added createTimelineSnapshot

src/masto/timelines.ts

@@ -109,3 +109,57 @@ export function useTimeline(
     },
   ] as const;
 }
+
+export function createTimelineSnapshot(
+  timeline: Accessor<Timeline>,
+  limit: Accessor<number>,
+) {
+  const [shot, {refetch}] = createResource(
+    () => [timeline(), limit()] as const,
+    async ([tl, limit]) => {
+      const ls = await tl.list({ limit }).next();
+      return ls.value?.map((x) => [x]) ?? [];
+    },
+  );
+
+  const [snapshot, setSnapshot] = createStore([] as mastodon.v1.Status[][]);
+
+  createEffect(() => {
+    const nls = shot();
+    if (!nls) return;
+    const ols = Array.from(snapshot);
+    // The algorithm below assumes the snapshot is not changing
+    for (let i = 0; i < nls.length; i++) {
+      if (i >= ols.length) {
+        setSnapshot(i, nls[i]);
+      } else {
+        if (nls[i].length !== ols[i].length) {
+          setSnapshot(i, nls[i]);
+        } else {
+          const oth = ols[i],
+            nth = nls[i];
+          for (let j = 0; j < oth.length; j++) {
+            const ost = oth[j],
+              nst = nth[j];
+            for (const key of Object.keys(
+              nst,
+            ) as unknown as (keyof mastodon.v1.Status)[]) {
+              if (ost[key] !== nst[key]) {
+                setSnapshot(i, j, key, nst[key]);
+              }
+            }
+          }
+        }
+      }
+    }
+  });
+
+  return [snapshot, shot, {
+    refetch,
+    mutate: setSnapshot
+  }] as const;
+}
+
+export function createTimeline(timeline: Accessor<Timeline>) {
+  // TODO
+}