Add support for AttachmentBackfill sync messages.

app/src/main/java/org/thoughtcrime/securesms/attachments/AttachmentExtensions.kt

@@ -0,0 +1,96 @@
+/*
+ * Copyright 2025 Signal Messenger, LLC
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package org.thoughtcrime.securesms.attachments
+
+import android.content.Context
+import android.text.TextUtils
+import okio.ByteString.Companion.toByteString
+import org.signal.core.util.Base64
+import org.thoughtcrime.securesms.util.MediaUtil
+import org.thoughtcrime.securesms.util.Util
+import org.whispersystems.signalservice.api.messages.SignalServiceAttachmentRemoteId
+import org.whispersystems.signalservice.api.util.toByteArray
+import org.whispersystems.signalservice.internal.push.AttachmentPointer
+import java.io.IOException
+
+/**
+ * Converts an [Attachment] to an [AttachmentPointer]. Will return null if any essential data is invalid.
+ */
+fun Attachment.toAttachmentPointer(context: Context): AttachmentPointer? {
+  val attachment = this
+
+  if (TextUtils.isEmpty(attachment.remoteLocation)) {
+    return null
+  }
+
+  if (TextUtils.isEmpty(attachment.remoteKey)) {
+    return null
+  }
+
+  try {
+    val remoteId = SignalServiceAttachmentRemoteId.from(attachment.remoteLocation!!)
+
+    var attachmentWidth = attachment.width
+    var attachmentHeight = attachment.height
+
+    if ((attachmentWidth == 0 || attachmentHeight == 0) && MediaUtil.hasVideoThumbnail(context, attachment.uri)) {
+      val thumbnail = MediaUtil.getVideoThumbnail(context, attachment.uri, 1000)
+
+      if (thumbnail != null) {
+        attachmentWidth = thumbnail.width
+        attachmentHeight = thumbnail.height
+      }
+    }
+
+    return AttachmentPointer.Builder().apply {
+      cdnNumber = attachment.cdn.cdnNumber
+      contentType = attachment.contentType
+      key = Base64.decode(attachment.remoteKey!!).toByteString()
+      digest = attachment.remoteDigest?.toByteString()
+      size = Util.toIntExact(attachment.size)
+      uploadTimestamp = attachment.uploadTimestamp
+      width = attachmentWidth.takeIf { it > 0 }
+      height = attachmentHeight.takeIf { it > 0 }
+      fileName = attachment.fileName
+      incrementalMac = attachment.incrementalDigest?.toByteString()
+      chunkSize = attachment.incrementalMacChunkSize.takeIf { it > 0 }
+      flags = attachment.toFlags()
+      caption = attachment.caption
+      blurHash = attachment.blurHash?.hash
+      clientUuid = attachment.uuid?.toByteArray()?.toByteString()
+
+      if (remoteId is SignalServiceAttachmentRemoteId.V2) {
+        cdnId = remoteId.cdnId
+      }
+
+      if (remoteId is SignalServiceAttachmentRemoteId.V4) {
+        cdnKey = remoteId.cdnKey
+      }
+    }.build()
+  } catch (e: IOException) {
+    return null
+  } catch (e: ArithmeticException) {
+    return null
+  }
+}
+
+private fun Attachment.toFlags(): Int {
+  var flags = 0
+
+  if (this.voiceNote) {
+    flags = flags or AttachmentPointer.Flags.VOICE_MESSAGE.value
+  }
+
+  if (this.borderless) {
+    flags = flags or AttachmentPointer.Flags.BORDERLESS.value
+  }
+
+  if (this.videoGif) {
+    flags = flags or AttachmentPointer.Flags.GIF.value
+  }
+
+  return flags
+}