package xyz.fancystuff.pluvius.runtime

object OverlayParser {
    fun parse(rawList: List<String>) = rawList
            .map { toSyntaxToken(it) }
            .fold(listOf<OverlaySyntaxToken>()) { acc, item -> foldToList(acc, item) }
            .map { it as OverlayItem }

    private fun toSyntaxToken(line: String): OverlaySyntaxToken =  when {
        line.isBlank() -> BlankLine
        isGroupItem(line) -> OverlayGroupItem(line)
        else -> OverlayItem(name = getOverlayPackageFromLine(line), isEnabled = isOverlayEnabled(line))
    }

    private fun foldToList(acc: List<OverlaySyntaxToken>, item: OverlaySyntaxToken) = when(item) {
        BlankLine -> acc // do not add blankLine
        is OverlayGroupItem -> listOf(*acc.toTypedArray(), item)  // add header
        is OverlayItem -> {  //inject groupName to a item and remove previous object if it is a GroupItem
            val prevItem = acc.last()
            when(prevItem) {
                is OverlayGroupItem -> listWithLastItemReplaced(acc, OverlayItem(prevItem.group, item.name, item.isEnabled))
                is OverlayItem -> listWithItemAdded(acc, OverlayItem(prevItem.group, item.name, item.isEnabled))
                else -> acc
            }
        }
    }

    private fun listWithItemAdded(acc: List<OverlaySyntaxToken>, item: OverlaySyntaxToken): List<OverlaySyntaxToken> {
        return listOf(*acc.toTypedArray(), item) //adding new item
    }

    private fun listWithLastItemReplaced(acc: List<OverlaySyntaxToken>, item: OverlaySyntaxToken): List<OverlaySyntaxToken> {
        val list = acc.subList(0, acc.size - 1) //removing last item
        return listOf(*list.toTypedArray(), item) //adding new item
    }

    private fun isGroupItem(line: String) = !line.startsWith("[")
    private fun isOverlayEnabled(overlay: String) = overlay.contains("[x]")
    private fun getOverlayPackageFromLine(line: String) = line.substring(4)
}