fix: portal before host (#36)

## 📜 Description

Fixed a problem when portal is not moved to the host if it's rendered
before.

## 💡 Motivation and Context

First of all it's important to mention that only Android doesn't have
this bug. It happens because on Android we have following lifecycle:
- set `hostName`
- register `Host`
- mount children (call corresponding `addView`)

On iOS (and web) from the other side the sequence looks next:
- mount children
- update props (set `hostName`)
- register `Host`

> The problem is not present with `@gorhom/portal`, because there we
simply store children in `context` and render them when `PortalHost` is
mounted.

I decided to follow similar pattern, so after registering host we need
to check if we can attach portals to it and if we can then attach. To
implement this I added
`registerPendingPortal`/`unregisterPendingPortals` methods to
`PortalRegistry`. So when we want to move `PortalView`, but host is not
found -> we register pending portals. When we call `registerHost` then
we check if it has pending portals and if yes, then we go through each
pending portal and call `onHostAvailableMethod`. Additionally inside
`PortalView` we track `isWaitingForHost` to properly cleanup pending
portals.

Even though Android doesn't have this problem I decided to implement
this fix there too, because I think it can be a timing issue and may be
changed in the future (so let's have a fix in advance).

Web implementation follows the same concept, except the view
registration. Instead of view we register a callback that can teleport
our view.

Closes #35

## 📢 Changelog

<!-- High level overview of important changes -->
<!-- For example: fixed status bar manipulation; added new types
declarations; -->
<!-- If your changes don't affect one of platform/language below - then
remove this platform/language -->

### Example

- added "portal before host"  example;
- removed "lottie" example (because we have messenger example now that
better showcase a use-case of the lib).

### E2E

- added "portal before host" test case;

### Web

- added `registerPendingPortal`/`unregisterPendingPortals` to
`PortalRegistry`;
- rename `setHost` -> `registerHost` to match iOS/Android naming;

### iOS

- added `registerPendingPortal`/`unregisterPendingPortals` to
`PortalRegistry`;
- added `onHostAvailable` to `PortalView`;
- call `onHostAvailable` from `registerHost` if we have `pendingPortals`
for this host;
- added `isWaitingForHost` to `PortalView` to remove `pendingPortals` if
we change host/detach view;

### Android

- added `registerPendingPortal`/`unregisterPendingPortals` to
`PortalRegistry`;
- added `onHostAvailable` to `PortalView`;
- call `onHostAvailable` from `registerHost` if we have `pendingPortals`
for this host;
- added `isWaitingForHost` to `PortalView` to remove `pendingPortals` if
we change host/detach view;

## 🤔 How Has This Been Tested?

Tested on Pixel 9 Pro (API 33), iPhone 16 Pro (iOS 18.5), Chrome
141.0.7390.108

## 📸 Screenshots (if appropriate):

|When|Android|iOS|Web|
|------|--------|---|----|
|Before|<img width="382" height="807" alt="image"
src="https://github.com/user-attachments/assets/472f8685-23a5-45a2-8145-f28b704213a6"
/>|<img width="400" height="874" alt="image"
src="https://github.com/user-attachments/assets/6541b050-001d-4ab6-91c0-49d70c99266d"
/>|<img width="387" height="828" alt="image"
src="https://github.com/user-attachments/assets/780b4d59-7737-4f46-b0d7-cd143e902f40"
/>|
|After|<img width="375" height="797" alt="image"
src="https://github.com/user-attachments/assets/90709cc7-1056-40f2-9727-462c188811f6"
/>|<img width="400" height="874" alt="image"
src="https://github.com/user-attachments/assets/a4fbf2d4-ce60-4de3-b953-2c5b63b06945"
/>|<img width="382" height="822" alt="image"
src="https://github.com/user-attachments/assets/96be9964-2c37-4f81-a282-fa0dbbbc20f4"
/>|

## 📝 Checklist

- [x] CI successfully passed
- [x] I added new mocks and corresponding unit-tests if library API was
changed

Author: kirillzyusko

android/src/main/java/com/teleport/global/PortalRegistry.kt

@@ -1,21 +1,52 @@
 package com.teleport.global
 
 import com.teleport.host.PortalHostView
+import com.teleport.portal.PortalView
 import java.lang.ref.WeakReference
 
 object PortalRegistry {
   private val hosts: MutableMap<String, WeakReference<PortalHostView>> = HashMap()
+  private val pendingPortals: MutableMap<String, MutableList<WeakReference<PortalView>>> = HashMap()
 
