Saving retrieved images to disk on Android and Desktop

composeApp/src/androidMain/kotlin/net/codinux/banking/ui/MainActivity.kt

@@ -9,11 +9,14 @@ import app.cash.sqldelight.async.coroutines.synchronous
 import app.cash.sqldelight.driver.android.AndroidSqliteDriver
 import net.codinux.banking.dataaccess.BankmeisterDb
 import net.codinux.banking.ui.config.DI
+import net.codinux.banking.ui.service.ImageService
 
 class MainActivity : ComponentActivity() {
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
 
+        ImageService.context = this.applicationContext
+
         DI.setRepository(AndroidSqliteDriver(BankmeisterDb.Schema.synchronous(), this, "Bankmeister.db"))
 
         setContent {

composeApp/src/androidMain/kotlin/net/codinux/banking/ui/service/ImageService.android.kt

@@ -1,12 +1,45 @@
 package net.codinux.banking.ui.service
 
+import android.content.Context
 import android.graphics.BitmapFactory
 import androidx.compose.ui.graphics.ImageBitmap
 import androidx.compose.ui.graphics.asImageBitmap
+import net.codinux.log.Log
+import java.io.File
 import java.net.URL
+import java.security.MessageDigest
+
+
+object ImageService {
+
+    lateinit var context: Context
+
+}
+
+private val cacheDir by lazy { File(ImageService.context.cacheDir, "imageCache").also { it.mkdirs() } }
+
+private val messageDigest = MessageDigest.getInstance("SHA-256")
 
 actual fun createImageBitmap(imageBytes: ByteArray): ImageBitmap =
     BitmapFactory.decodeByteArray(imageBytes, 0, imageBytes.size).asImageBitmap()
 
-actual suspend fun fetchBytesFromUrl(url: String): ByteArray =
+actual suspend fun fetchBytesFromUrl(url: String): ByteArray {
-    URL(url).openStream().buffered().use { it.readBytes() }
+    var imageFile: File? = null
+    try {
+        val urlHash = messageDigest.digest(url.toByteArray())
+                .joinToString("") { "%02x".format(it) }
+        imageFile = File(cacheDir, urlHash)
+
+        if (imageFile.exists()) {
+            return imageFile.readBytes()
+        }
+    } catch (e: Throwable) {
+        Log.error(e) { "Could not create SHA-256 or read image bytes from file for url '$url'" }
+    }
+
+    val imageBytes = URL(url).openStream().buffered().use { it.readBytes() }
+
+    imageFile?.writeBytes(imageBytes)
+
+    return imageBytes
+}

composeApp/src/commonMain/kotlin/net/codinux/banking/ui/composables/BankIcon.kt

@@ -5,10 +5,7 @@ import androidx.compose.foundation.layout.size
 import androidx.compose.material.Icon
 import androidx.compose.material.LocalContentAlpha
 import androidx.compose.material.LocalContentColor
-import androidx.compose.runtime.Composable
+import androidx.compose.runtime.*
-import androidx.compose.runtime.getValue
-import androidx.compose.runtime.mutableStateOf
-import androidx.compose.runtime.remember
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.graphics.vector.ImageVector

composeApp/src/desktopMain/kotlin/net/codinux/banking/ui/service/ImageService.desktop.kt

@@ -2,11 +2,37 @@ package net.codinux.banking.ui.service
 
 import androidx.compose.ui.graphics.ImageBitmap
 import androidx.compose.ui.graphics.toComposeImageBitmap
+import net.codinux.log.Log
 import org.jetbrains.skia.Image
+import java.io.File
 import java.net.URL
+import java.security.MessageDigest
+
+
+private val cacheDir = File("data/imageCache").also { it.mkdirs() }
+
+private val messageDigest = MessageDigest.getInstance("SHA-256")
 
 actual fun createImageBitmap(imageBytes: ByteArray): ImageBitmap =
     Image.makeFromEncoded(imageBytes).toComposeImageBitmap()
 
-actual suspend fun fetchBytesFromUrl(url: String): ByteArray =
+actual suspend fun fetchBytesFromUrl(url: String): ByteArray {
-    URL(url).openStream().buffered().use { it.readAllBytes() }
+    var imageFile: File? = null
+    try {
+        val urlHash = messageDigest.digest(url.toByteArray())
+            .joinToString("") { "%02x".format(it) }
+        imageFile = File(cacheDir, urlHash)
+
+        if (imageFile.exists()) {
+            return imageFile.readBytes()
+        }
+    } catch (e: Throwable) {
+        Log.error(e) { "Could not create SHA-256 or read image bytes from file for url '$url'" }
+    }
+
+    val imageBytes = URL(url).openStream().buffered().use { it.readAllBytes() }
+
+    imageFile?.writeBytes(imageBytes)
+
+    return imageBytes
+}