feat: add bracket content parsing and corresponding tests

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

@@ -5,6 +5,7 @@ import com.github.h0tk3y.betterParse.grammar.Grammar
 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
 
 class RegexParser : Grammar<RegexItem>() {
@@ -14,8 +15,29 @@ class RegexParser : Grammar<RegexItem>() {
   val alternationSymbol by literalToken("|")
   val openParenSymbol by literalToken("(")
   val closeParenSymbol by literalToken(")")
-  val bracketOpen by literalToken("[")
-  val bracketClose by literalToken("]")
+  val bracketContent by
+          token(
+                  name = "bracketContent",
+                  matcher = { seq, from ->
+                    if (seq[from] != '[') {
+                      0 // 대괄호로 시작하지 않으면 매칭 실패
+                    } else {
+                      // 대괄호의 시작 위치에서부터 ']'를 찾음
+                      var to = seq.indexOf(']', from)
+                      // 이스케이프 ']' 건너 뛰기
+                      while (to >= 0 && to > from && seq[to - 1] == '\\') {
+                        to = seq.indexOf(']', to + 1)
+                      }
+                      if (to < 0) {
+                        0
+                      } else if (to == from + 1) {
+                        0 // 빈 대괄호는 허용하지 않음
+                      } else {
+                        to - from + 1 // 대괄호의 시작 위치부터 ']'까지의 길이
+                      }
+                    }
+                  }
+          )
 
   val dot by literalToken(".")
   val charToken by regexToken("[a-zA-Z0-9]")
@@ -26,6 +48,7 @@ class RegexParser : Grammar<RegexItem>() {
           char 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
                   (skip(openParenSymbol) and (parser(::rootParser)) and skip(closeParenSymbol))
 
   val term: Parser<RegexItem> by

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

@@ -92,6 +92,21 @@ class CharItem(val value: String) : RegexItem {
   }
 }
 
+class BracketItem(val content: String) : RegexItem {
+  override fun toString(): String = "[$content]"
+  
+  // TODO: 범위 처리
+  override fun findMatch(str: String): AvailableState {
+    // 대괄호 안의 내용과 일치하는 첫 문자를 찾음
+    return when {
+      str.isNotEmpty() && content.contains(str[0]) -> {
+        AvailableState(sequenceOf(State(str[0].toString(), str.substring(1))))
+      }
+      else -> AvailableState()
+    }
+  }
+}
+
 fun matchMany(
         str: String,
         item: RegexItem,

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

@@ -116,4 +116,15 @@ class ParserTest {
         assert(result.match("+").isSuccess)
         assert(!result.match("a").isSuccess)
     }
+    @Test
+    fun testBracketContent() {
+        val input = "[abc]"
+        val parser = RegexParser()
+        val result = parser.parseToEnd(input)
+        assertEquals("[abc]", result.toString())
+        assert(result.match("a").isSuccess)
+        assert(result.match("b").isSuccess)
+        assert(result.match("c").isSuccess)
+        assert(!result.match("d").isSuccess)
+    }
 }