refactor(okhttp): inject AmethystDns instead of using a singleton

Drop the AmethystDns.shared lazy companion. Construct one
amethystDns in AppModules and thread it through:

- DualHttpClientManager / OkHttpClientFactory
- DualHttpClientManagerForRelays / OkHttpClientFactoryForRelays
- MediaCallEventListenerFactory / MediaCallEventListener
- DnsInvalidatingEventListener.Factory
- AmethystDnsStore

This matches the dependency-injection style the rest of AppModules
uses and lets tests inject a mock Dns where needed. Behavior is
unchanged — every consumer still shares the same single instance,
just by construction rather than by a static singleton.

amethyst/src/main/java/com/vitorpamplona/amethyst/AppModules.kt

@@ -53,6 +53,7 @@ import com.vitorpamplona.amethyst.service.location.LocationState
 import com.vitorpamplona.amethyst.service.notifications.AlwaysOnNotificationServiceManager
 import com.vitorpamplona.amethyst.service.notifications.NotificationDispatcher
 import com.vitorpamplona.amethyst.service.notifications.PokeyReceiver
+import com.vitorpamplona.amethyst.service.okhttp.AmethystDns
 import com.vitorpamplona.amethyst.service.okhttp.AmethystDnsStore
 import com.vitorpamplona.amethyst.service.okhttp.DualHttpClientManager
 import com.vitorpamplona.amethyst.service.okhttp.DualHttpClientManagerForRelays
@@ -202,10 +203,15 @@ class AppModules(
     // Key cache service to download and decrypt encrypted files before caching them.
     val keyCache = EncryptionKeyCache()
 
-    // Persists the shared DNS resolver's positive cache across process restarts so cold starts
-    // don't pay ~700 sync getaddrinfo calls. Restored entries fall through to the
-    // stale-while-revalidate path on first lookup.
-    val dnsStore = AmethystDnsStore(appContext)
+    // Concurrent, caching DNS resolver shared by every OkHttp client built below — a host
+    // resolved for an image fetch is reused when a relay handshake or NIP-05 lookup hits the
+    // same host.
+    val amethystDns = AmethystDns()
+
+    // Persists [amethystDns]'s positive cache across process restarts so cold starts don't pay
+    // ~700 sync getaddrinfo calls. Restored entries fall through to the stale-while-revalidate
+    // path on first lookup.
+    val dnsStore = AmethystDnsStore(appContext, amethystDns)
 
     // manages all the other connections separately from relays.
     val okHttpClients =
@@ -215,6 +221,7 @@ class AppModules(
             isMobileDataProvider = connManager.isMobileOrNull,
             keyCache = keyCache,
             scope = applicationIOScope,
+            dns = amethystDns,
         )
 
     // Offers easy methods to know when connections are happening through Tor or not
@@ -296,6 +303,7 @@ class AppModules(
             proxyPortProvider = torManager.activePortOrNull,
             isMobileDataProvider = connManager.isMobileOrNull,
             scope = applicationIOScope,
+            dns = amethystDns,
         )
 
     // Connects the INostrClient class with okHttp

amethyst/src/main/java/com/vitorpamplona/amethyst/service/okhttp/AmethystDns.kt

@@ -273,12 +273,6 @@ class AmethystDns(
             Executors.newFixedThreadPool(8) { r ->
                 Thread(r, "amethyst-dns-refresh").apply { isDaemon = true }
             }
-
-        /**
-         * Process-wide instance shared by every OkHttp client built in the app, so a host resolved
-         * for an image fetch is reused when a relay handshake or NIP-05 lookup hits the same host.
-         */
-        val shared: AmethystDns by lazy { AmethystDns() }
     }
 }
 

amethyst/src/main/java/com/vitorpamplona/amethyst/service/okhttp/AmethystDnsStore.kt

@@ -40,7 +40,7 @@ import com.vitorpamplona.quartz.utils.Log
  */
 class AmethystDnsStore(
     private val context: Context,
-    private val dns: AmethystDns = AmethystDns.shared,
+    private val dns: AmethystDns,
 ) {
     private val prefs by lazy { context.getSharedPreferences(PREFS_NAME, Context.MODE_PRIVATE) }
 

amethyst/src/main/java/com/vitorpamplona/amethyst/service/okhttp/DnsInvalidatingEventListener.kt

@@ -34,17 +34,22 @@ import java.io.IOException
  * Used by the relay client. The media path uses [MediaCallEventListener], which folds the same
  * invalidation into its `finish` method alongside its existing timing logging.
  */
-class DnsInvalidatingEventListener private constructor() : EventListener() {
+class DnsInvalidatingEventListener(
+    private val dns: AmethystDns,
+) : EventListener() {
     override fun callFailed(
         call: Call,
         ioe: IOException,
     ) {
-        AmethystDns.shared.invalidate(call.request().url.host)
+        dns.invalidate(call.request().url.host)
     }
 
-    object Factory : EventListener.Factory {
-        private val INSTANCE = DnsInvalidatingEventListener()
+    /** Per-client factory. The listener is stateless, so the same instance serves every call. */
+    class Factory(
+        dns: AmethystDns,
+    ) : EventListener.Factory {
+        private val listener = DnsInvalidatingEventListener(dns)
 
