ListEventCompressor

ListEventCompressor.kt

import ca.odell.glazedlists.event.ListEvent
import java.util.*

data class ChangeRange(val firstIndex: Int, var count: Int, val type: ChangeType) {

    // ~ Delegated --------------------------------------------------------------------------------

    val lastIndex: Int
        get() = firstIndex + count - 1

    // ~ Methods ----------------------------------------------------------------------------------

    override fun toString(): String {
        return "$type($firstIndex .. $lastIndex)"
    }

    // ~ Inner Types ------------------------------------------------------------------------------

    enum class ChangeType {INSERT, UPDATE, DELETE }
}

fun ListEvent<*>.compress(): List<ChangeRange> {
    val changes = LinkedList<ChangeRange>()

    var batchedRange: ChangeRange? = null

    while (nextBlock()) {
        val count = blockEndIndex - blockStartIndex + 1
        when (type) {
            ListEvent.INSERT -> {
                if (batchedRange == null) {
                    batchedRange = ChangeRange(blockStartIndex, count, type = INSERT)

                } else if (batchedRange.type != INSERT || blockStartIndex != batchedRange.lastIndex + 1) {
                    changes += batchedRange
                    batchedRange = ChangeRange(blockStartIndex, count, type = INSERT)

                } else {
                    batchedRange.count += count
                }
            }
            ListEvent.UPDATE -> {
                if (batchedRange == null) {
                    batchedRange = ChangeRange(blockStartIndex, count, type = UPDATE)

                } else if (batchedRange.type != UPDATE || blockStartIndex != batchedRange.lastIndex + 1) {
                    changes += batchedRange
                    batchedRange = ChangeRange(blockStartIndex, count, type = UPDATE)

                } else {
                    batchedRange.count += count
                }
            }
            ListEvent.DELETE -> {
                if (batchedRange == null) {
                    batchedRange = ChangeRange(blockStartIndex, count, type = DELETE)

                } else if (batchedRange.type != DELETE || blockStartIndex != batchedRange.firstIndex) {
                    changes += batchedRange
                    batchedRange = ChangeRange(blockStartIndex, count, type = DELETE)

                } else {
                    batchedRange.count += count
                }
            }
        }
    }

    batchedRange?.let { changes += it }

    return changes
}