using Unity.Collections;
using UnityEngine;
using Unity.Jobs;
using Unity.Burst;

public class LongJob : MonoBehaviour
{
    public long totalSteps = 1;
    public long intermediateSteps = 1;

    private LongLongJob theJob;

    private NativeArray<long> results;
    private JobHandle longHandle;
    private int numJobs = 0;
    private long currentStep = 0;
    private int jobIndex = 0;

    [BurstCompile]
    struct LongLongJob : IJob
    {
        public long input;
        public NativeArray<long> output;
        public long steps;
        public int resultIndex;

        public void Execute()
        {
            for (long i = 0; i < steps; i++)
            {
                output[resultIndex]++;
            }

            output[resultIndex] += input;
        }
    }

    private void scheduleJob(long inputValue, long steps, int index)
    {
            theJob = new LongLongJob()
            {
                steps = steps,
                input = inputValue,
                output = results,
                resultIndex = index
            };

            longHandle = theJob.Schedule(longHandle);
    }
    void Start()
    {
        numJobs = (int)((totalSteps + intermediateSteps - 1) / intermediateSteps);
        results = new NativeArray<long>(numJobs, Allocator.Persistent, NativeArrayOptions.ClearMemory);
    }

    private bool done = false;
    void Update()
    {

        if (currentStep < totalSteps && longHandle.IsCompleted)
        {
            longHandle.Complete();
            long previousResults = jobIndex > 0 ? results[jobIndex - 1] : 0;
            Debug.Log("Previous intermediate result: " + jobIndex + " = " + previousResults);
            long nextSteps = totalSteps - currentStep > intermediateSteps
                ? intermediateSteps
                : totalSteps - currentStep;
            scheduleJob(previousResults, nextSteps, jobIndex++);
            currentStep += nextSteps;
        } else if(currentStep >= totalSteps && longHandle.IsCompleted && !done) {
            longHandle.Complete();
            Debug.Log("Result: " + results[results.Length - 1]);
            done = true;
        }

    }

    private void OnDestroy()
    {
        longHandle.Complete();
        results.Dispose();
    }
}