Export retained notification images in HTML

app/src/main/java/se/ajpanton/notificationlog/data/EncryptedImageStore.kt

@@ -2,6 +2,8 @@ package se.ajpanton.notificationlog.data
 
 import android.content.Context
 import java.io.File
+import java.io.DataInputStream
+import java.io.FileNotFoundException
 
 /** Stores copied notification image bytes independently of the source app's URI lifetime. */
 class EncryptedImageStore(context: Context) {
@@ -9,6 +11,7 @@ class EncryptedImageStore(context: Context) {
     private val cipher = AesGcmCipher(LogEncryptionKeyProvider().getOrCreate())
 
     fun save(id: String, bytes: ByteArray) {
+        require(id.matches(IMAGE_ID_PATTERN)) { "Invalid notification image ID." }
         val payload = cipher.encrypt(bytes)
         File(directory, "$id.bin").outputStream().use { output ->
             output.write(payload.initializationVector.size)
@@ -16,4 +19,26 @@ class EncryptedImageStore(context: Context) {
             output.write(payload.cipherText)
         }
     }
+
+    fun read(id: String): ByteArray? {
+        require(id.matches(IMAGE_ID_PATTERN)) { "Invalid notification image ID." }
+        val file = File(directory, "$id.bin")
+        if (!file.exists()) return null
+        try {
+            DataInputStream(file.inputStream()).use { input ->
+                val ivLength = input.readUnsignedByte()
+                require(ivLength in 12..32) { "Invalid notification image IV length." }
+                val initializationVector = ByteArray(ivLength).also(input::readFully)
+                val cipherText = input.readBytes()
+                require(cipherText.isNotEmpty()) { "Empty encrypted notification image." }
+                return cipher.decrypt(EncryptedPayload(initializationVector, cipherText))
+            }
+        } catch (error: FileNotFoundException) {
+            return null
+        }
+    }
+
+    private companion object {
+        val IMAGE_ID_PATTERN = Regex("[0-9a-f-]{36}")
+    }
 }

app/src/main/java/se/ajpanton/notificationlog/data/NotificationLogEntryJson.kt

@@ -16,7 +16,8 @@ object NotificationLogEntryJson {
                     .put("packageName", entry.packageName)
                     .put("appName", entry.appName)
                     .put("action", entry.action.name)
-                    .put("contents", entry.contents),
+                    .put("contents", entry.contents)
+                    .put("imageId", entry.imageId),
             )
         }
     }.toString().encodeToByteArray()
@@ -32,6 +33,7 @@ object NotificationLogEntryJson {
                 appName = entry.getString("appName"),
                 action = NotificationAction.valueOf(entry.getString("action")),
                 contents = if (entry.isNull("contents")) null else entry.getString("contents"),
+                imageId = entry.optString("imageId").takeIf { it.isNotEmpty() },
             )
         }
     }