{% extends "base.html" %}

{% block script %}
const STATE_BACK = "back";
const STATE_FORWARD = "forward";

function switch_state(new_state) {
	history.replaceState(
		new_state,
		document.title,
		location.pathname+location.hash);
}

function go_back() {
	switch_state(STATE_FORWARD);
	history.back();
}
function go_forward() {
	switch_state(STATE_BACK);
	history.forward();
}

// there are three states
// default: register focus listener,
//	    on focus: go back and switch to the state forward
// back: user came from a later history entry
//	 -> switch to the state forward,
//	    forward him to the previous history entry
// forward: user came from a previous history entry
//	 -> switch to the state back,
//	    forward him to the next history entry
switch (history.state) {
	case STATE_BACK:
		go_back();
		break;
	case STATE_FORWARD:
		go_forward();
		break;
	default:
		if (!document.hidden) {
			go_back();
			break;
		}
		
		document.addEventListener("visibilitychange", go_back);
		break;
}
{% endblock %}

{% block content %}
<noscript><p>Javascript isn't enabled. So you need to manually go back in history to restore this tab.</p></noscript>
<p>If you see this site something went wrong or you reached the end of the history or you disabled javascript.</p>
{% endblock %}