Linkify community and user names

This commit makes user and community names clickable in post/comments. Closes #71?

app/build.gradle

@@ -1,5 +1,6 @@
 plugins {
     id 'com.android.application'
+    id 'org.jetbrains.kotlin.android'
 }
 
 android {
@@ -34,6 +35,11 @@ android {
             versionNameSuffix ' (DEBUG)'
         }
     }
+
+    sourceSets {
+        main.java.srcDirs += 'src/main/kotlin'
+    }
+
     compileOptions {
         sourceCompatibility JavaVersion.VERSION_11
         targetCompatibility JavaVersion.VERSION_11

app/src/main/java/eu/toldi/infinityforlemmy/activities/ViewSubredditDetailActivity.java

@@ -690,9 +690,8 @@ public class ViewSubredditDetailActivity extends BaseActivity implements SortTyp
                     qualifiedName = LemmyUtils.actorID2FullName(communityData.getActorId());
                     if (communityName == null) {
                         communityName = communityData.getTitle();
-
-                        setupVisibleElements();
                     }
+                    setupVisibleElements();
                     communityId = communityData.getId();
                     setupSubscribeChip();
 

app/src/main/java/eu/toldi/infinityforlemmy/fragments/SidebarFragment.java

@@ -40,6 +40,7 @@ import eu.toldi.infinityforlemmy.markdown.MarkdownUtils;
 import eu.toldi.infinityforlemmy.subreddit.FetchSubredditData;
 import eu.toldi.infinityforlemmy.subreddit.SubredditData;
 import eu.toldi.infinityforlemmy.subreddit.SubredditViewModel;
+import eu.toldi.infinityforlemmy.utils.LemmyUtils;
 import io.noties.markwon.AbstractMarkwonPlugin;
 import io.noties.markwon.Markwon;
 import io.noties.markwon.MarkwonConfiguration;
@@ -97,7 +98,7 @@ public class SidebarFragment extends Fragment {
         mAccessToken = getArguments().getString(EXTRA_ACCESS_TOKEN);
         subredditName = getArguments().getString(EXTRA_SUBREDDIT_NAME);
         communityQualifiedName = getArguments().getString(EXTRA_COMMUNITY_QUALIFIED_NAME);
-        if (subredditName == null) {
+        if (communityQualifiedName == null) {
             Toast.makeText(activity, R.string.error_getting_community_name, Toast.LENGTH_SHORT).show();
             return rootView;
         }
@@ -166,7 +167,7 @@ public class SidebarFragment extends Fragment {
         });
 
         mSubredditViewModel = new ViewModelProvider(activity,
-                new SubredditViewModel.Factory(activity.getApplication(), mRedditDataRoomDatabase, communityQualifiedName))
+                new SubredditViewModel.Factory(activity.getApplication(), mRedditDataRoomDatabase, LemmyUtils.qualifiedCommunityName2ActorId(communityQualifiedName)))
                 .get(SubredditViewModel.class);
         mSubredditViewModel.getSubredditLiveData().observe(getViewLifecycleOwner(), subredditData -> {
             if (subredditData != null) {

app/src/main/java/eu/toldi/infinityforlemmy/markdown/MarkdownUtils.java

@@ -52,6 +52,7 @@ public class MarkdownUtils {
                 .usePlugin(LinkifyPlugin.create(Linkify.WEB_URLS))
                 .usePlugin(TableEntryPlugin.create(context))
                 .usePlugin(ClickableGlideImagesPlugin.create(context))
+                .usePlugin(new MarkwonLemmyLinkPlugin())
                 .build();
     }
 
@@ -71,6 +72,7 @@ public class MarkdownUtils {
                 .usePlugin(LinkifyPlugin.create(Linkify.WEB_URLS))
                 .usePlugin(TableEntryPlugin.create(context))
                 .usePlugin(GlideImagesPlugin.create(context))
+                .usePlugin(new MarkwonLemmyLinkPlugin())
                 .build();
     }
 

