feat(send): build durable transfer details and sharing flow

shared/src/iosMain/kotlin/com/vnidrop/app/Platform.ios.kt

@@ -5,7 +5,9 @@ import androidx.compose.runtime.remember
 import com.vnidrop.app.core.rememberFileSystemService
 import com.vnidrop.app.notifications.IosLocalNotificationService
 import platform.Foundation.NSBundle
-import platform.Foundation.NSTemporaryDirectory
+import platform.Foundation.NSApplicationSupportDirectory
+import platform.Foundation.NSSearchPathForDirectoriesInDomains
+import platform.Foundation.NSUserDomainMask
 import platform.UIKit.UIDevice
 
 @Composable
@@ -17,7 +19,7 @@ fun rememberIosAppDependencies(): AppDependencies {
 			environment = PlatformEnvironment(
 				name = device.systemName() + " " + device.systemVersion,
 				appVersion = NSBundle.mainBundle.objectForInfoDictionaryKey("CFBundleShortVersionString") as? String ?: "0.1.0",
-				defaultCoreDataDir = NSTemporaryDirectory() + "vnidrop",
+				defaultCoreDataDir = iosApplicationDataDirectory(),
 				defaultUsername = device.name.takeIf(String::isNotBlank) ?: "Receiver",
 			),
 			deviceInfoProvider = IosDeviceInfoProvider(device),
@@ -27,6 +29,11 @@ fun rememberIosAppDependencies(): AppDependencies {
 	}
 }
 
+private fun iosApplicationDataDirectory(): String =
+	(NSSearchPathForDirectoriesInDomains(NSApplicationSupportDirectory, NSUserDomainMask, true).firstOrNull() as? String)
+		?.trimEnd('/')?.plus("/VniDrop")
+		?: error("iOS Application Support directory is unavailable")
+
 private class IosDeviceInfoProvider(
 	private val device: UIDevice,
 ) : DeviceInfoProvider {

shared/src/iosMain/kotlin/com/vnidrop/app/feature/send/PlatformPreviewStore.ios.kt

@@ -0,0 +1,62 @@
+package com.vnidrop.app.feature.send
+
+import kotlinx.cinterop.ExperimentalForeignApi
+import kotlinx.cinterop.BetaInteropApi
+import kotlinx.cinterop.addressOf
+import kotlinx.cinterop.readBytes
+import kotlinx.cinterop.usePinned
+import platform.Foundation.NSData
+import platform.Foundation.NSDate
+import platform.Foundation.NSFileManager
+import platform.Foundation.NSFileModificationDate
+import platform.Foundation.NSFileSize
+import platform.Foundation.NSNumber
+import platform.Foundation.create
+import platform.Foundation.dataWithContentsOfFile
+import platform.Foundation.timeIntervalSince1970
+import platform.Foundation.writeToFile
+
+actual fun createPlatformPreviewStore(appDataDir: String): PlatformPreviewStore =
+	IosPreviewStore(appDataDir.trimEnd('/') + "/ui/previews")
+
+@OptIn(ExperimentalForeignApi::class, BetaInteropApi::class)
+private class IosPreviewStore(private val directory: String) : PlatformPreviewStore {
+	private val files = NSFileManager.defaultManager
+
+	override fun list(): List<PreviewFileInfo> {
+		ensureDirectory()
+		return files.contentsOfDirectoryAtPath(directory, null).orEmpty().filterIsInstance<String>().mapNotNull { name ->
+			val id = name.removeSuffix(".preview").toULongOrNull() ?: return@mapNotNull null
+			val attributes = files.attributesOfItemAtPath("$directory/$name", null) ?: return@mapNotNull null
+			val size = (attributes[NSFileSize] as? NSNumber)?.longLongValue ?: 0L
+			val modified = ((attributes[NSFileModificationDate] as? NSDate)?.timeIntervalSince1970 ?: 0.0) * 1000.0
+			PreviewFileInfo(id, size, modified.toLong())
+		}
+	}
+
+	override fun read(transferId: ULong): ByteArray? {
+		val data = NSData.dataWithContentsOfFile(path(transferId)) ?: return null
+		return data.bytes?.readBytes(data.length.toInt())
+	}
+
+	override fun writeAtomically(transferId: ULong, bytes: ByteArray): Boolean {
+		ensureDirectory()
+		if (files.fileExistsAtPath(path(transferId))) return true
+		val temporary = "$directory/.$transferId.tmp"
+		val data = bytes.usePinned { pinned -> NSData.create(bytes = pinned.addressOf(0), length = bytes.size.toULong()) }
+		if (!data.writeToFile(temporary, atomically = true)) return false
+		val moved = files.moveItemAtPath(temporary, path(transferId), null)
+		if (!moved) files.removeItemAtPath(temporary, null)
+		return moved
+	}
+
+	override fun delete(transferId: ULong) {
+		files.removeItemAtPath(path(transferId), null)
+	}
+
+	private fun ensureDirectory() {
+		files.createDirectoryAtPath(directory, withIntermediateDirectories = true, attributes = null, error = null)
+	}
+
+	private fun path(transferId: ULong) = "$directory/$transferId.preview"
+}

