limit number of log entries

closes #263

app/src/main/java/com/trianguloy/urlchecker/modules/list/LogModule.java

@@ -17,6 +17,7 @@ import com.trianguloy.urlchecker.modules.AModuleData;
 import com.trianguloy.urlchecker.modules.AModuleDialog;
 import com.trianguloy.urlchecker.url.UrlData;
 import com.trianguloy.urlchecker.utilities.GenericPref;
+import com.trianguloy.urlchecker.utilities.JavaUtils;
 
 import java.util.Date;
 
@@ -29,6 +30,10 @@ public class LogModule extends AModuleData {
         return new GenericPref.Str("log_data", "", cntx);
     }
 
+    public static GenericPref.Int LOG_LIMIT(Context cntx) {
+        return new GenericPref.Int("log_limit", 0, cntx); // 0 means unlimited
+    }
+
     @Override
     public String getId() {
         return "log";
@@ -53,10 +58,12 @@ public class LogModule extends AModuleData {
 class LogDialog extends AModuleDialog {
 
     private final GenericPref.Str log;
+    private final GenericPref.Int limit;
 
     public LogDialog(MainDialog dialog) {
         super(dialog);
         log = LogModule.LOG_DATA(dialog);
+        limit = LogModule.LOG_LIMIT(dialog);
     }
 
     @Override
@@ -67,15 +74,21 @@ class LogDialog extends AModuleDialog {
     @Override
     public void onInitialize(View views) {
         // new instance, log date
-        log.add((log.get().isEmpty() ? "" : "\n")
-                + "--- " + new Date().toLocaleString() + " ---\n"
-        );
+        addLine("--- " + new Date().toLocaleString() + " ---");
     }
 
     @Override
     public void onPrepareUrl(UrlData urlData) {
         // new url, log it
-        log.add("> " + urlData.url + "\n");
+        addLine("> " + urlData.url);
+    }
+
+    private void addLine(String line) {
+        var text = log.get();
+        if (limit.get() > 0) text = JavaUtils.limitLines(text, '\n', limit.get() - 1);
+        if (!text.isEmpty()) text += "\n";
+        text += line.replace("\n", "%0A");
+        log.set(text);
     }
 }
 
@@ -97,6 +110,8 @@ class LogConfig extends AModuleConfig {
     public void onInitialize(View views) {
         views.findViewById(R.id.view).setOnClickListener(v -> showLog(false));
         views.findViewById(R.id.edit).setOnClickListener(v -> showLog(true));
+
+        LogModule.LOG_LIMIT(getActivity()).attachToEditText(views.findViewById(R.id.limit), 0);
     }
 
     /**

app/src/main/java/com/trianguloy/urlchecker/utilities/GenericPref.java

@@ -105,6 +105,32 @@ public abstract class GenericPref<T> {
         protected void save(Integer value) {
             prefs.edit().putInt(prefName, value).apply();
         }
+
+        /**
+         * This editText will be set to the pref value, and when the editText changes the value will too.
+         * The special empty value will be set when the input is empty.
+         */
+        public void attachToEditText(EditText editText, int empty) {
+            editText.setText(get() == empty ? "" : get().toString());
+            editText.addTextChangedListener(new DefaultTextWatcher() {
+                @Override
+                public void afterTextChanged(Editable s) {
+                    try {
+                        // empty -> set empty
+                        if (s.length() == 0) set(empty);
+                        else {
+                            var value = Integer.parseInt(s.toString());
+                            if (value == empty) s.clear(); // empty input -> clear
+                            set(value);
+                        }
+                    } catch (NumberFormatException e) {
+                        // shouldn't be possible, but just in case
+                        s.clear();
+                        s.append(get() == empty ? "" : get().toString());
+                    }
+                }
+            });
+        }
     }
 
     /**

app/src/main/java/com/trianguloy/urlchecker/utilities/JavaUtils.java

@@ -65,6 +65,26 @@ public interface JavaUtils {
         return match;
     }
 
+    /**
+     * Takes the [limit] last lines of a [text], separated by [delimiter].
+     * This is equivalent to text.split(delimiter).takeLast(limit).join(delimiter) but using java sdk 14 (and hopefully more efficient)
+     */
+    static String limitLines(String text, char delimiter, int limit) {
+        // early exit
+        if (limit <= 0 || text.isEmpty()) return "";
+
+        // find the first character of the last (first) line required
+        var i = text.length() - 1; // character pointer
+        var lines = 0; // count full lines (delimiters encountered)
+        while (i >= 0 && lines < limit) {
+            if (text.charAt(i) == delimiter) lines++; // delimiter found
+            i--; // continue
+        }
+        // split if necessary
+        if (lines >= limit) text = text.substring(i + 2); // found the lines, split
+        return text;
+    }
+
     /**
      * Returns the object, or default if null
      * java.util.Optional requires api 24

app/src/main/res/layout/config_log.xml

@@ -9,6 +9,26 @@
         android:layout_height="wrap_content"
         android:text="@string/mLog_desc" />
 
+    <LinearLayout
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:orientation="horizontal">
+
+        <TextView
+            android:layout_width="0dp"
+            android:layout_height="wrap_content"
+            android:layout_gravity="center_vertical"
+            android:layout_weight="1"
+            android:text="@string/mLog_limit" />
+
+        <EditText
+            android:id="@+id/limit"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:hint="@string/mLog_unlimited"
+            android:inputType="number" />
+    </LinearLayout>
+
     <LinearLayout
         android:layout_width="match_parent"
         android:layout_height="match_parent"

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

@@ -272,6 +272,8 @@ This module has been deprecated in favor of the 'Uri parts' module"</string>
     <string name="mLog_view">View log</string>
     <string name="mLog_edit">Edit log</string>
     <string name="mLog_empty">No data</string>
+    <string name="mLog_limit">Maximum number of entries to keep. Recommended value: 100. Set empty for unlimited</string>
+    <string name="mLog_unlimited">Unlimited</string>
     <!-- -->
     <string name="mHosts_name">Hosts labeler</string>
     <string name="mHosts_desc">"This module labels hosts, configured either by specifying them manually or by using a remote hosts-like file. You can use it to warn about dangerous or special sites. The builtin configuration specifies StevenBlack's hosts (adware/malware, fakenews, gambling and adult content) from https://github.com/StevenBlack/hosts"</string>