Improve range split function and add unit tests

android/build.gradle

@@ -175,6 +175,8 @@ dependencies {
   implementation "com.facebook.react:react-android" // version substituted by RNGP
   implementation "com.facebook.react:hermes-android" // version substituted by RNGP
   implementation project(":react-native-reanimated")
+
+  testImplementation "junit:junit:4.13.2"
 }
 
 if (isNewArchitectureEnabled()) {

android/src/main/java/com/expensify/livemarkdown/MarkdownParser.java

@@ -1,5 +1,7 @@
 package com.expensify.livemarkdown;
 
+import static com.expensify.livemarkdown.RangeSplitter.splitRangesOnEmojis;
+
 import androidx.annotation.NonNull;
 
 import com.facebook.react.bridge.ReactContext;
@@ -32,38 +34,6 @@ public MarkdownParser(@NonNull ReactContext reactContext) {
 
   private native String nativeParse(@NonNull String text, int parserId);
 
-    private void splitRangesOnEmojis(List<MarkdownRange> markdownRanges, String type) {
-    List<MarkdownRange> emojiRanges = new ArrayList<>();
-    for (MarkdownRange range : markdownRanges) {
-      if (range.getType().equals("emoji")) {
-        emojiRanges.add(range);
-      }
-    }
-
-    int i = 0;
-    int j = 0;
-    while (i < markdownRanges.size() && j < emojiRanges.size()) {
-      MarkdownRange currentRange = markdownRanges.get(i);
-      MarkdownRange emojiRange = emojiRanges.get(j);
-
-      if (!currentRange.getType().equals(type) || currentRange.getEnd() < emojiRange.getStart()) {
-        i += 1;
-        continue;
-      } else if (emojiRange.getStart() >= currentRange.getStart() && emojiRange.getEnd() <= currentRange.getEnd()) {
-        // Split range
-        MarkdownRange startRange = new MarkdownRange(currentRange.getType(), currentRange.getStart(), emojiRange.getStart() - currentRange.getStart(), currentRange.getDepth());
-        MarkdownRange endRange = new MarkdownRange(currentRange.getType(), emojiRange.getEnd(), currentRange.getEnd() - emojiRange.getEnd(), currentRange.getDepth());
-
-        markdownRanges.add(i + 1, startRange);
-        markdownRanges.add(i + 2, endRange);
-        markdownRanges.remove(i);
-        i = i + 1;
-      }
-      j += 1;
-    }
-  }
-
-
   private List<MarkdownRange> parseRanges(String rangesJSON, String innerText) {
     List<MarkdownRange> markdownRanges = new ArrayList<>();
     try {
@@ -84,8 +54,8 @@ private List<MarkdownRange> parseRanges(String rangesJSON, String innerText) {
     } catch (JSONException e) {
       return Collections.emptyList();
     }
-    splitRangesOnEmojis(markdownRanges, "italic");
-    splitRangesOnEmojis(markdownRanges, "strikethrough");
+    markdownRanges = splitRangesOnEmojis(markdownRanges, "italic");
+    markdownRanges = splitRangesOnEmojis(markdownRanges, "strikethrough");
     return markdownRanges;
   }
   public synchronized List<MarkdownRange> parse(@NonNull String text, int parserId) {

android/src/main/java/com/expensify/livemarkdown/MarkdownRange.java

@@ -36,4 +36,32 @@ public int getLength() {
   public int getDepth() {
     return mDepth;
   }
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+
+    if (o instanceof MarkdownRange other) {
+      return this.mType.equals(other.mType)
+        && this.mStart == other.mStart
+        && this.mEnd == other.mEnd
+        && this.mLength == other.mLength
+        && this.mDepth == other.mDepth;
+    }
+    return false;
+  }
+
+  @NonNull
+  @Override
+  public String toString() {
+    return "MarkdownRange{" +
+      "type='" + mType + "'" +
+      ", start=" + mStart +
+      ", end=" + mEnd +
+      ", length=" + mLength +
+      ", depth=" + mDepth +
+      "}";
+  }
 }

android/src/main/java/com/expensify/livemarkdown/RangeSplitter.java

@@ -0,0 +1,53 @@
+package com.expensify.livemarkdown;
+
+import androidx.annotation.NonNull;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class RangeSplitter {
+  public static ArrayList<MarkdownRange> splitRangesOnEmojis(@NonNull List<MarkdownRange> markdownRanges, @NonNull String type) {
+    ArrayList<MarkdownRange> emojiRanges = new ArrayList<>();
+    ArrayList<MarkdownRange> oldRanges = new ArrayList<>(markdownRanges);
+    ArrayList<MarkdownRange> newRanges = new ArrayList<>();
+    for (MarkdownRange range : oldRanges) {
+      if (range.getType().equals("emoji")) {
+        emojiRanges.add(range);
+      }
+    }
+
+    int i = 0;
+    int j = 0;
+    while (i < oldRanges.size()) {
+      MarkdownRange currentRange = oldRanges.get(i);
+      if (!currentRange.getType().equals(type)) {
+        newRanges.add(currentRange);
+        i += 1;
+        continue;
+      }
+
+      // Iterate through all emoji ranges before the end of the current range, splitting the current range at each intersection.
+      while (j < emojiRanges.size()) {
+        MarkdownRange emojiRange = emojiRanges.get(j);
+        if (emojiRange.getStart() > currentRange.getEnd()) {
+          break;
+        }
+
+        int currentStart = currentRange.getStart();
+        int currentEnd = currentRange.getEnd();
+        int emojiStart = emojiRange.getStart();
+        int emojiEnd = emojiRange.getEnd();
+        if (emojiStart >= currentStart && emojiEnd <= currentEnd) { // Intersection
+          MarkdownRange newRange = new MarkdownRange(currentRange.getType(), currentStart, emojiStart - currentStart, currentRange.getDepth());
+          currentRange = new MarkdownRange(currentRange.getType(), emojiEnd, currentEnd - emojiEnd, currentRange.getDepth());
+
+          newRanges.add(newRange);
+        }
+        j += 1;
+      }
+      newRanges.add(currentRange);
+      i += 1;
+    }
+    return newRanges;
+  }
+}

