Added caching on failed (4xx) network requests

Author: spacecowboy

app/src/main/java/com/nononsenseapps/feeder/FeederApplication.kt

@@ -29,6 +29,7 @@ import com.nononsenseapps.feeder.db.room.SyncRemoteDao
 import com.nononsenseapps.feeder.di.androidModule
 import com.nononsenseapps.feeder.di.archModelModule
 import com.nononsenseapps.feeder.di.networkModule
+import com.nononsenseapps.feeder.model.ForceCacheOnSomeFailuresInterceptor
 import com.nononsenseapps.feeder.model.TTSStateHolder
 import com.nononsenseapps.feeder.model.UserAgentInterceptor
 import com.nononsenseapps.feeder.notifications.NotificationsWorker
@@ -42,7 +43,6 @@ import com.nononsenseapps.jsonfeed.cachingHttpClient
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.cancel
 import kotlinx.coroutines.withContext
-import okhttp3.Cache
 import okhttp3.CacheControl
 import okhttp3.OkHttpClient
 import org.conscrypt.Conscrypt
@@ -113,6 +113,7 @@ class FeederApplication : Application(), DIAware, ImageLoaderFactory {
                     cacheDirectory = (filePathProvider.httpCacheDir),
                 ) {
                     addNetworkInterceptor(UserAgentInterceptor)
+                    addNetworkInterceptor(ForceCacheOnSomeFailuresInterceptor)
                     if (BuildConfig.DEBUG) {
                         addInterceptor { chain ->
                             val request = chain.request()
@@ -138,8 +139,6 @@ class FeederApplication : Application(), DIAware, ImageLoaderFactory {
                 val okHttpClient =
                     instance<OkHttpClient>()
                         .newBuilder()
-                        // This is not used by Coil but no need to risk evicting the real cache
-                        .cache(Cache(filePathProvider.cacheDir.resolve("dummy_img"), 1024L))
                         .addInterceptor { chain ->
                             chain.proceed(
                                 when (!repository.loadImageOnlyOnWifi.value || currentlyUnmetered(this@FeederApplication)) {

app/src/main/java/com/nononsenseapps/feeder/model/ForceCacheOnSomeFailuresInterceptor.kt

@@ -0,0 +1,32 @@
+package com.nononsenseapps.feeder.model
+
+import com.nononsenseapps.feeder.util.logDebug
+import okhttp3.Interceptor
+import okhttp3.Response
+
+object ForceCacheOnSomeFailuresInterceptor : Interceptor {
+    override fun intercept(chain: Interceptor.Chain): Response {
+        val response = chain.proceed(chain.request())
+        // If server already set cache-control, don't override it
+        if (response.headers("cache-control").isNotEmpty()) {
+            return response
+        }
+        return when (response.code) {
+            in 400..499 -> {
+                logDebug("FEEDER", "cache-control forced for code ${response.code}")
+                // Cache for 60 minutes
+                // The intent is primarily to cache 404s for incorrect favicons
+                // but all 4xx errors are probably wise not to hammer
+                response
+                    .newBuilder()
+                    .header("cache-control", "max-age=3600")
+                    // Remove any headers that might conflict with caching
+                    .removeHeader("pragma")
+                    .removeHeader("expires")
+                    .removeHeader("x-cache")
+                    .build()
+            }
+            else -> response
+        }
+    }
+}