package com.deeper.orchestra.common.paginator.new

import com.google.firebase.firestore.DocumentSnapshot
import com.google.firebase.firestore.MetadataChanges
import com.google.firebase.firestore.Query
import timber.log.Timber
import java.util.concurrent.Semaphore

class NewPaginator(
    private val queryDesc: Query,
    private val initialPageSize: Int,
    private val pageSize: Int
) {

    private var isOlderPageLoading = false
    private var isLastOlderPageLoaded = false
    private var lastOlderDocument: DocumentSnapshot? = null
    private var olderSemaphore = Semaphore(0)

    var callback: ((List<DocumentSnapshot>) -> Unit)? = null

    fun init() {
        loadOlderPage(initialPageSize)
    }

    fun loadOlderPage(size: Int = pageSize) {
        if (isOlderPageLoading || isLastOlderPageLoaded) {
            return
        }

        isOlderPageLoading = true

        var query = queryDesc

        if (lastOlderDocument != null) {
            query = query.startAfter(lastOlderDocument)
            println(lastOlderDocument!!["_uid"])
        }

        query
            .limit(size.toLong())
            .addSnapshotListener(MetadataChanges.INCLUDE) { value, error ->
                if (error != null) {
                    Timber.e(error)
                    return@addSnapshotListener
                }

                if (!value!!.metadata.isFromCache) {
                    lastOlderDocument = value.documents.last()
                    isLastOlderPageLoaded = value.documents.size < size
                    callback!!(value.documents)
                    isOlderPageLoading = false
                    olderSemaphore.release()
                }
            }

        olderSemaphore.acquire()
    }
}