feat: add iOS origin sharing, idleTTL prop, and origin-pooling demo (#30, #28) (#34)

- Add iOS support for shared-origin factory pooling (same-origin sandboxes
  reuse a single RCTReactNativeFactory)
- Add idleTTL prop to defer ReactHost/factory cleanup after last surface
  unmounts, enabling warm starts for same-origin remounts
- Add origin-pooling demo app demonstrating both features on iOS and Android

Ref: #28
Ref: #30

Co-authored-by: Ryan Karn <rkarn@amazon.com>

Author: ryan-karn

apps/origin-pooling/App.tsx

@@ -0,0 +1,308 @@
+/**
+ * Origin Pooling Demo
+ *
+ * Dynamically add/remove sandboxes under two shared origins (alpha, beta)
+ * plus an isolated (no-origin) option. Same-origin sandboxes share a
+ * ReactHost / Hermes VM; removing the last one triggers the idle TTL.
+ *
+ * Messaging is handled inside the sandbox widget via globalThis.postMessage.
+ * The host only logs messages received via onMessage.
+ */
+import SandboxReactNativeView from '@callstack/react-native-sandbox'
+import React, {useCallback, useRef, useState} from 'react'
+import {
+  Button,
+  Platform,
+  SafeAreaView,
+  ScrollView,
+  StatusBar,
+  StyleSheet,
+  Text,
+  View,
+} from 'react-native'
+
+type SandboxEntry = {key: string; label: string; origin: string}
+type LogEntry = {source: string; text: string; ts: number}
+
+let nextId = 0
+
+const ORIGIN_ALPHA = 'alpha'
+const ORIGIN_BETA = 'beta'
+const COLOR_ALPHA = '#8232ff'
+const COLOR_BETA = '#e67e22'
+const COLOR_ISOLATED = '#6c757d'
+
+/** Alpha uses a function-based TTL (4 seconds) */
+const ALPHA_TTL = () => 4000
+/** Beta and isolated use a static TTL (2 seconds) */
+const DEFAULT_TTL = 2000
+
+export default function App() {
+  const [sandboxes, setSandboxes] = useState<SandboxEntry[]>([])
+  const [log, setLog] = useState<LogEntry[]>([])
+  const logScrollRef = useRef<ScrollView>(null)
+
+  const addLog = useCallback((source: string, text: string) => {
+    setLog(prev => [...prev.slice(-49), {source, text, ts: Date.now()}])
+  }, [])
+
+  const addSandbox = useCallback((origin: string) => {
+    const id = String(++nextId)
+    setSandboxes(prev => [...prev, {key: id, label: `#${id}`, origin}])
+  }, [])
+
+  const removeSandbox = useCallback((key: string) => {
+    setSandboxes(prev => prev.filter(s => s.key !== key))
+  }, [])
+
+  const clearLog = useCallback(() => setLog([]), [])
+
+  const alphas = sandboxes.filter(s => s.origin === ORIGIN_ALPHA)
+  const betas = sandboxes.filter(s => s.origin === ORIGIN_BETA)
+  const isolated = sandboxes.filter(s => s.origin === '')
+
+  return (
+    <SafeAreaView style={styles.safe}>
+      <Text style={styles.heading}>Origin Pooling Demo</Text>
+      <Text style={styles.subtitle}>
+        Same-origin sandboxes share a VM. Alpha: function-based TTL (4s). Beta:
+        static TTL (2s).
+      </Text>
+
+      <View style={styles.controls}>
+        <Button
+          title="+ Alpha"
+          color={COLOR_ALPHA}
+          onPress={() => addSandbox(ORIGIN_ALPHA)}
+        />
+        <Button
+          title="+ Beta"
+          color={COLOR_BETA}
+          onPress={() => addSandbox(ORIGIN_BETA)}
+        />
+        <Button
+          title="+ Isolated"
+          color={COLOR_ISOLATED}
+          onPress={() => addSandbox('')}
+        />
+        <Button title="Clear Log" onPress={clearLog} />
+      </View>
+
+      {/* Alpha sandboxes */}
+      <Text style={[styles.groupLabel, {color: COLOR_ALPHA}]}>
