Harden DSL parsing against escapes and malformed tags

Fixed escape-aware headword parsing for \{, \}, \[ and trailing backslash.
Fixed O(n^2) tag scan and nested bracket handling in article rendering.

app/src/main/java/com/example/research/data/parser/DslHeadwordParser.kt

@@ -24,10 +24,11 @@ object DslHeadwordParser {
         }
 
         if (trimmed.indexOf('{') == -1 && trimmed.indexOf('[') == -1) {
+            val unescaped = unescape(trimmed)
             return ParsedHeadword(
-                simplified = trimmed,
-                displayText = trimmed,
-                searchableText = trimmed.lowercase()
+                simplified = unescaped,
+                displayText = unescaped,
+                searchableText = unescaped.lowercase()
             )
         }
 
@@ -60,12 +61,12 @@ object DslHeadwordParser {
         val searchableText = createSearchableText(trimmed)
 
         return ParsedHeadword(
-            simplified = simplified,
-            displayText = displayText,
-            searchableText = searchableText
+            simplified = unescape(simplified),
+            displayText = unescape(displayText),
+            searchableText = unescape(searchableText)
         )
     }
-    
+
     private fun buildDisplayText(
         reconstructedPrefix: String,
         simplified: String,
@@ -96,7 +97,7 @@ object DslHeadwordParser {
                 .orEmpty()
         }
     }
-    
+
     private fun createSearchableText(originalHeadword: String): String {
         return removeFormattingTags(
             removeCurlyBraceMatches(originalHeadword, removeEmpty = true)
@@ -129,8 +130,17 @@ object DslHeadwordParser {
         if (value.indexOf('{') == -1 && value.indexOf('}') == -1) return value
 
         return buildString(value.length) {
-            value.forEach { char ->
-                if (char != '{' && char != '}') append(char)
+            var index = 0
+            while (index < value.length) {
+                val char = value[index]
+                if (char == '\\' && index + 1 < value.length) {
+                    append(char)
+                    append(value[index + 1])
+                    index += 2
+                } else {
+                    if (char != '{' && char != '}') append(char)
+                    index++
+                }
             }
         }
     }
@@ -138,6 +148,10 @@ object DslHeadwordParser {
     private fun firstFormattingTagIndex(value: String): Int {
         var index = 0
         while (index < value.length) {
+            if (value[index] == '\\' && index + 1 < value.length) {
+                index += 2
+                continue
+            }
             if (value[index] == '[' && formattingTagEnd(value, index) > index) {
                 return index
             }
@@ -149,8 +163,12 @@ object DslHeadwordParser {
     private fun firstCurlyContent(value: String): String? {
         var index = 0
         while (index < value.length) {
+            if (value[index] == '\\' && index + 1 < value.length) {
+                index += 2
+                continue
+            }
             if (value[index] == '{') {
-                val end = value.indexOf('}', startIndex = index + 1)
+                val end = matchingCurlyEnd(value, index + 1)
                 if (end > index + 1) {
                     return value.substring(index + 1, end)
                 }
@@ -161,7 +179,7 @@ object DslHeadwordParser {
     }
 
     private fun substringBeforeFirstBracket(value: String): String {
-        val bracketIndex = value.indexOf('[')
+        val bracketIndex = indexOfUnescaped(value, '[')
         return if (bracketIndex >= 0) value.substring(0, bracketIndex) else value
     }
 
@@ -171,8 +189,12 @@ object DslHeadwordParser {
         var index = 0
 
         while (index < value.length) {
+            if (value[index] == '\\' && index + 1 < value.length) {
+                index += 2
+                continue
+            }
             if (value[index] == '{') {
-                val end = value.indexOf('}', startIndex = index + 1)
+                val end = matchingCurlyEnd(value, index + 1)
                 if (end >= 0 && (removeEmpty || end > index + 1)) {
                     if (builder == null) {
                         builder = StringBuilder(value.length)
@@ -197,6 +219,10 @@ object DslHeadwordParser {
         var index = 0
 
         while (index < value.length) {
+            if (value[index] == '\\' && index + 1 < value.length) {
+                index += 2
+                continue
+            }
             if (value[index] == '[') {
                 val tagEnd = formattingTagEnd(value, index)
                 if (tagEnd > index) {
@@ -217,6 +243,56 @@ object DslHeadwordParser {
         }?.toString() ?: value
     }
 
+    private fun matchingCurlyEnd(value: String, startIndex: Int): Int {
+        var index = startIndex
+        while (index < value.length) {
+            when {
+                value[index] == '\\' && index + 1 < value.length -> index += 2
+                value[index] == '{' -> return -1
+                value[index] == '}' -> return index
+                else -> index++
+            }
+        }
+        return -1
+    }
+
+    private fun indexOfUnescaped(
+        value: String,
+        target: Char,
+        startIndex: Int = 0,
+    ): Int {
+        var index = startIndex.coerceAtLeast(0)
+        while (index < value.length) {
+            if (value[index] == '\\' && index + 1 < value.length) {
+                index += 2
+            } else if (value[index] == target) {
+                return index
+            } else {
+                index++
+            }
+        }
+        return -1
+    }
+
+    private fun unescape(value: String): String {
+        val firstEscape = value.indexOf('\\')
+        if (firstEscape < 0) return value
+
+        return buildString(value.length) {
+            append(value, 0, firstEscape)
+            var index = firstEscape
+            while (index < value.length) {
+                if (value[index] == '\\' && index + 1 < value.length) {
+                    append(value[index + 1])
+                    index += 2
+                } else {
+                    append(value[index])
+                    index++
+                }
+            }
+        }
+    }
+
     private fun formattingTagEnd(value: String, openBracketIndex: Int): Int {
         val tokenStart = openBracketIndex + 1
         if (tokenStart >= value.length) return -1

app/src/main/java/com/example/research/ui/article/DslAnnotatedParser.kt

@@ -119,7 +119,7 @@ object DslAnnotatedParser {
                     i++
                 }
                 '[' -> {
-                    val end = dsl.indexOf(']', i + 1)
+                    val end = tagCloseIndex(dsl, i + 1)
                     if (end != -1) {
                         val tagStart = i + 1
                         var tagEnd = end
@@ -228,6 +228,19 @@ object DslAnnotatedParser {
         splitOversizedBlocks(result)
     }
 
+    private fun tagCloseIndex(value: String, startIndex: Int): Int {
+        var index = startIndex
+        while (index < value.length) {
+            when {
+                value[index] == '\\' && index + 1 < value.length -> index += 2
+                value[index] == '[' -> return -1
+                value[index] == ']' -> return index
+                else -> index++
+            }
+        }
+        return -1
+    }
+
     private fun splitOversizedBlocks(blocks: List<DslBlock>): List<DslBlock> {
         if (blocks.none { it.text.length > MAX_BLOCK_TEXT_LENGTH }) return blocks
         return blocks.flatMap { block ->