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/*
* Instant Page Copyright (C) 2019-2023 Alexandre Dieulot
* https://github.com/instantpage/instant.page/blob/master/LICENSE
* Licence: MIT | https://mit-license.org/
*/
(function () {
function fetch(url, method, callback) {
const http = new XMLHttpRequest();
http.onreadystatechange = function () {
if (http.readyState === 4 && http.status === 200) {
if (callback) callback(http);
}
};
http.open(method, url);
http.send();
return http;
}
self.addEventListener("DOMContentLoaded", function () {
const prefetches = new Set();
const prefetchElement = document.createElement("link");
const isSupported = prefetchElement.relList
&& prefetchElement.relList.supports
&& prefetchElement.relList.supports("prefetch")
&& window.IntersectionObserver
&& "isIntersecting" in IntersectionObserverEntry.prototype;
const allowQueryString = "instantAllowQueryString" in document.body.dataset;
const allowExternalLinks = "instantAllowExternalLinks" in document.body.dataset;
const useWhitelist = "instantWhitelist" in document.body.dataset;
const mousedownShortcut = "instantMousedownShortcut" in document.body.dataset;
const DELAY_TO_NOT_BE_CONSIDERED_A_TOUCH_INITIATED_ACTION = 1111;
let mouseoverTimer;
let lastTouchTimestamp;
let delayOnHover = 65;
let useMousedown = false;
let useMousedownOnly = false;
let useViewport = false;
if ("instantIntensity" in document.body.dataset) {
const intensity = document.body.dataset.instantIntensity;
if (intensity.substr(0, "mousedown".length) == "mousedown") {
useMousedown = true;
if (intensity == "mousedown-only") { useMousedownOnly = true; }
} else if (intensity.substr(0, "viewport".length) == "viewport") {
if (!(navigator.connection
&& (navigator.connection.saveData
|| (navigator.connection.effectiveType
&& navigator.connection.effectiveType.includes("2g"))))) {
if (intensity == "viewport") {
/*
Biggest iPhone resolution (which we want): 414 × 896 = 370944
Small 7" tablet resolution (which we don’t want): 600 × 1024 = 614400
Note that the viewport (which we check here) is smaller than the resolution due to the UI’s chrome
*/
if (document.documentElement.clientWidth * document.documentElement.clientHeight < 450000) { useViewport = true; }
} else if (intensity == "viewport-all") {
useViewport = true;
}
}
} else {
const milliseconds = parseInt(intensity);
if (!isNaN(milliseconds)) { delayOnHover = milliseconds; }
}
}
if (isSupported) {
const eventListenersOptions = { capture: true, passive: true };
if (!useMousedownOnly) { document.addEventListener( "touchstart", touchstartListener, eventListenersOptions,); }
if (!useMousedown) {
document.addEventListener( "mouseover", mouseoverListener, eventListenersOptions,);
} else if (!mousedownShortcut) {
document.addEventListener( "mousedown", mousedownListener, eventListenersOptions,);
}
if (mousedownShortcut) { document.addEventListener( "mousedown", mousedownShortcutListener, eventListenersOptions,); }
if (useViewport) {
let triggeringFunction;
if (window.requestIdleCallback) {
triggeringFunction = function (callback) { requestIdleCallback(callback, { timeout: 1500 }); }
} else {
triggeringFunction = function (callback) { callback(); }
}
triggeringFunction(function () {
const intersectionObserver = new IntersectionObserver(
function (entries) {
entries.forEach(function (entry) {
if (entry.isIntersecting) {
const linkElement = entry.target;
intersectionObserver.unobserve(linkElement);
preload(linkElement.href);
}
});
},
);
document.querySelectorAll("a").forEach(function (linkElement) {
if (isPreloadable(linkElement)) { intersectionObserver.observe(linkElement); }
});
});
}
}
function touchstartListener(event) {
/*
Chrome on Android calls mouseover before touchcancel so `lastTouchTimestamp`
must be assigned on touchstart to be measured on mouseover.
*/
lastTouchTimestamp = performance.now();
const linkElement = event.target.closest("a");
if (!isPreloadable(linkElement)) { return; }
preload(linkElement.href);
}
function mouseoverListener(event) {
if (performance.now() - lastTouchTimestamp < DELAY_TO_NOT_BE_CONSIDERED_A_TOUCH_INITIATED_ACTION) { return; }
const linkElement = event.target.closest("a");
if (!isPreloadable(linkElement)) { return; }
linkElement.addEventListener("mouseout", mouseoutListener, { passive: true });
mouseoverTimer = setTimeout(function () {
preload(linkElement.href);
mouseoverTimer = undefined;
}, delayOnHover);
}
function mousedownListener(event) {
const linkElement = event.target.closest("a");
if (!isPreloadable(linkElement)) { return; }
preload(linkElement.href);
}
function mouseoutListener(event) {
if (event.relatedTarget && event.target.closest("a") == event.relatedTarget.closest("a")) { return; }
if (mouseoverTimer) { clearTimeout(mouseoverTimer); mouseoverTimer = undefined; }
}
function mousedownShortcutListener(event) {
if (performance.now() - lastTouchTimestamp < DELAY_TO_NOT_BE_CONSIDERED_A_TOUCH_INITIATED_ACTION) { return; }
const linkElement = event.target.closest("a");
if (event.which > 1 || event.metaKey || event.ctrlKey) { return; }
if (!linkElement) { return; }
linkElement.addEventListener("click", function (event) {
if (event.detail == 1337) { return; }
event.preventDefault();
}, { capture: true, passive: false, once: true });
const customEvent = new MouseEvent("click", {
view: window,
bubbles: true,
cancelable: false,
detail: 1337,
});
linkElement.dispatchEvent(customEvent);
}
function isPreloadable(linkElement) {
if (!linkElement || !linkElement.href) { return; }
if (useWhitelist && !("instant" in linkElement.dataset)) { return; }
if (!allowExternalLinks && linkElement.origin != location.origin && !("instant" in linkElement.dataset)) { return; }
if (!["http:", "https:"].includes(linkElement.protocol)) { return; }
if (linkElement.protocol == "http:" && location.protocol == "https:") { return; }
if (!allowQueryString && linkElement.search && !("instant" in linkElement.dataset)) { return; }
if (linkElement.hash && linkElement.pathname + linkElement.search == location.pathname + location.search) { return; }
if ("noInstant" in linkElement.dataset) { return; }
return true;
}
function preload(url) {
if (prefetches.has(url)) { return; }
const prefetcher = document.createElement("link");
prefetcher.rel = "custom-prefetch";
prefetcher.href = url;
fetch(url, "GET", function () {
document.head.appendChild(prefetcher);
prefetches.add(url);
});
}
});
})();
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