refactor BstTextPrefixer.textPrefix (#11746)

* refactor BstTextPrefixer.textPrefix

1. add more unit test about nested brace cases
2. refactor the `textPrefix` method to make it clear

* rewrite unit test

use @ParameterizedTest and @CsvSource to rewrite unit test

src/main/java/org/jabref/logic/bst/util/BstTextPrefixer.java

@@ -23,49 +23,65 @@ public class BstTextPrefixer {
     private BstTextPrefixer() {
     }
 
-    public static String textPrefix(int inNumOfChars, String toPrefix) {
-        int numOfChars = inNumOfChars;
+    public static String textPrefix(int numOfChars, String toPrefix) {
         StringBuilder sb = new StringBuilder();
-
+        PrefixState prefixState = new PrefixState(0, 0, numOfChars);
         char[] cs = toPrefix.toCharArray();
-        int n = cs.length;
-        int i = 0;
-
-        int braceLevel = 0;
+        while (prefixState.index < cs.length && prefixState.numOfChars > 0) {
+            char c = cs[prefixState.index++];
+            handleOpeningBrace(cs, prefixState, c);
+            handleClosingBrace(prefixState, toPrefix, c);
+            boolean isNormalCharacter = c != '{' && c != '}';
+            if (isNormalCharacter) {
+                prefixState.numOfChars--;
+            }
+        }
+        sb.append(toPrefix, 0, prefixState.index);
+        // Append any remaining closing braces if unbalanced
+        while (prefixState.braceLevel-- > 0) {
+            sb.append('}');
+        }
+        return sb.toString();
+    }
 
-        while ((i < n) && (numOfChars > 0)) {
-            char c = cs[i];
-            i++;
-            if (c == '{') {
-                braceLevel++;
-                if ((braceLevel == 1) && (i < n) && (cs[i] == '\\')) {
-                    i++; // skip backslash
-                    while ((i < n) && (braceLevel > 0)) {
-                        if (cs[i] == '}') {
-                            braceLevel--;
-                        } else if (cs[i] == '{') {
-                            braceLevel++;
-                        }
-                        i++;
-                    }
-                    numOfChars--;
-                }
-            } else if (c == '}') {
-                if (braceLevel > 0) {
-                    braceLevel--;
-                } else {
-                    LOGGER.warn("Unbalanced brace in string for purify$: {}", toPrefix);
+    private static void handleOpeningBrace(char[] cs, PrefixState prefixState, char c) {
+        if (c != '{') {
+            return;
+        }
+        prefixState.braceLevel++;
+        if ((prefixState.braceLevel == 1) && (prefixState.index < cs.length) && (cs[prefixState.index] == '\\')) {
+            prefixState.index++; // skip backslash
+            while ((prefixState.index < cs.length) && (prefixState.braceLevel > 0)) {
+                if (cs[prefixState.index] == '}') {
+                    prefixState.braceLevel--;
+                } else if (cs[prefixState.index] == '{') {
+                    prefixState.braceLevel++;
                 }
-            } else {
-                numOfChars--;
+                prefixState.index++;
             }
+            prefixState.numOfChars--;
         }
-        sb.append(toPrefix, 0, i);
-        while (braceLevel > 0) {
-            sb.append('}');
-            braceLevel--;
+    }
+
+    private static void handleClosingBrace(PrefixState prefixState, String toPrefix, char c) {
+        if (c != '}') {
+            return;
         }
+        if (prefixState.braceLevel > 0) {
+            prefixState.braceLevel--;
+        } else {
+            LOGGER.warn("Unbalanced brace in string for purify$: {}", toPrefix);
+        }
+    }
 
-        return sb.toString();
+    private static class PrefixState {
+        public int index;
+        public int braceLevel;
+        public int numOfChars;
+        public PrefixState(int index, int braceLevel, int numOfChars) {
+            this.index = index;
+            this.braceLevel = braceLevel;
+            this.numOfChars = numOfChars;
+        }
     }
 }

src/test/java/org/jabref/logic/bst/util/BstTextPrefixerTest.java

@@ -1,25 +1,31 @@
 package org.jabref.logic.bst.util;
 
-import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 
-class BstTextPrefixerTest {
-
-    @Test
-    void prefix() {
-        assertPrefix("i", "i");
-        assertPrefix("0I~ ", "0I~ ");
-        assertPrefix("Hi Hi", "Hi Hi ");
-        assertPrefix("{\\oe}", "{\\oe}");
-        assertPrefix("Hi {\\oe   }H", "Hi {\\oe   }Hi ");
-        assertPrefix("Jonat", "Jonathan Meyer and Charles Louis Xavier Joseph de la Vall{\\'e}e Poussin");
-        assertPrefix("{\\'e}", "{\\'e}");
-        assertPrefix("{\\'{E}}doua", "{\\'{E}}douard Masterly");
-        assertPrefix("Ulric", "Ulrich {\\\"{U}}nderwood and Ned {\\~N}et and Paul {\\={P}}ot");
-    }
-
-    private static void assertPrefix(final String string, final String string2) {
-        assertEquals(string, BstTextPrefixer.textPrefix(5, string2));
+public class BstTextPrefixerTest {
+    @ParameterizedTest
+    @CsvSource({
+        "i, i",
+        "0I~ , 0I~ ",
+        "Hi Hi, Hi Hi ",
+        "{\\oe}, {\\oe}",
+        "Hi {\\oe   }H, Hi {\\oe   }Hi ",
+        "Jonat, Jonathan Meyer and Charles Louis Xavier Joseph de la Vall{\\'e}e Poussin",
+        "{\\'e}, {\\'e}",
+        "{\\'{E}}doua, {\\'{E}}douard Masterly",
+        "Ulric, Ulrich {\\\"{U}}nderwood and Ned {\\~N}et and Paul {\\={P}}ot",
+        "abcd{e}, abcd{efg}hi",
+        "ab{cd}e, ab{cd}efghi",
+        "ab{cd}e, ab{cd}efghi{}",
+        "Hi {{\\o}}, Hi {{\\oe   }}Hi ",
+        "Hi {\\{oe   }}H, Hi {\\{oe   }}Hi ",
+        "Hi {\\\"oe   }H, Hi {\\\"oe   }Hi ",
+        "Hi {\\{\\oe   }}H, Hi {\\{\\oe   }}Hi "
+    })
+    void assertPrefix(final String expectedResult, final String toPrefixInput) {
+        assertEquals(expectedResult, BstTextPrefixer.textPrefix(5, toPrefixInput));
     }
 }