+            }
+
+            @Override
+            protected List<LanguageTool.Suggestion> onExecute(Context context, Bundle args) throws Throwable {
+                CharSequence text = args.getCharSequence("text").toString();
+                return LanguageTool.getSuggestions(context, text);
+            }
+
+            @Override
+            protected void onExecuted(Bundle args, List<LanguageTool.Suggestion> suggestions) {
+                // https://developer.android.com/reference/android/text/style/SuggestionSpan
+                final Context context = getContext();
+                Editable edit = etBody.getText();
+
+                for (LanguageTool.Suggestion suggestion : suggestions) {
+                    Log.i("LT suggestion=" + suggestion);
+                    SuggestionSpan span = new SuggestionSpan(context,
+                            suggestion.replacements.toArray(new String[0]),
+                            SuggestionSpan.FLAG_MISSPELLED);
+                    int start = suggestion.offset;
+                    int end = start + suggestion.length;
+                    edit.setSpan(span, start, end, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE | Spanned.SPAN_COMPOSING);
+                }
+            }
+
+            @Override
+            protected void onException(Bundle args, Throwable ex) {
+                Log.unexpectedError(getParentFragmentManager(), ex);
+            }
+        }.execute(this, args, "compose:lt");
+    }
+
     private boolean onActionStyle(int action, View anchor) {
         Log.i("Style action=" + action);
         return StyleHelper.apply(action, getViewLifecycleOwner(), anchor, etBody);

app/src/main/java/eu/faircode/email/LanguageTool.java

@@ -0,0 +1,122 @@
+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 2018-2022 by Marcel Bokhorst (M66B)
+*/
+
+import android.content.Context;
+
+import org.json.JSONArray;
+import org.json.JSONException;
+import org.json.JSONObject;
+
+import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.io.InputStream;
+import java.net.URL;
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
+import java.util.ArrayList;
+import java.util.List;
+
+import javax.net.ssl.HttpsURLConnection;
+
+public class LanguageTool {
+    private static final int LT_TIMEOUT = 20; // seconds
+    private static final String LT_URI = "https://api.languagetool.org/v2/";
+
+    static List<Suggestion> getSuggestions(Context context, CharSequence text) throws IOException, JSONException {
+        // https://languagetool.org/http-api/swagger-ui/#!/default/post_check
+        String request =
+                "text=" + URLEncoder.encode(text.toString(), StandardCharsets.UTF_8.name()) +
+                        "&language=auto";
+
+        URL url = new URL(LT_URI + "check");
+        HttpsURLConnection connection = (HttpsURLConnection) url.openConnection();
+        connection.setRequestMethod("POST");
+        connection.setDoOutput(true);
+        connection.setReadTimeout(LT_TIMEOUT * 1000);
+        connection.setConnectTimeout(LT_TIMEOUT * 1000);
+        connection.setRequestProperty("User-Agent", WebViewEx.getUserAgent(context));
+        connection.setRequestProperty("Accept", "application/json");
+        connection.setRequestProperty("Content-Length", Integer.toString(request.length()));
+        connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
+        connection.connect();
+
+        try {
+            connection.getOutputStream().write(request.getBytes());
+
+            int status = connection.getResponseCode();
+            if (status != HttpsURLConnection.HTTP_OK) {
+                String error = "Error " + status + ": " + connection.getResponseMessage();
+                try {
+                    InputStream is = connection.getErrorStream();
+                    if (is != null)
+                        error += "\n" + Helper.readStream(is);
+                } catch (Throwable ex) {
+                    Log.w(ex);
+                }
+                throw new FileNotFoundException(error);
+            }
+
+            String response = Helper.readStream(connection.getInputStream());
+
+            List<Suggestion> result = new ArrayList<>();
+
+            JSONObject jroot = new JSONObject(response);
+            JSONArray jmatches = jroot.getJSONArray("matches");
+            for (int i = 0; i < jmatches.length(); i++) {
+                JSONObject jmatch = jmatches.getJSONObject(i);
+
+                Suggestion suggestion = new Suggestion();
+                suggestion.title = jmatch.getString("shortMessage");
+                suggestion.description = jmatch.getString("message");
+                suggestion.offset = jmatch.getInt("offset");
+                suggestion.length = jmatch.getInt("length");
+
+                JSONArray jreplacements = jmatch.getJSONArray("replacements");
+
+                suggestion.replacements = new ArrayList<>();
+                for (int j = 0; j < jreplacements.length(); j++) {
+                    JSONObject jreplacement = jreplacements.getJSONObject(j);
+                    suggestion.replacements.add(jreplacement.getString("value"));
+                }
+
+                if (suggestion.replacements.size() > 0)
+                    result.add(suggestion);
+            }
+
+            return result;
+        } finally {
+            connection.disconnect();
+        }
+    }
+
+    static class Suggestion {
+        String title; // shortMessage
+        String description; // message
+        int offset;
+        int length;
+        List<String> replacements;
+
+        @Override
+        public String toString() {
+            return title;
+        }
+    }
+}