contents for reading

composeApp/src/jvmMain/kotlin/net/sergeych/toread/BookPlatform.jvm.kt

@@ -665,16 +665,34 @@ private fun ReadingPosition.toFormatHintsJson(): String =
     buildString {
         append("""{"firstVisibleItemIndex":$itemIndex,"firstVisibleItemScrollOffset":$scrollOffset""")
         readAloudSentenceIndex?.let { append(""","readAloudSentenceIndex":$it""") }
+        if (backStack.isNotEmpty()) {
+            append(""","backStack":[""")
+            append(backStack.take(MaxStoredReadingBackStack).joinToString(",") { it.toFormatHintsJson() })
+            append("]")
+        }
         append("}")
     }
 
 private fun String.toReadingPosition(): ReadingPosition? {
+    val position = toReadingPositionObject() ?: return null
+    val backStackJson = Regex(""""backStack"\s*:\s*\[(.*)]""").find(this)?.groupValues?.getOrNull(1)
+    val backStack = backStackJson
+        ?.let { ReadingPositionObjectRegex.findAll(it).mapNotNull { match -> match.value.toReadingPositionObject() }.toList() }
+        .orEmpty()
+        .take(MaxStoredReadingBackStack)
+    return position.copy(backStack = backStack)
+}
+
+private fun String.toReadingPositionObject(): ReadingPosition? {
     val index = Regex(""""firstVisibleItemIndex"\s*:\s*(\d+)""").find(this)?.groupValues?.getOrNull(1)?.toIntOrNull()
     val offset = Regex(""""firstVisibleItemScrollOffset"\s*:\s*(\d+)""").find(this)?.groupValues?.getOrNull(1)?.toIntOrNull()
     val sentenceIndex = Regex(""""readAloudSentenceIndex"\s*:\s*(\d+)""").find(this)?.groupValues?.getOrNull(1)?.toIntOrNull()
     return if (index != null && offset != null) ReadingPosition(index, offset, sentenceIndex) else null
 }
 
+private val ReadingPositionObjectRegex = Regex("""[{][^{}]*[}]""")
+private const val MaxStoredReadingBackStack = 10
+
 private fun String.toSearchPrefixes(): List<String> =
     SearchPrefixRegex.findAll(lowercase()).map { it.value }.distinct().toList()