Initial project import

tools/v/vlib/veb/veb_livereload.v

@@ -0,0 +1,48 @@
+module veb
+
+import time
+
+// Note: to use live reloading while developing, the suggested workflow is doing:
+// `v -d veb_livereload watch --keep run your_veb_server_project.v`
+// in one shell, then open the start page of your veb app in a browser.
+//
+// While developing, just open your files and edit them, then just save your
+// changes. Once you save, the watch command from above, will restart your server,
+// and your HTML pages will detect that shortly, then they will refresh themselves
+// automatically.
+
+// veb_livereload_server_start records, when the veb server process started.
+// That is later used by the /script.js and /current endpoints, which are active,
+// if you have compiled your veb project with `-d veb_livereload`, to detect
+// whether the web server has been restarted.
+const veb_livereload_server_start = time.ticks().str()
+
+// handle_veb_livereload_current serves a small text file, containing the
+// timestamp/ticks corresponding to when the veb server process was started
+@[if veb_livereload ?]
+fn (mut ctx Context) handle_veb_livereload_current() {
+	ctx.send_response_to_client('text/plain', veb_livereload_server_start)
+}
+
+// handle_veb_livereload_script serves a small dynamically generated .js file,
+// that contains code for polling the veb server, and reloading the page, if it
+// detects that the veb server is newer than the veb server, that served the
+// .js file originally.
+@[if veb_livereload ?]
+fn (mut ctx Context) handle_veb_livereload_script() {
+	res := '"use strict";
+function veb_livereload_checker_fn(started_at) {
+	fetch("/veb_livereload/" + started_at + "/current", { cache: "no-cache" })
+		.then((response) => response.text())
+		.then(function (current_at) {
+			// console.log(started_at); console.log(current_at);
+			if (started_at !== current_at) {
+				// the app was restarted on the server:
+				window.location.reload();
+			}
+		});
+}
+const veb_livereload_checker = setInterval(veb_livereload_checker_fn, ${ctx.livereload_poll_interval_ms}, "${veb_livereload_server_start}");
+'
+	ctx.send_response_to_client('text/javascript', res)
+}