Save flag selection on post submission and load it on page start (per board)

frontend/ts/dom/flags.ts

@@ -22,15 +22,49 @@ function setupQRFlags($flags: JQuery<HTMLSelectElement>) {
 	);
 }
 
+function getBoard() {
+	const pathParts = location.pathname.split("/");
+	if(pathParts.length < 2) return null;
+	return pathParts[1];
+}
+
+function loadFlagSelection() {
+	const board = getBoard();
+	const savedFlag = localStorage.getItem(`flag_${board}`);
+	if(board !== null && savedFlag !== null) {
+		const $sel = $<HTMLSelectElement>("select")
+			.filter((_,el) => el.name === "post-flag");
+		const num = $sel.find("option")
+				.filter((_,el) => el.value === savedFlag).length;
+		if(num > 0) {
+			$sel.val(savedFlag);
+			$sel.trigger("change");
+		}
+	}
+}
+
+function saveFlagSelection(ev: JQuery.SubmitEvent) {
+	const board = getBoard();
+	if(!board) return;
+	const flag = $(ev.target)
+		.find<HTMLSelectElement>("select")
+		.filter((_,ev) => ev.name === "post-flag")
+		.val() as string;
+	localStorage.setItem(`flag_${board}`, flag);
+}
 
 export function initFlags() {
 	const $flagChanger = $<HTMLSelectElement>("select")
-		.filter((_, el) => el.name == "post-flag");
+		.filter((_, el) => el.name === "post-flag");
 	if($flagChanger.length < 1) return;
 
 	updateFlagPreview($flagChanger);
-	$flagChanger.on("change", (ev:JQuery.ChangeEvent) => {
-		updateFlagPreview($(ev.target))
-	});
+	$flagChanger.on("change", (ev:JQuery.ChangeEvent) =>
+		updateFlagPreview($(ev.target)));
 	setupQRFlags($flagChanger);
+
+	loadFlagSelection();
+	$("form").filter((_,el) =>
+		el.getAttribute("action") === path.join(webroot || "/", "post"))
+		.on("submit", saveFlagSelection);
 }