#include <iostream>
#include <chrono>
#include <cassert>
#include "scheduler.h"

void Scheduler::workerEntry() {
	while (true) {
		Job *job = nullptr;

		{
			lock_guard commMutGuard(commMut);
			if (jobs.size() > 0) {
				job = jobs.front();
				jobs.pop();
			}
		}

		if (job) {
			job->callback();
		} else if (finishFlag) {
			break;
		} else {
			this_thread::sleep_for(chrono::milliseconds(100));
		}
	}
}

Scheduler::Scheduler(int nthreads)
		: nthreads(nthreads) {

	assert(nthreads > 0);

	workers.reserve(nthreads);
	for (int i = 0; i < nthreads; i++) {
		workers.emplace_back([this]() { workerEntry(); });
	}
}

Scheduler::~Scheduler() {
	finish();
}

void Scheduler::submit(const function<void()> &func) {
	Job *job = new Job(func);
	lock_guard commMutGuard(commMut);
	jobs.push(job);
}

void Scheduler::finish() {
	if (hasJoined) return;

	{
		lock_guard commMutGuard(commMut);
		finishFlag = true;
	}

	for (int i = 0; i < nthreads; i++) {
		workers[i].join();
	}

	hasJoined = true;
}