feat: rebuild board grid experience

packages/definitions/src/section.ts

@@ -1,2 +1,33 @@
 export const sectionKinds = ["category", "empty", "dynamic"] as const;
 export type SectionKind = (typeof sectionKinds)[number];
+
+export const boardLanes = ["left", "main", "right"] as const;
+export type BoardLane = (typeof boardLanes)[number];
+
+export const rootSectionOffsets = {
+  left: -1,
+  main: 0,
+  right: 1,
+} as const satisfies Record<BoardLane, number>;
+
+export const getRootSectionLane = (xOffset: number | null | undefined): BoardLane => {
+  if (xOffset === rootSectionOffsets.left) return "left";
+  if (xOffset === rootSectionOffsets.right) return "right";
+  return "main";
+};
+
+export const getBoardLaneColumnCount = (
+  layout: {
+    columnCount: number;
+    leftGutterColumnCount?: number | null;
+    rightGutterColumnCount?: number | null;
+  },
+  lane: BoardLane,
+) => {
+  const total = Math.max(1, Math.floor(layout.columnCount));
+  const left = Math.min(Math.max(0, Math.floor(layout.leftGutterColumnCount ?? 0)), total - 1);
+  const right = Math.min(Math.max(0, Math.floor(layout.rightGutterColumnCount ?? 0)), total - left - 1);
+  if (lane === "left") return left;
+  if (lane === "right") return right;
+  return total - left - right;
+};