#include "Museum.h"

using namespace std;

Museum::Museum() : people(*this), canvas(*this), collision(*this), pathfinding(*this) {
	this->worker = new std::thread(&Museum::work, this);
}

Museum::~Museum() {
	this->working = false;
	this->worker->join();
	if (this->worker != nullptr) {
		delete this->worker;
		this->worker = nullptr;
	}
}

void Museum::update() {
	unsigned long long next_snapshot = this->snapshot_ticks;
	if (!this->history.empty()) next_snapshot += this->history.top().tick;
	if (this->tick >= next_snapshot || this->history.empty()) {
		this->history.push(this->save_snapshot());
	}

	this->people.update();
	this->canvas.update();
	this->collision.update();
	this->tick++;
}

void Museum::skip_forward() {
	lock_guard<mutex> guard(this->jump_mutex);
	this->jump++;
}
void Museum::skip_backward() {
	lock_guard<mutex> guard(this->jump_mutex);
	this->paused = true;
	this->jump--;
}

void Museum::process_jump() {
	lock_guard<mutex> guard(this->jump_mutex);

	if (this->jump > 0) {
		// forward jump
		for (; this->jump != 0; this->jump--) {
			for (size_t i = 0; i < this->snapshot_ticks; i++)
				this->update();
		}
	} else if (this->jump < 0) {
		// backward jump
		for (; this->jump != 0; this->jump++) {
			if (this->history.empty()) continue;
			this->restore_snapshot(this->history.top());
			if (this->tick > 0) this->history.pop();
		}
	}
}

void Museum::work() {
	while (this->working) {
		// immediately process jumps, even if paused
		this->process_jump();

		// wait with regular update if paused
		if (this->paused) continue;

		// regular update
		auto next = chrono::steady_clock::now() + this->tick_interval;
		this->update();
		this_thread::sleep_until(next);
	}
}

static void memories_concat(Memories & a, Memories b) {
	a.insert(a.end(), make_move_iterator(b.begin()), make_move_iterator(b.end()));
}

Museum::Snapshot Museum::save_snapshot() {
	Snapshot snapshot = {
		.tick = this->tick,
		.memories = {},
	};
	memories_concat(snapshot.memories, this->canvas.save());
	memories_concat(snapshot.memories, this->people.save());
	return snapshot;
}

void Museum::restore_snapshot(const Snapshot & snapshot) {
	this->tick = snapshot.tick;
	this->canvas.restore(snapshot.memories);
	this->people.restore(snapshot.memories);
}