feat(dapps): show the bundled DApps catalog until one can be fetched

The DApps catalog lived only in memory and every read waited on first(), so
with the catalog URL unreachable the DApps screen waited forever.

feature-dapp-impl now bundles dapps_full.json at build time. On the first
sync the repository tries the network once and, if that fails, publishes the
bundled catalog so every read returns; the fetched catalog replaces it as
soon as it arrives.

The download task moves to scripts/bundled-config.gradle and serves both
the chain list and the DApps catalog. runtime and feature-dapp-impl unit
tests return defaults for android.util.Log, which the fallback calls.

feature-dapp-impl/build.gradle

@@ -1,6 +1,7 @@
 apply plugin: 'kotlin-parcelize'
 apply from: '../tests.gradle'
 apply from: "../scripts/secrets.gradle"
+apply from: "../scripts/bundled-config.gradle"
 
 android {
 
@@ -21,6 +22,14 @@ android {
     }
     namespace 'io.novafoundation.nova.feature_dapp_impl'
 
+    testOptions {
+        unitTests {
+            // android.util.Log.* throws "Method ... not mocked" in plain JVM unit tests; the first-install
+            // fallback logs the failed fetch it recovers from.
+            returnDefaultValues = true
+        }
+    }
+
     packagingOptions {
         resources.excludes.add("META-INF/NOTICE.md")
     }
@@ -96,3 +105,10 @@ dependencies {
     testImplementation jUnitDep
     testImplementation mockitoDep
 }
+
+// The DApps catalog a first install shows when none can be fetched (AssetBundledDappCatalog).
+bundleConfigAsset(
+    "bundleDappsConfig",
+    "https://raw.githubusercontent.com/pezkuwichain/pezkuwi-wallet-utils/master/dapps/dapps_full.json",
+    "bundled-config/dapps.json"
+) { it instanceof Map && it.dapps instanceof List && !it.dapps.isEmpty() }

feature-dapp-impl/src/main/java/io/novafoundation/nova/feature_dapp_impl/data/repository/BundledDappCatalog.kt

@@ -0,0 +1,34 @@
+package io.novafoundation.nova.feature_dapp_impl.data.repository
+
+import android.content.Context
+import android.util.Log
+import com.google.gson.Gson
+import io.novafoundation.nova.common.utils.LOG_TAG
+import io.novafoundation.nova.feature_dapp_impl.data.network.metadata.DappMetadataResponse
+
+/** The DApps catalog the APK was built with: what is shown until a catalog can be fetched. */
+fun interface BundledDappCatalog {
+
+    fun load(): DappMetadataResponse?
+
+    companion object {
+        val None = BundledDappCatalog { null }
+    }
+}
+
+class AssetBundledDappCatalog(
+    private val context: Context,
+    private val gson: Gson,
+) : BundledDappCatalog {
+
+    companion object {
+        // Written at build time by the `bundleDappsConfig` task in feature-dapp-impl/build.gradle.
+        const val ASSET_PATH = "bundled-config/dapps.json"
+    }
+
+    override fun load(): DappMetadataResponse? = runCatching {
+        context.assets.open(ASSET_PATH).bufferedReader().use { gson.fromJson(it, DappMetadataResponse::class.java) }
+    }.onFailure {
+        Log.e(LOG_TAG, "No usable bundled DApps catalog", it)
+    }.getOrNull()
+}

feature-dapp-impl/src/main/java/io/novafoundation/nova/feature_dapp_impl/data/repository/RealDAppMetadataRepository.kt

@@ -1,6 +1,8 @@
 package io.novafoundation.nova.feature_dapp_impl.data.repository
 
