refactor(ui): isolate session components (#33670)

packages/session-ui/src/components/markdown-worker-queue.ts

@@ -0,0 +1,64 @@
+export function createLatestWorkerQueue<T extends { key: string }>(input: {
+  run: (request: T) => Promise<void>
+  supersede: (request: T) => void
+  dispose: (key: string) => void
+}) {
+  type Slot = { type: "highlight"; key: string; request?: T }
+  const jobs: Array<Slot | { type: "dispose"; key: string }> = []
+  const slots = new Map<string, Slot>()
+  let running: Promise<void> | undefined
+  let cursor = 0
+
+  const schedule = () => {
+    if (running) return
+    running = Promise.resolve()
+      .then(async () => {
+        while (cursor < jobs.length) {
+          const job = jobs[cursor++]!
+          if (job.type === "dispose") {
+            input.dispose(job.key)
+            continue
+          }
+          if (slots.get(job.key) === job) slots.delete(job.key)
+          const request = job.request
+          job.request = undefined
+          if (request) await input.run(request)
+        }
+      })
+      .finally(() => {
+        jobs.splice(0, cursor)
+        cursor = 0
+        running = undefined
+        if (jobs.length > 0) schedule()
+      })
+  }
+
+  return {
+    highlight(request: T) {
+      const slot = slots.get(request.key)
+      if (slot) {
+        if (slot.request) input.supersede(slot.request)
+        slot.request = request
+        return
+      }
+      const next: Slot = { type: "highlight", key: request.key, request }
+      slots.set(request.key, next)
+      jobs.push(next)
+      schedule()
+    },
+    dispose(key: string) {
+      const slot = slots.get(key)
+      if (slot?.request) input.supersede(slot.request)
+      if (slot) {
+        slot.request = undefined
+        slots.delete(key)
+      }
+      jobs.push({ type: "dispose", key })
+      schedule()
+    },
+    pending: () => slots.size,
+    async idle() {
+      while (running) await running
+    },
+  }
+}