Allow to escape closing brackets in json query

src/main/kotlin/ru/dbotthepony/kstarbound/json/JsonPath.kt

@@ -282,6 +282,13 @@ class JsonPath private constructor(val pieces: ImmutableList<Piece>) {
 		 *
 		 * This allows to effectively escape dots (`.`), because
 		 * when reading array index, everything is read up until closing bracket.
+		 * To escape a bracket, use backward slash, like this:
+		 *
+		 * `someValue.a[bb\]s]`
+		 *
+		 * Which will parse `bb]s` as last index string
+		 *
+		 * Back slashes do not have unique treatment outside bracket context
 		 *
 		 * Another change is - empty keys
 		 * (sequences like `..a. .key.value` -> `"" -> "" -> "a" -> " " -> "key" -> "value"`)
@@ -293,15 +300,21 @@ class JsonPath private constructor(val pieces: ImmutableList<Piece>) {
 
 			val current = StringBuilder()
 			var readingIndex = false
+			var escapeNext = false
 
 			for (char in path) {
 				if (readingIndex) {
-					if (char == ']') {
+					if (escapeNext) {
+						escapeNext = false
+						current.append(char)
+					} else if (char == ']') {
 						val finish = current.toString()
 						val finishInt = finish.toIntOrNull()
 						pieces.add(Piece(finish, if (finishInt != null) Hint.ARRAY else null))
 						current.clear()
 						readingIndex = false
+					} else if (char == '\\') {
+						escapeNext = true
 					} else {
 						current.append(char)
 					}
@@ -311,6 +324,7 @@ class JsonPath private constructor(val pieces: ImmutableList<Piece>) {
 						current.clear()
 					} else if (char == '[') {
 						readingIndex = true
+						escapeNext = false
 					} else {
 						current.append(char)
 					}