+import android.util.Log
 import io.novafoundation.nova.common.utils.CollectionDiffer
+import io.novafoundation.nova.common.utils.LOG_TAG
 import io.novafoundation.nova.common.utils.Urls
 import io.novafoundation.nova.common.utils.retryUntilDone
 import io.novafoundation.nova.core_db.dao.BrowserHostSettingsDao
@@ -11,6 +13,8 @@ import io.novafoundation.nova.feature_dapp_api.data.repository.DAppMetadataRepos
 import io.novafoundation.nova.feature_dapp_impl.data.mappers.mapDAppMetadataResponseToDAppMetadatas
 import io.novafoundation.nova.feature_dapp_impl.data.network.metadata.DappMetadataApi
 import io.novafoundation.nova.feature_dapp_impl.data.network.metadata.DappMetadataRemote
+import io.novafoundation.nova.feature_dapp_impl.data.network.metadata.DappMetadataResponse
+import kotlinx.coroutines.CancellationException
 import kotlinx.coroutines.channels.BufferOverflow
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.MutableSharedFlow
@@ -19,7 +23,8 @@ import kotlinx.coroutines.flow.first
 class RealDAppMetadataRepository(
     private val dappMetadataApi: DappMetadataApi,
     private val remoteApiUrl: String,
-    private val browserHostSettingsDao: BrowserHostSettingsDao
+    private val browserHostSettingsDao: BrowserHostSettingsDao,
+    private val bundledCatalog: BundledDappCatalog = BundledDappCatalog.None,
 ) : DAppMetadataRepository {
 
     private val dappMetadatasFlow = MutableSharedFlow<DappCatalog>(replay = 1, onBufferOverflow = BufferOverflow.DROP_OLDEST)
@@ -29,7 +34,30 @@ class RealDAppMetadataRepository(
     }
 
     override suspend fun syncDAppMetadatas() {
-        val response = retryUntilDone { dappMetadataApi.getParachainMetadata(remoteApiUrl) }
+        if (dappMetadatasFlow.replayCache.isEmpty()) {
+            // Every read below waits for a first catalog. Try the network once, and if that fails show the
+            // catalog the APK was built with, so the DApps screen opens; the fetched one replaces it below.
+            val firstTry = try {
+                dappMetadataApi.getParachainMetadata(remoteApiUrl)
+            } catch (e: CancellationException) {
+                throw e
+            } catch (e: Exception) {
+                Log.e(LOG_TAG, "First DApps catalog fetch failed, showing the bundled catalog", e)
+                null
+            }
+
+            if (firstTry != null) {
+                applyCatalog(firstTry)
+                return
+            }
+
+            bundledCatalog.load()?.let { dappMetadatasFlow.emit(mapDAppMetadataResponseToDAppMetadatas(it)) }
+        }
+
+        applyCatalog(retryUntilDone { dappMetadataApi.getParachainMetadata(remoteApiUrl) })
+    }
+
+    private suspend fun applyCatalog(response: DappMetadataResponse) {
         val dappMetadatas = mapDAppMetadataResponseToDAppMetadatas(response)
         syncHostSettings(response.dapps)
         dappMetadatasFlow.emit(dappMetadatas)

feature-dapp-impl/src/main/java/io/novafoundation/nova/feature_dapp_impl/di/modules/DappMetadataModule.kt

@@ -1,5 +1,7 @@
 package io.novafoundation.nova.feature_dapp_impl.di.modules
 
+import android.content.Context
+import com.google.gson.Gson
 import dagger.Module
 import dagger.Provides
 import io.novafoundation.nova.common.data.network.NetworkApiCreator
@@ -8,6 +10,7 @@ import io.novafoundation.nova.core_db.dao.BrowserHostSettingsDao
 import io.novafoundation.nova.feature_dapp_api.data.repository.DAppMetadataRepository
 import io.novafoundation.nova.feature_dapp_impl.BuildConfig
 import io.novafoundation.nova.feature_dapp_impl.data.network.metadata.DappMetadataApi
+import io.novafoundation.nova.feature_dapp_impl.data.repository.AssetBundledDappCatalog
 import io.novafoundation.nova.feature_dapp_impl.data.repository.RealDAppMetadataRepository
 
