1 files changed, 74 insertions, 0 deletions
diff --git a/client/src/groups.js b/client/src/groups.js
new file mode 100644
index 0000000..03f5369
--- /dev/null
+++ b/client/src/groups.js
@@ -0,0 +1,74 @@
+import { useMemo } from 'preact/hooks';
+
+export const GroupContainer = ({ items, first, render }) => {
+	const groups = useMemo(
+		() => {
+			const groupMap = Object.fromEntries(
+				Object.values(items).map(item => [
+					item.id,
+					{
+						id: item.id,
+						items: [item],
+						next: {},
+						depth: {},
+					},
+				 ]),
+			);
+
+			for (const item of Object.values(items)) {
+				const parent = item.inReplyTo.length === 1 && item.inReplyTo[0].id;
+
+				if (parent && items[parent].replies.length === 1) {
+					const self = groupMap[item.id];
+					for (const s of self.items) {
+						groupMap[parent].items.push(s);
+						groupMap[s.id] = groupMap[parent];
+					}
+				}
+			}
+
+			const uniqueGroups = new Set(Object.values(groupMap));
+			const groups = {};
+			for (const group of uniqueGroups) {
+				group.next.up = group.items[0].inReplyTo.map(i => groupMap[i.id].id);
+				group.next.down = group.items[group.items.length-1].replies.map(i => groupMap[i.id].id);
+				groups[group.items[0].id] = group;
+			}
+
+			const updateDepth = (group, dir) => {
+				if (group.depth[dir] !== undefined) {
+					return group.depth[dir];
+				}
+
+				// @TODO: count nodes properly using Set,
+				// this counts nodes multiple times if subgraphs converge
+				let count = group.items.length;
+				for (const id of group.next[dir]) {
+					// go through groupMap here, since when moving 'up',
+					// were not hitting only group-headers
+		 			count += updateDepth(groupMap[id], dir);
+
+		 			if (count >= 9) {
+			 			count = Infinity;
+			 			break;
+		 			}
+				}
+
+				group.depth[dir] = count;
+				return count;
+			};
+
+			for (const group of Object.values(groups)) {
+				updateDepth(group, 'up');
+				updateDepth(group, 'down');
+			}
+
+			return groups;
+		},
+		[items]
+	);
+
+	first = groups[first].id;
+
+	return render({ groups, first });
+};