fix: image loading when using markdown img and bigImageUrl

When receiving a message with the same image in the markdown body and in
the extras client::notification.bigImageUrl, then there is a clash on
the file system.

One request succeeds and the other fails with the following error. This
commit ensures that there is only one coil image loader instance, so
that there shouldn't be file system race conditions.

    WebSocket(1): received message {"id":845,"appid":21,...}
    Failed - http://192.168.178.2:8000/1.jpg?v=1718369188 - java.lang.IllegalStateException: closed
    java.lang.IllegalStateException: closed
        at okio.RealBufferedSource.rangeEquals(RealBufferedSource.kt:466)
        at okio.RealBufferedSource.rangeEquals(RealBufferedSource.kt:130)
        at coil.decode.SvgDecodeUtils.isSvg(DecodeUtils.kt:19)
        at coil.decode.SvgDecoder$Factory.isApplicable(SvgDecoder.kt:104)
        at coil.decode.SvgDecoder$Factory.create(SvgDecoder.kt:99)
        at coil.ComponentRegistry.newDecoder(ComponentRegistry.kt:100)
        at coil.intercept.EngineInterceptor.decode(EngineInterceptor.kt:197)
        at coil.intercept.EngineInterceptor.access$decode(EngineInterceptor.kt:42)
        at coil.intercept.EngineInterceptor$execute$executeResult$1.invokeSuspend(EngineInterceptor.kt:131)
        at coil.intercept.EngineInterceptor$execute$executeResult$1.invoke(EngineInterceptor.kt)
        at coil.intercept.EngineInterceptor$execute$executeResult$1.invoke(EngineInterceptor.kt)
        at kotlinx.coroutines.intrinsics.UndispatchedKt.startUndispatchedOrReturn(Undispatched.kt:78)
        at kotlinx.coroutines.BuildersKt__Builders_commonKt.withContext(Builders.common.kt:167)
        at kotlinx.coroutines.BuildersKt.withContext(Unknown Source)
        at coil.intercept.EngineInterceptor.execute(EngineInterceptor.kt:130)
        at coil.intercept.EngineInterceptor.access$execute(EngineInterceptor.kt:42)
        at coil.intercept.EngineInterceptor$execute$1.invokeSuspend(EngineInterceptor.kt)
        at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
        at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:108)
        at kotlinx.coroutines.internal.LimitedDispatcher$Worker.run(LimitedDispatcher.kt:115)
        at kotlinx.coroutines.scheduling.TaskImpl.run(Tasks.kt:103)
        at kotlinx.coroutines.scheduling.CoroutineScheduler.runSafely(CoroutineScheduler.kt:584)
        at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.executeTask(CoroutineScheduler.kt:793)
        at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.runWorker(CoroutineScheduler.kt:697)
        at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.run(CoroutineScheduler.kt:684)
    Successful (NETWORK) - http://192.168.178.2:8000/1.jpg?v=1718369188

app/src/main/kotlin/com/github/gotify/CoilInstance.kt

@@ -16,13 +16,62 @@ import java.io.IOException
 import okhttp3.OkHttpClient
 import org.tinylog.kotlin.Logger
 
-internal class CoilHandler(private val context: Context, private val settings: Settings) {
-    private val imageLoader = makeImageLoader()
+object CoilInstance {
+    private var holder: Pair<SSLSettings, ImageLoader>? = null
 
