From c1e28224aa2e1450031669d9a7e359b63e04687d Mon Sep 17 00:00:00 2001
From: Volpeon <git@volpeon.ink>
Date: Wed, 22 Jul 2026 19:40:59 +0200
Subject: Init

---
 src/scripts/lib/dom.ts | 59 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 59 insertions(+)
 create mode 100644 src/scripts/lib/dom.ts

(limited to 'src/scripts/lib/dom.ts')

diff --git a/src/scripts/lib/dom.ts b/src/scripts/lib/dom.ts
new file mode 100644
index 0000000..a88686a
--- /dev/null
+++ b/src/scripts/lib/dom.ts
@@ -0,0 +1,59 @@
+function isAbove(a: HTMLElement, b: HTMLElement) {
+	return a.offsetTop + a.clientHeight < b.offsetTop;
+}
+
+export function getVerticalNeighbor(
+	dir: -1 | 1,
+	items: Iterable<HTMLElement>,
+	current: HTMLElement,
+) {
+	let candidates: HTMLElement[] = [];
+
+	if (dir === -1) {
+		let adjacentY = Number.MIN_SAFE_INTEGER;
+
+		for (const item of items) {
+			if (!isAbove(item, current)) {
+				continue;
+			}
+
+			if (item.offsetTop > adjacentY) {
+				adjacentY = item.offsetTop;
+				candidates = [item];
+			} else if (item.offsetTop === adjacentY) {
+				candidates.push(item);
+			}
+		}
+	} else {
+		let adjacentY = Number.MAX_SAFE_INTEGER;
+
+		for (const item of items) {
+			if (!isAbove(current, item)) {
+				continue;
+			}
+
+			if (item.offsetTop < adjacentY) {
+				adjacentY = item.offsetTop;
+				candidates = [item];
+			} else if (item.offsetTop === adjacentY) {
+				candidates.push(item);
+			}
+		}
+	}
+
+	const currentX = current.offsetLeft + 0.5 * current.clientWidth;
+	let match = candidates[0];
+	let bestDist = Number.MAX_SAFE_INTEGER;
+
+	for (const candidate of candidates) {
+		const candidateX = candidate.offsetLeft + 0.5 * candidate.clientWidth;
+		const dist = Math.abs(currentX - candidateX);
+
+		if (dist < bestDist) {
+			bestDist = dist;
+			match = candidate;
+		}
+	}
+
+	return match;
+}
-- 
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