package link.roadio.riff.userstate

/** One publication deadline; repeated delivery and no-ops never call changed(). */
class DirtyCadence(
    private val softMs: Long = 5_000,
    private val hardMs: Long = 30_000,
) {
    private var first: Long? = null
    private var last: Long? = null

    init {
        require(softMs > 0 && hardMs >= softMs)
    }

    fun changed(now: Long) {
        require(now >= 0)
        if (first == null) first = now
        last = now
    }

    fun deadline(): Long? = first?.let { minOf(Math.addExact(it, hardMs), Math.addExact(checkNotNull(last), softMs)) }

    fun due(now: Long): Boolean = deadline()?.let { now >= it } ?: false

    fun clear() {
        first = null
        last = null
    }

    fun copy(): DirtyCadence =
        DirtyCadence(softMs, hardMs).also {
            it.first = first
            it.last = last
        }
}

/** Accumulates actual playing time; seeking, pauses and buffering contribute nothing. */
class StartQualification(
    private val thresholdMs: Long,
) {
    private var last: Long? = null
    private var elapsed = 0L
    private var wasPlaying = false
    var qualified: Boolean = false
        private set

    init {
        require(thresholdMs > 0)
    }

    fun observe(
        now: Long,
        playing: Boolean,
    ): Boolean {
        val previous = last
        if (previous != null) {
            require(now >= previous)
            if (wasPlaying) elapsed = Math.addExact(elapsed, now - previous)
        }
        last = now
        wasPlaying = playing
        if (!qualified && elapsed > thresholdMs) {
            qualified = true
            return true
        }
        return false
    }
}