-    private fun makeImageLoader(): ImageLoader {
+    @Throws(IOException::class)
+    fun getImageFromUrl(context: Context, url: String?): Bitmap {
+        val request = ImageRequest.Builder(context)
+            .data(url)
+            .build()
+        return (get(context).executeBlocking(request).drawable as BitmapDrawable).bitmap
+    }
+
+    fun getIcon(context: Context, app: Application?): Bitmap {
+        if (app == null) {
+            return BitmapFactory.decodeResource(context.resources, R.drawable.gotify)
+        }
+        val baseUrl = Settings(context).url
+        try {
+            return getImageFromUrl(
+                context,
+                Utils.resolveAbsoluteUrl("$baseUrl/", app.image)
+            )
+        } catch (e: IOException) {
+            Logger.error(e, "Could not load image for notification")
+        }
+        return BitmapFactory.decodeResource(context.resources, R.drawable.gotify)
+    }
+
+    @OptIn(ExperimentalCoilApi::class)
+    fun evict(context: Context) {
+        try {
+            get(context).apply {
+                diskCache?.clear()
+                memoryCache?.clear()
+            }
+        } catch (e: IOException) {
+            Logger.error(e, "Problem evicting Coil cache")
+        }
+    }
+
+    @Synchronized
+    fun get(context: Context): ImageLoader {
+        val newSettings = Settings(context).sslSettings()
+        val copy = holder
+        if (copy != null && copy.first == newSettings) {
+            return copy.second
+        }
+        return makeImageLoader(context, newSettings).also { holder = it }.second
+    }
+
+    private fun makeImageLoader(
+        context: Context,
+        sslSettings: SSLSettings
+    ): Pair<SSLSettings, ImageLoader> {
         val builder = OkHttpClient.Builder()
-        CertUtils.applySslSettings(builder, settings.sslSettings())
-        return ImageLoader.Builder(context)
+        CertUtils.applySslSettings(builder, sslSettings)
+        val loader = ImageLoader.Builder(context)
             .okHttpClient(builder.build())
             .diskCache {
                 DiskCache.Builder()
@@ -33,39 +82,6 @@ internal class CoilHandler(private val context: Context, private val settings: S
                 add(SvgDecoder.Factory())
             }
             .build()
-    }
-
-    @Throws(IOException::class)
-    fun getImageFromUrl(url: String?): Bitmap {
-        val request = ImageRequest.Builder(context)
-            .data(url)
-            .build()
-        return (imageLoader.executeBlocking(request).drawable as BitmapDrawable).bitmap
-    }
-
-    fun getIcon(app: Application?): Bitmap {
-        if (app == null) {
-            return BitmapFactory.decodeResource(context.resources, R.drawable.gotify)
-        }
-        try {
-            return getImageFromUrl(
-                Utils.resolveAbsoluteUrl("${settings.url}/", app.image)
-            )
-        } catch (e: IOException) {
-            Logger.error(e, "Could not load image for notification")
-        }
-        return BitmapFactory.decodeResource(context.resources, R.drawable.gotify)
-    }
-
-    fun get() = imageLoader
-
-    @OptIn(ExperimentalCoilApi::class)
-    fun evict() {
-        try {
-            imageLoader.diskCache?.clear()
-            imageLoader.memoryCache?.clear()
-        } catch (e: IOException) {
-            Logger.error(e, "Problem evicting Coil cache")
-        }
+        return sslSettings to loader
     }
 }

app/src/main/kotlin/com/github/gotify/SSLSettings.kt

@@ -1,6 +1,6 @@
 package com.github.gotify
 
-internal class SSLSettings(
+internal data class SSLSettings(
     val validateSSL: Boolean,
     val caCertPath: String?,
     val clientCertPath: String?,

app/src/main/kotlin/com/github/gotify/messages/MessagesActivity.kt

@@ -31,6 +31,7 @@ import androidx.recyclerview.widget.LinearLayoutManager
 import androidx.recyclerview.widget.RecyclerView
 import coil.request.ImageRequest
 import com.github.gotify.BuildConfig
+import com.github.gotify.CoilInstance
 import com.github.gotify.MissedMessageUtil
 import com.github.gotify.R
 import com.github.gotify.Utils
@@ -102,7 +103,7 @@ internal class MessagesActivity :
         listMessageAdapter = ListMessageAdapter(
             this,
             viewModel.settings,
-            viewModel.coilHandler.get()
+            CoilInstance.get(this)
         ) { message ->
             scheduleDeletion(message)
         }
@@ -169,13 +170,13 @@ internal class MessagesActivity :
     }
 
