feat: add anchor operator support in RegexParser and implement AnchorItem class

lib/src/main/kotlin/org/example/Parser.kt

@@ -2,19 +2,20 @@ package org.example
 
 import com.github.h0tk3y.betterParse.combinators.*
 import com.github.h0tk3y.betterParse.grammar.Grammar
+import com.github.h0tk3y.betterParse.grammar.parseToEnd
 import com.github.h0tk3y.betterParse.grammar.parser
 import com.github.h0tk3y.betterParse.lexer.literalToken
 import com.github.h0tk3y.betterParse.lexer.regexToken
 import com.github.h0tk3y.betterParse.lexer.token
 import com.github.h0tk3y.betterParse.parser.Parser
-import com.github.h0tk3y.betterParse.grammar.parseToEnd
 
 class RegexParser : Grammar<RegexItem>() {
   private var groupCounter = 0
 
   // val bracketContent by regexToken("[^\\]]*")
-  val escapedCharacter by regexToken("\\\\[+*?.()|\\[\\]]")
+  val escapedCharacter by regexToken("\\\\[+*?.$^()|\\[\\]]")
   val postfixOperator by regexToken("[+*?]")
+  val anchorOperator by regexToken("[$^]")
   val alternationSymbol by literalToken("|")
   val openParenSymbol by literalToken("(")
   val closeParenSymbol by literalToken(")")
@@ -49,6 +50,7 @@ class RegexParser : Grammar<RegexItem>() {
 
   val item: Parser<RegexItem> by
           char or
+                  (anchorOperator map { AnchorItem(it.text) }) or
                   (dot asJust DotItem()) or
                   (escapedCharacter map { CharItem(it.text.substring(1)) }) or
                   (bracketContent map { BracketItem(it.text.substring(1, it.text.length - 1)) }) or

lib/src/main/kotlin/org/example/RegexItem.kt

@@ -139,6 +139,28 @@ class GroupItem(val item: RegexItem, val name: String) : RegexItem {
   }
 }
 
+class AnchorItem(val anchor: String) : RegexItem {
+  override fun toString(): String = anchor
+
+  override fun findMatch(str: String, position: Int): AvailableState {
+    // 앵커는 문자열의 시작(^) 또는 끝($)과 매칭됨
+    return when (anchor) {
+      "^" -> if (position == 0) {
+        AvailableState(sequenceOf(State(str, 0, 0)))
+      } else {
+        AvailableState() // 시작 앵커가 실패하면 빈 시퀀스 반환
+      }
+      "$" -> if (position == str.length) {
+        AvailableState(sequenceOf(State(str, str.length, str.length)))
+      } else {
+        AvailableState() // 끝 앵커가 실패하면 빈 시퀀스 반환
+      }
+      // 다른 앵커는 지원하지 않음
+      else -> throw IllegalArgumentException("Unknown anchor: $anchor")
+    }
+  }
+}
+
 fun matchMany(
         str: String,
         item: RegexItem,

lib/src/test/kotlin/org/example/ParserTest.kt

@@ -137,6 +137,15 @@ class ParserTest {
         }
     }
     @Test
+    fun testAnchorOperators() {
+        checkRegex("^abc$") {
+            "abc".shouldMatch()
+            "ab".shouldNotMatch()
+            "abcd".shouldNotMatch()
+            "xabc".shouldNotMatch()
+        }
+    }
+    @Test
     fun testCaptureGroups() {
         val input = "(a)(b)"
         val result = compileRegex(input)