Archipelago — open-source initial import

neode-ui/src/composables/useElectrsSync.ts

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+import { ref, computed, onUnmounted } from 'vue'
+
+/** Shape of GET /electrs-status (see core electrs_status.rs ElectrsSyncStatus). */
+export interface ElectrsSyncStatus {
+  indexed_height: number
+  bitcoin_height: number
+  network_height: number
+  progress_pct: number
+  status: string // "starting" | "waiting" | "syncing" | "indexing" | "synced" | "error"
+  stale: boolean
+  error: string | null
+  index_size: string | null
+  tor_onion: string | null
+}
+
+/**
+ * Polls GET /electrs-status while active. Used to show an ElectrumX sync screen
+ * *before* the real Electrum UI — the Electrum server only accepts client
+ * connections (and the UI only works) once the on-chain index is built, which
+ * is a long initial process.
+ *
+ * Fails OPEN: if the status can't be fetched we report not-syncing, so a status
+ * outage never blocks the normal iframe path. We only gate the UI when we
+ * positively know the index is still being built (status !== "synced").
+ */
+export function useElectrsSync() {
+  const status = ref<ElectrsSyncStatus | null>(null)
+  let timer: ReturnType<typeof setInterval> | null = null
+
+  async function poll() {
+    try {
+      const res = await fetch('/electrs-status', { cache: 'no-store' })
+      if (res.ok) status.value = (await res.json()) as ElectrsSyncStatus
+    } catch {
+      /* keep last known value; fail open */
+    }
+  }
+
+  function start() {
+    if (timer) return
+    void poll()
+    timer = setInterval(() => void poll(), 8000)
+  }
+
+  function stop() {
+    if (timer) {
+      clearInterval(timer)
+      timer = null
+    }
+  }
+
+  /** True only when we know ElectrumX is still building its index. */
+  const syncing = computed(() => !!status.value && status.value.status !== 'synced')
+
+  onUnmounted(stop)
+  return { status, syncing, start, stop }
+}