Switch RepoDataFetcher backend to OkHttp

This change adds caching to both repository and app metadata,
incidentally adding better offline support.

Closes #8
Closes #159
Partially resolves #150
Partially resolves #322

app/src/main/java/app/accrescent/client/data/RepoDataFetcherImpl.kt

@@ -4,11 +4,12 @@ import android.content.Context
 import app.accrescent.client.R
 import app.accrescent.client.data.net.AppRepoData
 import app.accrescent.client.data.net.RepoData
-import app.accrescent.client.util.openHttpConnection
 import app.accrescent.client.util.verifySignature
 import dagger.hilt.android.qualifiers.ApplicationContext
 import kotlinx.serialization.json.Json
-import java.io.ByteArrayOutputStream
+import okhttp3.OkHttpClient
+import okhttp3.Request
+import java.io.IOException
 import java.net.URL
 import java.security.GeneralSecurityException
 import javax.inject.Inject
@@ -17,6 +18,7 @@ private val format = Json { ignoreUnknownKeys = true }
 
 class RepoDataFetcherImpl @Inject constructor(
     @ApplicationContext private val context: Context,
+    private val okHttpClient: OkHttpClient,
 ) : RepoDataFetcher {
     override fun fetchRepoData(): RepoData {
         val repoDataUrl = "$REPOSITORY_URL/repodata.$PUBKEY_VERSION.json"
@@ -38,10 +40,12 @@ class RepoDataFetcherImpl @Inject constructor(
     }
 
     private fun fetchFileString(url: URL): String {
-        val outBuf = ByteArrayOutputStream()
+        val request = Request.Builder().url(url).build()
 
-        url.openHttpConnection().use { it.downloadTo(outBuf) }
-
-        return outBuf.toString()
+        return okHttpClient
+            .newCall(request)
+            .execute()
+            .use { it.body?.string() }
+            ?: throw IOException("request body expected but not found")
     }
 }

app/src/main/java/app/accrescent/client/di/OkHttpModule.kt

@@ -0,0 +1,31 @@
+package app.accrescent.client.di
+
+import android.content.Context
+import dagger.Module
+import dagger.Provides
+import dagger.hilt.InstallIn
+import dagger.hilt.android.qualifiers.ApplicationContext
+import dagger.hilt.components.SingletonComponent
+import okhttp3.Cache
+import okhttp3.OkHttpClient
+import java.io.File
+import javax.inject.Singleton
+
+// The cache size in bytes
+private const val CACHE_SIZE: Long = 50 * 1024 * 1024
+
+@Module
+@InstallIn(SingletonComponent::class)
+object OkHttpModule {
+    @Provides
+    @Singleton
+    fun getOkHttpClient(@ApplicationContext context: Context) = OkHttpClient()
+        .newBuilder()
+        .cache(
+            Cache(
+                directory = File(context.cacheDir.toURI()),
+                maxSize = CACHE_SIZE,
+            )
+        )
+        .build()
+}

gradle/libs.versions.toml

@@ -15,6 +15,7 @@ ksp = "1.9.21-1.0.16"
 lifecycle = "2.6.2"
 material = "1.11.0"
 nav-compose = "2.7.6"
+okhttp = "4.12.0"
 room = "2.6.1"
 serialization = "1.6.2"
 work = "2.9.0"
@@ -40,6 +41,7 @@ lifecycle-process = { group = "androidx.lifecycle", name = "lifecycle-process",
 lifecycle-viewmodel-compose = { group = "androidx.lifecycle", name = "lifecycle-viewmodel-compose", version.ref = "lifecycle" }
 material = { group = "com.google.android.material", name = "material", version.ref = "material" }
 navcompose = { group = "androidx.navigation", name = "navigation-compose", version.ref = "nav-compose" }
+okhttp = { group = "com.squareup.okhttp3", name = "okhttp", version.ref = "okhttp" }
 room-compiler = { group = "androidx.room", name = "room-compiler", version.ref = "room" }
 room-ktx = { group = "androidx.room", name = "room-ktx", version.ref = "room" }
 room-runtime = { group = "androidx.room", name = "room-runtime", version.ref = "room" }