+        {'origin="alpha"'} ({alphas.length})
+      </Text>
+      <ScrollView
+        horizontal
+        style={styles.cardRow}
+        contentContainerStyle={styles.cardRowContent}>
+        {alphas.map(sb => (
+          <SandboxCard
+            key={sb.key}
+            entry={sb}
+            color={COLOR_ALPHA}
+            idleTTL={ALPHA_TTL}
+            onRemove={() => removeSandbox(sb.key)}
+            onMessage={data =>
+              addLog(`alpha ${sb.label}`, JSON.stringify(data))
+            }
+            onError={err =>
+              addLog(`alpha ${sb.label}`, `ERROR: ${err.name} — ${err.message}`)
+            }
+          />
+        ))}
+        {alphas.length === 0 && (
+          <Text style={styles.empty}>No alpha sandboxes yet.</Text>
+        )}
+      </ScrollView>
+
+      {/* Beta sandboxes */}
+      <Text style={[styles.groupLabel, {color: COLOR_BETA}]}>
+        {'origin="beta"'} ({betas.length})
+      </Text>
+      <ScrollView
+        horizontal
+        style={styles.cardRow}
+        contentContainerStyle={styles.cardRowContent}>
+        {betas.map(sb => (
+          <SandboxCard
+            key={sb.key}
+            entry={sb}
+            color={COLOR_BETA}
+            idleTTL={DEFAULT_TTL}
+            onRemove={() => removeSandbox(sb.key)}
+            onMessage={data => addLog(`beta ${sb.label}`, JSON.stringify(data))}
+            onError={err =>
+              addLog(`beta ${sb.label}`, `ERROR: ${err.name} — ${err.message}`)
+            }
+          />
+        ))}
+        {betas.length === 0 && (
+          <Text style={styles.empty}>No beta sandboxes yet.</Text>
+        )}
+      </ScrollView>
+
+      {/* Isolated sandboxes */}
+      <Text style={[styles.groupLabel, {color: COLOR_ISOLATED}]}>
+        no origin / isolated ({isolated.length})
+      </Text>
+      <ScrollView
+        horizontal
+        style={styles.cardRow}
+        contentContainerStyle={styles.cardRowContent}>
+        {isolated.map(sb => (
+          <SandboxCard
+            key={sb.key}
+            entry={sb}
+            color={COLOR_ISOLATED}
+            idleTTL={DEFAULT_TTL}
+            onRemove={() => removeSandbox(sb.key)}
+            onMessage={data =>
+              addLog(`isolated ${sb.label}`, JSON.stringify(data))
+            }
+            onError={err =>
+              addLog(
+                `isolated ${sb.label}`,
+                `ERROR: ${err.name} — ${err.message}`
+              )
+            }
+          />
+        ))}
+        {isolated.length === 0 && (
+          <Text style={styles.empty}>No isolated sandboxes yet.</Text>
+        )}
+      </ScrollView>
+
+      {/* Event log */}
+      <Text style={styles.logTitle}>Event Log</Text>
+      <ScrollView
+        ref={logScrollRef}
+        style={styles.logScroll}
+        onContentSizeChange={() => logScrollRef.current?.scrollToEnd()}>
+        {log.map((e, i) => (
+          <Text key={i} style={styles.logLine}>
+            <Text style={styles.logSource}>[{e.source}]</Text> {e.text}
+          </Text>
+        ))}
+      </ScrollView>
+    </SafeAreaView>
+  )
+}
+
+type SandboxCardProps = {
+  entry: SandboxEntry
+  color: string
+  idleTTL: number | (() => number)
+  onRemove: () => void
+  onMessage: (data: unknown) => void
+  onError: (err: {name: string; message: string}) => void
+}
+
+function SandboxCard({
+  entry,
+  color,
+  idleTTL,
+  onRemove,
+  onMessage,
+  onError,
+}: SandboxCardProps) {
