perf: Avoid stringifying extended document (#2480)

Author: slavek-kucera

server/common/src/main/java/org/eclipse/lsp/cobol/common/mapping/ExtendedDocument.java

@@ -15,6 +15,9 @@
 package org.eclipse.lsp.cobol.common.mapping;
 
 import lombok.Getter;
+
+import java.util.List;
+
 import org.eclipse.lsp4j.Location;
 import org.eclipse.lsp4j.Position;
 import org.eclipse.lsp4j.Range;
@@ -156,6 +159,29 @@ public String toString() {
     return baseText.toString();
   }
 
+  /**
+   * Checks if a line segment can be trimmed to empty string
+   * @param lineno line number to investigate
+   * @param start start column
+   * @param end end column (exclusive)
+   * @return segment consists of trimmable characters only
+   */
+  public boolean isLineEmptyBetweenColumns(int lineno, int start, int end) {
+    assert 0 <= lineno;
+    assert 0 <= start;
+    assert start <= end;
+    List<ExtendedTextLine> lines = baseText.getLines();
+    if (lineno >= lines.size())
+      return true;
+    List<MappedCharacter> chars = lines.get(lineno).getCharacters();
+    for (int i = start; i < chars.size() && i < end; ++i) {
+      // emulates behavior of trim function
+      if (chars.get(i).getCharacter() > ' ')
+        return false;
+    }
+    return true;
+  }
+
   private Range updateRangeDueToChanges(Range range) {
     if (isDirty()) {
       range = new Range(updatePositionDueToChanges(range.getStart()), updatePositionDueToChanges(range.getEnd()));

server/common/src/test/java/org/eclipse/lsp/cobol/common/mapping/ExtendedDocumentTest.java

@@ -116,5 +116,10 @@ void testInsertCopybookAfterLine() {
     assertEquals(documentUri, location.getUri());
   }
 
-
+  @Test
+  void testIsLineEmptyBetweenColumns() {
+    assertTrue(document.isLineEmptyBetweenColumns(0, 0, 8));
+    assertFalse(document.isLineEmptyBetweenColumns(0, 7, 100));
+    assertTrue(document.isLineEmptyBetweenColumns(1000, 0, 1));
+  }
 }

server/engine/src/main/java/org/eclipse/lsp/cobol/core/preprocessor/delegates/copybooks/CopybookPreprocessorService.java

@@ -218,17 +218,7 @@ private boolean firstInstruction(ExtendedDocument extendedDocument, Position sta
     if (start.getCharacter() < 7) {
       return true;
     }
-    String text = extendedDocument.toString();
-    String[] lines = text.split("\\r?\\n");
-    if (lines.length <= start.getLine()) {
-      return true;
-    }
-    String line = lines[start.getLine()];
-    if (line.length() < 7) {
-      return true;
-    }
-    line = line.substring(7, Math.min(start.getCharacter(), line.length()));
-    return line.trim().isEmpty();
+    return extendedDocument.isLineEmptyBetweenColumns(start.getLine(), 7, start.getCharacter());
   }
 
   private CopybookName getCopybookName(CobolPreprocessor.CopySourceContext ctx) {

server/engine/src/main/java/org/eclipse/lsp/cobol/core/preprocessor/delegates/replacement/ReplacingServiceImpl.java

@@ -230,10 +230,10 @@ private String handleSeparator(String trim) {
   }
 
   private void replace(@NonNull ExtendedDocument extendedDocument, @NonNull Pair<String, String> pattern, @NonNull Range scope) {
-    if (StringUtils.isBlank(extendedDocument.toString())) {
+    String text = extendedDocument.toString();
+    if (StringUtils.isBlank(text)) {
       return;
     }
-    String text = extendedDocument.toString();
     try {
       Matcher matcher = Pattern.compile(pattern.getLeft(), Pattern.CASE_INSENSITIVE).matcher(text);
       while (matcher.find()) {