Add links to non markdown formatted https urls in MarkdownActivity.

Author: Fox2Code

app/src/main/java/com/fox2code/mmm/markdown/MarkdownActivity.java

@@ -59,10 +59,12 @@ protected void onCreate(@Nullable Bundle savedInstanceState) {
         TextView textView = findViewById(R.id.markdownView);
         new Thread(() -> {
             try {
+                Log.d(TAG, "Downloading");
                 String markdown = new String(Http.doHttpGet(url, true), StandardCharsets.UTF_8);
-                Log.i(TAG, "Download successful");
+                Log.d(TAG, "Done!");
                 runOnUiThread(() -> {
-                    MainApplication.getINSTANCE().getMarkwon().setMarkdown(textView, markdown);
+                    MainApplication.getINSTANCE().getMarkwon().setMarkdown(
+                            textView, MarkdownUrlLinker.urlLinkify(markdown));
                     if (markdownBackground != null) {
                         markdownBackground.setClickable(true);
                         markdownBackground.setOnClickListener(v -> this.onBackPressed());

app/src/main/java/com/fox2code/mmm/markdown/MarkdownUrlLinker.java

@@ -0,0 +1,60 @@
+package com.fox2code.mmm.markdown;
+
+import android.util.Log;
+
+import com.fox2code.mmm.BuildConfig;
+
+import java.util.ArrayList;
+
+public class MarkdownUrlLinker {
+    private static final String TAG = "MarkdownUrlLinker";
+
+    public static String urlLinkify(String url) {
+        int index = url.indexOf("https://");
+        if (index == -1) return url;
+        ArrayList<LinkifyTask> linkifyTasks = new ArrayList<>();
+        int extra = 0;
+        while (index != -1) {
+            int end = Math.min(url.indexOf('\n', index),
+                    url.indexOf(' ', index));
+            if (end == -1) end = url.length();
+            if (index == 0 ||
+                    '\n' == url.charAt(index - 1) ||
+                    ' ' == url.charAt(index - 1)) {
+                int endDomain = url.indexOf('/', index + 9);
+                if (endDomain != -1 && endDomain < end) {
+                    linkifyTasks.add(new LinkifyTask(index, end));
+                    extra += (end - index) + 4;
+                    if (BuildConfig.DEBUG) {
+                        Log.d(TAG, "Linkify url: " + url.substring(index, end));
+                    }
+                }
+            }
+            index = url.indexOf("https://", end);
+        }
+        if (linkifyTasks.isEmpty()) return url;
+        LinkifyTask prev = LinkifyTask.NULL;
+        StringBuilder stringBuilder = new StringBuilder(url.length() + extra);
+        for (LinkifyTask linkifyTask : linkifyTasks) {
+            stringBuilder.append(url, prev.end, linkifyTask.start)
+                    .append('[').append(url, linkifyTask.start, linkifyTask.end)
+                    .append("](").append(url, linkifyTask.start, linkifyTask.end).append(')');
+            prev = linkifyTask;
+        }
+        if (prev.end != url.length()) stringBuilder.append(url, prev.end, url.length());
+        Log.d(TAG, "Added Markdown link to " + linkifyTasks.size() + " urls");
+        return stringBuilder.toString();
+    }
+
+    private static class LinkifyTask {
+        static final LinkifyTask NULL = new LinkifyTask(0, 0);
+
+        private final int start;
+        private final int end;
+
+        private LinkifyTask(int start, int end) {
+            this.start = start;
+            this.end = end;
+        }
+    }
+}