Improve pages cache creation

app/src/main/java/org/koitharu/kotatsu/local/data/PagesCache.kt

@@ -10,6 +10,7 @@ import org.koitharu.kotatsu.utils.ext.copyToSuspending
 import org.koitharu.kotatsu.utils.ext.longHashCode
 import org.koitharu.kotatsu.utils.ext.subdir
 import org.koitharu.kotatsu.utils.ext.takeIfReadable
+import org.koitharu.kotatsu.utils.ext.takeIfWriteable
 import java.io.File
 import java.io.InputStream
 import javax.inject.Inject
@@ -18,9 +19,14 @@ import javax.inject.Singleton
 @Singleton
 class PagesCache @Inject constructor(@ApplicationContext context: Context) {
 
-	private val cacheDir = context.externalCacheDir ?: context.cacheDir
+	private val cacheDir = checkNotNull(findSuitableDir(context)) {
+		val dirs = (context.externalCacheDirs + context.cacheDir).joinToString(";") {
+			it.absolutePath
+		}
+		"Cannot find any suitable directory for PagesCache: [$dirs]"
+	}
 	private val lruCache = createDiskLruCacheSafe(
-		dir = cacheDir.subdir(CacheDir.PAGES.dir),
+		dir = cacheDir,
 		size = FileSize.MEGABYTES.convert(200, FileSize.BYTES),
 	)
 
@@ -29,7 +35,7 @@ class PagesCache @Inject constructor(@ApplicationContext context: Context) {
 	}
 
 	suspend fun put(url: String, inputStream: InputStream): File = withContext(Dispatchers.IO) {
-		val file = File(cacheDir, url.longHashCode().toString())
+		val file = File(cacheDir.parentFile, url.longHashCode().toString())
 		try {
 			file.outputStream().use { out ->
 				inputStream.copyToSuspending(out)
@@ -50,3 +56,10 @@ private fun createDiskLruCacheSafe(dir: File, size: Long): DiskLruCache {
 		DiskLruCache.create(dir, size)
 	}
 }
+
+private fun findSuitableDir(context: Context): File? {
+	val dirs = context.externalCacheDirs + context.cacheDir
+	return dirs.firstNotNullOfOrNull {
+		it.subdir(CacheDir.PAGES.dir).takeIfWriteable()
+	}
+}

app/src/main/java/org/koitharu/kotatsu/utils/ext/FileExt.kt

@@ -23,6 +23,8 @@ fun File.subdir(name: String) = File(this, name).also {
 
 fun File.takeIfReadable() = takeIf { it.exists() && it.canRead() }
 
+fun File.takeIfWriteable() = takeIf { it.exists() && it.canWrite() }
+
 fun ZipFile.readText(entry: ZipEntry) = getInputStream(entry).bufferedReader().use {
 	it.readText()
 }
@@ -74,4 +76,4 @@ private fun computeSizeInternal(file: File): Long {
 	} else {
 		return file.length()
 	}
-}
+}