Add app package

packages/app/src/topics.ts

@@ -0,0 +1,41 @@
+import {throttle} from 'throttle-debounce'
+import {derived} from 'svelte/store'
+import {inc} from '@welshman/lib'
+import {custom} from '@welshman/store'
+import {createSearch} from './util'
+import {repository} from './core'
+
+export type Topic = {
+  name: string
+  count: number
+}
+
+export const topics = custom<Topic[]>(setter => {
+  const getTopics = () => {
+    const topics = new Map<string, number>()
+    for (const tagString of repository.eventsByTag.keys()) {
+      if (tagString.startsWith("t:")) {
+        const topic = tagString.slice(2).toLowerCase()
+
+        topics.set(topic, inc(topics.get(topic)))
+      }
+    }
+
+    return Array.from(topics.entries()).map(([name, count]) => ({name, count}))
+  }
+
+  setter(getTopics())
+
+  const onUpdate = throttle(3000, () => setter(getTopics()))
+
+  repository.on("update", onUpdate)
+
+  return () => repository.off("update", onUpdate)
+})
+
+export const topicSearch = derived(topics, $topics =>
+  createSearch($topics, {
+    getValue: (topic: Topic) => topic.name,
+    fuseOptions: {keys: ["name"]},
+  }),
+)