 @Module
@@ -23,10 +26,13 @@ class DappMetadataModule {
     @FeatureScope
     fun provideDRepository(
         api: DappMetadataApi,
-        dappHostSettingsDao: BrowserHostSettingsDao
+        dappHostSettingsDao: BrowserHostSettingsDao,
+        context: Context,
+        gson: Gson
     ): DAppMetadataRepository = RealDAppMetadataRepository(
         dappMetadataApi = api,
         remoteApiUrl = BuildConfig.DAPP_METADATAS_URL,
-        browserHostSettingsDao = dappHostSettingsDao
+        browserHostSettingsDao = dappHostSettingsDao,
+        bundledCatalog = AssetBundledDappCatalog(context, gson)
     )
 }

feature-dapp-impl/src/test/java/io/novafoundation/nova/feature_dapp_impl/data/repository/RealDAppMetadataRepositoryTest.kt

@@ -0,0 +1,73 @@
+package io.novafoundation.nova.feature_dapp_impl.data.repository
+
+import io.novafoundation.nova.core_db.dao.BrowserHostSettingsDao
+import io.novafoundation.nova.feature_dapp_impl.data.network.metadata.DappMetadataApi
+import io.novafoundation.nova.feature_dapp_impl.data.network.metadata.DappMetadataRemote
+import io.novafoundation.nova.feature_dapp_impl.data.network.metadata.DappMetadataResponse
+import kotlinx.coroutines.CompletableDeferred
+import kotlinx.coroutines.launch
+import kotlinx.coroutines.runBlocking
+import kotlinx.coroutines.yield
+import org.junit.Assert.assertEquals
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.mockito.Mock
+import org.mockito.Mockito.`when`
+import org.mockito.junit.MockitoJUnitRunner
+import java.io.IOException
+
+@RunWith(MockitoJUnitRunner::class)
+class RealDAppMetadataRepositoryTest {
+
+    @Mock
+    lateinit var hostSettingsDao: BrowserHostSettingsDao
+
+    private val bundled = catalogOf("https://bundled.example")
+    private val remote = catalogOf("https://remote.example")
+
+    @Test
+    fun `a first install shows the bundled catalog until one is fetched`() = runBlocking {
+        `when`(hostSettingsDao.getBrowserAllHostSettings()).thenReturn(emptyList())
+        val network = CompletableDeferred<DappMetadataResponse>()
+        var calls = 0
+        val api = object : DappMetadataApi {
+            override suspend fun getParachainMetadata(url: String): DappMetadataResponse {
+                calls++
+                if (calls == 1) throw IOException("unreachable")
+                return network.await()
+            }
+        }
+        val repository = RealDAppMetadataRepository(api, "url", hostSettingsDao) { bundled }
+
+        val sync = launch { repository.syncDAppMetadatas() }
+        while (!repository.isDAppsSynced()) yield()
+
+        assertEquals("https://bundled.example", repository.getDAppCatalog().dApps.single().url)
+
+        network.complete(remote)
+        sync.join()
+
+        assertEquals("https://remote.example", repository.getDAppCatalog().dApps.single().url)
+    }
+
+    @Test
+    fun `the bundled catalog is not read when the fetch works`() = runBlocking {
+        `when`(hostSettingsDao.getBrowserAllHostSettings()).thenReturn(emptyList())
+        var bundledReads = 0
+        val api = object : DappMetadataApi {
+            override suspend fun getParachainMetadata(url: String) = remote
+        }
+        val repository = RealDAppMetadataRepository(api, "url", hostSettingsDao) { bundledReads++; bundled }
+
+        repository.syncDAppMetadatas()
+
+        assertEquals(0, bundledReads)
+        assertEquals("https://remote.example", repository.getDAppCatalog().dApps.single().url)
+    }
+
+    private fun catalogOf(url: String) = DappMetadataResponse(
+        popular = emptyList(),
+        categories = emptyList(),
+        dapps = listOf(DappMetadataRemote(name = "d", icon = "i", url = url, categories = emptyList(), desktopOnly = null))
+    )
+}