shared/src/iosMain/kotlin/com/vnidrop/app/feature/send/TransferShareActions.ios.kt

@@ -0,0 +1,66 @@
+package com.vnidrop.app.feature.send
+
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.remember
+import kotlinx.cinterop.ExperimentalForeignApi
+import kotlinx.cinterop.BetaInteropApi
+import platform.Foundation.NSString
+import platform.Foundation.NSTemporaryDirectory
+import platform.Foundation.NSURL
+import platform.Foundation.NSUTF8StringEncoding
+import platform.Foundation.create
+import platform.Foundation.writeToFile
+import platform.UIKit.UIActivityViewController
+import platform.UIKit.UIApplication
+import platform.UIKit.UIDocumentPickerViewController
+import platform.UIKit.UIModalPresentationFormSheet
+
+@OptIn(ExperimentalForeignApi::class)
+@Composable
+actual fun rememberTransferShareActions(): TransferShareActions = remember {
+	object : TransferShareActions {
+		override val canUseNativeShare = true
+		// Core NFC tag writing requires the NFC entitlement. Keep the action
+		// visible but disabled until that capability is provisioned for the app.
+		override val nfcAvailability = NfcShareAvailability.Unavailable
+
+		override fun exportInvitation(ticket: String, transferName: String, onResult: (Result<Unit>) -> Unit) {
+			onResult(runCatching {
+				val url = createInvitation(ticket, transferName)
+				val picker = UIDocumentPickerViewController(forExportingURLs = listOf(url), asCopy = true)
+				present(picker)
+			})
+		}
+
+		override fun shareInvitation(ticket: String, transferName: String, onResult: (Result<Unit>) -> Unit) {
+			onResult(runCatching {
+				val url = createInvitation(ticket, transferName)
+				val controller = UIActivityViewController(activityItems = listOf(url), applicationActivities = null)
+				controller.modalPresentationStyle = UIModalPresentationFormSheet
+				presenter().presentViewController(controller, animated = true, completion = null)
+			})
+		}
+
+		override fun writeInvitationToNfc(ticket: String, onResult: (Result<Unit>) -> Unit) {
+			onResult(Result.failure(UnsupportedOperationException("NFC tag writing is not enabled for this build")))
+		}
+		override fun cancelNfcWrite() = Unit
+	}
+}
+
+@OptIn(ExperimentalForeignApi::class, BetaInteropApi::class)
+private fun createInvitation(ticket: String, transferName: String): NSURL {
+	val path = NSTemporaryDirectory().trimEnd('/') + "/" + invitationFileName(transferName)
+	val text = NSString.create(string = ticket)
+	require(text.writeToFile(path, atomically = true, encoding = NSUTF8StringEncoding, error = null)) {
+		"The invitation file could not be created"
+	}
+	return NSURL.fileURLWithPath(path)
+}
+
+private fun presenter() = UIApplication.sharedApplication.keyWindow?.rootViewController
+	?: error("Could not find an iOS view controller")
+
+private fun present(controller: platform.UIKit.UIViewController) {
+	presenter().presentViewController(controller, animated = true, completion = null)
+}