Add surrounded parser

src/main/scala/dev/vgerasimov/slowparse/parser.scala

@@ -209,6 +209,22 @@ object Parsers:
   def until(parser: P[?], collector: P[?] = anyChar): P[Unit] =
     unCapture(rep(!parser ~ collector)(greedy = true))
 
+  // TODO: remove, seems completely unneeded
+  def surrounded[A](
+    fromParser: P[?],
+    toParser: P[?],
+    contentParser: P[A]
+  ): P[A] = fromParser.!! ~ contentParser ~ toParser.!!
+
+  def surrounded[A](
+    surroundingParser: P[?],
+    contentParser: P[A]
+  ): P[A] = surrounded(surroundingParser, surroundingParser, contentParser)
+
+  def surrounded(
+    surroundingParser: P[?]
+  ): P[String] = surrounded(surroundingParser, (!surroundingParser ~ anyChar.!).*).mkString
+
   /** Parses given character. */
   def char(char: Char): P[Unit] = input => {
     input.safeHead match
@@ -351,6 +367,9 @@ object Parsers:
 
 end Parsers
 
+extension (self: P[List[?]])
+  def mkString: P[String] = self.map(_.mkString)
+
 extension (self: String)
   private[slowparse] def safeHead: String = safeSlice(0, 1)
   private[slowparse] def safeSlice(from: Int = 0, until: Int = Int.MaxValue): String = self match

src/test/scala/dev/vgerasimov/slowparse/ParserTest.scala

@@ -230,6 +230,26 @@ class ParserTest extends ParserTestSuite:
     testSuccess(parser)("\nabc", "")
   }
 
+  test("*surrounded* should parse everything surrounded by two parsers") {
+    val parser = surrounded(P("a"), P("b"), d.+.!)
+    testSuccess(parser)("a123b", "123")
+    testSuccess(parser)("a12b3b", "12")
+    testFailure(parser)("a*1*b")
+  }
+
+  test("*surrounded* should parse everything surrounded by one parser") {
+    val parser = surrounded(P("*"), d.+.!)
+    testSuccess(parser)("*123*", "123")
+    testSuccess(parser)("*12*", "12")
+    testFailure(parser)("*12abc*")
+  }
+
+  test("*surrounded* should parse all characters surrounded by one parser") {
+    val parser = surrounded(P("```"))
+    testSuccess(parser)("```\nhello\nworld```", "\nhello\nworld")
+    testFailure(parser)("``fail``")
+  } 
+
   test("cut fails when needed") {
     val andThenParser: P[String] = P(P("val ") ~ alpha.rep(1).! | P("def ") ~ alpha.rep(1).!)
     testFailure(andThenParser)("val 1234")