-  fun register(
+  fun registerHost(
     name: String,
     view: PortalHostView,
   ) {
     hosts[name] = WeakReference(view)
+
+    pendingPortals[name]?.let { portals ->
+      val iterator = portals.iterator()
+      while (iterator.hasNext()) {
+        val portalRef = iterator.next()
+        portalRef.get()?.onHostAvailable() ?: iterator.remove()
+      }
+      pendingPortals.remove(name)
+    }
   }
 
-  fun unregister(name: String) {
+  fun unregisterHost(name: String) {
     hosts.remove(name)
   }
 
   fun getHost(name: String?): PortalHostView? = hosts[name]?.get()
+
+  fun registerPendingPortal(
+    hostName: String,
+    portal: PortalView,
+  ) {
+    val portals = pendingPortals.getOrPut(hostName) { mutableListOf() }
+    portals.add(WeakReference(portal))
+  }
+
+  fun unregisterPendingPortal(
+    hostName: String,
+    portal: PortalView,
+  ) {
+    pendingPortals[hostName]?.let { portals ->
+      portals.removeAll { it.get() == null || it.get() == portal }
+      if (portals.isEmpty()) {
+        pendingPortals.remove(hostName)
+      }
+    }
+  }
 }

android/src/main/java/com/teleport/host/PortalHostView.kt

@@ -12,15 +12,15 @@ class PortalHostView(
   fun setName(newName: String?) {
     if (name == newName) return
 
-    name?.let { PortalRegistry.unregister(it) }
+    name?.let { PortalRegistry.unregisterHost(it) }
     name = newName
-    newName?.let { PortalRegistry.register(it, this) }
+    newName?.let { PortalRegistry.registerHost(it, this) }
   }
 
   // region Lifecycle
   override fun onDetachedFromWindow() {
     super.onDetachedFromWindow()
-    name?.let { PortalRegistry.unregister(it) }
+    name?.let { PortalRegistry.unregisterHost(it) }
   }
   // endregion
 }

android/src/main/java/com/teleport/portal/PortalView.kt

@@ -11,8 +11,15 @@ class PortalView(
   context: Context,
 ) : ReactViewGroup(context) {
   private var hostName: String? = null
+  private var isWaitingForHost = false
 
   fun setHostName(name: String?) {
+    if (isWaitingForHost) {
+      hostName?.let { PortalRegistry.unregisterPendingPortal(it, this) }
+      isWaitingForHost = false
+    }
+
+    // Gather children BEFORE updating hostName, since getChildCount() and getChildAt() depend on it
     val children = mutableListOf<View>()
     val count = childCount
     for (i in count - 1 downTo 0) {
@@ -24,17 +31,40 @@ class PortalView(
     hostName = name
 
     val target: ViewGroup =
-      if (hostName != null) {
-        PortalRegistry.getHost(hostName) ?: this
-      } else {
-        this
-      }
+      hostName?.let { hostNameValue ->
+        val host = PortalRegistry.getHost(hostNameValue)
+        if (host != null) {
+          host
+        } else {
+          PortalRegistry.registerPendingPortal(hostNameValue, this)
+          isWaitingForHost = true
+          this
+        }
+      } ?: this
 
     for (child in children) {
       target.addView(child)
     }
+  }
+
+  internal fun onHostAvailable() {
+    isWaitingForHost = false
+
+    val host = PortalRegistry.getHost(hostName)
+    if (host != null) {
+      // Use super methods to get actual children from this view, not from the host
+      val children = mutableListOf<View>()
+      val count = super.getChildCount()
+      for (i in count - 1 downTo 0) {
+        val child = super.getChildAt(i) ?: continue
+        children.add(0, child)
+        super.removeViewAt(i)
+      }
 
-    requestLayout()
+      for (child in children) {
+        host.addView(child)
+      }
+    }
   }
 
   private fun isTeleported(): Boolean = hostName != null && PortalRegistry.getHost(hostName) != null
@@ -103,4 +133,14 @@ class PortalView(
     // When teleported, do nothing—children are handled by the host's accessibility tree
   }
   // endregion
+
+  // region Lifecycle
+  override fun onDetachedFromWindow() {
+    super.onDetachedFromWindow()
+    if (isWaitingForHost) {
+      hostName?.let { PortalRegistry.unregisterPendingPortal(it, this) }
+      isWaitingForHost = false
+    }
+  }
+  // endregion
 }

e2e/flows/portal-before-host.yml

@@ -0,0 +1,13 @@
+appId: teleport.example
+---
+- launchApp
+- tapOn:
+    id: "portal_before_host"
+- takeScreenshot:
+    path: e2e/PortalBeforeHost
+- runScript:
+    file: ../scripts/compare-screenshots.js
+    env:
+      base: screenshots/${DEVICE}/PortalBeforeHost
+      target: PortalBeforeHost
+      diff: 0.3