     private fun refreshAll() {
-        viewModel.coilHandler.evict()
+        CoilInstance.evict(this)
         startActivity(Intent(this, InitializationActivity::class.java))
         finish()
     }
 
     private fun onRefresh() {
-        viewModel.coilHandler.evict()
+        CoilInstance.evict(this)
         viewModel.messages.clear()
         launchCoroutine {
             loadMore(viewModel.appId).forEachIndexed { index, message ->
@@ -211,9 +212,7 @@ internal class MessagesActivity :
                 .size(100, 100)
                 .target(t)
                 .build()
-            viewModel.coilHandler
-                .get()
-                .enqueue(request)
+            CoilInstance.get(this).enqueue(request)
         }
         selectAppInMenu(selectedItem)
     }

app/src/main/kotlin/com/github/gotify/messages/MessagesModel.kt

@@ -3,7 +3,6 @@ package com.github.gotify.messages
 import android.app.Activity
 import androidx.lifecycle.ViewModel
 import coil.target.Target
-import com.github.gotify.CoilHandler
 import com.github.gotify.Settings
 import com.github.gotify.api.ClientFactory
 import com.github.gotify.client.api.MessageApi
@@ -13,7 +12,6 @@ import com.github.gotify.messages.provider.MessageState
 
 internal class MessagesModel(parentView: Activity) : ViewModel() {
     val settings = Settings(parentView)
-    val coilHandler = CoilHandler(parentView, settings)
     val client = ClientFactory.clientToken(settings)
     val appsHolder = ApplicationHolder(parentView, client)
     val messages = MessageFacade(client.createService(MessageApi::class.java), appsHolder)

app/src/main/kotlin/com/github/gotify/service/WebSocketService.kt

@@ -17,7 +17,7 @@ import androidx.annotation.RequiresApi
 import androidx.core.app.NotificationCompat
 import androidx.core.content.ContextCompat
 import com.github.gotify.BuildConfig
-import com.github.gotify.CoilHandler
+import com.github.gotify.CoilInstance
 import com.github.gotify.MarkwonFactory
 import com.github.gotify.MissedMessageUtil
 import com.github.gotify.NotificationSupport
@@ -62,7 +62,6 @@ internal class WebSocketService : Service() {
     private val lastReceivedMessage = AtomicLong(NOT_LOADED)
     private lateinit var missingMessageUtil: MissedMessageUtil
 
-    private lateinit var coilHandler: CoilHandler
     private lateinit var markwon: Markwon
 
     override fun onCreate() {
@@ -71,8 +70,7 @@ internal class WebSocketService : Service() {
         val client = ClientFactory.clientToken(settings)
         missingMessageUtil = MissedMessageUtil(client.createService(MessageApi::class.java))
         Logger.info("Create ${javaClass.simpleName}")
-        coilHandler = CoilHandler(this, settings)
-        markwon = MarkwonFactory.createForNotification(this, coilHandler.get())
+        markwon = MarkwonFactory.createForNotification(this, CoilInstance.get(this))
     }
 
     override fun onDestroy() {
@@ -377,7 +375,7 @@ internal class WebSocketService : Service() {
             .setDefaults(Notification.DEFAULT_ALL)
             .setWhen(System.currentTimeMillis())
             .setSmallIcon(R.drawable.ic_gotify)
-            .setLargeIcon(coilHandler.getIcon(appIdToApp[appId]))
+            .setLargeIcon(CoilInstance.getIcon(this, appIdToApp[appId]))
             .setTicker("${getString(R.string.app_name)} - $title")
             .setGroup(NotificationSupport.Group.MESSAGES)
             .setContentTitle(title)
@@ -406,7 +404,7 @@ internal class WebSocketService : Service() {
             try {
                 b.setStyle(
                     NotificationCompat.BigPictureStyle()
-                        .bigPicture(coilHandler.getImageFromUrl(notificationImageUrl))
+                        .bigPicture(CoilInstance.getImageFromUrl(this, notificationImageUrl))
                 )
             } catch (e: Exception) {
                 Logger.error(e, "Error loading bigImageUrl")