Merge "Using an efficient circular buffer as a logging structure." into main

    companion object {

        const val HISTORY_SIZE = 20

        const val HISTORY_SIZE = 50

        val DATE_FORMAT = SimpleDateFormat("MM-dd HH:mm:ss.SSS", Locale.US)

    }

}

import androidx.annotation.VisibleForTesting

import androidx.annotation.VisibleForTesting.Companion.PACKAGE_PRIVATE

import java.util.ArrayDeque

import java.util.Deque

@VisibleForTesting(otherwise = PACKAGE_PRIVATE)

class MSDLHistoryLoggerImpl(private val maxHistorySize: Int) : MSDLHistoryLogger {

    // Use an [ArrayDequeue] with a fixed size as the history structure

    private val history: Deque<MSDLEvent> = ArrayDeque(maxHistorySize)

    // Use an Array with a fixed size as the history structure. This will work as a ring buffer

    private val history: Array<MSDLEvent?> = arrayOfNulls(size = maxHistorySize)

    // The head will point to the next available position in the structure to add a new event

    private var head = 0

    override fun addEvent(event: MSDLEvent) {

        // Keep the history as a FIFO structure

        if (history.size == maxHistorySize) {

            history.removeFirst()

        }

        history.addLast(event)

        history[head] = event

        // Move the head pointer, wrapping if necessary

        head = (head + 1) % maxHistorySize

    }

    override fun getHistory(): List<MSDLEvent> = history.toList()

    override fun getHistory(): List<MSDLEvent> {

        val result = mutableListOf<MSDLEvent>()

        repeat(times = maxHistorySize) { i ->

            history[(i + head) % maxHistorySize]?.let { result.add(it) }

        }

        return result

    }

}