-        override fun create(call: Call): EventListener = INSTANCE
+        override fun create(call: Call): EventListener = listener
     }
 }

amethyst/src/main/java/com/vitorpamplona/amethyst/service/okhttp/DualHttpClientManager.kt

@@ -38,8 +38,9 @@ class DualHttpClientManager(
     isMobileDataProvider: StateFlow<Boolean?>,
     keyCache: EncryptionKeyCache,
     scope: CoroutineScope,
+    dns: AmethystDns,
 ) : IHttpClientManager {
-    val factory = OkHttpClientFactory(keyCache, userAgent)
+    val factory = OkHttpClientFactory(keyCache, userAgent, dns)
 
     val defaultHttpClient: StateFlow<OkHttpClient> =
         combine(proxyPortProvider, isMobileDataProvider) { proxy, mobile ->

amethyst/src/main/java/com/vitorpamplona/amethyst/service/okhttp/DualHttpClientManagerForRelays.kt

@@ -35,8 +35,9 @@ class DualHttpClientManagerForRelays(
     proxyPortProvider: StateFlow<Int?>,
     isMobileDataProvider: StateFlow<Boolean?>,
     scope: CoroutineScope,
+    dns: AmethystDns,
 ) : IHttpClientManager {
-    val factory = OkHttpClientFactoryForRelays(userAgent)
+    val factory = OkHttpClientFactoryForRelays(userAgent, dns)
 
     val defaultHttpClient: StateFlow<OkHttpClient> =
         combine(proxyPortProvider, isMobileDataProvider) { proxy, mobile ->

amethyst/src/main/java/com/vitorpamplona/amethyst/service/okhttp/MediaCallEventListener.kt

@@ -44,6 +44,7 @@ import java.net.Proxy
 class MediaCallEventListener(
     private val dispatcher: Dispatcher,
     private val connectionPool: ConnectionPool,
+    private val dns: AmethystDns,
 ) : EventListener() {
     private var callStartNanos = 0L
     private var dnsStartNanos = 0L
@@ -129,7 +130,7 @@ class MediaCallEventListener(
         // dead IPs for up to 24h. Per-attempt connectFailed isn't enough — a multi-A-record
         // host can have one bad IP and OkHttp will recover by trying the next one.
         if (error != null) {
-            AmethystDns.shared.invalidate(host)
+            dns.invalidate(host)
         }
 
         val totalMs = (System.nanoTime() - callStartNanos) / 1_000_000
@@ -178,6 +179,7 @@ class MediaCallEventListener(
 class MediaCallEventListenerFactory(
     private val dispatcher: Dispatcher,
     private val connectionPool: ConnectionPool,
+    private val dns: AmethystDns,
 ) : EventListener.Factory {
-    override fun create(call: Call): EventListener = MediaCallEventListener(dispatcher, connectionPool)
+    override fun create(call: Call): EventListener = MediaCallEventListener(dispatcher, connectionPool, dns)
 }

amethyst/src/main/java/com/vitorpamplona/amethyst/service/okhttp/OkHttpClientFactory.kt

@@ -35,6 +35,7 @@ import java.util.concurrent.TimeUnit
 class OkHttpClientFactory(
     keyCache: EncryptionKeyCache,
     val userAgent: String,
+    private val dns: AmethystDns,
 ) {
     // val logging = LoggingInterceptor()
     val keyDecryptor = EncryptedBlobInterceptor(keyCache)
@@ -63,8 +64,8 @@ class OkHttpClientFactory(
             .Builder()
             .dispatcher(dispatcher)
             .connectionPool(connectionPool)
-            .dns(AmethystDns.shared)
-            .eventListenerFactory(MediaCallEventListenerFactory(dispatcher, connectionPool))
+            .dns(dns)
+            .eventListenerFactory(MediaCallEventListenerFactory(dispatcher, connectionPool, dns))
             .followRedirects(true)
             .followSslRedirects(true)
             .addInterceptor(DefaultContentTypeInterceptor(userAgent))

amethyst/src/main/java/com/vitorpamplona/amethyst/service/okhttp/OkHttpClientFactoryForRelays.kt

@@ -29,6 +29,7 @@ import java.time.Duration
 
 class OkHttpClientFactoryForRelays(
     userAgent: String,
+    private val dns: AmethystDns,
 ) {
     companion object {
         // by picking a random proxy port, the connection will fail as it should.
@@ -55,8 +56,8 @@ class OkHttpClientFactoryForRelays(
         OkHttpClient
             .Builder()
             .dispatcher(myDispatcher)
-            .dns(AmethystDns.shared)
-            .eventListenerFactory(DnsInvalidatingEventListener.Factory)
+            .dns(dns)
+            .eventListenerFactory(DnsInvalidatingEventListener.Factory(dns))
             .followRedirects(true)
             .followSslRedirects(true)
             .addInterceptor(DefaultContentTypeInterceptor(userAgent))