1 files changed, 151 insertions, 0 deletions
diff --git a/static/js/ext/preload.js b/static/js/ext/preload.js
new file mode 100644
index 0000000..ac3ef5c
--- /dev/null
+++ b/static/js/ext/preload.js
@@ -0,0 +1,151 @@
+if (htmx.version && !htmx.version.startsWith("1.")) {
+	console.warn("WARNING: You are using an htmx 1 extension with htmx " + htmx.version +
+		".  It is recommended that you move to the version of this extension found on https://htmx.org/extensions")
+}
+// This adds the "preload" extension to htmx.  By default, this will
+// preload the targets of any tags with `href` or `hx-get` attributes
+// if they also have a `preload` attribute as well.  See documentation
+// for more details
+htmx.defineExtension("preload", {
+
+	onEvent: function(name, event) {
+
+		// Only take actions on "htmx:afterProcessNode"
+		if (name !== "htmx:afterProcessNode") {
+			return;
+		}
+
+		// SOME HELPER FUNCTIONS WE'LL NEED ALONG THE WAY
+
+		// attr gets the closest non-empty value from the attribute.
+		var attr = function(node, property) {
+			if (node == undefined) {return undefined;}
+			return node.getAttribute(property) || node.getAttribute("data-" + property) || attr(node.parentElement, property)
+		}
+
+		// load handles the actual HTTP fetch, and uses htmx.ajax in cases where we're
+		// preloading an htmx resource (this sends the same HTTP headers as a regular htmx request)
+		var load = function(node) {
+
+			// Called after a successful AJAX request, to mark the
+			// content as loaded (and prevent additional AJAX calls.)
+			var done = function(html) {
+				if (!node.preloadAlways) {
+					node.preloadState = "DONE"
+				}
+
+				if (attr(node, "preload-images") == "true") {
+					document.createElement("div").innerHTML = html // create and populate a node to load linked resources, too.
+				}
+			}
+
+			return function() {
+
+				// If this value has already been loaded, then do not try again.
+				if (node.preloadState !== "READY") {
+					return;
+				}
+
+				// Special handling for HX-GET - use built-in htmx.ajax function
+				// so that headers match other htmx requests, then set
+				// node.preloadState = TRUE so that requests are not duplicated
+				// in the future
+				var hxGet = node.getAttribute("hx-get") || node.getAttribute("data-hx-get")
+				if (hxGet) {
+					htmx.ajax("GET", hxGet, {
+						source: node,
+						handler:function(elt, info) {
+							done(info.xhr.responseText);
+						}
+					});
+					return;
+				}
+
+				// Otherwise, perform a standard xhr request, then set
+				// node.preloadState = TRUE so that requests are not duplicated
+				// in the future.
+				if (node.getAttribute("href")) {
+					var r = new XMLHttpRequest();
+					r.open("GET", node.getAttribute("href"));
+					r.onload = function() {done(r.responseText);};
+					r.send();
+					return;
+				}
+			}
+		}
+
+		// This function processes a specific node and sets up event handlers.
+		// We'll search for nodes and use it below.
+		var init = function(node) {
+
+			// If this node DOES NOT include a "GET" transaction, then there's nothing to do here.
+			if (node.getAttribute("href") + node.getAttribute("hx-get") + node.getAttribute("data-hx-get") == "") {
+				return;
+			}
+
+			// Guarantee that we only initialize each node once.
+			if (node.preloadState !== undefined) {
+				return;
+			}
+
+			// Get event name from config.
+			var on = attr(node, "preload") || "mousedown"
+			const always = on.indexOf("always") !== -1
+			if (always) {
+				on = on.replace('always', '').trim()
+			}
+
+			// FALL THROUGH to here means we need to add an EventListener
+
+			// Apply the listener to the node
+			node.addEventListener(on, function(evt) {
+				if (node.preloadState === "PAUSE") { // Only add one event listener
+					node.preloadState = "READY"; // Required for the `load` function to trigger
+
+					// Special handling for "mouseover" events.  Wait 100ms before triggering load.
+					if (on === "mouseover") {
+						window.setTimeout(load(node), 100);
+					} else {
+						load(node)() // all other events trigger immediately.
+					}
+				}
+			})
+
+			// Special handling for certain built-in event handlers
+			switch (on) {
+
+				case "mouseover":
+					// Mirror `touchstart` events (fires immediately)
+					node.addEventListener("touchstart", load(node));
+
+					// WHhen the mouse leaves, immediately disable the preload
+					node.addEventListener("mouseout", function(evt) {
+						if ((evt.target === node) && (node.preloadState === "READY")) {
+							node.preloadState = "PAUSE";
+						}
+					})
+					break;
+
+				case "mousedown":
+					 // Mirror `touchstart` events (fires immediately)
+					node.addEventListener("touchstart", load(node));
+					break;
+			}
+
+			// Mark the node as ready to run.
+			node.preloadState = "PAUSE";
+			node.preloadAlways = always;
+			htmx.trigger(node, "preload:init") // This event can be used to load content immediately.
+		}
+
+		// Search for all child nodes that have a "preload" attribute
+		event.target.querySelectorAll("[preload]").forEach(function(node) {
+
+			// Initialize the node with the "preload" attribute
+			init(node)
+
+			// Initialize all child elements that are anchors or have `hx-get` (use with care)
+			node.querySelectorAll("a,[hx-get],[data-hx-get]").forEach(init)
+		})
+	}
+})