+  return (
+    <View style={[styles.card, {borderColor: color}]}>
+      <View style={[styles.cardHeader, {backgroundColor: color}]}>
+        <Text style={styles.cardLabel}>
+          {entry.origin || 'isolated'} {entry.label}
+        </Text>
+        <Text style={styles.cardRemove} onPress={onRemove}>
+          ✕
+        </Text>
+      </View>
+      <SandboxReactNativeView
+        origin={entry.origin || undefined}
+        allowedOrigins={[ORIGIN_ALPHA, ORIGIN_BETA]}
+        idleTTL={idleTTL}
+        componentName="SandboxApp"
+        jsBundleSource="sandbox"
+        onMessage={onMessage}
+        onError={onError}
+        style={styles.sandboxView}
+      />
+    </View>
+  )
+}
+
+const styles = StyleSheet.create({
+  safe: {
+    flex: 1,
+    backgroundColor: '#f5f5f5',
+    paddingTop: Platform.OS === 'android' ? StatusBar.currentHeight : 0,
+  },
+  heading: {
+    fontSize: 20,
+    fontWeight: '700',
+    textAlign: 'center',
+    marginTop: 8,
+    marginBottom: 2,
+  },
+  subtitle: {
+    fontSize: 11,
+    color: '#6c757d',
+    textAlign: 'center',
+    marginBottom: 6,
+    paddingHorizontal: 16,
+  },
+  controls: {
+    flexDirection: 'row',
+    justifyContent: 'space-evenly',
+    paddingHorizontal: 8,
+    paddingBottom: 4,
+  },
+  groupLabel: {
+    fontSize: 12,
+    fontWeight: '600',
+    paddingHorizontal: 12,
+    paddingTop: 2,
+  },
+  cardRow: {height: 150, flexGrow: 0},
+  cardRowContent: {paddingHorizontal: 8, gap: 8},
+  card: {
+    width: 200,
+    borderWidth: 2,
+    borderRadius: 8,
+    overflow: 'hidden',
+  },
+  cardLabel: {
+    color: '#fff',
+    fontSize: 11,
+    fontWeight: '600',
+    textAlign: 'center',
+    paddingVertical: 2,
+    flex: 1,
+  },
+  cardHeader: {
+    flexDirection: 'row',
+    alignItems: 'center',
+  },
+  cardRemove: {
+    color: '#fff',
+    fontSize: 14,
+    fontWeight: '700',
+    paddingHorizontal: 8,
+    paddingVertical: 2,
+  },
+  sandboxView: {flex: 1},
+  empty: {
+    color: '#999',
+    fontStyle: 'italic',
+    alignSelf: 'center',
+    paddingTop: 60,
+  },
+  logTitle: {
+    fontSize: 14,
+    fontWeight: '600',
+    paddingHorizontal: 12,
+    paddingTop: 4,
+  },
+  logScroll: {flex: 1, paddingHorizontal: 12, paddingTop: 4},
+  logLine: {fontSize: 11, fontFamily: 'monospace', marginBottom: 2},
+  logSource: {fontWeight: '700', color: '#8232ff'},
+})

apps/origin-pooling/README.md

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+# Origin Pooling Demo
+
+Validates features of sandboxes sharing the same origin.  
+
+## Origin-based Pooling
+
+Sandboxes with the same `origin` prop share a single ReactHost / Hermes VM.
+
+- **Alpha** sandboxes share origin `alpha` → same VM
+- **Beta** sandboxes share origin `beta` → same VM
+- **Isolated** sandboxes get their own VM every time (no origin)
+
+Use the `+ Alpha`, `+ Beta`, and `+ Isolated` buttons to dynamically add
+sandboxes. Each card has a **Ping** button and a **✕** button
+to remove itself.
+
+## Lazy Kill
+
+When the last sandbox for an origin unmounts, the underlying ReactHost is
+**not** destroyed immediately — it lingers for 2 seconds (`idleTTL={2000}`).
+If a new sandbox with the same origin mounts within that window, it reuses
+the warm host (no cold start). Compare the `render` time of a cold start
+vs a warm re-mount.
+
+## Running
+
+```bash
+# From repo root
+yarn
+cd apps/origin-pooling
+npx react-native run-ios
+# or
+npx react-native run-android
+```