utybo/Lixy

package guru.zoroark.lixy
 
internal class OffsetCharSequence(
    val charSequence: CharSequence,
    val offsetBy: Int
) : CharSequence {
    init {
        if (offsetBy > charSequence.length)
            error("Invalid offset, exceeds original sequence's length")
    }
 
    override val length: Int
        get() = charSequence.length - offsetBy
 
    override fun get(index: Int): Char =
        if (index + offsetBy >= charSequence.length)
            throw IndexOutOfBoundsException("Index ${index + offsetBy} is out of bounds (max. ${charSequence.length}")
        else
            charSequence[index + offsetBy]
 
    override fun subSequence(startIndex: Int, endIndex: Int): CharSequence =
        charSequence.subSequence(startIndex + offsetBy, endIndex + offsetBy)
 
}
 
internal fun CharSequence.offsetBy(startAt: Int): CharSequence =
    OffsetCharSequence(this, startAt)