android/src/test/java/com/expensify/livemarkdown/RangeSplitterTest.java

@@ -0,0 +1,81 @@
+package com.expensify.livemarkdown;
+
+import static com.expensify.livemarkdown.RangeSplitter.splitRangesOnEmojis;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+public class RangeSplitterTest {
+
+  @Test
+  public void testNoOverlap() {
+    List<MarkdownRange> markdownRanges = new ArrayList<>();
+    markdownRanges.add(new MarkdownRange("strikethrough", 0, 10, 1));
+    markdownRanges.add(new MarkdownRange("emoji", 12, 2, 1));
+
+    markdownRanges = splitRangesOnEmojis(markdownRanges, "strikethrough");
+
+    assertEquals(2, markdownRanges.size());
+    assertEquals(new MarkdownRange("strikethrough", 0, 10, 1), markdownRanges.get(0));
+    assertEquals(new MarkdownRange("emoji", 12, 2, 1), markdownRanges.get(1));
+  }
+
+  @Test
+  public void testOverlapDifferentType() {
+    List<MarkdownRange> markdownRanges = new ArrayList<>();
+    markdownRanges.add(new MarkdownRange("strikethrough", 0, 10, 1));
+    markdownRanges.add(new MarkdownRange("emoji", 3, 4, 1));
+
+    markdownRanges = splitRangesOnEmojis(markdownRanges, "italic");
+
+    assertEquals(2, markdownRanges.size());
+    assertEquals(new MarkdownRange("strikethrough", 0, 10, 1), markdownRanges.get(0));
+    assertEquals(new MarkdownRange("emoji", 3, 4, 1), markdownRanges.get(1));
+  }
+
+  @Test
+  public void testSingleOverlap() {
+    List<MarkdownRange> markdownRanges = new ArrayList<>();
+    markdownRanges.add(new MarkdownRange("strikethrough", 0, 10, 1));
+    markdownRanges.add(new MarkdownRange("emoji", 3, 4, 1)); // This range should split the strikethrough range
+
+    markdownRanges = splitRangesOnEmojis(markdownRanges, "strikethrough");
+
+    // Sort is needed because ranges may get mixed while splitting
+    Collections.sort(markdownRanges, (r1, r2) -> Integer.compare(r1.getStart(), r2.getStart()));
+
+    assertEquals(3, markdownRanges.size());
+    assertEquals(new MarkdownRange("strikethrough", 0, 3, 1), markdownRanges.get(0));
+    assertEquals(new MarkdownRange("emoji", 3, 4, 1), markdownRanges.get(1));
+    assertEquals(new MarkdownRange("strikethrough", 7, 3, 1), markdownRanges.get(2));
+  }
+
+  @Test
+  public void testMultipleOverlapsMultipleTypes() {
+    List<MarkdownRange> markdownRanges = new ArrayList<>();
+    markdownRanges.add(new MarkdownRange("italic", 0, 20, 1));
+    markdownRanges.add(new MarkdownRange("strikethrough", 2, 12, 1));
+    markdownRanges.add(new MarkdownRange("emoji", 3, 1, 1));
+    markdownRanges.add(new MarkdownRange("emoji", 8, 2, 1));
+    markdownRanges.add(new MarkdownRange("strikethrough", 22, 5, 1));
+
+    markdownRanges = splitRangesOnEmojis(markdownRanges, "strikethrough");
+
+    // Sort is needed because ranges may get mixed while splitting
+    Collections.sort(markdownRanges, (r1, r2) -> Integer.compare(r1.getStart(), r2.getStart()));
+
+    assertEquals(7, markdownRanges.size());
+    assertEquals(new MarkdownRange("italic", 0, 20, 1), markdownRanges.get(0));
+    assertEquals(new MarkdownRange("strikethrough", 2, 1, 1), markdownRanges.get(1));
+    assertEquals(new MarkdownRange("emoji", 3, 1, 1), markdownRanges.get(2));
+    assertEquals(new MarkdownRange("strikethrough", 4, 4, 1), markdownRanges.get(3));
+    assertEquals(new MarkdownRange("emoji", 8, 2, 1), markdownRanges.get(4));
+    assertEquals(new MarkdownRange("strikethrough", 10, 4, 1), markdownRanges.get(5));
+    assertEquals(new MarkdownRange("strikethrough", 22, 5, 1), markdownRanges.get(6));
+  }
+}