app/src/main/kotlin/eu/toldi/infinityforlemmy/markdown/MarkwonLemmyLinkPlugin.kt

@@ -0,0 +1,88 @@
+package eu.toldi.infinityforlemmy.markdown
+
+
+import android.text.Spannable
+import android.text.SpannableStringBuilder
+import android.text.style.URLSpan
+import android.text.util.Linkify
+import eu.toldi.infinityforlemmy.utils.LemmyUtils
+import io.noties.markwon.*
+import io.noties.markwon.core.CorePlugin
+import io.noties.markwon.core.CoreProps
+import org.commonmark.node.Link
+import java.util.regex.Pattern
+
+// Source : https://github.com/dessalines/jerboa/blob/main/app/src/main/java/com/jerboa/util/markwon/MarkwonLemmyLinkPlugin.kt
+class MarkwonLemmyLinkPlugin : AbstractMarkwonPlugin() {
+
+    companion object {
+        /**
+         * pattern that matches all valid communities; intended to be loose
+         */
+        const val communityPatternFragment: String = """[a-zA-Z0-9_]{3,}"""
+
+        /**
+         * pattern to match all valid instances
+         */
+        const val instancePatternFragment: String =
+                """([a-zA-Z0-9][a-zA-Z0-9-]{0,61}[a-zA-Z0-9]\.)+[a-zA-Z]{2,}"""
+
+        /**
+         * pattern to match all valid usernames
+         */
+        const val userPatternFragment: String = """[a-zA-Z0-9_]{3,}"""
+
+        /**
+         * Pattern to match lemmy's unique community pattern, e.g. !commmunity[@instance]
+         */
+        val lemmyCommunityPattern: Pattern =
+                Pattern.compile("(?<!\\S)!($communityPatternFragment)(?:@($instancePatternFragment))?\\b")
+
+        /**
+         * Pattern to match lemmy's unique user pattern, e.g. @user[@instance]
+         */
+        val lemmyUserPattern: Pattern =
+                Pattern.compile("(?<!\\S)@($userPatternFragment)(?:@($instancePatternFragment))?\\b")
+
+    }
+    override fun configure(registry: MarkwonPlugin.Registry) {
+        registry.require(CorePlugin::class.java) { it.addOnTextAddedListener(LemmyTextAddedListener()) }
+    }
+
+    private class LemmyTextAddedListener : CorePlugin.OnTextAddedListener {
+        override fun onTextAdded(visitor: MarkwonVisitor, text: String, start: Int) {
+            // we will be using the link that is used by markdown (instead of directly applying URLSpan)
+            val spanFactory = visitor.configuration().spansFactory().get(
+                    Link::class.java,
+            ) ?: return
+
+            // don't re-use builder (thread safety achieved for
+            // render calls from different threads and ... better performance)
+            val builder = SpannableStringBuilder(text)
+            if (addLinks(builder)) {
+                // target URL span specifically
+                val spans = builder.getSpans(0, builder.length, URLSpan::class.java)
+                if (!spans.isNullOrEmpty()) {
+                    val renderProps = visitor.renderProps()
+                    val spannableBuilder = visitor.builder()
+                    for (span in spans) {
+                        CoreProps.LINK_DESTINATION[renderProps] = if (span.url.startsWith("!")) { LemmyUtils.qualifiedCommunityName2ActorId(span.url.drop(1)) } else { LemmyUtils.qualifiedUserName2ActorId(span.url.drop(1)) }
+                        SpannableBuilder.setSpans(
+                                spannableBuilder,
+                                spanFactory.getSpans(visitor.configuration(), renderProps),
+                                start + builder.getSpanStart(span),
+                                start + builder.getSpanEnd(span),
+                        )
+                    }
+                }
+            }
+        }
+
+        fun addLinks(text: Spannable): Boolean {
+            val communityLinkAdded = Linkify.addLinks(text, lemmyCommunityPattern, null)
+            val userLinkAdded = Linkify.addLinks(text, lemmyUserPattern, null)
+
+            return communityLinkAdded || userLinkAdded
+        }
+    }
+}

app/src/main/res/values/strings.xml

@@ -1352,4 +1352,6 @@
     <string name="instance_cannot_be_empty">The instance field cannot be left empty.</string>
     <string name="username_cannot_be_empty">The username field cannot be left empty.</string>
     <string name="password_cannot_be_empty">The password field cannot be left empty.</string>
+    <!-- TODO: Remove or change this placeholder text -->
+    <string name="hello_blank_fragment">Hello blank fragment</string>
 </resources>

build.gradle

@@ -9,6 +9,7 @@ buildscript {
     }
     dependencies {
         classpath 'com.android.tools.build:gradle:7.4.2'
+        classpath 'org.jetbrains.kotlin:kotlin-gradle-plugin:1.8.20'
 
         // NOTE: Do not place your application dependencies here; they belong
         // in the individual module build.gradle files